Snel tareipcaling Stan ee 4 W f] l] l] M l] W l] l] ae aS 38} 1384 MN {] (| Marine Biological Laboratory library f Woods Hole, Mass. i M AN (] (] Mi aii (] (] MN Ol M | U] Presented by } () e ) W Dr, Walter H. Wolff {| Ht August, 1954 fl | (| | () ia eet neal i @ bhwOTOO TOEO O WANN 0 001 IOHM/18lN Adventures WITH ANIMALS AND PLANTS r Se oe ea inne \ ORE eo, ee 4 SO Nanna. | a ae a wi Eeneo eee, aA here pe eS apres a cea Aprpemmennntes< espn ats a ag ‘ ADVENTURES WITH ANIMALS AND PLANTS BY ELSBETH KROEBER WALTER H. WOLFF A GENERAL BIOLOGY D. C.. HEATH AND COMPANY BOSTON The Authors ELSBETH KROEBER is First Assistant in Biological Science; Adminis- trative Assistant at the Midwood High School, Brooklyn, New York. She was formerly Chairman of the Department of Biology at James Madison High School, Brooklyn, New York. WALTER H. WOLFF is Principal of the William Cullen Bryant High School, Queens, New York. Among his former positions are the follow- ing: Instructor, School of Education, The City College, College of the City of New York, and Chairman of the Department of Biology and General Science, DeWitt Clinton High School, Bronx, New York. THE ILEUSTRATIONS The cover design for this book was executed by Richard Bartlett from a drawing by W. A. Dwiggins, the frontispiece and title page were painted by Else Bostelmann, the text drawings were made by Paul Wenck and Joseph Lenhard, and the diagrams by Magnuson and Vincent. The photo- graphs reproduced in the text are acknowledged where they occur. The montage on page 2 was assembled with the professional assistance of Marion Howe. Copyright, 1948, 1950 by D. C. Heath and Company No part of the material covered by this copyright may be repro- duced in any form without written permission of the publisher. Offices: | Boston New York CHICAGO ATLANTA San FRANCISCO LC ALLAS LONDON Printed in the United States of America (5¢4) PREFACE As you begin the study of biology you begin a most exciting adventure, the study of animals and plants — the living things of the earth. You are one of these living things, so you will learn much about yourself. The study of living things is not only exciting; it is impor- tant to all mankind. Our knowledge of biology has made it possible for us to avoid many diseases, to provide more and better food, and to understand our- selves better. The study and teaching of biology is the lifework of many people. They are professional biologists. It is possible that you will make the study of biology your lifework. If so, you will find much in this book to help you toward that goal. In writing Adventures with Animals and Plants, however, the authors had in mind, principally, the much larger num- ber of people who will not become pro- fessional biologists. All of us need to know many of the facts and principles of biology in order to understand our- selves and make the best use of many of the things we see, hear about, and read about. Whether or not you make biology your lifework, you will want to know how a professional biologist works and thinks, how he discovers the facts and principles that are so useful to all of us. Biologists, and other scientists as well, use a special method of discovering OF f ee wt ae = R ARYV | % | Ld wae | e\ \ ew / and testing facts and principles. It is called the scientific method. As you study this book, the scientific method will be brought to your attention many times. Hygiene, which is the science of main- taining health and the prevention of dis- ease, is based upon a knowledge of many parts of biology. Throughout the book you will find information that will be useful to you in keeping healthy. We learn the facts and principles of biology by three methods. One is by ob- serving animals and plants, writing down what we observe, and comparing what we see with what others have learned. By a second method we also use observa- tion, but we observe and interpret the results of an experiment which was set up to try to answer some question or problem. A third method is to read what others have learned by the use of the first two methods. In using this book you will make use of all three methods: you will read, you will observe, and you will experiment. Perhaps, if you are a keen observer, or become one, you will discover something no one else has ever learned. In this book you will read about many of the facts that biologists have learned by observations and experiments, and you will learn what conclusions or prin- ciples have been stated to summarize or explain the facts. You will frequently Vill find suggestions for helpful class discus- sions and for experiments that will either add to the information contained in the text or make the text discussions more clear. These suggestions are grouped at the end of each Problem and are called Exercises. At the most appropriate places in each Problem these Exercises are re- ferred to. You cannot possibly do all of them; the authors hope you will find time to do many of them. Each of these Exercises has been chosen with great care to help you understand some part of bi- ology, to help you to learn how a biolo- gist works (the scientific method), or to help you to find out something new. The Questions at the ends of the Prob- 1ems are designed for your use in re- viewing what you learn in studying the Problem. If you can answer all the Ques- tions, you can feel pretty sure that you have done a good job on that section of the text. If you are one of those who like biol- ogy very much, you will want to try some of the Further Activities in Biology that are listed at the end of each Prob- lem. You may also wish to read some of the many books and articles that are listed at the end of the book, just before the Index. Since this book was designed to fit the courses of study in schools throughout Preface the United States, it may contain some topics that are not required in your school. Therefore your teacher may pre- fer not to assign certain sections of it. Some sections are marked “Optional.” These may be omitted, if your teacher so desires, without interfering with your understanding of the parts that follow. All the authors’ long experience in teaching, directing other teachers, and writing for students has been applied to the writing of this text, which is a suc- cessor to Adventures with Living Things. To insure accuracy, the authors have asked a number of people to read por- tions of this book. In addition to the large number of specialists who critically read many portions of the authors’ earlier text, they wish now to thank: Mr. Maurice Bleifeld, Chairman, Department of Biology, Newtown High School, Queens, N. Y.; Professor A. L. Kroeber, Emeritus, University of California, Pro- fessor Laurence H. Snyder, Dean, The Graduate College, University of Okla- homa; and Dr. Charles Tanzer, DeWitt Clinton High School, New York City. The authors thank also Mrs. Charlotte O. Wolff for assistance in preparing the Index. EcspetH KROEBER Watter H. Wo.rr rr rer TABLE OF CONTENTS [INrropuction: Biologists Study Animals and Plants Unit I. THE LIVING THINGS OF THE EARTH ARE MANY AND VARIED ProstEeM 1. What Kinds of Animals Inhabit the Earth? THE VERTEBRATES THE INVERTEBRATES ProsLeM 2. What Kinds of Plants Inhabit the Earth? FLOWERLESS PLANTS PLANTS WITH FLOWERS AND SEEDS ProsLeM 3. How Are Living Things Named and Classified? I. ALE LIVING THINGS ARE BASICALLY ALIKE ProsLtEM 1. Of What Are All Living Things Composed? ProBLeEM 2. How Do Their Activities Keep Cells Alive? ProBLeEM 3. How Are the Cells Arranged in Animals and Plants? Ill. GREEN PLANTS MAKE THE.FOOD USED BY ALE LIVING GEIINGS PrositemM 1. What Part Do Leaves Play in Making and Using Foods? ProsLeEM 2. What Part Do Roots and Stems Play in Making and Using Food? IV. HOW A COMPLEX ANIMAL USES FOOD FOR ENERGY AND GROWTH ProsLeM 1. How Can We Choose Foods Wisely? . How Does the Digestive System Make Foods Usable? ProsteM 3. How Are Materials Moved to and from Our Body Cells? ProsLeM 4. How Are All Our Cells Provided with a Constant Supply of Oxygen? PRoBLEM 5. How Does the Body Get Rid of Wastes Formed by Cell Activity? ProsLeM 6. What Substances Help Regulate Cell Activities? 68931 PROBLEM N 246 ¥ Table of Contents V. WHY LIVING THINGS BEHAVE AS THEY DO 260 ProsLeM 1. What Are the Simplest Forms of Behavior in Animals? 261 ProsLemM 2. What Makes Complex Behavior Possible in Many-celled Animals? 260 ProsteM 3. How Does the Behavior of Complex Animals Differ from That of Simpler Forms? 286 ProsteM 4. How Do Plants Respond to Their Environment? 301 VI. CONSTANT CARE IS NEEDED FOR MAINTAINING OUR HEALTH 310 ProsteM 1. How Are Our Bodies Protected against Microorganisms? 311 ProsteM 2. What Have Scientists Learned about Conquering Some Common Diseases? 320 ProBLEM 3. (Optional) How Have Recent Discoveries Changed Some of Our Ideas about Disease? 338 ProsLtEM 4. How Do We Attempt to Stop the Spread of Disease? 343 ProsteM 5. How May We Achieve Better Health for All? 359 VII. HOW LIVING THINGS AFFECT ONE ANOTHER 372 Prostem 1. What Makes Possible the Continued Existence of Plants and Animals? 373 ProsLteM 2. What Are Our Relationships to Other Organisms? 381 ProsteM 3. How Do We Try to Solve Our Insect Problems? 389 ProstemM 4. Why Must We Practice Conservation? 399 VII. HOW ANIMALS AND PLANTS MAKE MORE OF THEIR OWN KIND 410 ProstemM 1. How Do the Simple Animals and Plants Reproduce? 411 ProsLemM 2. How Do the More Complex Animals Reproduce? 421 ProBLeM 3. How Do the More Complex Plants Reproduce? 438 IX. THE ORGANISM IS THE PRODUCT OF ITS HEREDITY AND ITS ENVIRONMENT 454 ProsLeM 1. Why Do Offspring Resemble Their Parents? 455 PROBLEM 2. How Can Some of the Differences betaveen Parents | and Offspring Be Explained? 464 | PropLeM 3. How Can New Hereditary Characters Appear? 479 ProstemM 4. How Does the Environment Affect the Characters of an Organism? 485 Table of Contents Xi Unit ProsLEM 5. What Have We Learned about Producing New Types } of Animals and Plants? 493 ProsLtEM 6. To What Extent Can Mankind Be Improved? 508 X. THE EARTH AND ITS INHABITANTS HAVE CHANGED THROUGH THE AGES 520 ProsLemM 1. What Can We Learn from Rocks about the History of the Earth? 521 ProstemM 2. What Can We Learn from Fossils about Prehistoric Living Things? 533 ProsLEM 3. What Puzzling Facts May Be Explained by Our Theory of the Origin of New Organisms? 547 ProsLeEM 4. What Theories Have Been Offered to Explain the Origin of Different Kinds of Animals and Plants? 555 ProsteM 5. What Were the Stages of Mans Development on the Earth? 564 BIBLIOGRAPHY 580 GLOSSARY 583 INDEX 599 How To Use This Book 1. How this book is organized. Adven- tures with Animals and Plants is divided into Units, each of which presents a major topic in biology. When you have finished studying a Unit you will have learned the most important facts pre- sented in that Unit, and should under- stand the important ideas growing out of those facts. To aid you in reaching this understanding, each Unit is divided into two or more Problems. These Problems may be said to be the chapters of the book. Each Problem title poses a ques- tion, the answer to which is to be ob- tained by studying the text that follows. When the answers to all the Problem questions contained in a single Unit are understood, you will have all the infor- mation necessary to an understanding of the statement at the head of that Unit. Each Problem is composed of “para- graphs” headed by a title in boldface type. Each of these paragraphs supplies some information necessary for arriving at the answer to the Problem question. A simple, step-by-step study of the para- graphs, as suggested in the following sec- tion, will help to put you on the road to success in your biology course. 2. How to learn from this book. There Xl are many devices in this book designed to help you to learn biology readily. Of these, the Unit headings, Problem ques- tions, and paragraph titles are the most important, because they tell you what you are supposed to learn. From the very beginning of any study period you should know. what you are trying to learn. After reading a paragraph title, think. over the meaning of the title and ask yourself what; you already know about that subject. When you have thought through and organized your previous knowledge, you will be better equipped to grasp the additional infor- mation that is supplied by the book. You will find it helpful to do the Exercises referred to throughout the text as you are studying the section those Exercises are intended to supplement. Perhaps the class as a whole can plan with the teacher how to do some of the Exercises. This is more interesting than following direc- tions laid down by others. If, at first reading of the text, you do not understand a sentence, finish the par- agraph to find out if your questions are answered. Then go back and re-read the sentence as it stands in relation to the rest of the paragraph. If you still have questions, make a note of them and have them explained in class. If it is a word that you do not understand, look it up. If that is not possible, make a note of the How to Use This Book word so that you can learn its meaning in class. The field of biology makes use of many special words that you will need to learn. These words are printed in italics and defined when they first ap- pear. If you do not recall the meaning of a word when it is used later in the book, look it up in the Index to find where it was used first. A good way to learn the special vocabulary of biology is to pre- pare a glossary for yourself in your note- book. A glossary is simply a special dic- tionary. You can list the new terms you learn and write their definitions in your own words. As a basis on which to build your own more complete list of words you will find a glossary prepared by the authors beginning on page 583. There are many illustrations in this book. Every one has been chosen to add to your understanding and information. It will be useful for you to look at them carefully and to study the legends. Both the printed text and the illustra- tions will undoubtedly raise questions in your mind. These are the most precious results of study because they lead to interesting class discussions and, later, to a more complete understanding of the subject. Such questions will also empha- size to you that in biology, as in other sciences, there is much that remains to be learned. Adventures WITH ANIMALS AND PLANTS Fic. 1 All animals and plants are subjects for biologists to study. Students of biology learn what kinds of living things there are, how they are constructed, how they re- main alive, why they behave as they do, how they reproduce, why they resemble their parents, why there are so many kinds, how they are dependent upon each other, how man affects them, and how they affect man. (PHOTOS BY CRUICKSHANK-NATIONAL AUDU- BON SOCIETY, NATIONAL ZOOLOGICAL SOCIETY, TYRELL-NATIONAL AUDUBON SOCIETY, PHILIP GENDREAU, RALPH: ANDERSON, AND MUSEUM OF NATURAL HISTORY ) Biologists Study Animals and Plants What is biology? Biology is the study of living things. This means that biology is the study of all animals, including man, of all plants, and of those simple living things which we do not know whether to call animal or plant. Since biology is the study of all living things, all of us have been biologists (students of biology) in a small way all of our lives. When you learned the name of the robin you were, for the moment, a bi- ologist. To be more exact you were a zoologist (zoh-ol’-o-jist), a student of animals. Would it make it seem more important if you knew that this branch of zoology was called ornithology, the study of birds? You were learning biol- ogy when you noticed that a dog would dash after a ball (the science of animal behavior) and when you noted green leaves come out in the spring (botany, the science of plants). You were an unwilling biologist, too, when you had measles or scarlet fever and discovered how other organisms can affect man. Evidently biology is the study of living things in any way in which a biologist wants to study them. You may think that this makes biology a large and varied science—and so it does. There are many sub-sciences that make up the larger science of biology. You have just read the names of a few of them; there are many others which you will read about in this book. What to study about living things. Most people will say that one of the first things to learn about a living thing is its name. This is true. Most of the living things you see frequently have common names and you will want to learn some of them. You can learn to know an oak tree from a maple tree and a woodchuck from a skunk. In some cities you will see maples, elms, and poplars along the streets; in others palms and pepper trees. You will enjoy knowing these names as well as_ the names of common breeds of dogs and cats and of many other animals and plants. But more important than the names of living things is a knowledge of their structure; that is, the parts of which a living thing is made and how these parts fit together to make a whole organism (or’gan-ism), a single living thing. Since you are more interested in your- selves than in any other organism, it is especially useful to you to know the structure of your body. When you have completed a year’s work in biology, you will know something about how you and all other human beings are constructed: what your heart is like and your stomach and your brain and the other parts of your body. Of course in one year’s time you will not be able to learn very much about living things. The men and women who spend their 4 entire lives studying just one part of biology do not then feel that they have mastered it completely. The knowledge of how organisms are constructed becomes especially valuable when you go on to learn how organisms carry on life activities. If you know how you digest and absorb food, how you breathe, how your blood circulates, how your actions are controlled, how it happens that human beings are like their parents, and how human beings have developed through the ages, you will have important information about yourself. To understand this well you will need to learn something about the structures of other organisms, such as lower animals and even plants, and how they carry on their life activities. Man and other living things. There are even better reasons for learning how other organisms carry on their life ac- tivities. Consider plants; it is important to you and to me that plants be raised for our use. If the wheat crop is a great deal smaller than usual, we may have less bread; if the corn crop fails, cattle and hogs are scarcer and the price of meat goes up. In fact, if there were no plants on this earth we would not be here at all. Then consider the many animals such as rabbits, moles, and particularly in- sects, that injure crops and _ interfere with the production of food and mak- ing a living. There are also many organ- isms that attack man directly, causing disease. It is well to know something about all these organisms and to know how we can protect ourselves and our crops against them. Men are constantly affected by other living things. Biologists Study Animals and Plants The work of biologists. Since the field of biology is so large, the work of bi- ologists is varied. Some biologists live out of doors, exploring and learning about plants and animals at first hand by observation and recording. Some biologists work in the Jaboratory, ex- perimenting with living things or with chemicals in test tubes; some study plants or animals at close range through the microscope to learn the secrets of living matter. Before you plunge into the study of living things let us see how some of these biologists do their work. Biologists explore the world. Do you know what kinds of plants and animals live on this earth? Do you know what plants and animals live on the island of Borneo or along the Amazon River? Could you describe a scene in the Gobi Desert of Asia or picture to yourself the plants that make summer beautiful within the Arctic Circle? It seems that similar questions have always interested man. There have al- ways been men bold and adventurous enough to undertake long voyages to distant parts of the earth merely to see and collect the plants and animals liv- ing there. About two hundred years ago Carolus Linnaeus (lin-nee’us), a young student at a Swedish university, was sent by his country to Lapland to make collections of living things. He started alone, carry- ing in his leather bag a simple micro- scope, a telescope, paper for drying plants, and writing materials for taking notes. For many months he endured great hardships. During this time he reached the Arctic Ocean on foot. Then he returned to his university with a few Biologists Study Animals and Plants specimens of rocks and animals and plants, and complete notes on every- thing he had seen. He had learned a great deal about the customs of the native Lapps, had become acquainted with the wild animals of the country, and had made a thorough study of the plants, for botany was the subject of greatest interest to him. It