What is animal science. Zoology - the science of animals

Zoology as a science. Sections of zoology.

Zoology - animal science, forms part of the science of living beings, biology.

Subject Zoology is the study of the animal world in relation to the structure and functions of the body of animals, their development, distribution on earth, their mutual relationships in structure and origin, and their relationship to the surrounding world. Due to the absence of a sharp boundary between plants and animals, the field of zoology comes into contact with the field of botany and, to a certain extent, mixes with it in the doctrine of the lower representatives of both groups.

The department of zoology devoted to the study of the structure of animals has the general name morphology.

The study of the structure of an animal or a known group of animals, independently of others, constitutes the subject descriptive anatomy; if the structure of animals is studied by comparing different forms, then this branch of zoology is called comparative anatomy; the general task of the latter is to clarify the laws of animal structure.

The finest structure of animals, studied using a microscope, serves as the subject of a special branch of morphology - histology, but since there is no sharp, definite boundary between the study of the structure of animals without auxiliary optical means and study with the help of optical instruments (simple and complex microscopes), then the field of histology is not demarcated in a certain way from the field of anatomy.

The functions of the body of animals constitute the subject physiology; physiology can be aimed at elucidating the activities of a known specific organism, while others are considered only to the extent necessary for understanding the phenomena occurring in the animal under study, or physiology, called in this case comparative, studies all animals from the point of view of their functions, trying to find out general laws of the phenomena being studied.

A special branch of animal physiology is the study of their mental life - zoopsychology.

The relationship of animals to the world around them is the subject animal biology in the narrow sense of the word (in a broader sense, biology is the totality of sciences about living beings); here we can also deal either with the biology of a given animal or with the general biology of animals, if we study the general laws of relationships between animals and the surrounding world, both organic and inorganic. This includes the study of the influence on animals of various external conditions: temperature, light, environmental composition, its physical properties, pressure, movement or immobility of the environment, etc., as well as relationships with other organisms that are their enemies, prey, means protection, food source, etc.

Not limiting itself to the study of an animal in its adult, developed state, zoology considers how an animal develops before reaching its final adult state; this branch of zoology is called developmental history, or ontogeny, or embryology. Embryology includes both the study of phenomena occurring inside the egg, embryonic development itself, and those changes that then occur in the animal - postembryonic development.

The mutual relations between animals can be considered from the point of view of their origin; a branch of zoology that seeks to find out how the animal kingdom developed, through what changes and under the influence of what factors new forms of animal life were developed, and in what genetic (by origin) relationships different groups of animals stand with each other, is called animal phylogeny. Its task is to establish the genealogy of the animal kingdom.

A significant role in relation to comparative anatomy and the phylogeny of animals is played by the study of fossil remains of animals that lived in previous geological eras - animal paleontology or zoopaleontology.

An important branch of zoology in modern times is the study of the distribution of animals on earth - animal geography or zoogeography. Based on the facts of the distribution of animals and with the help of paleontology, geology and general biology of animals, zoogeography seeks to elucidate the causes and laws of the modern distribution of animals. From the point of view of modern views on the origin of the animal kingdom, the distribution of animals is the same result of a number of previous conditions as the very structure of animals; At the same time, zoogeography is a valuable criterion for testing the theories of the origin of animals.

All of the listed branches of zoology are in close connection with each other, pursuing their own special goals.

All zoology breaks down into general And special.

The subject of the first is the study of data and laws relating to the entire animal world; the subject of the second is a detailed study of individual groups based on the general views of zoology.

Departments of special zoology have special names according to the groups to which they are devoted: the science of mammals - mammalogy, about birds - ornithology, about reptiles - herpetology, about amphibians - batrachology, fish - ichthyology, shellfish - malacology, insects - entomology, spiders - arachnology, worms - helminthology, sponges - spongiology; other similar names are less common.

It should be distinguished from theoretical zoology, which aims at the purely scientific study of animals. applied zoology. Based on the data of theoretical zoology, applied zoology studies animals exclusively from the point of view of human economic interests, from the point of view of their benefit or harm (direct or indirect), methods of conservation, reproduction or, on the contrary, their extermination. Two branches of applied zoology have become very important - applied entomology (the science of insects) and applied ichthyology (the science of fish).

