pronounced zoh AHL uh jee, is the study of animals. Zoologists try to answer many
questions about animals. For example, they conduct research to determine how animals carry
out the activities of their lives. They also study how different species are related to
one another and how species have evolved (changed over long periods). Zoologists observe
the ways animals interact with one another and their environment. They also try to find
out how people and animals affect one another.
The study of zoology has benefited people in many ways. Human beings and animals have many
similar body parts and body functions. As a result, zoology forms a basis for
understanding human medicine and other health-related fields. Some animals, such as
certain insects and worms, can be harmful to people. Zoological research has led to better
methods of dealing with such animals. Zoological studies also have helped in the
management of wildlife and other natural resources and in the breeding of domestic
What zoologists study
No one knows for certain how many kinds of animals there are in the world. More than 1
million species have been identified, and new ones are discovered every year. No zoologist
can know more than a small part of all that is known about animals. As a result, most
zoologists specialize in a certain area of study.
Many branches of zoology deal with a particular kind of animal. For example, entomology is
the study of insects, the largest group of animals. Mammalogy deals with those animals
that have hair and that feed their babies on the mother's milk. Ichthyology is the study
of fish. A zoologist in any of these fields might spend an entire lifetime studying a
single species of animal.
Other areas of zoology deal with certain characteristics that many animals have in common.
Taxonomy is the study of naming and classifying animals. As part of their work,
taxonomists establish relationships among different animal groups. For instance, they have
shown that bats are more closely related to mice and other mammals than they are to birds.
Comparative anatomy is the study of differences and similarities in the body structures of
different animals. A comparative anatomist might compare the circulatory systems of
sharks, frogs, and cats. Paleontology is the study of prehistoric organisms.
Paleontologists and comparative anatomists have made important contributions to knowledge
about the evolution of many animals.
Zoologists who study embryology deal with the formation and development of organisms from
fertilized eggs to birth. Physiology is the study of the functions of animals.
Physiologists may observe how the heart pumps blood, how nerves transmit impulses, and how
Other areas of zoology include genetics and ecology. Genetics is the study of heredity,
the passing on of characteristics from parents to their young. This field of zoology is
important in breeding livestock and in understanding certain human diseases. In addition,
through genetic engineering, scientists have been able to alter the genes (units of
heredity) of various organisms (see GENETIC ENGINEERING). Ecology is the study of the
relationship of organisms to their environment. A knowledge of ecology helps in managing
the limited resources of the earth without harming plant and animal populations.
How zoologists work
Many zoologists work in modern laboratories at universities, research centers, zoos, and
museums. Other zoologists do field studies in the outdoors. These studies might be
performed in a wildlife refuge, at the North Pole, in the jungle, at sea, or anywhere else
Like other scientists, zoologists conduct research by gathering information in an orderly
way. Zoologists often begin their research with an observation that arouses different
thoughts as to its meaning. For example, a zoologist working in a laboratory might notice
that some rats are much smaller than others. Following this observation, the zoologist
would attempt to explain why the rats are smaller by making a scientific guess called a
hypothesis. The zoologist might hypothesize that the group of small rats lacked a
substance that affects normal growth.
After making the hypothesis, the zoologist would test the hypothesis by a series of
experiments. In this example, the zoologist might compare the blood of both groups of rats
to see if any substance was missing in the blood of the smaller rats. Suppose, in this
case, that a substance called growth hormone was absent in the small rats. Additionally,
injections of growth hormone restored normal growth in the rats. At this point, the
zoologist would develop a theory that would state a connection between this substance and
growth. For example, the zoologist might state that growth hormone is necessary for normal
growth in rats. Testing the theory in different situations for long periods of time might
prove or disprove the theory.
When a zoologist adds to the knowledge of zoology, he or she writes a report of the
findings. Such reports are published in scientific journals that are read by zoologists
and other interested people.
People have always been interested in animals. Prehistoric people had an interest in those
animals that were useful as food or clothing, as well as those that were dangerous. Early
cave paintings show some of these animals.
During the 300's B.C., the Greek philosopher Aristotle described the structures and habits
of animals found in Greece. He based his conclusions on his own observations and those of
others. He is sometimes called the father of zoology. Galen, a Greek physician, studied
anatomy and physiology in the A.D. 100's. He made observations of dissected animals and
experimented with living animals. Galen's work greatly influenced the early medical
After the fall of the Roman Empire in the A.D. 400's, zoology and the other sciences made
little progress. During the 1500's and 1600's, however, there was a rebirth of learning.
Andreas Vesalius, an anatomist born in present-day Belgium, argued against Galen in On the
Structure of the Human Body (1543), a book that contained the first detailed portrayal of
the human body. Many of Vesalius' careful observations are still accepted today. The
development of the compound microscope led to many discoveries. Cells, bacteria, and
protozoans were observed for the first time.
Many zoological discoveries occurred in the 1700's and 1800's. In 1758, the Swedish
naturalist, Carolus Linnaeus, published a classification system for animals. The system
enabled all scientists to use a universally accepted name for each animal that had been
discovered. In the early 1800's, Baron Cuvier of France made important contributions to
paleontology and comparative anatomy. Cuvier concluded that several animals had become
extinct. See CLASSIFICATION, SCIENTIFIC.
Until the end of the 1700's, most people believed that each species of life had remained
unchanged and no new species had appeared since the world began. In 1809, the Chevalier de
Lamarck, a French naturalist, proposed a theory of evolution of new species based on the
influence of the environment. For example, Lamarck said that giraffes had developed long
necks by stretching for leaves. Long necks, he said, would then be passed on to the next
generation of giraffes. Discoveries in genetics later showed that Lamarck was wrong. But
his ideas influenced many scientists, among them the British naturalist Charles Darwin.
Darwin made tremendous contributions to zoology. In 1859, he published The Origin of
Species, one of the most influential zoology books ever written. In it, Darwin presented
the theory of natural selection to explain how evolution works. See EVOLUTION; NATURAL
Important findings continued to occur in zoology during the 1900's. Many of them were made
in the areas of genetics, physiology, and developmental biology. An important area of
zoology that developed in the mid-1900's is ethology, the study of animal behavior. The
Austrian naturalist Konrad Lorenz helped found this field with his study of the behavior
Careers in zoology
Zoology offers a broad range of career opportunities. The majority of these careers
require a college education. In addition to zoology courses, students who wish to become
zoologists must take courses in mathematics, chemistry, and physics. Many students also
take courses in computer science. A number of careers in zoology require additional
training in graduate or professional schools.
Many zoologists teach and conduct research in colleges and universities. Other zoologists
work in zoos and museums. Many scientists with zoological training work to make more food
available for people. These agricultural scientists work with cattle, hogs, sheep, and
other farm animals. They use genetic engineering, selective breeding, and other methods to
produce more and bigger animals for food. Zoologists with special training in fishery
biology attempt to improve the production of fish for food.
Some zoologists work with animals in the field. These zoologists include game wardens,
park managers, and ethologists. Manufacturers sometimes hire zoologists to test the effect
that a product, such as a fertilizer or insecticide, will have on animals in their natural
environment. Zoologists also may work as writers, illustrators, or photographers.