is said that he traveled more than four thousand miles. Linnaeus’ accounts of his journey in- spired other biologists to explore foreign lands. Often these trips last for several years during which the biologist is far from any civilized country, completely dependent upon his ability to make friends with native tribes. He has to win their confidence slowly, learn their language, and persuade them to take long trips on foot, on horseback, or by boat through parts of the country the natives may fear. Here the explorer devotes himself to his search for new types of animals and plants. Many of these are collected and stored to be taken back to museums and universities. Complete notes are kept of all observations so that no mistake will be made when the scien- tific reports are later prepared. Some of these exploring scientists are also excel- their own sketches of the strange scenes they see. Exploring is not at an end. Exploring nowadays is frequently very complex. Large expeditions are organized. They include experts in many branches of science and are equipped with scientific instruments of many kinds. Photog- raphers and secretary-historians are among the specialists included. Despite their size, such expeditions still meet lent artists and prepare Fic. 2 What water-living plants and animals might this collector find? (wWard’s NATURAL SCIENCE ESTABLISHMENT) with exciting adventures. Even as you read this, investigators are at work in the field in many parts of the world, searching high in the mountains, and deep in the sea, in the frozen wastes of the arctic and antarctic, and in the hot, wet jungles. Exploring the depths of the ocean. You may join exploring biologists in imagi- nation, if you wish. Would you care to stroll through a garden in the warm seas twenty feet below the surface? Get into your bathing suit, strap your div- ing helmet to your shoulders, and climb down the ladder that hangs over the side of the boat. When you reach the last rung, drop off. You will sink gently to the bottom. Take care not to scratch yourself on the corals that are part of the lovely undersea gardens. If you have remembered your zinc pad and lead pencil, you will be able to take notes as soon as your eyes grow accustomed to the dim light. The sunlight filters through this clear tropical water and flashes from the bril- liant reds and yellows of the many kinds of fish. The beauty of the ocean floor with its brightly colored animals will delight you as it has the biologists who have gone down many times to study this active world of living things. Some have described its beauties, others have painted its scenes, and still others have Biologists Study Animals and Plants re Py Fic. 3 The Central: Asiatic expedition of the American Museum of Natural History meets with an accident in the Mongolian Desert. What abilities must the explorer have besides a knowledge of biology? (AMERICAN MU- SEUM OF NATURAL HISTORY ) Fic. 4 Exploring in a jungle. Dr. William Beebe and two fellow scientists take motion pictures of living things on the floor of a jungle in Venezuela. (JOCELYN CRANE —NEW YORK ZOOLOGICAL SO- CIETY ) photographed the graceful forms so that everyone may now enjoy the gardens undersea. When the water is clear and not too deep, living things in the sea can be seen through panes of glass in the bottom of a boat. Diving in a helmet has many advantages, however. And now that helmets have been perfected almost anyone can explore the shallow seas. But for exploration down to a depth of half a mile a bathysphere is used. This is a ball of steel with thick glass windows and a powerful electric Biologists Study Animals and Plants io. Fig. 5 Photographed off the Florida coast. W hat information can biologists obtain by under- water trips? How else can they get such infor- mation? (MILLER DUNN CO.) light casting a beam out into the sur- rounding blackness. Long before these methods of study- ing the life of the sea had been de- veloped, other devices were in use. Nets made of steel had been dragged on the bottom of the sea, sometimes as much as three miles down, and then hauled to the surface so that the catch might be studied. Nets had been invented that could be dragged through the water at certain depths and closed before they were pulled in. In this way biologists fi would know, for example, that certain fish live at depths of half a mile, coming no closer to the surface nor going much farther down. Dredges with steel jaws had been dropped to the bottom and closed so that samples of the sand and (mud) could be collected and examined. This disclosed the fact that the thousands of square miles of ocean OOZze bottom is the graveyard of tiny animals aliter udeathe mA single one of these tiny animals is too small to be seen by the naked eye yet that have died have formed thick deposits of this ooze. whose skeletons sank the countless billions Thus slowly the labors of many men are making it possible to describe life in the darkness of the ocean depths. Exploring nearer home. Not all biolo- gists interested in getting acquainted with plants and animals have wandered to the far corners of the earth to dis- cover and describe them. Many have remained at home, knowing that with patient observation much could be learned about animals and plants nearby. One of the most famous of the stay- at-home observers was Jean Henri Fabre (fah’br). For most of the years of his long and useful life Fabre watched the insects in his garden and in the sunny fields. He would crouch, motionless, for long hours at a stretch, intently watch- ing the behavior of some insect. It was by such patient observation that he saw insects hunt food and store it, fight enemies, and mate. He saw how eggs were laid and how they hatched. Then he wrote exact descriptions of what he had seen. He left many simple and inter- esting accounts of his observations; most of them have been translated from Fic. 6 An outdoor museum, part of the Nature Trail at Tuxedo, New York. Could ’ b) you build a simple nature trail? What besides names might be given on the various tags that you see? (AMERICAN MUSEUM OF NATURAL HISTORY) the French so that you can read them. Other stay-at-home observers may study birds, or snakes, or other animals. Such study can satisfy a love of the out of doors and add to the store of bio- logical knowledge. Backyard exploration for you. Equipped with a pad and a pencil, you too can start on a tour of exploration. You may fill notebooks with your observations of the wild things in a park, in a field, or in a city lot. You can collect specimens and lay out a museum of your own. Or you may choose to mark off a small plot on the bank of the creek flowing by your house, the edge of a nearby wood, or a city yard. If you study this with care you will be amazed at the many organisms you will find. One biologist collected several hundred different kinds of insects from his own small backyard in three vears. Your backyard may be only a roof sill. A sheltered board regularly supplied with bread crumbs or a window will bring passing birds. A piece of sod brought in from out of doors and watered carefully will grow into a miniature jungle. There will be much. for you to observe and many experi- ments for you to try. With a camera you can add to the pleasure of backyard exploration and provide a_ treasured album. A study of biology can lead to many outdoor hobbies: the collecting of in- sects, fossils, shells, or plants; the raising of pets such as guinea pigs, rabbits, and white mice; the studying of insects in their homes; the planting and care of a garden. The biologist’s laboratory. While some biologists explore, many more work in the laboratory — the workshop of the Biologists Study Animals and Plants Fic. 7 A corner of the Boy Scout Museum at Bear Mountain, New York. What suggestions for hobbies does this picture give you? (AMERICAN MUSEUM OF NAT- URAL HISTORY) scientist. The well-equipped workshop has sinks with faucets of different sizes; stone tables with vacuum and air pres- sure outlets and connections for gas and electricity; rows of shelves for bot- tles of dyes, acids, testing agents, glass- ware of many kinds, and some reference books, cupboards dissecting instruments and other instru- with microscopes, ments of various sorts. There may be an incubator, a pressure cooker, a refrig- erator. The laboratory is the place in which biologists perform their “labors,” in which they investigate, observe, ex- periment, draw conclusions, and record their studies of living things. That is why boys and girls who set up little places at home for the study of living things may speak of them as biologists’ workshops or laboratories. A peep into a laboratory. The great Russian biologist, Ivan Pavlov (1849- ii hg 1936), in the early years of the present century wished to learn something of animal behavior. Let us visit him in his laboratory. He used dogs as experimental animals because they were easy to work with. Pavlov wanted to find out how the saliva can be made to flow in a dog. But before he could begin his experiment he had to perform a difficult operation. He opened a small hole in the dog’s face and inserted a tube to which a jar was attached. When Pavlov showed food to the dog, the saliva flowed into the jar and _ the could be measured. It took weeks to train the dog to stand still in a harness while he was fed. After these preparations Pavlov was ready for his experiment. He rang a bell each time he put food before the dog. This was continued for some time. Then, one day, Pavlov rang the bell without putting the food before the amount Io dog. The saliva flowed from the dog’s mouth just the same and in the same amounts. This experiment was per- formed many times, and with many dif- ferent dogs. Always the sound of the bell made the flow of saliva start. Then Pavlov varied his experiment, in one variation, as he showed the food he touched the dog on its hindquarters instead of ringing a bell; in another variation he showed the food and at the same time showed the dog a paper on which a large circle had been drawn. In each experiment, after enough repe- titions there was a flow of saliva even when the food was withheld. Pavlov showed in this way that not only the normal cause, but also an unusual cause, could lead to the flow of saliva in the dog. The experiments taught scientists something about the way in which animals learn. You will read more about this later in the book. But notice how carefully the stage was set for the experiment. Weeks Biologists Study Animals and Plants Fic. 8 (left) The modern research microscope is far different from the simple in- strument of Leeuwwenhoek’s day. (SPENCER LENS CO.) Fic. 9 (right) One of Leeu- wenhoek’s many micro- scopes. A lens was fastened into the metal plate. The rest of the microscope is the object holder, which, by the use of screws, was used to place the object in proper position. Compare this with the modern research micro- scope. (BAUSCH AND LOMB) spent in training the dog; years of study to make possible the delicate operation, skillful construction of the cages and harness; patient watching for results, accurate measurement and recording of the facts day after day; the repetition of the experiment with many dogs — all this was necessary to make successful what may have seemed to you at first to have been a relatively simple job. Biologists study the “invisible.” The man who first saw “invisible” or micro- scopic creatures was a Dutchman, Anton van Leeuwenhoek (1632-1723), whose hobby was making lenses. When he had ground and polished a small bead of glass until he was sure it would magnify well, he used it to examine all kinds of tiny objects to find out what they really looked like. It was a great day for him and for biology when he examined a drop of the rain water that had been standing in a barrel. Picture his amazement and de- light when he found that the drop was Biologists Study Animals and Plants Fic. 10 The man is using an electron microscope. With its use it is possible to obtain photographs 200,000 times as large as the objects. You can see that the electron micro- scope bears no resemblance to the compound micro- scope. (R.C.A.) a little world of wriggling, squirming creatures never before seen by man. When he reported his discovery, men in other countries used their lenses to examine similar drops of water. They, too, saw these living things that had been invisible until then. They studied them, filled notebooks with descriptions of their activities, and drew careful dia- grams to illustrate their structures. The biologist improves his tools. As improved, smaller and smaller living things were found and examined. Today, good microscopes enable us to study objects so tiny that 50,000 of them laid end to end would measure only one inch. But increase in magnifying power has not been the only advance. More important than that microscopes were II has been the increase in clearness of vision. Modern microscopes are impressive instruments of shiny enamel and polished chromium but improvement in appear- ance is much less important than the improvements in the lenses. They are marvels of fine grinding, far, far better than any in the early microscopes. Modern the early ones in another way; they magnify twice, by two sets of lenses. They are therefore called compound microscopes. The two magnifications are multiplied. If the lens near the object magnifies fifty instruments are unlike times and the lens near the eye ten times, the total magnification is 500. The microscope that biologists or physicians use can generally magnify 1800 times, T2 Ultraviolet and electron microscopes. In using the ordinary microscope we use light that the eye can see. A little over forty years ago it was discovered that one could obtain higher magnifica- tion by using ultraviolet light. Ultra- violet light cannot be seen by the human eye but can be photographed. By this means magnifications of 4000 or even higher are possible. Objects that had been invisible under the best microscope could now be seen. More recently an electron microscope based on new prin- ciples has been invented. Recent im- provements have given us a microscope that magnifies 20,000 times. Then by enlarging the negatives a magnification of about 200,000 times can be obtained! In just a few years biologists have suc- ceeded in photographing objects that no one had ever hoped to see. You may expect the newspapers and magazines to Biologists Study Animals and Plants Fic. 11 Dr. Alexander Flem- ing in his laboratory, exam- ming some mold cultures in test tubes. You will read more about his great con- tribution to the world. He discovered the drug, peni- cillin. (WIDE WoRLD) carry exciting accounts of new discov- eries in the future as the electron micro- scope is applied to living things and new facts are learned about their tiniest parts. The study of living things goes on. All the world over there are biologists, both men and women, as well as boys and girls, who continue to study living things. Their activities are as varied as the activities of the living things that they study. There are so many problems to study — there is so much we do not yet know — that biological study is end- less and always fascinating. A glance at the newspaper will dis- close the fact that discoveries are being made daily. As this is written it is knowa that there are four or more kinds of penicillin made by mold plants. They have been used successfully to combat certain types of disease germs. But we Biologists Study Animals and Plants do not yet know how these types of penicillin differ or what the chemical make-up of penicillin is. By the time you read this it is likely that much more will be known about this spectacular drug. The problem of cancer is of tremen- dous interest to men and women. How can we detect it as soon as it starts so that we can save a human life? What causes it? Do we know exactly how such organs as the liver and the spleen function in man? How do vitamins act to prevent certain diseases? Is “intelli- gence” — whatever it is — inherited? If so, how? If not, what produces it? What can we do to improve it in boys and girls? What makes us act as we do? 13 And basic to all these questions: What kind of material is the living stuff in all plants and animals? Will we ever be able to make such living stuff in the laboratory? There are thousands of such questions .that can be asked, and, fortunately, there are thousands of men and women in every country trying to answer them. The most fascinating part of the study of biology is that at any moment a com- plete or a partial answer to a problem may be provided. When you read this book you may know the answer to a question that the authors did not know when they wrote it. The pursuit of biological knowledge goes on always with continuing success. In UNIT I you will consider these problems: PROBLEM 1. PROBLEM 2. What Kinds of Animals Inhabit the Earth? What Kinds of Plants Inhabit the Earth? ProsteM 3. How Are Living Things Named and Classified? MAIO “td so ~ MASS. / A ae ‘> Md unit | THE LIVING THINGS OF THE EARTH ARE MANY AND VARIED Vic. 12 Zebras and gnus at a water hole in South Africa. Some biologists prefer to study the animals and plants of foreign lands. Others are most interested in those that live near by. (SOUTH AFRICAN RAILWAYS) PROBLEM | What Kinds of Animals Inhabit the Earth? The animal kingdom. We often speak of two large groups of animals: the vertebrates, animals with a backbone; and the invertebrates, animals without a backbone. A backbone consists of sep- little bones (vertebrae — ver'te- bree). Ihe vertebrate group is very large and is subdivided into five classes: the mammals, the birds, the reptiles (snakes and their relatives), the am- phibians (frogs and their relatives), and the fish. All these animals, different as they may seem at first glance, have im- portant resemblances. Besides the back- bone, they all have a brain in a boxlike skull (cranium). Attached to the brain is a spinal cord. It lies along the animal’s back, protected by the backbone. All animals having these characteristics are called vertebrates. The vertebrates, together with some other less familiar animals, are called chordates (core’dates). We shall not refer again to the other chordates. The name phylum (fy’lum) is given to such a big grouping as the chordates. The invertebrates are arranged in arate many groups or phyla (fy’la). There are many more kinds of invertebrates than vertebrates. And the number of individ- uals is much larger, too, Commonly known invertebrates are the insects, the spiders, the lobsters, the clams, the snails, the starfish, the worms, the jellyfishes, the corals, the sponges, and the mi- croscopic animals known as protozoa (proe-toe-zoe’ah). All these belong to the animal kingdom. So the ants which are insects have as much right to be called animals as dogs or horses or birds. All belong to the animal kingdom. Subdividing the animal kingdom. You read that the animal kingdom is divided into large groups called phyla. A phylum may be divided into subphyla; generally it is divided into classes. Now this book and many other textbooks are divided into units and the units are subdivided into problems and the problems into para- graphs. On more or less the same prin- ciple a phylum is divided into classes and the class is divided into orders. In a later problem you will see that the subdivid- ing does not stop there; it goes right on until you have the following: Phylum Class Order Family Genus Species The word species (spee’shees) means kind of animal (or plant) such as the dog species or cat species, the lion species, the horse species, and so on. Sometimes the species is subdivided even further into varieties or breeds. In reading about animals in this prob- lem you will concern yourselves mostly with phyla and classes and some of the species of animals they include. 