Zoology is the science of animals, which deals with the study of representatives of the corresponding genus (Animalia). This includes all types of organisms that feed on food containing protein, carbohydrates and fats. Such species differ from plants in that they constantly synthesize what they need for life from specific sources.

Many representatives of the animal species are able to move independently. Mushrooms have always been considered plants. However, they noticed that they have the ability to absorb from external sources. There are also organisms that synthesize starch from inorganic molecules. However, they do not have the ability to move. In other words, it is impossible to give a general concept and highlight alternative criteria between animals and plants, since they do not exist.

Categorization

In this case, there is a division into many directions, which are differentiated depending on what particular object is being studied and what problems are being studied. Zoology is a science that is divided into two main areas. Namely, the study of invertebrate and vertebrate animals. These areas may also include the following disciplines:

Protistology. In this case, the study of protozoa is carried out.

Ichthyology is the study of fish.

Malacology is the study of mollusks.

Acarology - the study of mites.

Entomology is the study of insects.

Carcinology is the study of crustacean organisms.

Herpetology is the study of reptiles and amphibians.

Ornithology - the study of birds.

Theriology is the study of mammals.

How important is zoology to humanity?

Let's consider this point in more detail. This science has a rather unique history of development. Animal zoology has always played an important role in human life. Looking at these individuals, their behavior, skills, we better understood the environment. After all, humanity had to independently learn how to hunt birds and animals, how and where to fish, how to protect themselves from predators. And all these skills could be learned from animals. Zoology is a science with ancient roots and an interesting, rich history.

For the first time in the 4th century BC. This science became known from the books of the great scientist - Aristotle. This is a reliable fact. In his books, he described the origin of about 500 species of different animals. Some of them had red blood, and some had no blood at all. Also in the works of this scientist the significance of each type of animal, as well as their development and structure, was outlined. Such a detailed description has become a real encyclopedia.

In the Middle Ages, history continued to develop this science. Zoology moved one step forward every year. Some important information about animals, which became known in ancient times, was forgotten. Scientists focused their attention only on the reproduction, hunting and maintenance of animals. The lost interest was revived only during the Renaissance. At that time, attention was paid to navigation and trade. Thanks to this, numerous expeditions were carried out aimed at studying new species of plants and animals about which nothing was previously known.

Carl Linnaeus also played an important role in the development of zoology. It was he who classified the animal world and gave scientific names for each definition in it.

However, this is not the end of the development history of this science. Zoology improved significantly in the second half of the 19th century. This is after Charles Darwin published a book on the Origin of Species by Means of Natural Selection. In his work he proved a certain fact. It lies in the fact that the world around us is modified due to natural selection. That is, new individuals survive and survive, and only the strongest remain. Thanks to this basis, zoology - the science of animals - began to develop rapidly. These successes will become known in taxonomy. A description of the appearance of new animal species will appear there.

Also, the history of the formation of zoology will become known in Russia after expeditions to the east and north of Siberia. They were carried out by A.F. Middendorf, N.M. Przhevalsky, Semenov-Tyan-Shansky. Scientific expeditions were also conducted in Central Asia in embryology by I. I. Mechnikov and A. O. Kovalevsky, in paleontology by V. O. Kovalevsky, in physiology by I. M. Sechenov and I. P. Pavlov.

Zoology today

This may include the body of animal sciences. Certain directions are taken into account here. Namely:

As stated earlier, zoology is the study of birds, mammals and insects. For easier understanding, this science has been divided into special sections. This will be discussed further below.

Main branches of zoology

These include:

In general, zoology is a science that is directly related to other disciplines and areas. For example, it has a very close connection with medicine.

Diverse animal world

It is very large and multifaceted. Animals live everywhere - in fields, steppes and forests, air, seas, oceans, lakes and rivers.

There are many individuals that benefit not only nature, but also humans. For example, these are bees, beetles, flies and butterflies. They pollinate many flowers and plants. Birds are also important in nature. They transport plant seeds over long distances.

There are also animals that harm plants and destroy crops. However, this does not prove that their existence is meaningless. They can be the main link in the food chain of various individuals. All this determines the importance of zoology. Zoology in this direction is an indispensable science.

Domestic and wild animals

It is very important for every person to get proteins and carbohydrates from meat. Previously, there were no shops or supermarkets; this product was obtained through hunting. Then people learned to fish and acquired skills in fish breeding.

