Zoology is the branch of biology that studies animals, from tiny invertebrates to the largest vertebrates on Earth.
Zoologists investigate how animals are built, how they behave, how they reproduce, how they interact with other organisms, and how they have changed through evolution. Because animals live in nearly every environment on Earth, zoology connects anatomy, genetics, ecology, behavior, evolution, and conservation into one broad field of study.
Animals range from simple sponges and jellyfish to insects, fish, reptiles, birds, and mammals.
Learn MoreScientists group animals by shared characteristics and evolutionary relationships.
Learn MoreDifferent body structures help animals move, feed, sense their surroundings, and survive.
Learn MoreAnimals communicate, find food, avoid danger, care for young, and respond to their environments.
Learn MoreTraits shaped over generations can help animals survive in particular habitats and conditions.
Learn MoreStudying animals helps scientists understand populations, habitats, threats, and ways to protect biodiversity.
Learn MoreThe animal kingdom contains an enormous variety of species with very different shapes, sizes, diets, and ways of life. Many animals are invertebrates, meaning they do not have a backbone, and this group includes insects, spiders, crustaceans, mollusks, worms, corals, and many others. Vertebrates have a backbone and include fishes, amphibians, reptiles, birds, and mammals. Each group contains species adapted to particular environments, from deep oceans and tropical forests to deserts, polar regions, underground habitats, and cities.
Zoologists classify animals so they can describe biological relationships clearly. Modern classification uses visible traits, anatomy, development, genetics, and other evidence to build evolutionary family trees. Organisms that share a recent common ancestor are generally placed closer together than organisms whose lineages separated much earlier. Classification can change when new fossils, genetic evidence, or other discoveries reveal a better explanation of how groups are related.
Animal bodies are organized in many different ways. Some animals have radial symmetry, with body parts arranged around a central point, while many others have bilateral symmetry, with left and right sides. Structures such as skeletons, muscles, circulatory systems, lungs, gills, digestive organs, and nervous systems vary among groups. Zoologists study these structures to understand how animals perform basic life functions and how body design is connected to movement, feeding, reproduction, and habitat.
Behavior includes the actions animals use to survive and reproduce. Some behaviors are strongly influenced by inherited instincts, while others can be shaped by learning and experience. Animals may communicate through sound, scent, color, movement, touch, or electrical signals. They may live alone or in complex social groups, migrate across long distances, build shelters, cooperate during hunting, defend territories, or care for offspring in different ways. Studying behavior helps zoologists understand how animals respond to opportunities and challenges in their environments.
An adaptation is an inherited feature that became common in a population because it improved survival or reproduction under particular conditions. Camouflage can make an animal harder to see, specialized teeth can help process certain foods, and thick fur can reduce heat loss in cold climates. Adaptations are not choices made by individual animals; they develop across many generations through evolutionary processes such as natural selection. The same trait can be useful in one environment but less useful in another.
Zoological research is important for conservation because protecting animals requires understanding their populations, habitats, food sources, migration routes, breeding patterns, and threats. Scientists may use field observations, tracking devices, genetic samples, camera traps, acoustic recordings, and population surveys to gather information. These data can help identify declining species, important habitats, or changes in ecosystems. Conservation decisions are strongest when they combine careful scientific evidence with long-term habitat protection and responsible management.