16 The Living Things of the Earth INT: Codfish Fic. 13 Examples of each of the five chief classes of vertebrates. THE VERTEBRATES CLASS — MAMMALS How we can recognize mammals. Mam- mals have a backbone, they are verte- brates. But they differ from the other vertebrates in that they have hair or fur. Some mammals have very little hair; there is little hair on an elephant’s body and even less on a whale’s. But every vertebrate with any hair at all is a mam- mal. The other striking distinguishing characteristic of all the mammary or milk glands by which the mammals is young are fed. Mammals breathe by means of lungs and they are warm- blooded (that is, their body temperature is fairly constant, it does not change much with changes in the temperature of the surroundings) but these are not characteristics that make them different from all other vertebrates because birds, too, have lungs and are warm-blooded. Mammals also have two pairs of legs but so do all frogs and some reptiles as well. There are about 4000 species of mammals. Because of their complex structure they are spoken of as the “highest” animals. This would be a good time for you to begin EXercIsE 1. Man and the apes. Mammals are sub- divided into groups (called orders). The group most important to us is the one containing ourselves. All mammals are somewhat like man in structure but the great apes, such as the chimpanzees, the gorillas, and the orangutans, resemble man in structure much more closely than do any other animals. For this reason man and the apes are placed in the same group. The monkeys also belong to this group. Mammals with grinding teeth. This is a large group. It really includes sev- eral orders. You probably know giraffes, deer, buffalos, cows, gazelles and goats; horses and zebras; elephants; and_ rhi- noceroses. Most of these animals have single or double hoofs. The hoof is an enlarged and thickened toenail. How- ever, elephants, rhinoceroses, and some others lack a hoof and have several toes. All of them have grinding teeth used in chewing grass and leaves. Many of them, such as cows, sheep, deer, and PROBLEM 1. The Kinds of Animals of the Earth 17 Fic. 14 (above) The Canada lynx or bobcat. (uv. s. BU- REAU OF BIOLOGICAL SURVEY) Fic. 15 (upper right) Go- rilla. (CHICAGO PARK _ DIS- TRICT ) Fig. 16 (right) Camel (NEW YORK ZOOLOGICAL SOCIETY ) Why are all of these animals called mammals? To which groups of mammals does each belong? Why is the gorilla placed in the same order as man? others have a stomach with a large pouch which serves as a reservoir for the food swallowed while the animal grazes. Later as the animal rests this food comes up again into the mouth and is chewed as “cud.” Mammals with long eyeteeth. These are the carnivores (car’ni-vores). The long eyeteeth are used for tearing flesh. But some carnivores eat other foods too. Bears relish berries and small insects such as ants. Some, like the hyena, eat car- 18 The Living Things of the Earth rion (dead animals). But most carni- vores hunt and kill. Bears, wolves, foxes, skunks, and many others have blunt, strong claws. In cats, tigers, and lions the sharp claws are pulled back when not in use. Gnawing mammals. We all know the gnawing mammals, or rodents. There are about 2000 species spread over prac- tically the whole globe, in the hot desert and in the arctic snow and ice. Some burrow in the ground, some live in trees, and others live in the water. You know rabbits, rats, mice, squirrels, and woodchucks. You may have seen beavers, or perhaps the dams they build. If you live in our West you have heard the whistling marmot; you have seen the prairie dogs on our great plains. Most rodents are small and timid. The two pairs of front teeth (incisors) can in- flict an ugly wound but unless cornered the animal will not bite. The front teeth, used for gnawing and chiseling, are worn down by constant use. But they keep growing as long as the animal lives. Mammals that live in the sea. A whale is so dependent on the water and so fishlike in shape and general appearance that at first glance you might not classify it as a mammal. But it has the two dis- tinguishing characteristics of a mammal: it has mammary (milk) glands and _ its skin, although mostly naked, has a few bristles of hair. Like other mammals it is warm-blooded and brings forth its young alive. Whales have large amounts of fat called “blubber.” This protects them against the cold. Man converts the fat into oil, obtaining as much as 150 barrels of oil from a good-sized whale. . INT There have been many fanciful stories about whales. A whale cannot swallow a man whole nor does it even attack man except when fighting back. And whales do not spout water. When a whale comes to the surface and breathes out, the water vapor in its hot breath condenses (just as yours does on a cold day) and the little drops of water that are formed look like a stream of water shooting up into the air. There are other mammals that live in the sea: walruses, seals, and sea lions. Examination of their structure and par- ticularly their teeth shows that they are really carnivores. The seals and sea lions spend part of the time on land resting or waddling about awkwardly by using their flippers as legs. Mammals that fly. The bats are mam- mals that fly. They can fly better than many birds. Being mammals, they do not have feathers; they have hair. Bats resemble a tailless mouse with big ears and large folds of skin under the arms which are used as wings. All day long they hang head down, hooked to the rafters of some building or in a cave or hollow tree. Some species sleep in col- onies of several thousands, coming out at night to search for food. Most bats live on insects, some eat fruits, and a few, the vampire bats, suck the blood of other mammals. It is not true that bats fly into people’s hair nor do our bats hurt you in any way. Simple mammals. The marsupials (mar-soo’pee-els) are simpler than the mammals you have just read about. Among the marsupials the young are born in a very undeveloped and-heipless state, and the female carries the young PROBLEM 1. Ibe Kinds of Animals of the Earth 19 Fic. 17 Like all other car- nivores, the sea lion is equipped with sharp pointed teeth. (INTERNATIONAL NEWS PHOTOS) Fic. 18 The opossum is the only pouched mammal found outside of Australia. What use does it make of its tail? (GEHR) Fic. 19 This picture of a brown bat shows how the membranes attached to body and legs are stretched out by the long finger bones. (AMERICAN MUSEUM OF NAT- URAL HISTORY ) 20 The Living Things of the Earth Fic. 20 The spiny anteater of Australia and a model of the egg it has laid. (AMERICAN MUSEUM OF NATURAL HISTORY ) in a pouch for a long time after birth. See Figure 384, page 433. The kanga- roos of Australia and the opossums of our country belong to this group. In one common species, the Virginia opos- sum, the animal when discovered pre- tends it is dead; it “plays possum.” There are several other kinds of mar- supials in Australia besides kangaroos. The simplest mammals lay eggs. Duck- bills lay eggs and have bills like a duck but since they have mammary glands and hair they are considered to be mam- mals. Spiny anteaters and armadillos are other simple mammals. Now do Exer- CISES 2, 3, and 4. If you would like to continue your study of mammals, you will find it useful to refer to some of the interesting books on mammals listed in the bibliography at the end of the book. CLASS — BIRDS The characteristics of birds. Birds have feathers. There are no exceptions. That UNE ein | Fig. 21 The duckbill of Australia. This mammal also ‘lays eggs. (AMERICAN MUSEUM OF NATURAL HISTORY ) is the characteristic by which you recog- nize them. The feathers are usually lacking on the legs, which are covered with scales. There are two other char- acteristics almost as striking as the first: birds have beaks or bills without teeth and the forelimbs have the structure of wings. Birds, like blooded; their temperature, in general, mammals, are warm- is higher than that of mammals. Some of them, indeed, have a temperature of 112°, Like mammals they have four- chambered hearts and they breathe by means of lungs. There is much that you can discover for yourself if you will fol- low the directions ir £xERCISES 5 and 6 carefully. Subdivision of the class. This class is subdivided into many different orders but the differences between the orders are technical and difficult to learn. In this section, we shall use a simple group- ing based mostly on the kind of feet and bill: birds of prey, scratching birds, PROBLEM I. birds that wade or swim, perching birds, and birds that cannot fly. Birds of prey. These are the eagles, hawks, vultures, and owls. Their wings spread wide and firm; their talons (claws) are cruel, curved daggers which can be driven deep into the body of a other bird; their strong beaks used for tearing flesh are hooked and sharp. Some hawks, eagles, small mammal or and vultures are easily recognized in flight because of their remarkable ability to soar, that is, to remain aloft with almost no movement of the wings. They do this by taking advantage of the air currents. In spite of common belief, birds of prey, with few exceptions, are useful to man. Their natural food is rabbits, field mice, other small mammals, and even certain species of insects which are destructive to crops. The vultures and some of their rela- tives are scavengers, they feed on the dead and decaying flesh of animals. Forehead Upper mandible Lower mandible Throat Wing coverts Breast Abdomen Scales The Kinds of Animals of the Earth 21 Scratching birds. These live on the ground and scratch for seeds and small insects; such birds are the common fowl, the grouse or partridge, and the turkey. Some of these birds are strong and swift flyers, too, but for the most part they rely on their legs instead of their wings. Domestic fowl such as chickens, ducks, and turkeys have prac- tically lost the power of flight. Birds that wade or swim. These are, mostly, large birds. They squawk and call hoarsely but never sing. Their food comes from the water and they spend much of their time in the water or on it. IThe!storks, the herons, the cranes, and the flamingos (fla-ming’gos) wade. Their tall legs keep their bodies well out of the water and their long pointed beaks and flexible necks make it pos- sible for them to snatch the frogs or fish that make up their diet. Among the swimming birds are the ducks, geese, and swans. Their legs are Nape — Back = Scapulars a Rump Upper tail coverts Lower tail coverts Tail feathers Fie. 22. This drawing of a mockingbird is labeled to show the names of the various parts. It is helpful to know these names when you are learning to identify birds. Bird descriptions in books use these terms because all students of birds know them. Could you describe the colors of a robin or of a canary, using some of these words? 22 The Living Things of the Earth Fic. 23. A young owl. The owl hunts at night. W hat do you notice about the size of its pupils? How does this help the owl? (AMERICAN MU- SEUM OF NATURAL HISTORY — OVERTON ) Fic. 24 The American eagle. In which way is it fitted for obtaining food? (NATURE MAGAZINE — TISHER ) WINER strong and attached far back enabling them to exert a powerful push against the water. The position of the legs makes it easy for them to tp their heads down for a dive. Their feet are large and webbed. Water birds all produce much oil which protects their feathers from get- ting wet. This fact has given rise to the common expression, “as water rolls off a. duckissback.”’ Birds which cannot fly. A few species live wholly on land and never fly. The ostrich, the largest living bird, and its less familiar relatives have wings which are too small to be of any use. But all are good runners, running as fast as sixty miles an hour. When attacked and cornered, an ostrich defends itself by means of a kick which is dangerous to man. Perching birds. These, for the most part, are the birds that sing. You may know best the house (English) sparrows and the starlings of our crowded cities; the robins and the bluebirds of our suburbs; or the swallows and the crows of the countryside. These, and about four hundred fifty other species, are perching birds. They are the birds to which man owes much thanks for keep- ing down insect pests and for eating the seeds of weeds that would spoil crops and gardens. The songbirds often steal our fruit, but their bill of fare consists largely of insects or seeds of weeds that are harmful to man. Migration of birds. Many birds and some other animals migrate. They move from one place to another and back again in the course of a year. The migrating season is generally the spring PROBLEM I. and the fall. Many of our songbirds spend the summer in the more northerly states and the winter in the south. Some winter over in the northern states and fly to the arctic in the spring. Migrat- ing birds may perform amazing feats of flying. The arctic tern, a water bird, builds its nest in the far north; several months later it flies to the antarctic. Although the route has not yet been completely traced, it is known that these birds fly about 11,000 miles each way. The golden plovers travel a shorter dis- tance, from Canada to South America, 2000 miles or more, but they fly over the ocean in one stretch. They complete the journey in two days and nights without stopping to rest or feed. There are many interesting questions about migration still unsolved. “How can birds travel so far without food and rest?” “How can they find their way?” “How can some return not only to the same state and town but to the very nest in which they were reared?” And difficult as any: “Why do birds migrate, anyway?” Bird flight. Upward and forward mo- tion of birds is supplied by a powerful downward and backward beat of the wings against the air. The large wing feathers overlap while the wings beat backward, but the feathers separate as the wing comes forward and up. Because the feathers separate during the forward motion, little resistance is offered to the air and not much speed is lost. When birds soar, they move their wings very little; instead, they depend on air cur- rents, just as a glider does. What helps the bird in its flight? Its wings are enormously long as compared The Kinds of Animals of the Earth 22 Fic. 25 Compare the position of the eyes of this sandhill crane with the position of the owl’s eyes. Note also the legs and bill. (NEW yorK ZOOLOGICAL SOCIETY) SUL - ff Wer: tiff” fp Fish hawk Flycatcher \ ~~ Fic. 26 The bill often tells you something about the bird’s food. For what kinds of food is each bill fitted? The Living Things of the Earth untr 1 1. REDSTART ; 4. GOLDEN PLOVER 2.60 SPECIES 5. WESTERN TANAGER 3. SCARLET TANAGER 6. PACIFIC COAST BIRDS Fic. 27. Spring migration routes of some common birds. Some of these birds follow the same routes south in the fall. Which of these birds travel the longest distance? Some of the 60 species which follow route 2 are the bobolink, chuck-will’s-widow, the gray-cheeked thrush, the bank swallow, the black-poll warbler, and the night- hawk. The picture above the map is of Canada geese taken during migration. You will find it interesting to find out the migration routes of the Canada goose. (EWING GALLOWAY ) PROBLEM 1. The Kinds of Animals of the Earth 25 a eee Fic. 28 Carolina Wren Fic. 29 Sierra Junco The birds of Figures 28, 29, 30, and 32 are called perching birds. What do these birds eat? How are they helpful to man? What can we do to protect them? The birds that built the nests of Figure 31 are also helpful. Can you find out why? (Fig. 28, HUGH DAVIs; Fig. 29, NATURE MAG- AZINE; Figs. 30, 31, and 32, AMERICAN MUSEUM OF NATURAL HISTORY) 1 SN i i “ : Fic. 31 Nests of the cliff swallow Fic. 32, Hummingbird 26 The Living Things of the Earth UNL Fic. 33. The garter snake. This snake is one of the commonest found in the United States. It is frequently seen on farms, even near the buildings, and frequently, also, in lawns and gardens of thickly settled communities. The garter snake may bite when it is handled roughly, but its bite is harmless, except as a possible source of infection. It does not lay its eggs as many other snakes do. The eggs hatch within the mother’s body and the young are born alive. All snakes move by wriggling and by many small movements of their ribs which are attached to the sharp scales on their underside. (U. S. BUREAU’ OF BIOLOGICAL SURVEY ) to the size of the body, there are very powerful breast muscles which move these wings. The breast bone to which the muscles are attached and many other bones are hollow, making the body ex- ceptionally light in weight. In the bibliography at the end of the book there are listed several books about birds. Perhaps you will wish to read one of them and learn more about birds. CLASS — REPTILES What is a reptile? Like mammals and birds, reptiles have lungs. Some lay eggs as do the birds; some bring forth their young alive. But they differ from mam- mals and birds in that they are covered with scales. Scales, you remember, are characteristic of fish also. How, then, can one distinguish between reptiles and fish? This is easy, for fish in general get air from the water by means of gills, and their scales are slimy. Reptiles have lungs and dry scaly skins. ; Reptiles are the first vertebrate ani- mals you have met in this book that are cold-blooded. The body of the cold- blooded animal is sometimes warm and sometimes cold, depending on the sur- roundings. Reptiles are most common in the tropics; as you go northward you may expect to find fewer and fewer rep- tiles. In a climate such as that of the northeastern cold, reptiles are active and visible during only a short season, As fall comes on states where winters are they become sluggish and soon go into a state of hibernation (winter sleep) un- derground. Some reptiles run on four legs, some on two, while some wriggle without any legs at ail. Many live on land; others dwell in fresh water or in the salty ocean. Zoologists divide them into three main orders which you can easily recognize: the snakes and lizards, PROBLEM I. Fic. 34 How many ratiles has this rattlesnake? It is not true that one can tell a rattle- snake’s age by the number of rattles. (U. S. BUREAU OF BIO- LOGICAL SURVEY) Fic. 35 The head of a rattle- snake ready to strike. Where is the poison gland located with relation to the fangs? : Poison duct Fang (tooth) G alligators and crocodiles, and turtles. Our poisonous snakes. The feeling of horror that snakes arouse in some people is unreasonable. As a child you may have seen your elders shrink at the sight of a snake and you may have learned to imitate them. Children left to them- selves have no more fear of snakes than of any other animals that seem strange. Most snakes are harmless; poisonous snakes are the exception. In this country there are only four kinds of poisonous snakes: the rattlesnake, the copperhead, the water moccasin, and the coral snake. On our continent man is rarely bitten, even where poisonous snakes are nu- merous, for with the exception of the water moccasin our poisonous snakes are timid; they do not attack unless they are disturbed. Still more rarely does any one die of the bite. An understanding of the methods of treating a bite and the C er RS ERS The Kinds of Animals of the Earth 27 Poison gland Gland-squeezing muscle ip) Jaw-opening = muscle courage to remain calm almost always prevent serious results from the poison. The poison is injected through a pair of large, hollow, very sharp fangs (teeth). These are in the upper jaw, folded back out of the way until the snake strikes. The swiftly-moving little tongue contains no poison; the snake uses it to learn of its surroundings. Rattlesnakes are widely scattered over the United States. When disturbed, they sound their rattles, which are located at the tip of the tail, so that it is easy to avoid them. It is only when they are taken by surprise that they strike with- out warning. The amount of poison in- jected depends on the size of the snake. Large rattlers are therefore more dan- gerous than small ones. The copperhead is found in various regions in the north- ern half of the country. The water moccasin and the coral snake are not 28 The Living Things of the Earth TINT St vs Fig. 36 (above) An adult copperhead may be two or two and one half feet long. As in rattlers and water moc- casins, the head is triangular. (U.S. BU- REAU OF BIOLOGICAL SURVEY) Fic. 37 (right) This x-ray photograph of a snake shows the long backbone and the many ribs which help in locomotion. (GENERAL ELECTRIC X-RAY CORP.) uncommon in the south. The water moc- casin, which lives in swamps, is some- times called “cottonmouth” because the inside of its mouth is white. The coral snake is smaller than the water moccasin and has short fangs but when it bites, it hangs on, and sometimes its bite is serious. It often burrows in damp ground. Do Exercises 7 and 8. Peculiarities of snakes. Snakes have an enormously long backbone, consist- ing of many vertebrae each of which, except at the tail end, has a pair of ribs. Muscles connect the ribs with the scales on the lower part of the snake. By mov- ing the ribs, the scales are hooked onto the uneven surface of the ground, one after the other. Thus the wriggles on its scales, but this happens snake really so fast and evenly that it looks like a smooth gliding motion. No snakes have legs, although the pythons (pie’thons) of Asia have tiny stumps of hind legs which are not used. Because of its peculiar formation, a snake’s mouth can be opened so wide that it will admit an animal broader than the head of the snake. The animal must be swallowed whole since the teeth are not used for biting off or chew- ing food, At irregular intervals as snakes grow they develop a new skin under- neath the old one. The old skin is then shed as in the photograph, Figure 39. Snakes of other countries. While snakes in our part of the world are not a real danger, in India, Central and South America, and other tropical regions PROBLEM. I. snakes are a serious menace. It is esti- mated that in India alone they kill about 20,000 people every year. One of the most deadly snakes of India is the cobra. It- is vicious, and injects a particularly strong