Humanity has also learned to domesticate wild livestock and use it for its own purposes. Its cultivation made it possible to obtain products such as meat, milk, eggs, etc. Thanks to animals, people learned to extract wool, fluff and leather and used it for their needs.

About 10 thousand years ago, humans first domesticated the wild wolf. These were the very first ancestors of the dog. Now these animals are considered the most faithful and devoted friends of people.

But livestock farming began with the domestication of horses. They were indispensable on the farm.

Differences and similarities between animals

All individuals of a given species are usually distinguished by type, respiratory structure, reproduction, development, and so on. Animals differ from plants in that they do not have a hard cellulose shell. They feed on ready-made organic substances. Animals are characterized by active movement. As a result, they can look for their own food.

Conclusion

All of the above indicates the versatility of this definition. Zoology plays an important role in the life of every creature on our planet. This was discussed above. Everything is interconnected in this world. And zoology is life itself.

Zoology is a collective science. Even if a person works alone in the forest or in a laboratory, he must constantly know about the work of his colleagues, must know what has been done before him. Otherwise, he will only mark time or open what is already open.

Animal science has evolved over thousands of years. And each subsequent generation of scientists, accepting or even rejecting something, still used the experience of their predecessors.

There were many scientists who devoted their lives to zoology. And there were thousands of them - famous and anonymous, but who left their mark on science. Perhaps their contribution is so small that it is completely lost among other great and not so great discoveries. However, thanks to these scientists, thanks to their discoveries, Gesner and Linnaeus, Lamarck and Cuvier, Wallace and Darwin appeared. Thanks to these and thousands of other scientists, the animals of our planet became known to humanity.

Scientists have discovered and described more than a million species of inhabitants of our planet. Of these, there are about a million insects. Let's remember Aristotle: he described only 60 species of insects, Linnaeus knew already 1929. There are now over 20,000 species of crustaceans known. Aristotle knew only 15, Linnaeus - 89 species. We now know more than 10,000 species of fish. Aristotle knew 117 species, Linnaeus - 250. The same can be said about birds, mammals and other animals.

Total count: Aristotle knew 454 species, Linnaeus - 4200 species, modern scientists - more than a million. This means that in two thousand years - from Aristotle to Linnaeus - the list of animals increased only nine times. And in two hundred years - from Linnaeus to the present day - almost three hundred times.

There are many reasons, of course; but the most important thing is that the science of animals itself has expanded and deepened.

We would not soon have recognized the animals of our planet if Linnaeus had not introduced his system; we could not study animals without comparative anatomy, the “father” of which was Cuvier, without Darwin and his theory of natural selection. But the more people got to know animals, the more difficult it became to study them. After all, even the most experienced zoologist cannot remember at least some of the animals known today.

And zoology began to be divided into sections. One section began to be called arachnology- he studied arachnids (in our time, more than 35 thousand species are known). Another section that studies insects is called entomology; section dedicated to mollusks - malacology; the science of fish is called ichthyology; branch of zoology that studies reptiles - herpetology, and amphibians - bitrachiology; ostocology studies crustaceans, ornithology- birds; mammaliology, or theriology, - mammals.

For example, as long as people knew relatively little about arachnids, there was no need to distinguish them. We learned more - and a special science took shape. Ticks are also arachnids. But for the time being, when not much was known about ticks, there was no separate science. But people became convinced that there are a large number of these animals, and that many of them are carriers of dangerous diseases. And a new science appeared - acarology.

Zoologists who specialize in insects are called entomologists. But there are about a million species of insects. Naturally, zoologists-entomologists, in turn, specialize: some deal with butterflies, others with beetles, others with bedbugs, and so on. People who deal with ants too, of course. entomologists. But the science of ants, and these insects are already known, as some scientists believe, to be 15 thousand, and others - about 20 thousand species, has taken shape as an independent one - myrmecology.

Thus, let's say a person who studies ticks is, of course, a zoologist. But this would be too general a definition. More precisely, he is a zoologist-arachnologist (since ticks are arachnids). But since he is a specialist in ticks, he can be called a zoologist-arachnologist-acarologist.

But what does it mean to study certain animals?

This means: observing them, where and how they live, what and how they eat, how they reproduce and treat their offspring, and finally, simply determining what kind of animal it is, whether it is already known to science or not, how common it is, where found and where not, how it works, and so on. But that’s not all: animals and birds, insects and fish do not live on their own, they are surrounded by other animals and plants. How do they influence each other? And finally, almost all animals come into contact with humans and modern technology in one way or another. And this, in turn, affects animals. What is it like?

What does it lead to?

And a lot of other questions have to be solved by zoologists.

The study of animals cannot, of course, do without knowledge of the laws of structure and morphogenesis of animals. This is what he does morphology, which includes anatomy and comparative anatomy. Anatomy is the science of the internal structure of the body in general, and comparative anatomy is the science that compares the structure of different groups of animals. Such a comparison helps resolve the issue of the similarities and differences between animals. But it is impossible to study modern animals without knowing about their origin, without having an idea about their distant ancestors. And this is what paleontology does.

Deals with issues of heredity genetics, A splanchonology studies the internal organs of animals.

There are still many sciences or their branches, sciences that already have “experience” and are very young, such as, for example, ecology- the study of animal life in connection with the environment, or ethology, which studies the behavior of animals.

And all together is zoology, because zoology is the science of animals “taken from all sides.”

Thanks to the development of zoology and all its parts, the list of known animals quickly expanded. And now, it would seem, there is not a single corner left on Earth that has not been explored by man. And everything living, it would seem, if not studied thoroughly, is included in the list. So, the list can be closed and a line drawn? In the century before last, many thought so. But they were very mistaken, these people: the 20th century showed that our planet and, in particular, the animal world of our planet are not so well studied.

It’s not for nothing that biologists say: “Now so many species are known.”

This means much more may be known tomorrow. Indeed, people continue to find and discover new animals.

Zoology is the science of animals and is part of the science of living beings, biology.

The subject of zoology is the study of the animal world in relation to the structure and functions of the body of animals, their development, distribution on earth, their mutual relationships in structure and origin, and their relationship to the surrounding world. Due to the absence of a sharp boundary between plants and animals, the field of zoology comes into contact with the field of botany and, to a certain extent, mixes with it in the doctrine of the lower representatives of both groups.

The department of zoology devoted to the study of the structure of animals is generally called morphology.

The study of the structure of an animal or a known group of animals, independently of others, constitutes the subject of descriptive anatomy; if the structure of animals is studied by comparing different forms, then this branch of zoology is called comparative anatomy; the general task of the latter is to clarify the laws of animal structure.

The finest structure of animals, studied with the help of a microscope, is the subject of a special branch of morphology - histology, but since there is no sharp, definite boundary between the study of the structure of animals without auxiliary optical means and study with the help of optical instruments (simple and complex microscopes), then the area histology is not demarcated in any particular way from the area of ​​anatomy.

The functions of the animal body are the subject of physiology; physiology can be aimed at elucidating the activities of a known specific organism, while others are considered only to the extent necessary for understanding the phenomena occurring in the animal under study, or physiology, called in this case comparative, studies all animals from the point of view of their functions, trying to find out general laws of the phenomena being studied.

A special branch of animal physiology is the study of their mental life - zoopsychology.

The relationship of animals to the world around them constitutes the subject of animal biology in the narrow sense of the word (in a broader sense, biology is the totality of sciences about living beings); here we can also deal either with the biology of a given animal or with the general biology of animals, if we study the general laws of relationships between animals and the surrounding world, both organic and inorganic. This includes the study of the influence on animals of various external conditions: temperature, light, environmental composition, its physical properties, pressure, movement or immobility of the environment, etc., as well as relationships with other organisms that are their enemies, prey, means protection, food source, etc.

Not limiting itself to the study of an animal in its adult, developed state, zoology considers how an animal develops before reaching its final adult state; This branch of zoology is called the history of development, or ontogeny, or embryology. Embryology includes both the study of phenomena occurring inside the egg, embryonic development itself, and those changes that then occur in the animal - postembryonic development.

The mutual relations between animals can be considered from the point of view of their origin; the branch of zoology that seeks to find out how the animal kingdom developed, through what changes and under the influence of what factors new forms of animal life were developed, and in what genetic (by origin) relationships different groups of animals stand among themselves is called animal phylogeny. Its task is to establish the genealogy of the animal kingdom.

An essential role in relation to comparative anatomy and the phylogeny of animals is played by the study of fossil remains of animals that lived in previous geological eras - animal paleontology or zoopaleontology.