venom (poison). There are also huge pythons in India which reach a length of more than thirty feet. They coil themselves around their victims and crush them to death. Some of the boa (boh’a) constrictors and anacondas of the tropical Americas may also reach a large size. Many reptiles, unlike other animals, keep on growing throughout their lives and they live long. Lizards — the closest relatives of snakes. People often call the little four-legged, soft-bodied salamander, so common in the woods, a lizard; but since it lacks The Kinds of Animals of the Earth 29 Fic. 39 (above) A hog-nosed snake losing its old skin. As a snake grows its skin becomes too small. A new skin forms under the old one. (AMERICAN MUSEUM OF NATURAL HISTORY) Fic. 38 (left) This swift is a typical lizard. Notice the claws on its toes. What characteris- tics of a lizard does it have? Why is it classed as a reptile? (AMERICAN MUSEUM OF NATURAL HISTORY ) a scaly covering you know it cannot be a reptile, and must not be called a lizard. Lizards have, as a rule, slender bodies with long tails and four rather short legs which can move with great speed. Lizards live in warm climates. Lizards of the United States are, with one exception, harmless. The one lizard which bites and has poison fangs is the red and black striped Gila (hee’la) monster. It lives in the deserts of Ari- zona and New Mexico. Alligators and crocodiles. Alligators and crocodiles are large reptiles which inhabit only the warmer portion of the globe. Even there they are sluggish, resting motionless in shallow streams with their eyes and nostrils above the surface of the water. However, the sight 30 The Living Things of the Earth unir 1 of some unwary animal along the banks will quickly rouse them to activity. Turtles. ‘Turtles have a complete back- bone, ribs, and all the other bones you should expect a vertebrate or a “back- boned” animal to have. The shell de- velops from the skin of the upper and lower surfaces and becomes attached to the backbone and the ribs. Head and legs are, of course, covered with the ordinary scales characteristic of reptiles. Turtles may eat plants, insects, frogs, fish, or any other small animals. Their horny, toothless jaws are sharp and strong and are used for tearing and 5 ae Fic. 40 (above) These tadpoles are the youn of the green frog. How do they differ from ai adult frog? (HUGH SPENCER) Fig. 41 (left) The snapping turtle is found in ponds or rivers. It has a dull brownish shell with notches at the back. Why are turtles classed as reptiles? (AMERICAN MUSEUM OF NATURAL HIS- TORY ) biting, much as teeth are used by other animals. In a few species the shells re- main soft. To become better acquainted with reptiles read one of the books listed in the bibliography. CLASS — AMPHIBIANS How we can recognize amphibians Amphibians, like reptiles, are cold- blooded vertebrates. Their skin is naked and in almost all species is soft and moist. They are called amphibians be- cause most of them spend the first part of their life in the water and the other PROBLEM IT. Wate icp... | a lee F Be Oe te Fic. 42 A green frog can jump fifty times its length. What structures make this possible? (AMERICAN MUSEUM OF NATURAL HISTORY) part on land. While in the water stage they obtain air by means of gills; in the land stage they use lungs for breathing. There are a few species which do not develop lungs at any stage and never leave the water, when full grown they resemble a legged tadpole. Amphibians with tails. Biologists divide the class Amphibians into two orders — those with tails and those without. The tailed forms, the salamanders and newts, might be mistaken for lizards until one discovers the moist, naked skin. They are timid, harmless creatures; their feet have no claws and their jaws are weak, unfitted for biting. They catch insects with the tongue. Some of the tailed am- phibians are brightly colored; others, like the hellbender, are dull and un- attractive. One that many of you may have found in the woods, under logs or leaves, is the beautiful red newt. Amphibians without tails. You are much more familiar with this group which includes the frogs and_ toads. The Kinds of Animals of the Earth 31 eg ra ¢ ~ ae . . Fic. 43. The American toad cannot jump as far as the frog. Can you tell why? (SCHNEIDER AND SCHWARTZ) They feed on insects which they catch with their long, slimy tongue. They lay their eggs in fresh water; these hatch into tadpoles which change into adults as legs and lungs form. Frogs when fully developed, continue to spend at least part of their time resting just under the sur- face of the water with eyes and nostrils raised above the surface. The hind feet are webbed and are equally useful for swimming and jumping. Toads, on the other hand, leave the pond and return only in the spring to lay their eggs. Their skin becomes so dry that it looks shriveled and warty. [he statement that you can get warts from handling toads was long ago proved to be untrue. Toads are not only harmless to us but are a great help to the gardener because they eat insects. Do EXeErcIsE 9. CLASS — FISHES What is a fish? As you turned from the most complex vertebrates, the mam- 32 The Living Things of the Earth Pe | ° as ees ou ee UNIT I bones. Gill covers are lacking. This shark has two shark suckers attached to its lower side. (NEW YORK ZOOLOGICAL SOCIETY) mals, to the simpler ones, you met first the birds, then the reptiles, then the There cold- blooded vertebrates even less complex; amphibians. are other these are the fishes. Their distinguishing characteristics are slimy scales, fins, and gills. Of course they have a backbone just as other vertebrates do. They are water dwellers, obtaining the oxygen they need from the air dissolved in the water. Out of water, fish die quickly because their gills cannot take oxygen from the atmosphere. Most fish have paired fins, usually two pairs, and other fins which occur singly. Make your own observations of fish by doing Exercises TOT T, and? 12. “Fish” that are not fish. The animals of this group are closely related to fish Dorsal fin 17 0959, Sa WW) Za) Ky = Gill cover Left pectoral fin Left pelvic fin but have skeletons made of a softer sub- stance called cartilage (car’til-aj). You may know cartilage by the name of gristle (griss’l). One of the commonest is the dogfish that destroys large num- bers of food fishes along the coast. Sharks are its larger cousins, with repu- tations often much worse than they de- serve. Most species of sharks do not attack man but eat only fish and other animals of the sea. Fish are numerous and varied. There is three times as much sea as land. You can see that there is plenty of room for fish. Great numbers live in both warm and cold waters; even in the arctic seas there are fish. Some kinds swim near the surface, others far below. It is es- timated that at present there are about Fic. 45 Which characteris- tics of fishes does this gold- fish have? Where are the gills? How many fins has the goldfish? PROBLEM I. The Kinds of Animals of the Earth 33 Fic. 46 Fish move by means of the muscular tail to which the broad tail fin is attached. They have other fins, both paired and unpaired, which are used principally for balancing. (NEW YORK ZOOLOGICAL SOCIETY) two and a quarter billion people in the world. But that is a tiny number compared to fish populations. Of the herring, alone, man catches and kills about eleven billion each year. It has been estimated that 200 billion other herring are eaten annually by larger fish. Yet the ocean remains well stocked with herring. Twelve thousand different spe- cies of fish have been described. They range in size from the large tuna fish, which weighs three quarters of a ton, to the guppy of your aquarium which measures a scant inch and weighs so little you could not feel its weight in your hand. Some interesting fish. The flatfish, that is, the flounders and the soles, are curiously built. They are extraordinarily flat from side to side and spend most of their time lying on one side half buried in the sand. Both eyes are on one side, the side which is always up. In the young fish the eyes are where you would expect them to be, one on each side of the head. Then one eye moves around and joins its mate. You may have heard of “flying fish,” but fish cannot really fly. All fish, when push themselves through the water entirely by means of their muscular tails. When near the sur- face this motion of the tail may drive them out of the water, so that fish are often seen jumping. The flying fish have very long paired fins which they spread as they jump. Thus, they glide through the air. Among the strangest fish are those that can breathe by means of lungs. They also have gills. Plan to do EXERCISE 13. Fish migration. Fish migrations are as interesting and as puzzling as are bird migrations and, naturally, much more dificult to study. Although eels had been known and caught as a food fish for thousands of years, until about thirty-five years ago no one knew where they laid their eggs or where the young grew to be adults. Each fall thousands of mature eels were seen to swim down the fresh water streams of Europe and America into the Atlantic Ocean. There they disappeared. Finally a scientific expedition tracked them to a region east of the Bermuda Islands where they lay swimming ee rapidly, 34 The Living Things of the Earth their eggs in deep waters. Then the parents die. The young fish remain for a year near where the eggs hatch. Then they begin the long journey to homes they have never seen in the rivers of the two continents. [he American eels turn toward the rivers of our country; their European cousins travel eastward. When they are mature, they swim back to the breeding grounds in the Atlantic Ocean. The salmon, which live in the ocean when adult, migrate into fresh water at spawning (egg-laying) time. They swim far up into the shallow headwaters of OIN Tea streams. Here the eggs are laid. Then most of the parents die. The young develop slowly and eventually swim out to the sea, where they remain until they are ready for spawning. Within the last few years much has been learned by the United States Bureau of Fisheries about the migrations of fish. Thousands of fish are tagged and fishermen are asked to return the tag with information as to the size of the fish and the place where it was caught. Fish are interesting to read about, see the bibliography at the end of the book. QUESTIONS . Into what five subdivisions or classes can the vertebrates be divided? What two or three characteristics do all vertebrates have? Starting with the largest group, the phylum, list the subdivisions em- ployed by biologists in classifying animals, 3. In what two respects do mammals differ from all the other kinds of vertebrates? Why may they be spoken of as the highest animals? How many species of mammals are known to scientists? 4. Which mammals are most like man in structure? 5. List.nine kinds of mammals that may be grouped together as plant eaters with grinding teeth. What is another characteristic of most of these mammals? Explain. 6. What are the characteristics of the carnivores? List some carnivores. 7. Give the name of the gnawing mammals. What can you tell about the gnawing teeth? 8. Give two reasons why a whale is classified as a mammal. State two interesting facts about whales. What other mammals inhabit the sea? Why are they classified with dogs or cats rather than with whales? g. Tell what you know about bats. 10. What are the characteristics of marsupials? Where do most of them live? Which animals in our country are closely related to the Aus- tralian kangaroo? W hy is the duckbill called a mammal? List two unusual characteristics of the duckbill. 11. By which one characteristic can you alw ays recognize a bird? are other characteristics of a bird? 12. How are birds classified? = N What 13. Describe and give examples of birds of prey. In general, are they useful or harmful to man? Explain. PROBLEM 1. Ihe Kinds of Animats of the Earth 14. 15. 16. 17. 18. 10. 21. List some of the scratching birds. What do they eat? List some wading birds. What are their characteristics? How do swimming birds differ from wading birds? Which is the largest living bird? What are its peculiarities? About how many species “of perching birds are there? What is the importance of these birds to man? What can you tell about bird migration as to: when birds migrate, in which direction birds migrate in the various seasons, and how far birds fly during migration. What problems in regard to migration are still unsolved? Explain how birds can fly. List three characteristics which enable birds to fly. How does soaring differ from flying? . By which characteristics do you recognize reptiles? When an animal is called cold-blooded, what really i is meant? Where are reptiles most common? Define hibernation. Into what three main groups (orders) are they divided? What are the four kinds of poisonous snakes found in this country? Tell some facts about each of them. . State the peculiarities of structure in snakes. Explain how they carry on locomotion and how they feed. . Tell something about the important snakes of other countries. . Describe how lizards resemble and differ from snakes. Which is the only poisonous lizard in our country? . Why may alligators and crocodiles be dangerous to man? ‘ Why are turtles called reptiles? What do they use as food and how are they fitted for getting this food? Of what importance are they to man? . What are the striking characteristics of amphibians? . Into what two groups (orders) are amphibians divided? Give an ex- ample of each order. Compare the tailed amphibians with lizards. . Discuss the habits of frogs and toads. Of what importance are toads to man? . State how you distinguish fish from other vertebrates. How do gills differ from lungs? . How do sharks differ from true fish? . How numerous are fish as compared to lend living vertebrates? How do fish vary in size and appearance? . Describe the migration of eels and salmon. EXERCISES Mammals 1. Collect pictures of mammals and group them according to order on charts or in a looseleaf notebook. 36 The Living Things of the Earth unrr 1 2. If possible, visit a zoo or natural history museum. Gather facts of interest about several different kinds of mammals. To which order does each belong? 3. Prepare special reports on topics such as the following: (a) The in- telligence of the great apes, (b) the mammals of a special region, such as Australia, (c) the mammals of my vicinity, (d) man’s use of mammals. 4. When you have finished the section on mammals, gather together all the important ideas you have learned about mammals under the following headings: a list of mammals with those of one order gathered together; the uses of mammals to man; the harm done to man by other mammals; unusual mammals; mistaken ideas or superstitions about mammals. Birds 5. Study of a living bird. If possible, observe a canary, a pigeon or a chicken. Or study a house sparrow or some other common bird, out of doors. How long is the bird? If you can handle it, find out how large the bird’s body is and how wide a wingspread it has. What markings does it have? Describe their location accurately. (Make use of the dia- gram in the text.) How far down on the legs do the feathers go? In what direction do the feathers on the wings and body point? Where are the longest feathers? the shortest? Describe the toes. Examine the eyes closely. Describe. How far around can the bird turn its head? Describe the beak and method of getting food. 6. Have you ever looked closely at a feather? Cut the quill crosswise to find out why it is so light. Use a hand lens for the study of the other parts. Cut a point on the end of a large quill and use it as a pen. Reptiles and Amphibians 7. Have you heard about the snake that swallows the end of its tail and rolls like a hoop? Have you heard of the milk snake that steals milk from the cow? Have you heard that horsehairs left in water will turn into snakes? Comment on each’ of these statements. State: (a) What your reason would lead you to believe and why, (b) whether in these cases observation or experiment might help you arrive at the truth, (c) what else you might do to convince yourself that each story is or is not true. 8. Are there poisonous snakes in your part of the country? Ask the class secretary to write to the nearest college or zoo to find out. What are they? Where are they likely to be found? How can you avoid being bitten? g. Using the facts presented in this book, write a brief report on the importance of reptiles and amphibians to man. Add more information if you are sure it has been obtained on good authority. State what authori- ties you consulted so that others can decide w hether or not to accept the information. PROBLEM 1. Je Kinds of Animals of the Earth Fishes 10. Study of a living fish. Examine a goldfish in a bowl of clear water. Where are the paired fins; the unpaired fins? Examine and describe a fin which is spread out. How are the scales arranged? Is this of any ad- vantage to the fish? Try to catch the fish with your hand. What do you notice? Describe the movement of the gill cover, What do you see under- neath it when it is raised? 11. State at least four ways in which the structure of a goldfish makes possible rapid movement through the water. 12. Stir the water in the goldfish bowl to make the fish swim quickly. What part of the fish pushes it forward? What part do the paired fins play in locomotion? 13. Organize a class trip to a fish market on a Thursday afternoon after school. List the kinds of fish. Take notes on their sizes, colors, and markings so that you can recognize them again. How much do they cost per pound? Compare the price with that of lamb, chicken, beef, and pork. Why can fish usually be sold more cheaply than meat? FurTHER ACTIVITIES IN BIOLOGY Mammals 1. Make plaster casts of the tracks of mammals. (See Mann and Has- tings, and others.) If you can get dogs, cats, rabbits, and white mice, you can take their footprints by wetting their feet with ink and leading them across sheets of wrapping paper. 2. Since the class Mammals is so large, you and your classmates might organize committees to make a special study of the different orders. If written reports are prepared, they could be organized into one large account of the mammals. 3. Breed white mice, guinea pigs, or rabbits, so that live mammals are available for study. 4. If you can, learn something about the habits of one of the follow- ing: rabbit, woodchuck, chipmunk, squirrel, prairie dog, deer. If possible, take “notes” with a camera. Birds 5. If there is no Junior Audubon Society in your school, ask the class secretary to write to the National Association of Audubon Societies, 1000 Fifth Avenue, New York City, for further information. 6. Are you a Scout? Have you earned the Bird Study Merit Badge? 7. Even if you live in a city, it will be easy for you to keep and breed pigeons on the roof. 8. Write to the Geological Survey, Washington, D.C., about bird- banding. Read the National Geographic Magazine, January, 1928. Report to the class on the subject. 37 38 The Living Things of the Earth unrr 1 Month Baltimore oriole Bluebird Blue jay Junco Red-breasted nuthatch Fig. 47. A bird calendar for Boston, Massachusetts. Which bird stays the year round? Which leave Boston in the fall? In the spring? See Exercise 13. g. Can you get birds to stay in your neighborhood? Establish winter feeding stations. See National Association Audubon Societies leaflets; or A. A. Allen, Book of Bird Life. 10. If you are good at making things with your hands, build bird houses and bird baths. You will enjoy watching the birds use them. See L. H. Baxter, Boy Bird-House Architecture. 11. Do you know any birds by their calls or songs? Some of them are very easy to recognize. Get phonograph records of bird songs to play in the classroom. Records can be purchased from the Laboratory of Orni- thology, Cornell University, Ithaca, New York. In some cities these rec- ords can be rented from The Audubon Society. 12. Make a collection of deserted bird nests and show them to the class. How many different kinds of materials go into the making of these nests? (Do not collect nests still in use. ) 13. When you have eames to recognize many kinds of birds you will enjoy making a “bird census.” List all the birds found in your locality. Examine Figure 47. It would be interesting for you to prepare a bird calendar for your part of the country. 14. Bird photography is a fascinating hobby. Much information can be obtained from the camera department of Nature Magazine and magazines on camping, hunting, and fishing. The finest achievement is a series of pictures showing the life of the bird from egg to adult. Reptiles and Amphibians 15. 0A terrarium (glass ) may be set up for salamanders, newts, and frogs. Mosses and small ferns will help to make a forest floor. 16. Can you plan an experiment to discover the effects of changes in temperature on cold-blooded animals like the snakes and lizards? Use ice and warm water but do not wet the animal. Why must you change the temperature slowly? PROBLEM! I. The Kinds of Animals of the Earth 39 I. Report on the best treatment for snake bites. 18. Frogs and toads make excellent subjects for night photography. Use a flashlight to find them, open the lens of your camera, and then burn a photoflash bulb. The flash lasts about one fiftieth of a second. The lens is closed afterward. Fishes 19. Use a natural history such as Hegner’s Parade of the Animal King- dom or copies of the National Geographic Magazine to learn more about fish and their relatives, the sharks. Prepare a short talk. 20. Have you ever maintained an aquarium of tropical fish? If you have, report briefly to your class on their structure and habits. Could you start an aquarium? 21 ool: up lungfish. Tell your classmates why biologists consider them important. THe INVERTEBRATES Animals without backbones. You know that invertebrates have no backbone. Whatever skeleton they may possess is either on the outside, like a coat of armor, or is so different from the skele- ton of the backboned animals that you would never confuse the two. And while all vertebrates are assigned to a single phylum the kinds of invertebrates are so varied that they are arranged in dif- ferent phyla. Zoologists are not all in agreement on just how many phyla the invertebrates should be divided into. However, all classifications include the nine important phyla we will study. In the diagram on page 4o there are draw- ings of one representative of each of these nine phyla. From the many thou- sands of possible kinds these nine were chosen: a grasshopper, a snail, a starfish, an earthworm, a hookworm, a planaria (a relative of the tapeworm), a jellyfish, a sponge, and an ameba. In this book only a very few of the thousands of species of invertebrates can be described. There are about 800,000 species of inverte- brates in contrast with the 40,000 species of vertebrates. “SaIIGOIIOA, Fic. 48 This circle graph will help you com- pare the numbers of species of invertebrates and vertebrates. It will also help compare the num- ber of species of insects with the total number of all other kinds of invertebrates. There are approximately 40,000 species of vertebrates and 800,000 species of invertebrates, of which 600,000 are insects. 40 The Living Things of the Earth unit 1 ARTHROPODS MOLLUSKS ECHINODERMS Starfish PLATYHELMINTHS Planaria—Flatworm PROTOZOA Fic. 49 The invertebrates are classified by zoologists into numerous phyla. One mem- ber of each of the nine principal phyla is illustrated above. Do you know other members of these phyla? PROBLEM I. The Kinds of Animals of the Earth 4) egger Fic. 50 These are representatives of each of the five principal groups of the Arthro- pod Phylum. Which common animal is an example of each group? PHYLUM — ARTHROPODS Jointed-Legged Invertebrates A glance at the arthropods. The in- vertebrates with jointed legs, or ar- thropods, are the most complex inverte- brates. You can recognize an arthropod by two characteristics: they have jointed legs and they have an external (outside) skeleton made not of bone or cartilage, but largely of a material called chitin (ky’tin). Most of the arthropods can be classified in five groups or classes. Examples of these five classes are repre- sented in Figure 50: the insects, the spiders, the hundred-leggers, the thou- sand-leggers, and the crustaceans (crus- tay’shuns) which include crabs and lobsters. What is an insect? Let us begin our study with the most common arthro- pods, the insects. Insects differ from the other arthropods in that they have six legs and three distinct body parts: a head with feelers called antennae (an- ten’nee), a thorax with three pairs of legs, and an abdomen (ab-doh’men). The abdomen never has legs. In the ab- domen you can see distinct rings called segments. Most insects have two pairs of wings, but you cannot depend on this as a way of recognizing insects, since some insects have only one pair and others have no wings at all. The wings, legs, and feelers are called appendages (ap-pend’a-jes). If you examine Figure 59 and the other pictures of insects, you will see the parts mentioned here. Most insects have large eyes, called compound eyes because each eye con- sists of many six-sided lenses. Insects can hear, too. Some have eardrums; some seem to use the feelers as organs of hearing. But the feelers seem to serve also as organs of smell and touch, Insect flight is very different from bird flight. In most insects the wings move with astonishing speed. The house fly’s beat is about 330 times a second. You can understand why it makes a buzz. How- ever, the speed is not the same in all in- sects. The grasshopper has been timed at twenty miles an hour. The “darning needle” can fly at the rate of sixty miles an hour but no insect flies far without stopping. The life story of an insect. Let us trace the life story of a common insect, a Fig. “51 42 The Living Things of the Earth UNIDSS ae] Three stages in the development of the monarch or milkweed butterfly are shown. The changing-over stage (pupa stage) is called the chrysalis. It has a hard coat. Which stage is not illustrated? (AMERICAN MUSEUM OF NATURAL HISTORY) butterfly or moth. The eggs laid by the parent develop into wormlike creatures called caterpillars. A caterpillar does not look at all like an insect; it certainly lacks the three-part division of the body and seems to have more than the typical number of legs. It has no wings and no feelers. After a period of steady feeding it either forms a hard protective coat or little itself. If the little house is spun, it is called a builds a house around cocoon (kuh-koon’). Many changes oc- cur within the cocoon and after some time the insect comes out a full-grown butterfly or moth. These insects, there- fore, 20 the caterpillar, called the Jarva: the through four stages: the egg, changing-over stage, called the pupa (pew’pa); and the adult. This compli- cated life history -is referred to as a complete metamorphosis — (change). Many other insects have these four stages in their life history. All the ants, bees, wasps, flies, mosquitoes and beetles have complete metamorphosis. There are other insects, the grasshop- per for example, that lack a pupa stage. In these there are only three stages: the egg, the nymph which is much like the parents, and the adult. This kind of life history is called incomplete metamor- phosis. If you are interested in insects you will want to do some of the things suggested on pages 68-70. PROBLEM I. Fig. 52 Silkworm moth. Adult (top), empty cocoons (center), larva (bottom). The adults lay eggs which hatch into larvae. Each larva spins a cocoon of 2400 to 3600 feet of silk fiber. Do you know what the larvae eat and how silk thread is made from the cocoons? (AMERICAN MUSEUM OF NATURAL HISTORY) Insects with scaly wings. This group These insects have large wings covered with includes moths and_ butterflies. tiny scales. The scales are often brightly colored and in some species are arranged in gay patterns. They are loosely at- tached, as you know if you have ever handled a butterfly or moth. If you use a microscope you can see that the “powder” that comes off the wing con- sists of these scales. The bodies of moths have much more “hair” on them than have those of butterflies; their bodies The Kinds of Animals of the Earth 43 Fic. 53 Luna moth. (BUREAU OF ENTOMOLOGY) ee Seer grees vr 3 de a Fic. 54 Coiled sucking tube of a moth. (GEN- ERAL BIOLOGICAL SUPPLY) are also heavier and often more clumsy. Butterflies and moths suck nectar (a sugary liquid) from flowers. The mouth parts form a tube, sometimes a very long tube, which is kept coiled up when not in use as illustrated in Figure 54. When extended some tubes will reach the nectar bags at the bottom of deep flowers. The feelers or antennae of moths are feather-like, while those of the butterfly are smooth and sometimes knobbed at the tip. If you watch moths and butterflies when they alight you will detect yet 44 The Living Things of the Earth uni 1 Fic. 55 (left) Have you ever seen the tongue of a housefly moving up and down as it lapped its food? (AMERICAN MUSEUM OF NATURAL HIs- TORY) Fic. 56 (below) The Hes- sian fly injures wheat. Its lar- vae suck the sap from tender parts of the stem. Can you find the halters that take the place of the second pair of wings? (U.S. BUREAU OF EN- TOMOLOGY ) > pee Fic. 57 (left) The mosquito keeps its piercing mouth parts in a sheath when not in use. The mouth parts form a tube through which blood is pumped from the victim, (AMERICAN MUSEUM OF NATURAL HISTORY ) a. % (outer lip) another difference: moths spread their wings flat when resting; butterflies hold Skin surface : \ them upright. \ The two-winged insects — flies. The Proboscis : ay rane members of this group have only one (piercing mouth parts) 1 pair of wings. There are stumps im PROBLEM I. Fic. 58 A praying mantis finishing her nest. How does the praying mantis resemble the grasshopper? How is it different? (SELENA JOHNSON) place of a second pair. They have mouth parts of various kinds. Some lap up their food, some chew, while others can only suck. Common examples of this order are the familiar housefly and the tiny fruit fly. Small flies do not become large flies. Increase in size occurs only in the larval stage, and the larva of the fly is a wormlike creature without wings or legs, called a maggot. The mosquitoes, gnats, and midges belong to this order, too. Grasshoppers and their relatives. Be- cause it is large, the grasshopper is a good insect to examine more closely. Grasshoppers are also called locusts, especially in Europe and Asia. It is likely that the locusts of Biblical times were grasshoppers. See Exercises 1 and 2. The grasshopper group (order) includes among others the crickets, katydids, cockroaches, and the praying mantes. Ferocious as the praying mantis looks it will do you no harm. It is the grass- hopper that may well be afraid, for off comes its head if the mantis catches it. * The Kinds of Animals of the Earth 45 Fore wing Hind wing Antenna Head Ear membrane Maxillary palpus Spiracles Labial palpus Abdomen Meta-meso-pro- thorax Fic. 59 Ina grasshopper one can easily see head, thorax, and abdomen. How many segments do you see in the abdomen? The appendages of the right side are shown. How many are there of each kind? The hind wings fold up like a fan. What might be the use of the front wings? Grasshoppers are equipped with exceed- ingly muscular hind legs. A grasshopper is capable of a standing broad jump fifty times the length of its body, while man’s latest Olympic record is only about twice his length! One grasshopper 46 can do little harm. But scmetimes in our western states, and in other parts of the world, they occur in vast numbers and may strip fields of everything green. Crops ef wheat or corn or even fruit trees may pe ruined within a few hours. Bugs. All smal] insects and even disease germs are called “bugs” by many people. The name bugs, however, is properly applied only to one group of insects. It is a group with which, for the most part, you do not want to have much to do. It includes among many others the fleas and bedbugs. The lice which live- on birds and mammals are closely related to the bugs. Of course, there are many bugs that do not live on other animals. Some live in the water striding over the surface or swimming near the top. Closely related to the true bugs, al- though belonging to a different order, are the plant lice and the scale insects. The plant lice, or aphids, are soft-bodied insects which cling tightly to plants and suck their juices, weakening the plant and often killing it. The scale insects attack many kinds of trees and shrubs. Like aphids they multiply into millions. They cover themselves with tiny scales like shields; thus protected, they feed on the sap. Beetles. All beetles have hard wing covers which completely cover the up- per side of the abdomen and fit so closely that you can scarcely see the seam down the middle of the back. The ladybird beetle made famous by “ladybug, ladybug, fly away home”’ is common even in cities; and the Colorado potato beetle is often found in the po- tato patch. Another common beetle is the firefly whose light goes on and off The Living Things of the Earth WNT ET : : 3 = Fic. 60 The Colorado potato beetle does much damage. How do you know it is a beetle? (vu. s. DEPARTMENT OF AGRICULTURE) like a tiny flashlight as frequently as once every second or even faster, and sometimes with great regularity. Its light is located on the lower side of the ab- domen. In the larva stage they are called glowworms and can be found shining in the grass. If you can collect half a tum- blerful of glowworms you will have enough light to read by. Insect communities. Most insects live quite solitary lives, but ants, most bees and wasps, and the “white ants” or termites live in large communities. They are the social insects. Each insect per- forms some special job which benefits the whole community. Of all the social insects, the ants, which are found in almost every part of the world, are the easiest to study. Most of you have had the experience of discovering an ant nest beneath a rock. You may have seen the ants pick up large white bundles, run back and forth, and finally dash off to some safe hiding place. Then they come back for more bundles until shortly the nest has been PROBLEM I. Fic. 61 Aphids (plant lice) and ants on a stem. The aphids produce a sweet liquid (honeydew) which the ants like. (HUGH SPENCER) cleared out. You may have heard these bundles called ant eggs, but they are much too large to be eggs; they are the pupae. Most of you, too, have seen in fields, or at the edge of the forest, mounds of earth with many ants scur- rying about. These anthills may be two or three feet in diameter and may house several thousand insects. Underground, in the dark, passage- ways are tunneled; chambers of many kinds are dug out. There is much rush- ing to and fro with bits of food or soil. All this work is done by the workers. Every nest houses many workers, thou- sands of them, and one much larger ant known as the queen, a female who does nothing except lay eggs. Sometimes, there are several queens in one nest. And there are, too, a very small number of male ants that do no work. But the vast majority are workers. Some workers de- vote themselves to the care of the young. All the feeding of larvae and the moving about of larvae or pupae from room to room is done by the workers. The Kinds of Animals of the Earth 47 ° SE Be cere “ay Fic. 62 An ant tending a mealy bug. Mealy bugs are relatives of the aphids. They also make honeydew. (AMERICAN CAN CO.) Eggs oS. Larva Pupa Ay Winged female Female minus wings (queen) Fic. 63 The life history of the little black ant. How many kinds of adults are there? What does each do? Among some species of ants there are workers that biologists have called soldiers because they have very large biting jaws and apparently devote them- selves to defending the rest of the com- munity within the nest. Some warlike species even raid the nests of other ants. Among other less warlike species the workers make mold gardens and raise aphids. See Figures 61 and 62. 48 The Living Things of the Earth unrr 1 The life of the the giants bee. Bumblebees are among bees. They live in fairly small colonies in the ground. Honey bees live in much larger com- munities than do bumblebees; each col- ony may consist of more than 35,000 individuals. They build their nests in caves or hollow trees or in_ beehives provided by man. ‘These are the bees that make the honey of commerce. Fic. 65 (above) From left to right these are worker, drone (male), and queen (female) bees. How can you tell one from the other? (ROOT) Fic. 66 (left) A swarm of bees. How does the beekeeper take advantage of swarming to start anew hive? How many bees would you judge to be in this swarm? (vu. Ss. BUREAU OF ENTO- MOLOGY) There are males, females, and worker bees. See Figure 65. As among ants, the queen is the central figure in the com- munity. She is fed and carefully guarded. She lays eggs, thousands of them, while the workers toil. They build the honey- comb of forms from a liquid which oozes out of their bodies. They cut the wax into plates with their jaws and build the amazingly exact six- sided chambers. When these rooms are wax which completed the queen deposits one egg in each. Other workers bring in food. Flying from flower to flower they gather nectar, a sweet liquid which they store temporarily in a special honey stomach. When they return to the hive they give it up again to feed to the young. Or they change it into thick honey and store it in the honeycomb. When a cell of the comb is filled with honey they cap it with wax. Often they gather pol- len from flowers. This they prepare PROBLEM I. into special food which is fed to a few larvae which develop into queen bees. In the meantime, they do much cleaning of the hive. The workers also meet the attacks of “robber” bees and other ani- mals. For this, the bee uses the sting. on the end of its abdomen. Most of the thousands of individuals in a honeybee colony are workers. The life of a worker may be only several weeks or at most several months, but the colony increases in number rapidly be- cause of the rapid rate of reproduction. From egg through larva and pupa stages requires only three weeks. Whether be- cause of the crowding or for some other reason, in the early spring and summer large numbers of bees together with the old queen bee leave the hive in a mass and start another colony. This is called swarming. One of the young queens that remains takes over the egg- laying duties in the old colony. For centuries man has domesticated bees for the sale of their honey and their wax, but bees have never been tamed. However, they will sting only when disturbed and frightened, injecting poi- son with the sting which is left in the wound. Insects that eat wood. The community life of the so-called “white ant,” prop- erly named termite, is just as interesting as that of bees or ants. Termites live mostly in the tropics but are spreading through the temperate zone where some of you may have become better ac- quainted with them. They burrow and build in wood, sometimes wrecking houses or other large wooden structures. Working in the dark, well concealed in the timbers, their presence in a building The Kinds of Animals of the Earth 49 Fic. 67 A beam of wood almost completely de- stroyed by termites. What can be done to pre- vent damage to wood by termites? (SCIENCE SERVICE) is sometimes not suspected until some day, when the framework has been weakened, the whole structure collapses. Sometimes, however, they are detected when they swarm in the spring. In warm climates or even in cooler climates where buildings are constantly kept warm, termites are a real danger. We can pro- tect ourselves against them by soaking the timbers in creosote or, better still, by using concrete for foundations and lower floors of buildings. This is effec- tive because termites must have at least a portion of their nest in moist soil or wood. How insects make a noise. In the sum- mer there is a steady chorus of crickets chirping. As it gets hot the male cicadas or “seventeen-year-locusts” add their loud, shrill song. When night comes on the katydids call from every tree, arguing endlessly, “Katy-did, Katy-didn’t.” It is so noisy that many a city dweller has 50 The Living Things of the Earth wondered what was meant by the “quiet” of the countryside. The sound-producing apparatus of the cricket is peculiar. The front pair of wings is thickened. The edges of the wing covers have a set of “teeth.” As one rough surface rubs over the other the stiff wings vibrate. It is the vibration that is heard as a shrill chirping. In katydids and cicadas the apparatus is slightly different. In these insects it is only the males that are so equipped. Other insects, such as bees and flies, make noise by the rapid beating of their wings. The insects. So numerous and so varied are the insects that many books have been filled with accounts of their extraor- fascinating lives. dinary structure and o - — This brief account has only scratched the surface. The biologists who. study insects (called entomologists, en-toh- mol’o-jists) can tell many exciting tales of the doings in the highly populated UNEEV I Fic. 68 The black widow spider magnified. With legs stretched out it is about one and one half inches in size. The lower side of the abdo- men with its distinct hour- glass is shown at the upper right. At the lower right cor- ner is the body of the male. How does it compare in size with the female? (vw. s. DEPARTMENT OF AGRICULTURE ) For. review do Exer- world. insect CISE 3. Other arthropods — the spiders. If you turn again to the chart on page 41 you will see that besides the very large and varied class of insects there are three other classes in the arthropod phylum. One of them is the spiders and their close relatives. Does it astonish you to learn that spiders are not insects? It should