An important branch of zoology in modern times is the study of the distribution of animals on earth - animal geography or zoogeography. Based on the facts of the distribution of animals and with the help of paleontology, geology and general biology of animals, zoogeography seeks to elucidate the causes and laws of the modern distribution of animals. From the point of view of modern views on the origin of the animal kingdom, the distribution of animals is the same result of a number of previous conditions as the very structure of animals; At the same time, zoogeography is a valuable criterion for testing the theories of the origin of animals.

All of the listed branches of zoology are in close connection with each other, pursuing their own special goals.

All zoology is divided into general and special.

The subject of the first is the study of data and laws relating to the entire animal world; the subject of the second is a detailed study of individual groups based on the general views of zoology.

Departments of special zoology have special names according to the groups to which they are devoted: the science of mammals - mammology, of birds - ornithology, of reptiles - herpetology, of amphibians - batrachology, fish - ichthyology, mollusks - malacology, insects - entomology, spiders - arachnology, worms - helminthology, sponges - spongiology; other similar names are less common.

Applied zoology should be distinguished from theoretical zoology, which aims at the purely scientific study of animals. Based on the data of theoretical zoology, applied zoology studies animals exclusively from the point of view of human economic interests, from the point of view of their benefit or harm (direct or indirect), methods of conservation, reproduction or, on the contrary, their extermination. Two branches of applied zoology have become very important - applied entomology (the science of insects) and applied ichthyology (the science of fish).

The modern organic world with all its diverse biomass can be divided into five:

• animals;
• plants;
• mushrooms;
• bacteria;
• viruses.

Each of them is studied by a whole complex of sciences. We will look at what sciences study representatives of the animal kingdom, what these disciplines are called, when they arose and what results they have achieved to date.

Science zoology

The main science that devotes itself to the study of the diversity and lifestyle of animals is zoology. It is precisely this that is the foundation on which knowledge about our smaller brothers rests.

What is zoology? It’s unlikely to be possible to answer in one sentence. After all, this is not just one dry science built on theory, it is a whole complex of sections and subsciences that collect materials about everything related to the animal world.

Therefore, we can answer this question something like this: zoology is the science of that part of the biomass of our planet that belongs to animals. Thus, the object of study of zoology is all animals - from the simplest unicellular to multicellular mammals. The subject of this science is considered to be the study of external and internal structure, physiological processes, distribution in nature, lifestyle and behavioral characteristics, interaction with each other and with the outside world.

Goals and objectives of science

To more fully understand what zoology is, it will help as follows:

• study the features of the functioning, structure, embryonic and historical development of all animal representatives;
• consider ways of adapting to environmental conditions and trace the features of ethology;
• determine their role in;
• identify the role of humans in the conservation and protection of the animal world.

In connection with this goal, the tasks of zoology are the following points:

1. Study of the external and internal structure, as well as the physiological characteristics of all animal representatives.
2. Comparison of their needs and their habitats.
3. Establishing the significance and role of individual groups in nature and human economic activity.
4. Conducting an analysis of the taxonomy of the animal world, identifying the most vulnerable groups, ensuring their protection and protection.

Having examined the goals, objectives, object and subject of zoology, we can say with confidence that zoology studies the animal world in all its manifestations.

Classification of zoological sections

Over two million species of animals are known. Each has its own unique characteristics, and when interacting with each other, they generally represent a unique system. Studying such a system requires a lot of time and effort. This is the work of a huge number of people. Therefore, all science represents special branches of zoology.

Classification of zoological sections by task

There is also a classification of zoological sections according to tasks for science. It consists of the following categories:

• taxonomy - a section dealing with the classification and determination of place in each animal representative;
• zoogeography is a science that studies their distribution and settlement throughout the territory of our planet;
• morphology is a science that studies the features of the external and internal structure;
• phylogenetics - studies the basis of the origin and historical development of the animal world;
• genetics - examines the patterns of heredity and variability in all generations;
• histology - studies the cellular structure of tissues;
• paleozoology - the science of fossil remains and extinct animals from all periods of the life of the planet;
• cytology - the science of the cell and its structure;
• ethology - studies the characteristics of behavioral mechanisms in animals in different situations;
• embryology - deals with the examination of embryos and the establishment of similarities and differences between all representatives of the animal world on the basis of embryonic analysis, as well as the characteristics of ontogenesis;
• ecology - studies the interaction of animals with each other, as well as adaptability to the conditions of the surrounding world and interaction with humans;
• physiology - features of all life processes;
• anatomy - studies the internal structure of animals.