not. Being arthropods, of course, they have a firm outer covering and jointed legs; but you will count four pairs of legs (not three), and only two body parts. Ihe head and thorax are joined together. And they lack three structures found in insects: wings, antennae, and compound eyes. Now draw the diagram suggested in EXERCISE 4. o1ve ec Most spiders can off a special liquid from the abdomen that hardens in the air into a silk thread. The webs may be used as homes or as a means of PROBLEM 1. Ihe Kinds of Animals of the Earth 51 "2 < \ Fic. 69 The garden spider spins an orb web of this kind. It rests motionless in the center. (HUGH DAVIS) catching prey. The house spider spins a tangled mass of threads in some quiet corner; this is a cobweb. Each species has its own characteristic web and many webs are complicated structures woven according to a definite pattern. The trapdoor spider digs a hole in the ground and covers it with a door open- ing outward on a hinge. Do spiders bite? The fear of spiders like the fear of snakes is the result of ignorance. Most garden spiders do not bite; or if they do the bite causes no more than a slight irritation. The com- mon house spider does not bite at all. The only dangerous spiders in the United States are the tarantula and the black widow or hourglass spider (see Fig. 68). The black widow thrives best in the tropics, but has been found in Fic. 70 The bite of the tarantula is rarely fatal. How do you know it is a spider? (uv. 8. BUREAU OF ENTOMOLOGY ) many parts of this country. It is easy to identify for it has a black body with a red spot shaped like an hourglass on the under side of the abdomen. Close relatives of the spiders. The scorpion is a close relative of the spider, though you might not recognize it as one. The scorpions of this country can- not do much harm. But in the tropics, where they may be as much as eight inches long, they may be dangerous. Then there are the tiny mites and ticks. Many of them live on, or just under, the skin of various mammals, including man. Some of them, like the chigger, cause fierce itchings. Some are carriers of dangerous disease germs. Another rela- tive of the spider is the harvestman. You may know it as daddy longlegs, from its unusually long and spindling legs. 52 | The Living Things of the Earth The house centipede enlarged. How do you know that this is not a millipede? (uv. s. DEPARTMENT OF AGRICULTURE ) Fic. 71 The hundred- and _ thousand-legged arthropods. A glance at the chart on page 41 will show you members of two more classes of arthropods, the “hundred- leggers” and the “thousand-leggers.” Their bodies are made up of a series of rings; that is why many persons think that they are worms. But they have jointed legs attached to each ring, and their bodies have a firm covering. The hundred-leggers or centipedes, have a pair of legs on each ring. The thousand- leggers, or millipedes, have two pairs of rather short legs to a ring. Both these classes are small and rather unimportant. great ar- thropod class, the crustaceans, includes The crustaceans. Another many forms that inhabit the sea, but some live on land and some in fresh water. It is difficult to state by what charac- teristics you can recognize crustaceans. About all that can be said here is that if an animal seems to be an arthropod and does not exactly fit into the insect, spider, or centipede groups, it is prob- TINT a Fic. 72 Rock barnacles. These are crustaceans. Almost 3000 of them have been counted on one square foot of rock. (Morris) ably a crustacean. The class includes the lobsters and crabs, the crayfish, water fleas, barnacles, shrimps, and hundreds of other kinds. Study some crustacean at first hand as described in Exercise 5. Some queer crustaceans. Perhaps all crustaceans deserve to be called queer. The lobster is just an ordinary kind of crustacean; but it has eyes that are on the ends of stalks, huge and powerful pincers or claws, and it glues its eggs to its legs. In spite of the saying “as red as a lobster,” live lobsters are not red at all; only cooked lobsters are red. The crab, too, has eyes on stalks. Its body is wider than long, and it seems to have no abdomen. ‘The queerest thing about the crab is its walk. It walks side- ways, but it manages pretty well. And in the water it is a good swimmer. Along the coast you can often buy soft-shelled crabs. These are common crabs that have recently lost their shells. All the crustaceans with hard coverings shed their coverings as their bodies become too large for the shells. PROBLEM I. Fic. 73 Lobster catching a |@m crab. Both are crustaceans. 7 How can you distinguish | lobsters from crabs? (AMERI- CAN MUSEUM OF NATURAL HISTORY ) mo Fic. 74 The scorpion is grouped with spiders, al- though it looks quite differ- ent. It carries its young on its back. The sting at the end of its abdomen can be waved over its head. (AMERI- CAN MUSEUM OF NATURAL HISTORY ) For strangeness, the barnacles take the prize. It was a long time before they were recognized as relatives of lobsters and crabs. A famous English biologist, T. H. Huxley, has given this striking description: “A barnacle may be said to be a crustacean fixed by its head and kicking the food into its mouth with its legs.” Exercises 6 and 7 would be good re- view exercises before you leave the group of jointed-legged invertebrates. You will next examine briefly eight other invertebrate phyla. We shall proceed from the more complex to the more simple forms. The Kinds of Animals of the Earth 53 ta | PHYLUM — MOLLUSKS The Soft-bodied Invertebrates What are mollusks? If you examine Figs. 75-78 you will see examples of three different groups (classes) of mol- lusks: those that have a foot which is used in creeping, like the snail, those that have feet used in seizing prey, like the octopus; and those that have a hatchet foot used in plowing through wet sand or mud, like the clams. Most have a shell of lime which protects the soft body. The shell takes very dif- ferent forms; it may be single or double and may even be carried internally. 54 The Living Things of the Earth WIN TD aT Fic. 75 (above) The octopus is a mollusk which has no shell. Its eight waving tentacles (or feet) bear sucking cups. With feet and beak it tears its prey to pieces. (NEW YORK AQUARIUM) Fig. 76 (right) This zebra snail is creeping on its foot. (DAVIS) Clams, oysters, and mussels. These mollusks have a shell in two parts. Often the shell is left open and the hatchet foot, a thick muscle, may stick out. Oysters and mussels, which spend their lives attached to rocks or other shells, have so small a foot that they can hardly be said to have one. Clams use their foot for locomotion. EXERCISE 8 is interesting although difficult. Snails with and without shells. Snails live in water and on land. Land-living 4 forms especially have a well-developed foot. They have a well-developed head too, with a real mouth, and eyes carried on long stalks. Many species carry a spiral shell from which the head and foot protrude. When danger threatens, both head and foot are drawn into the shell and the tough, slimy foot. seals the mouth of the shell so well that it is difficult to extract the animal. Snails that lack a shell are called slugs. They may do much damage in the vegetable garden. PROBLEM I. 7 y* * “{ “ Fas x ae > f i ‘ : : j : ie Sky H 3 a ~< B _— ——— i aii s me — — nah 0 ae a a Fic. 77. Although the slug is a mollusk, belong- ing to the same group as the snail, it has no shell. This one has just laid its eggs on a leaf. (MARY C. DICKERSON ) Mollusks and man. A great many spe- cies of mollusks are eaten by man. Snails are considered a delicacy by some people, and the octopus and squid are eaten in many parts of the world. Oysters, the many species of clams, the scallops, and the mussels are commonly eaten. Oysters are valuable also as the source of mother- of-pearl, from which buttons are made. Precious pearls are found only in certain tropical species and then rarely. There are comparatively few kinds of pests among mollusks. One of the worst is the “shipworm.” It bores into timber which is under water, riddling it with tunnels until the wood collapses. Now that ships are made of steel the damage done by shipworms is confined to wharves. The Kinds of Animals of the Earth 2) 2) =) | ‘| 1 | : PS» = ai es Fic. 78 The clam has a double shell and a hatchet foot. The clams above are using the foot to plow through the sand. (warp’s NATU- RAL SCIENCE ESTABLISHMENT) PHYLUM — ECHINODERMS Invertebrates with Spiny Skins A different body plan. The inverte- brates with spiny — skins called Echinoderms (eh-kine’o-derms). They are built on a plan different from that found in the more complex animals. Most animals have bilateral symmetry. This means that if they were cut down the middle the two halves would be about the same in appearance. But the invertebrates with spiny skins have radial symmetry, like a wheel. Just as the spokes of a wheel radiate from the hub, so the parts of these animals radi- ate from a central point. Besides this, are these animals have a spiny skin and a complicated system of water vessels that 56 The Living Things of the Earth rr a rR Fic. 79 The horny, rough upper surface of a common starfish. What kind of symmetry has it? (AMERICAN MUSEUM OF NATURAL HISTORY) help in locomotion. Some of them are brightly colored and are very beautiful in structure. If you live near the sea, you are surely acquainted with starfish, sea urchins, and perhaps sand dollars. In tropical waters the beautiful sea lilies, which you might well mistake for plants, grow attached to the sea bottom. All of these are spiny- skinned invertebrates. The starfish. The starfish lives in salt water near the shore. It is not a true fish, of course. It is a living flexible star with five arms and a spiny covering colored brown or red or purple. Hundreds of tiny tube feet with suction their ends dot the lower surface of the cups at animal. By pulling in and pushing out the many tube feet in succession the starfish moves and along slowly smoothly. “These tube feet help in | Rs be ~ - . fi 4 = breathing, too, and in food getting. By folding itself over an oyster and _ at- WNT Se eS “ >: . Fic. 80 The sea urchin has a beautifully marked shell beneath these spines. (AMERICAN MUSEUM OF NATURAL HISTORY ) taching its tube feet it pulls the shell open. Then it turns its stomach inside out and digests the living oyster in its shell. Starfish do much damage by feeding on mollusks. Oystermen formerly tried to destroy starfish by tearing them in half and throwing the pieces back into the sea. Unfortunately, this made the situation worse, for new parts similar to those lost will grow back, or regen- erate, making two animals where there had been but one before. Some starfish relatives. Similar to the starfish group but sufficiently different to be put in another class are the sea urchins and sand dollars. They, too, have their mouths on the lower side. They take in sand, in which they find small animals and plants which are their The sand dollar has a circular somewhat thickened in food. flattened shell the middle. The sea urchin is so covered with movable spines that it looks like a walking pincushion. Sea urchins are eaten by some people, their large masses of eggs are considered a great delicacy. PROBLEM I. Oesophagus Pharynx Mouth Head ganglion Hearts The Kinds of Animals of the Earth 57 Gizzard Intestine FA 71a 7a AA Fo 7 ae Sy ee ee Se J wel Blood vessels Nerve chain of ganglia Fic. 81 Front end of an earthworm cut open. The blood vessels, nerves, and many other parts are similar to those of more complex animals. See Figure 82, also. THREE PHYLA oF Worms PHYLUM — ANNELIDS Worms with Segments Earthworms and their relatives. Perhaps the most important of the Annelids (ann’ell-ids) are the earthworms. You will find them interesting to study. See Exercise 9. Most of the time earth- worms burrow underground where they literally eat their way through the earth, swallowing soil particles and de- caying plant material, which is_ their food. The food is used and the undi- gested soil is left behind in little ropes which hold together until they are dry. You may have seen them on the ground; they are called castings. Charles Darwin and his sons studied the activities of the earthworm with great care. They dis- covered that the animal often brought its castings to the surface and_ that, therefore, on a small scale, earthworms were constantly plowing and cultivating the soil, making themselves useful to man. If you look at Figure 81, you will see that the body is made up of rings or segments. All the phylum are segmented. One fresh water worms in_ this rather common is the leech. There are suckers at both ends of the body which enable it to stick tightly to the animal from which it sucks blood; that is the origin of the expression, “sticks like a leech.” It has teeth with which it breaks through the form that is skin and a substance in the saliva which prevents the clotting of blood; thus it can suck until it is full. PHYLUM — NEMATHELMINTHS Roundworms The hookworm and its relatives. There are other Nemathelminths (nem-a- thel’minths) but the hookworm is the best known of this group. In later chapters you will read more about them. Hookworms and some other members of this phylum live in the bodies of both man and other animals where they may cause disease. Most of the roundworms are tiny, too small to be seen with the naked eye. Their bodies have no seg- ments. They are present in large num- bers everywhere, particularly in the soil. 58 The Living Things of the Earth ¥ * a. x ¢ — wf Fic. 82. An earthworm burrowing in the soil. It looks shiny because its skin is moist. (SCHNEI- DER AND SCHWARTZ) Fic. 83 you see the eating tube which it can extend? (AMERICAN MUSEUM OF NATURAL HISTORY) Planaria is less than one inch long. Do UNIT I PHYLUM— PLATYHELMINTHS Flatworms Tapeworms and their relatives. The platyhelminths (pla-tee-hel’minths) — in- clude the tapeworms and the liver flukes, both of which are parasites. Tapeworms are flat like a ribbon, but it is a ribbon made up of separate pieces which can be dropped off one by one. Tapeworms may reach a length of twenty fect. Some species live in man’s intestines, hooked to the wall by the curved spikes and suckers on their heads. They live on the food which man has digested. You will read more about tapeworms later. Other flatworms that are of great im- portance to man because they attack him or his domesticated animals are the liver flukes. They are tiny worms that live in the liver of sheep and other animals. They do great damage. One very com- mon flatworm, Planaria (plan-air’ree-a), lives in sluggish streams, hidden under stones. Examine Figure 83. Although Planaria is of no economic importance, it has been studied and experimented with by many zoologists. PHYLUM — COELENTERATES Animals Whose Bodies Are Simple Sacs Sea anemones. The coelenterates (see- len’ter-ates) are of great interest to zo- ologists but most of them are of little economic importance. If you see gaily waving tentacles above a delicately tinted body fastened to the sea bottom you are looking at a sea anemone (a-nem/o-nee), the “flower” of the ocean. Many are brown in color; some forms are pink or rose-colored; others are orange or bluish PROBLEM I. The Kinds of Animals of the Earth Fic. 84 Sea anemones. These beautiful animals are several inches high. Where do they live? How do they get their food? (NATURF. MAGAZINE) green. The body is little more than a sac in which food is digested. The mouth is a slitlike opening in the upper end of the sac; the tentacles that surround it grasp the food which the water may wash within reach. They can shoot out long stinging hairs which paralyze or kill their prey. Once the food is caught the ten- tacles push it into the mouth. When the tide goes out leaving the little anemone in a rocky pool, it pulls in the tentacles and contracts its body until it is nothing but a small solid mound. Related to the sea anemones is hydra, a tiny fresh water form. You may have found it attached to the sides of an aquar- ium. See Figure 85. Animals that make rock. Coral animals, also, are attached to the sea bottoms. They resemble sea anemones but differ in several ways: they are usually much smaller; they are attached to one another in colonies; and they build shells of lime Fig. 85 Hydra, cut open and magnified. This is a tiny animal, seldom more than one fourth inch long. Look for the mouth surrounded by tentacles. These have stinging cells which can Rill small animals. Tentacles i ya Stinging cells Bud (will form a new hydra) Part by which Hydra attaches itself 60 The Living Things of the Earth WNIde tt Fig. 86 Organ-pipe coral. The tiny animal within each tube can extend brightly colored tentacles. (AMERICAN MUSEUM OF NATURAL HISTORY) outside their bodies. There are many spe- cies of coral animals. Each species con- structs of shell of a particular kind. Most corals inhabit the warm waters of tropical seas in vast colonies contain- ing thousands upon thousands of indi- viduals. When each animal dies its skel- eton remains behind; thus slowly but steadily a mass of shells piles up. This turns to stone —limestone. After long ages so much rock gathers that a reef or coral island may rise out of the water. Reefs are sometimes a thousand miles or more in length. The Bermudas are a group of coral islands. A third class — the jellyfish. Grownup coral animals and sea anemones spend most of their lives sitting down but in their younger stages they can move about. There are other forms, such as the jellyfish, that never settle down. The animal is really jellylike; clear, trans- parent, and soft. The body of the jelly- fish is more than g5 per cent water. When washed up on the dry beach the water soon evaporates away until just a shriveled shadow remains. Jellyfish look like inverted saucers floating in the water. See Figure 87. They vary in size from about one inch in diameter to several feet. The jellyfish moves through the water by waving its tentacles or by contracting its body. The contraction squeezes water out of the central cavity; this gives the jellyfish a little push in the opposite direction. Characteristics of the coelenterates. The coelenterates are all water-dwelling animals. Like the starfish they have ra- dial symmetry, but they are far simpler in make-up. Each animal is much like a simple sac. The sac has one opening called the mouth which is surrounded by tentacles with stinging hairs. PROBLEM I. oi iar e PPS yo iw . a. ad pee? TID Rye ee a ie cee aeean ae ae tet TREE ETE _— a ? Pe > ‘ if HiceShre go a 4 i % iY a q i fe & sae Fic. 87. This jellyfish has a long tube through which it eats. With its tentacles it catches and paralyzes its prey. (AMERICAN MUSEUM OF NAT- URAL HISTORY ) PHYLUM — PORIFERA Animals Riddled with Holes — Sponges The sponge. Only a few kinds of Por- ifera (pore-if’er-a) produce commercial sponges. The commercial sponge is the tough, fibrous covering or skeleton of many sponge animals that live in colonies. The body of a sponge animal, like the body of the sea anemone and coral ani- mal, is a simple sac but this sac has many The Kinds of Animals of the Earth 61 holes. Sponges grow fastened to the floor of tropical seas from which they are torn by dredges or cut loose by divers. After they have been killed they are hung in the air until the animals have decaved. Then the sponge is washed in water until nothing but the skeleton of the colony is left. PHYLUM — PROTOZOA The First Animals What are the protozoa? The tiny masses of living matter making up the bodies of all animals and plants are called cells. ‘The common animals and plants you know are made of billions and bil- lions of cells. But some animals and plants are made of only a single cell. As you would expect, such animals and _ plants are tiny, usually so small that they can be seen only by means of a microscope. The group of one-celled animals is called the Protozoa, which means “first” or sim- plest animals. Protozoa are found living in many dif- ferent places. Ponds and streams are often crowded with them, although the water looks clear. Some parts of the ocean are thronged with protozoa, as you will read. There are protozoa that live in the intes- tines of animals, and others that may live in our blood and cause serious illness (malaria). Altogether, they are as fasci- nating a group of animals as we know. Raising protozoa. It is easy to raise protozoa in hay infusions. You can make one by putting dried grass or hay into water which is then permitted to stand. Make a hay infusion according to direc- tions in Exercise 10. As the hay decays, some of its food materials dissolve in the pao ee Fr = | ferns ry | wee Fig. 88 Vorticella is one of the most interesting of the protozoa. On the rim of its open mouth is a row of cilia. Vorticella is anchored by a stalk, (HUGH SPENCER) Bilba photographed through a microscope. The outline is blurred by the movement of the cilia. Can you see the groove leading to the mouth? (HUGH SPENCER) Fic. go Living paramecium : The Living Things