Zoology of vertebrates

What is zoology? This is a section that deals with the study of all representatives of the animal world that have a notochord (during life, it transforms into a vertebral column with a spinal cord).

The objectives of this academic discipline include introducing students to the external and internal features of all classes of vertebrate animals, their behavior and way of life, distribution and role in nature and human life.

The main distinctive features of vertebrates, which are characteristic only of this group, are the following:

1. Only they have a chord - the progenitor of the spine. In some species it remains this way for life, but in most it develops into the spine.
2. The nervous system of such animals is clearly differentiated into the brain and spinal cord (with the exception of strictly chordates, in which it always remains in the form of a nerve cord above the notochord).
3. The digestive system of representatives of different classes opens outward with a mouth opening on the front of the body; the end of the digestive tube is transformed into gills in marine inhabitants. In terrestrials, lungs form inside.
4. All representatives have a heart - the center of the circulatory system.

It is these animals that the section of zoology on vertebrates is devoted to.

Zoology of invertebrate animals

What studies animals? These are the structural features, lifestyle and significance in nature of all animals that do not have the above characteristics. These animals include representatives of the following types:

• sponges;
• coelenterates;
• ringed, round and flatworms;
• shellfish;
• echinoderms;
• arthropods (arachnids, insects, crustaceans).

Invertebrates make up the majority of all known animals. In addition, they play an important role in human economic activity.

That is why the study of invertebrates is important and of great scientific interest.

Zoology of protozoa

Protozoa include all single-celled animals. Namely:

• sarcomastigophora (amoeba, rayfish, foraminifera, sunfish);
• flagellates (Volvox, Euglena, Trypanosoma, Opalina);
• ciliates (ciliary and sucking ciliates);
• sporozoans (gregarines, coccidia, toxoplasma, falciparum plasmodium).

Some amoebas, ciliates and all sporozoans are dangerous pathogens of serious diseases in both humans and animals. Therefore, a detailed study of their life cycle, feeding and reproduction methods is an important part in finding methods to combat them. That is why the zoology of protozoa is no less important a branch of science than all the others.

Brief outline of the development of science

This science is very interesting. Zoology has fascinated and seduced many minds at all times. And this is certainly justified. After all, watching our little brothers is really a very interesting and useful activity.

The main stages that the development of zoology went through are not much different from those in other sciences. These are the main four periods:

1. Ancient time. Ancient Greece - Aristotle, Ancient Rome - Pliny the Elder.
2. The Middle Ages were a time of stagnation. All sciences were under the influence of the church, the study of all living things was strictly prohibited.
3. The Renaissance is the most active period in the development of zoology. A lot of theoretical and practical data on the life of animals have been accumulated, basic laws have been formulated, systematics and taxa, and a binary nomenclature for the names of animals and plants have been introduced into use. The most famous names during this period were: Charles Darwin, Jean Baptiste Lamarck, Carl Linnaeus, John Ray, Saint-Hilaire, Anthony van Leeuwenhoek.
4. Modern times refer to the 19th-20th centuries. This is a period of development of knowledge about the molecular and genetic structure of animals, the discovery of biogenetic laws and mechanisms of embryonic and physiological development of animals of all types. The biggest names: Sechenov, Haeckel and Muller, Mechnikov, Kovalevsky.

Modern zoology

The 21st century is a time of digital technology and the triumph of unique heavy-duty technology. This gives great advantages to all sciences studying living nature, but at the same time it also poses new challenges for them.

What is zoology at the modern stage of development? This is a science that is preparing to answer the questions:

• What is the animal world?
• What laws does he live by and what characteristics does he have?
• How can a person use the animal diversity of the world for his own purposes without harming nature?
• Is it possible to artificially recreate lost (extinct) animal species?

Finding answers will take scientists a lot of time, despite the possession of such advanced technology.

The importance of zoology is difficult to overestimate. It has been mentioned more than once about the big role it plays in people’s lives, their health and economic activities. It has been studied for centuries and will always be studied, because there are still a very large number of unresolved questions about animals.