of the Earth UNIT 7 ae] Fic. 89 Three amebae photographed through a microscope. Can you see food vacuoles in the lowest one? The living material streams in all directions. (GENERAL BIOLOGICAL SUPPLY) Front end Ui Contractile vacuole Food vacuoles Macronucleus Mouth Micronucleus Gullet Contractile vacuole with canals Cilia Fic. 91 This drawing of a paramecium shows the groove through which food enters. How does the food get to this spot? What does a paramecium eat? How does it move? PROBLEM I. water which takes on a brown tint. Many kinds of microscopic creatures will soon be swarming in the infusion. When pond water is lacking, there- fore, you may turn to the hay infusion for your first look at the world of micro- scopic living things. If you are able to get the use of a microscope you can look forward to many happy hours of dis- covery. _ A giant among microscopic animals. One of the commonest inhabitants of the hay infusion is an enormous mcr o- organism (microscopic organism), which is just visible to the naked eye as a white speck darting about in the water. You may have heard its name, Paramecium (par-a-mee’see-um ). Paramecium is easy to raise and with a microscope fun to study. Do Exercise 11. It is not easy to examine a lively para- mecium with the microscope; it moves too fast. But it is possible to catch it in the fibers of cotton or even to thicken the water so that the paramecium pushes its way through with difficulty. Either one of these tricks will slow the animal enough for you to see that the little sub- marine-shaped paramecium is covered with tiny hairlike parts or cilia (sil’ee-a). The singular is cilium. These cilia beat vigorously and thus push the paramecium rapidly through the water. By lashing the cilia hard in the opposite direction the animal can go into reverse. The cilia are arranged diagonally in rows so that as they beat they make the paramecium roll over and over like a barrel at the same time that it moves forward or back- ward. As the paramecium rolls over, one can see that on one side there is a groove as The Kinds of Animals of the Earth 63 ») though part of its cigar-shaped body had been scooped out. This depression leads to a spot, the mouth. Longer cilia line the depression, their beat is inward so that any smaller microorganism caught by the current is swept to the mouth and into the paramecium. The microorganism of ever-changing shape. ExercIsr 12 gives you directions for studying this animal: Ameba. Because of its habit of clinging to some solid base and because it is almost transparent, it is dificult to find. Ameba is not trim and compact like paramecium, but spreading and shapeless. Its body is soft and jellylike — just a blob of living mat- ter. Some of the living material flows for a while in one direction and forms a projection called a false foot or pseu- dopod (siu’doe-pod). It is a temporary foot which can form on any part of the body; in fact, ordinarily an ameba has several pseudopods at the same time sticking out in different directions. Some- times, however, the material keeps on oozing in one direction, in this way the ameba, by ever changing its shape, crawls along over the surface of some leaf or stem under water. The pseudopods are used for feeding too. If some smaller microorganism or other particle of food lies in the ameba’s path, false feet flow out above, below, and on all sides of it and join together on the other side. The food particle is then inside the ameba, or, more correctly, the food particle is inside a little drop of water which is inside the ameba; for when the pseudopods join together they enclose a little water too. If the animal picks up some worthless particle like a grain of sand, it simply drops it behind as Flagellum Eye-spot Green bodies Fic. 92 Euglena is another of the protozoa. It lashes itself along with the whip-like hair. Be- cause it contains green bodies some biologists call it a plant. it flows along. At one moment the sand is inside the animal, the next moment it is out. There is a giant ameba that your teacher may be able to show you. It is called Chaos chaos. It is so large that it can be detected with the naked eye. Protozoa swarm in the ocean. One kind of protozoan which floats near the sur- face of the sea builds a complicated shell of lime about its tiny body. Now and again, when there is a sudden change in temperature or in other conditions, these organisms are killed. The millions of shells fall gently to the ocean floor like raindrops in a gentle rain. And so many have fallen throughout the centuries that deep beds of lime shells have been formed. Deposits of these shells can be found at the bottom of the ocean in many places. The chalk cliffs of southern Eng- land and the shores of northern France The Living Things of the Earth UNIT tT Fic. 93 Skeleton of a Radiolarian. These and other protozoan skeletons make up much of the material on the-ocean bottom. (AMERICAN MU- SEUM OF NATURAL HISTORY) are made of limestone rock composed principally of such shells. Long ago seamen noted that there were nights when the ocean sparkled with a thousand lights which seemed to dance on the waves as the vessels plowed along mile after mile. The light is produced by enormous numbers of protozoa called The means night light. As many as three mil- Noctiluca (nok-ti-loo’ka). name lion individuais may be found in a quart of sea water when conditions are just right for their growth. See Figures 92 and 93 for illustrations of other protozoans. The animals in review. Many pages back you started a study in order to be- come acquainted with the many living In doing circle of acquaintances among things of this earth. this your organisms grew so rapidly that you would have been hopelessly confused had you not learned some system for keeping them in separate PROBLEM 1. groups. This system is called classifica- tion. You first studied the mammals, the animals which are most closely related to you, yourself. Then you spent some time with the birds, the reptiles, the am- phibians, and the fish. The fish were the last vertebrates you studied. All of these had a backbone just as you have. You then met the invertebrates, the animals without backbones. It took a long time to get acquainted with man’s insect friends and enemies and the other, less familiar, arthropods. From then on you saw mostly water forms: the shelled mollusks, the spiny echinoderms, the worms, some of which burrow in the moist earth; the coelenterates whose beautiful colors and unusual shapes remind one of flowers; and the sponges. The Kinds of Animals of the Earth 65 There were still many animals for you to see, but in order to see them it was necessary for you to equip yourself with a microscope. Then suddenly a whole new world opened itself out to you: the world of Protozoa. A glimpse at these and you finished your study of the ani- mal kingdom. You saw only very few of the almost one million different kinds of animals. If you were to examine each living species for only one minute and if you were to keep at it day and night, it would take you almost two years to review the ani- mal kingdom. Study of the summary be- low will give you a scientific view of the journey you have just completed. Our attention must now be turned to the plant kingdom. SUMMARY This simplified table will help you review the animal kingdom. Puyzium I. Chordates (Chordata): The name is from the word “cord” and refers not to the spinal cord but to the notochord which is present in adults of some subphyla and which develops into the backbone of the vertebrates. Most zoolo- gists recognize four small subphyla other than the vertebrates we have studied. SuBPHYLUM. Vertebrates (Vertebrata) Crass 1. Mammals (Mammalia): Hair covering. Feed young on milk from mammary glands, Crass 2. Birds (Aves): Feathers. Crass 3. Reptiles (Reptilia): Dry scaly skin. Breathe by means of lungs. Crass 4. Amphibians (Amphibia): Thin, moist skin. All spend first part of life in water; most later live on land. Crass 5. Fish (Pisces): Scaly skins that are moist. Breathe by means of gills. The sharks discussed on page 32 along with certain other animals make up another small class. All the other phyla are invertebrate phyla. We studied the following: Puytum II. Arthropods (Arthropoda): A hard outside covering. Segmented bodies and jointed legs. Crass 1. Insects (/msecta): Head, thorax, and abdomen with three pairs of legs on thorax. Complete or incomplete metamorphosis in their develop- ment. May live on land or in water. Grasshopper and butterfly. 66 The Living Things of the Earth unir Crass 2. Spiders (Arachnoidea): Two body parts and four pairs of legs. Spider and scorpion. Crass 3. Centipedes (Chilopoda): Segmented body. Each segment has one pair of legs. Crass 4. Millipedes (Diplopoda): Segmented body. Each segment has two pairs of legs. Crass 5. Crustaceans (Crustacea): Five or more pairs of legs. Two pairs of antennae. Live in salt water, fresh water or in damp earth. Lobster, crab, barnacle. Puytum HI. Mollusks (Mollusca): Soft-bodied invertebrates with a shell. In some the shell is internal and reduced in size. Live in fresh or salt water or on land. Snail, slug, clam, octopus. Puytum IV. Echinoderms (Echinodermata): Radial symmetry, usually with five divisions. A spiny skin. Live only in salt water. Starfish, sea urchin, brittle star. PuHytumM V. Segmented Worms (Annelida): Long cylindrical body with segments or rings. Thin moist skin; most without legs. Earthworm, clam w orm, leech. Puyitum VI. Roundworms iN cris help enben: Cylindrical body without segments. Many very small, causing disease and living within other animals. Elegie orm, trichina worm. Puytum VII. Flatworms (Platybelminthes): Many live within bodies of other animals, causing disease. Planaria, tapeworm, liver fluke. PuyLtuM VIII. Coelenterates (Coelenterata): Baglike with one opening. Tentacles and stinging cells. Some free-swimming, some attached, some forming colonies. Jellyfish, sea anemone, coral, Hydra. PuyLtuM IX. Sponge Animals (Porifera): Baglike with many small openings through the sides. Attached. Some form colonies. Mostly salt water forms. Sponges. PHyLuM X. Protozoans (Protozoa): Single-celled. Live in fresh or salt water or where it is moist. Some live within bodies of other animals and may cause disease. Some form shells and build up limestone rock. QUESTIONS 1. How do the numbers of vertebrate and invertebrate species compare? Cite an example of each of the nine phyla of invertebrates mentioned. . What name is given to the most complex invertebrates? Give the two characteristics in which they differ from all other animals. Into what five groups (classes) do most of them fit? 3. Describe the principal characteristics of the insects. Be sure to use the correct terms. Describe the sense organs of a typical insect. How do some insects make noises? 4. Describe the life story of a butterfly, an insect that has complete metamorphosis. How is incomplete metamorphosis different? 5. Describe the insects with scaly wings. By what three characteristics can you distinguish moths from butterflies? Name a moth of com- mercial importance, 6. Which common insects belong to the group of two-winged insects? What name is given to the larval stage of the fly? List four relatives of the grasshopper. Describe body regions and ap- pendages of the grasshopper. Discuss the importance of the grass- hopper to man. nN “I PROBLEM 1. Ihe Kinds of Animals of the Earth 8. Il. I2. i: 14. 1G 16. Ie 18. 10. 20. 21. 22. 23. 24. Dive 26. 27. 28. 29. 30. Cite several examples of true bugs. Of what importance to man are plant lice and scale insects? . How can you recognize beetles? List some well known examples. . List four common ime of social insects. Why are they called social insects? Describe the life history and the community life of ants. How do bumblebees differ from honeybees? Name and describe the different kinds of bees in a hive. Describe the life of the worker bees. Describe swarming. Of what importance are termites? State three respects in which spiders differ in structure from insects. From what is the spider’s web built? How is it used? What can you say of the danger of being bitten by spiders? Describe four close relatives of the spider. How do the thousand-leggers resemble worms? Why are they classed as arthropods? Distinguish between centipedes and millipedes. Name several crustaceans. Where do most crustaceans live? What are some of the peculiar characteristics of lobsters, of crabs, and of barnacles? Mollusks are divided into three groups. Name one example of each. What have these three in common? How do they differ? Describe the shells of mollusks. Describe a snail with a shell. What is a slug? State how the mollusks are useful to man. How are they harmful? Cite an example of an animal that has bilateral symmetry and one that has radial symmetry. Explain these terms. What are the striking characteristics of the invertebrates with spiny skins? Name some examples of this group. Describe the starfish. Include: their appearance, where they live, how they move about, what they feed on, and how they eat. Define regen- eration. What are three large groups of worms? What do earthworms eat and how are they of importance to us? Why are earthworms said to be segmented? How are leeches of interest to us? In what two respects do roundworms differ from earthworms? What roundworm causes a disease? What two kinds of flatworms live in other animals? Describe one kind. Describe the appearance and structure of a sea anemone. Which relatives of the sea anemone live in a limestone shell? Explain how coral reefs are formed. The jellyfish i is a third type of animal whose body is a simple sac. How does it differ in its habits from sea anemones and coral animals? Explain how it carries on locomotion. Sum up the characteristics of the animals in this group of coelen- terates. 67 68 The Living Things of the Earth unir 1 31. What are the striking characteristics of sponges? 32. What name is given to the simplest animals? How do they differ from all other animals? Mention the various places where protozoa may live. 33. Give directions for making a hay infusion. What use can you make of it? 34. Define the word microorganism. Explain how the paramecium moves about and eats. 35. Describe the ameba and its habits. 36. Of what importance are the shell-building protozoa? 37. Imagine yourself starting on a long journey to review the animal kingdom, passing your own group — the mammals — first and ending with the simplest forms. Name in order the various groups you would see. EXERCISES 1. If possible obtain a large lubber grasshopper for study. Compare the three body regions as to size. To which region are the legs and wings (appendages) attached? How many rings or segments in the abdomen? Of how many pieces is each segment composed? With a hand lens find breathing pores or spiracles. They are connected with tubes branching through the body (tracheae). How might overlapping segments help the insect take in air? Describe the position of the compound eyes. Of what advantage is this? Look for simple eyes. Describe. What is the ad- vantage of having antennae segmented? Find a smooth oval spot, the Fic. 94 Mouth parts of the grasshopper. The two strong, jagged jaws (A) move from side to side. They are covered by the lips (B). The jointed structures like A short feelers hold and diregt the food. These mouth parts are well protected by being tough and horny. (ADAPTED FROM TURTOX DRAWING ) PROBLEM 1. Ihe Kinds of Animals of the Earth eardrum, on each side under the wings on the first segment of the abdo- men. Describe the two pairs of wings and discuss their use. Does your specimen differ from the picture in the text? How? How many joints are there in each of the three legs? What is each pair fitted for? Describe the foot closely. Study the mouth parts and compare with Fig. 94. How is each part used? 2. How does a butterfly resemble and differ from a grasshopper? Study a specimen. Follow the directions for study of the grasshopper, and describe each part of the butterfly. Feel the wing. If you have a microscope examine some of the powder which comes off on your finger. 3. Since there are half a million species of insects, it would be difficult to learn much about this large group in a short time. But you will have made a good beginning if you know exactly how you can recognize an insect, that is, if you have become acquainted with grasshoppers and their relatives, moths and butterflies, flies, bugs, beetles, and the social insects and can distinguish one order from another. Remember that be- coming acquainted includes recognizing them in all stages of their life histories. Write up all this in your notebook. 4. Draw a diagram of the top view of an insect and another of a spider to show the important differences between the two groups of animals. Ge Shrimp and lobsters are easy to obtain in the market; crayfish are common in fresh water streams. Study and describe the body regions and the appendages of one of these crustaceans. Study the antennae and the eyes and compare them with the antennae and eyes of the grasshopper. What differences can you find among the many pairs of legs of the crustacean? How might it use these various kinds of legs? Wie 4 is the advantage of jointed legs? Of segmentation in.the antennae? If you have live animals, place them in deep water in a large tank and then in a shallow tray to watch the methods of locomotion. Hold the crayfish in your hand; does it exert much strength in trying to escape? Do you think the animal is well protected by its ealur Gently touch the eyes with a pencil. What happens? Have you made any other observa- tions of your own? If so, discuss them with the class. O Arthropods affect man in many ways. Prepare lists of those that are useful and those that are harmful, telling how in each case. 7. You have become acquainted with four groups of arthropods be- sides the insects. Name a few forms in each of the five groups. Tell how they live. 8. Dissection of a clam. If you crack one valve of the shell and remove the pieces gently you will see the mantle, a thin skin next to the shell, and the gills. Can you find the muscles that hold the shells together? Open an oyster and compare its structure with that of the clam. g. Collect some earthworms and keep them in a box of earth with glass sides. Watch them. Write up your observations briefly but accurately. 10. To study the organisms in a hay infusion. Boil a small handful of hay and two or three wheat seeds in half a quart of water. Allow it to 70 The Living Things of the Earth unir 1 stand for several days; then add a little pond water. In about ten days you should have a good hay infusion. To slow up the protozoa for study you can add to your slide a little gum tragacanth (ask for it at the drug store). You will find instructions fan the use of the microscope on pages 113-114. How many kinds of protozoa do you see? Draw some. 1. How does a paramecium move? Which seems to be its front end? As it swims forward it rolls over. Does it roll clockwise or counterclock- wise? Which way does it roll when it swims backward? 2. Perhaps the most fascinating object to watch under the microscope is a large ameba. Do not use a bright light. How many pseudopods do you see? What seems to happen to the particles just inside the tip of a pseudopod at the “front” end of the animal? Does it ever lose a pseudo- pod? How do you know? How fast does it move? How does it change direction? Does it ever reverse the direction of its movement? FurTHER ACTIVITIES IN BIOLOGY 1. How to raise and observe grasshoppers. Construct a cage. Cover the bottom of a terrarium with sod on which grass is still growing. The grass must be watered regularly for the grasshoppers eat the grass and are dependent on the water which they get from the surface of the leaves. Cover the cage with a wire top or with a mosquito netting. Watch the insects eat. Observe all other activities. 2. How does the grasshopper jump? If you can obtain live grasshoppers, watch them jump. How many times its own length does a grasshopper jump? In what position are the hind legs when the insect is about to jump? Compare a grasshopper with a man doing a broad jump. Explain. Does the grasshopper use its legs for anything but jumping? 3. If you have any plants in the house or garden, examine the stems and leaves carefully for aphids or scale insects. Describe any that you find. Some kinds can be removed by holding the leaves and stems in soapy water. 4. Perhaps your class or biology club could buy an observation beehive to keep at the window of your laboratory. You will learn a great deal about the life of bees. Many books have been written on the social insects. Prepare a full es on one of the social insects. 6. Daphnia is a tiny crustacean that is easy to obtain and raise. Write to any large biological supply house and ask for directions. Fhe development of the snail is easy to follow if you use a hand lens. Keep several snails in an aquarium. The eggs are laid in masses, often on the glass. Note whether all the offspring of snails with right-handed shells also have right-handed shells. 8. Shell collecting 1 is SO popular a hobby that there are dealers all over the world who publish c catalogues of both common and rare kinds. Encyclopedias contain pictures in color of some of the most beautiful. ———————— PROBLEM 1. The Kinds of Animals of the Earth Make a collection of your own, using a shell book to learn the names of the animals. By exchanging specimens you may be able to get shells from other parts of the country. g. [he complete story of Charles Darwin's study of the effect of the earthworm on the soil is told in his book, The Formation of Vegetable Mold. It is not difficult to read. Prepare a report for the class. 10. If you follow directions carefully you can maintain a salt water aquarium. Starfish, sea anemones, and mussels will live in it if you have plenty of seaweed. A Turtox leaflet (General Biological Supply House, Chicago, Illinois) will provide complete directions. You may buy the plants, animals, and sea water from biological supply houses if you are far from the coast. . If you are talented in drawing prepare a mural for the walls of your speeseins showing examples of animals in each of the phyla from the ite to the arthropods. . If you have a good hay infusion and are skillful with the micro- Sse make daily observations and keep accurate notes. Always take samples of water from different levels in the j jar. You will make an inter- esting discovery in the course of several weeks. 13. Have you ever thought of owning a microscopic pet? It is really easy. Paramecia make the best pets Beene they are hardy. By heating a piece of glass tubing soften it until it can be drawn out to make a very narrow tube. Break this narrow tube so that you have a pipette with a narrow opening. Put a slide containing paramecia on a piece of black paper so that the paramecia can be seen with the naked eye. They will appear as white specks. Catch one by dipping the pipette into the water near it. Draw the pipette out quickly so that you catch only one para- mecium. Gently blow the paramecium out on another slide. Add some cool boiled hay infusion water. Then put the slide in a Petri dish (ask your teacher). The Petri dish must contain a piece of blotting paper soaked in water. This will moisten the air. To keep the bottom of your slide dry, put it on two match sticks that lie on the blotting paper. Cover the dish. The next day you should have two or more paramecia. Repeat this process, discarding one of the animals, and keeping the other. Vie! PROBLEM 2 What Kinds of Plants Inhabit the Earth? The two large groups of plants. In de- scribing animals it was convenient to speak of animals with a backbone and animals without a backbone. Later we sorted those without a backbone into different phyla. In describing plants we again very simply speak of two kinds, those with flowers and seeds and those without. People sometimes carelessly use the words flower and plant as though they mean the same thing. The flower, or blossom, is only part of a plant, just as the eye or the heart is only part of an animal. Some plants bear flowers at cer- tain times in the life of the plant. Others never bear flowers. The plants that never bear flowers are not the trees and the Spirogyra Agaricus grasses which you may be thinking of, Trees and grasses have flowers although they are often so tiny or so unlike ordi- nary flowers that they may escape your notice. Trees and grasses are therefore flowering plants, together with roses and violets and daisies and many others. The true “plants without flowers” bear no flowers of any kind nor do they form seeds; and besides, as you will see, most of them differ from the flowering plants in their general make-up. Some differ so widely that you might not recognize them as plants at all. You will study the plants without flowers first. There are three divisions or phyla of flowerless plants. BRYOPHYTES \ Pigeon-wheat moss Fic. 95 Examples of the four large groups in the plant kingdom, Which of these groups PROBLEM 2. The Kinds of Plants of the Earth ie: FLOWERLEss PLANTS PHYLUM — THALLOPHYTES The simplest plants. The first division, or phylum, of the plant kingdom con- tains plants which differ widely among themselves in appearance and in size. Some are single celled and microscopic; others grow to an enormous size. All are alike in that they do not have true roots or stems or leaves and that they never produce flowers or seeds. Some contain the green coloring matter so characteristic of plants. They are. called Algae (al’jee). Those that lack the green coloring matter are called Fungi (fun’- jeye). Of the algae some look bright green; in other algae the green coloring matter is more or less hidden by other colors so that these algae may look bluish green or even brown or red. The smaller algae. Have you ever seen a green scum on the water of a slowly PTERIDOPHYTES Naked seeds Christmas fern Pine tree with cones moving stream or small pond? If you lift the scum on a stick you discover that it is a bright green mass of long tangled threads. Each thread consists of a number of cells all alike. If you examine these threads with a microscope, it is likely that you will see a beautiful plant called Spirogyra. Each cell contains one or more green spirals. The plant has neither root nor stem nor leaf. See Fig. 97. It is just a living green thread which grows in the sunny water and may at some time become food for a water animal. With a microscope you can do Exer- GISE. 1. In the plant kingdom as in the animal kingdom, the simplest organisms are usually water dwellers. Some of these simple plants have one or several long whiplike projections by means of which they swim. Yes, many species of simple plants move about. Others, such as the SPERMATOPHYTES Covered seeds( (mR Com Of Blooming geranium are flowerless plants? How many other examples of plants in each group do you know? The Living Things of the Earth unr 1 “¢ Bot etter Fic. 96 Life in salt water. This is a common sight for those who live near rocky ocean shores. Do you see the strands of rockweed? To what large group of plants does it belong? What animals do you recognize? (AMERICAN MUSEUM OF NATURAL HISTORY ) ae” PS a a an * 3 5 ‘ 7 dh oy Fic. 97 Part of a single strand of Spirogyra, one of the pond scums. Do you see the spirals? They are bright green. Spirogyra lives in fresh water. (GENERAL BIOLOGICAL SUPPLY ) diatoms, have beautifully marked shells. They live in enormous numbers in salt and fresh water, serving as food for ani- mals. The shells of those that lived mil- lions of years ago have accumulated and are quarried and used in many ways. \ few of the simple plants live on land, usually where there is plenty of moisture, although some of them can stand much drying up. The thin flat very green growth found on the bark of trees is a mass of simple plants called Protococcus. You may have called it moss, but its structure is very different from that of a moss. Closely related to it are the algae which grow by the millions on the snow during o Explorers call these algae “red snow.” the summer in arctic regions. Larger algae. ‘There are other larger algae, that grow in salt water, the sea- y =~ c PROBLEM 2. The Kinds of Plants of the Earth we Fic. 98 This Amanita is very poisonous. It looks much like the common mushroom which you can buy in a market. (BLAKISTON) weeds. Some, like the common brown seaweed or rockweed (Fucus — few’cus), are fastened to the rocks in the region be- tween the tides. They can hold much moisture and are tough enough to stand the pounding of the surf. Some brown seaweeds, like the kelps, may reach a length of fifty yards or even twice that length. Formerly kelps were burned to yield iodine. They were gathered in large amounts off the coasts of Ireland, France, and elsewhere. Other seaweeds float near the surface in the open sea. You may have seen pieces of the green sea lettuce (U/va) which have been washed ashore and caught on the sand or rocks. At greater depths live red seaweeds, which are usually deli- cately branched piants of much smaller size. The agar-agar which the drug store sells and which is used in some experi- ments comes from a red seaweed found near Japan and near our west coast. Fic. 99 The bracket fungus is related to the mushrooms. Most of the plant is under the bark. (U. S. FOREST SERVICE) Mushrooms. As you read above, the simplest plants without flowers are of two kinds; those with green coloring matter, the algae; and those without green coloring matter, the fungi. Among the larger more conspicuous fungi are the mushrooms. About one half of the many kinds of mushrooms make good food. Some are too tough to be eaten and some are definitely poisonous. It is often so hard to tell the various kinds of mush- rooms apart that no one but an expert should decide which can be eaten. Mush- rooms live only where it is damp. Most are small, but some attain a weight of more than thirty pounds. Study a com- mon mushroom. See EXERCISE 2. Fungi you do not like — the molds. In damp weather stale bread often begins to smell musty —the peculiar smell of a fungus known as mold. If you give the mold a chance to develop and then ex- amine it closely you will see that what The Living Things of the Earth unir 1 f RRS SE GES f) Re oon GF Hat Pants itt Fic. 100 Drawings of several kinds of fresh-water algae. Hundreds of kinds of algae are found on soil and in swamps, lakes, ditches, and streams. Algae are the principal food of many kinds of small water animals, and these animals are the food of larger animals. The names of the algae are: (A) Stigeoclonium, (B) Chaetophora, (C, D) Oedogo- nium, (K) Anabaena, (¥) Micrasterias, (G) Euastrum, (H) Staurastrum, (1) Penium, (J) Scytonema, (IK) Amphipleura, (L) Stictodiscus, (M) Suriella, (REDRAWN BY PER- MISSION FROM Textbook of Botany, TRANSEAU, SAMPSON, AND TIFFANY, HARPER AND BROTHERS ) PROBLEM 2. at first looks like an ugly mass is really a very delicate simple plant. In fact, the bread may serve as a garden for several species of beautiful mold plants. The commonest one, known as the bread mold or Rhizopus (ry’zo-pus), consists of a miniature jungle of very fine, glis- tening, white threads. Little black balls appear at the tips of upright threads. These make the mass of white threads look gray and later sooty. You can raise a variety of molds by doing Exercise 3. Molds grow on many different foods if enough moisture is provided. There are some mold plants that look like patches of bright blue- green felt; others are salmon pink. The drug penicillin is prepared from some of the blue-green molds. In these the threads are shorter and even more interlaced so that without a powerful lens you cannot see separate threads at all. A plant that is both alga and fungus in one. Strictly speaking, this “plant” is two separate plants, one an alga, the other a fungus, but they are so closely combined that they look like one plant. The combination is called a lichen (ly’- ken). It looks grayish or yellowish green. You may have seen lichens on rocks or trunks of trees. Some, like the “reindeer moss,” grow on the ground. Lichens are extremely hardy plants; when all else has been killed by the cold they still survive. They are food for grazing animals, such as reindeer, of the arctic zone. Some are eaten by man. Fungi that help man bake and brew. The yeast plant is so small and so simple that even under the microscope it does not look like much of anything. It is merely a tiny, colorless, egg or rod- The Kinds of Plants of the Earth Tey shaped speck which cannot move. See Figure 362, page 413. It is classified as a plant and is clearly a fungus. There is one special kind of yeast that We raise in vast numbers. Millions upon millions of them are pressed into one yeast cake. Yeasts are useful because when they live in sugar solutions they change the sugar into alcohol and a gas called carbon dioxide. This change is called fermentation. When we want to bring about fermentation we often put yeast plants with soaked, crushed corn or other grains. When we make wines we add yeast plants to grapes, although until recently we depended on “wild” yeasts to change the sweet fruit juice into alcohol. Wild yeasts and molds, too, float about in the air. You are now ready for Exercises 4 and 5. Yeasts, as you may know, are also used in baking. They cause fermentation in the dough but the alcohol evaporates during the baking so you never taste it; the carbon dioxide gas forms bubbles in the solid mass of dough, “raising” it and making it light and porous. Bacteria. These very important plants are usually classed as fungi, although some biologists place them in a phylum by themselves. Most bacteria are so much smaller than yeasts that they are difficult to describe. As a matter of fact, there is probably not much to be seen in them. Most of them cannot move about but some can wriggle when in a liquid and a few can swim by means of long whip- like projections. There are giants and pygmies among bacteria, but even the few giants are so extremely small that they can be seen only with a good micro- scope. It has been calculated that if the 78 The Living Things of the Earth Fic. 101 Bacteria that cause pneumonia. The photograph was taken through a microscope. (AMERICAN MUSEUM OF NATURAL HISTORY ) bacterium which causes one kind of pneumonia were magnified to the size of a tennis ball, and if the man in whom the bacterium lodges were magnified in pro- portion, the man would be about twenty- five miles tall! But bacteria are interesting to man not for the way they look but for what they do. Some species live in man and cause disease but many more are harmless or even valuable. You will read more about them in Unit VI. PHYLUM — BRYOPHYTES The Mosses and Their Relatives The second large division of flowerless plants. ‘This group includes the mosses. | hey look somewhat more like the plants commonly recognized as plants. lor one thing, most of them live on land. For another, they are always green and, like the plants you know best, are anchored to the soil. Then, too, moss plants have simple leaves and rootlike and stemlike WINTRY Fic. 102 Physcomitrium, a tiny moss that you, may find in your garden. It is less than one-half inch bigh, (HUGH SPENCER) parts. Mosses range in size from less than one-eighth inch to more than one and one-half feet high. Mosses grow almost every where eX- cept in salt water. There are vast bogs of one kind of moss known as Sphagnum. The sphagnums are among the largest of mosses, having a stemlike part that grows to be many inches long. Stems and leaves are constructed so that they absorb water like a sponge and for this reason some kinds were formerly used for dress- ing wounds. The greatest usefulness of sphagnums arises from the fact that when they grow in water, the plants do not decay when they die. The accumu- lated dead plants become what is known as peat. Peat accumulations many feet drainine the 5 deep are common. After o° out in small — c bog, — c the peat can be du squares, dried and used as a fuel. PROBLEM 2. Fic. 103 The hay-scented fern. Not all ferns have leaves (fronds) as finely divided as this. (SCHNEIDER AND SCHWARTZ) PHYLUM — PTERIDOPHY TES Ferns and Their Relatives The third large division —the ferns. There is something about a fern that pleases the eye; for that reason you have all noticed ferns. They have been culti- vated, too, so that they are often seen in homes. There are almost four thou- sand different species growing in many parts of the world. Most species need moisture and thrive best in the shade of forest trees. But some, like the sensitive fern, live on the edge of the forest; a few, like the bracken or brake, grow in sunny fields. Most fern leaves (called fronds) are divided and often finely subdivided into leaflets. The leaf comes up from the ground tightly coiled like a fiddle- The Kinds of Plants of the Earth 79 Fic. 104 The “scouring rush” is a relative of the fern. It is harsh and gritty to the touch. (BROOK- LYN BOTANIC GARDEN) head; as it grows, it uncoils and spreads out its broad surface. In most ferns the leaves are the only parts that are visible; the woody stem lies underground and may extend for many feet just under- neath the surface of the soil. Like all the plants you have read about so far ferns never form flowers or seeds. In the tropics ferns grow to a much greater size and some develop strong stems above ground, In fact they may grow as trees sixty or more feet high. And there was a time some 200 million years ago or more when large tree ferns grew in vast numbers much farther north. 80 The Living Things of the Earth Large portions of the rich coal deposits of Pennsylvania are the remains of these ancient fernlike plants. And in those past ages, two small inconspicuous relatives of the fern also grew as tall trees, the club mosses and the horsetails. The club mosses are also commonly called ground pines. They are creeping plants that grow close to the forest floor. It is difficult to say which name is least fitting since they are neither “mosses” UNIT I nor “pines.” They are closely related to the ferns. Another common name for the horsetails is scouring rush (Figure 104). All the species included in this division or phylum have true roots, stems, and leaves, but they never bear flowers and they never produce seeds. If specimens are available, you should now be able to do Exercise 6. The whole class might well make a common project of EXERCISE 7. PLANTS WITH FLOWERS AND SEEDS PHYLUM — SPERMATOPHYTES So i a Characteristics of flowering plants. The plants of this, the fourth large division, not only produce flowers and seeds but they have another characteristic which is not possessed by any of the simpler plants except the ferns: they have well- developed roots, stems, and leaves. There is great variety in the size and appearance of these parts, as well as in the blossoms, as you can imagine when you learn that there are more than 125,000 different species in this division. They are the commonest land-living plants. But some grow in water. In fact they may be found in almost any environment. Some have a stem that is soft, grows rapidly, and dies at the end of the year. ‘They remain small and are called herbs. Others have stems that are woody and tough. If they have one main stem, they are trees; if they have several equally thick stems arising from the ground, in which case they usually do not grow very tall, they are called shrubs. Flowering 5 plants vary, too, in length of life. Those that start from seeds, grow, produce flowers and seeds and then die during one growing season are called annuals. Examples are the crabgrass, com- mon as a weed in many lawns, radishes, tomatoes, and lettuce of the garden, and farm crops such as oats, corn, and buck- wheat. Plants that start from seeds during one growing season but produce flowers and seeds and then die during the next season are called biennials. Many weeds are biennials. Among the farm and gar- den crops that are biennials are winter wheat, cabbage, and carrots. You will note that both annuals and biennials die after flowering. The other seed-pro- ducing plants are called perennials. These plants may live for many years, produc- ing flowers and seeds each growing sea- son. All of perennials as are certain garden and farm our trees and shrubs are crops such as asparagus, sugar cane, and tulips. Perennial grasses make the finest lawns. Perennial plants may live to a great age. The cypress of Mexico and some of the big trees (sequoias) of California have lived for 3000 to 4ooo years, PROBLEM 2. ; eal 7 Ry r- The Kinds of Plants of the Earth 81 Fic. 105 All the plants you see in this photograph are Spermatophytes. They bear flowers and seeds. If you were to go to the scene of the photograph, where would you be likely to find algae and fungi, mosses and liverworts, and ferns and horsetails? (EVA LUOMA) The two chief groups of flowering or seed plants. This division includes plants that you may not have thought of as “flowering” or seed plants, the cone bearers. Thus there are two large groups in this phylum: 1. The cone bearers and their relatives (Gymnosperms — jim/no-sperms). Botanists think of them as seed plants with uncovered or naked SS ee seeds. s€edS. 2. The true flowering plants (Angio- sperms — an’jee-o-sperms). To bot- anists they are the seed plants with covered seeds. \ Se The cone bearers. The scales of the cone hold the uncovered or naked seeds. These plants are called conifers (kon/i- furs) and most of them are evergreen. The leaves of conifers are usually hard needles or tiny scalelike leaves which can withstand the winter drought (lack of moisture) and cold. The needles live for two or more years, so the trees remain green at all times. There are many dif- ferent kinds of conifers or evergreens: the giant redwoods of the west, the many kinds of pines, firs, hemlocks, cedars, and smaller plants or shrubs like the yews. Some people carelessly call many of the evergreens “pines.” The true pines are 82 The Living Things of the Earth unrr 1 ~-