What Are the 6 Basic Animal Groups?

Animals are divided into classes that share common features, such as looks, eating habits or distinct characteristics.

Birds belong to the class of vertebrates (which contain internal skeletons), and distinguishing features of birds include their feathers, toothless bills, wings, and the fact they start life as eggs.


Mammals (Class Mammalia) are warm-blooded vertebrates classified as mammals that possess hair or fur, nurse their young, and store up fat reserves for energy storage. Based on their reproductive strategies, mammals can be divided into three main groups: monotremes, marsupials and placentals. Monotremes such as the platypus and echidna are egg-layers. Marsupials give birth to small offspring which they secrete milk from via their belly pouch. Humans, zebras, elephants are placental mammals with mammary glands which give birth fully developed young. Common features that distinguish mammals from other animals include hair, diaphragms, hinged lower jaws connected directly to their skulls and left aortic arches – they also possess their own left aortic arch! Additionally they possess their own special brain region called Neocortex!

Mammalian creatures can be divided into three distinct food groups: carnivores, herbivores or omnivores. Mammalian creatures feed on various things including invertebrates, other mammals, fruits, vegetables and plant matter such as roots bark seeds wood; these endotherms require more food than their ectotherm counterparts of similar size.

Mammals can be found both on land and water and tend to live solitary lives except during mating or nursing their young. Sometimes large social groups called herds or packs form, particularly predators such as lions and wolves. Furthermore, mammals can adapt to many temperatures – in cold environments they can grow thick fur coats to keep warm while in warmer environments they can sweat to regulate body temperatures.


The largest animal group is vertebrates, or class or phylum vertebrates, which encompasses all creatures with backbones such as fish, amphibians, reptiles and birds. Fish are included here among others such as amphibians, reptiles and birds. Class invertebrates contains many different animals like jellyfish, insects, flatworms roundworms clam snails squid cnidarians crustaceans and arachnids among others – plus this group includes crustaceans and arachnids among others.

Scientists are constantly discovering new species on Earth, with scientists constantly discovering more species. Since not all animals share important characteristics in common, scientists have organized them into classes. Each class has a name, while its members often share similar physical traits that allow scientists to distinguish one kind from another based on commonalities between members. Each member of a particular class is known as a species; when breeding between species takes place this can form species names which typically consist of several letters followed by either “genus” or “family”, such as Canis latrans for coyotes while that of gray wolves is Canis lupus

All mammals belong to the class Mammalia of Chordata and belong to their phylum. Mammals are warm-blooded creatures that give live birth; their fur covers four limbs ending in claws, nails or hooves for movement and they also produce milk via mammary glands that produce sufficient milk supply for their offspring’s nourishment.


Animals can be divided into classes that share certain features; for instance, mammals all share warm blooded bodies and motherly care for their young. Grouping the various species helps us better understand and identify them for conservation efforts to avoid them becoming extinct.

Scientists use multiple classification schemes for animals, but the five most widely recognized are mammals, birds, fish, reptiles and amphibians. All five belong to phylum chordata which means they possess backbones or similar structures known as notochords.

Birds, which belong to the phylum Chordata, are by far the most abundant living vertebrates and can be easily recognized by their feathers, wings and ability to fly. Furthermore, birds also lay eggs, are warm-blooded creatures with four chambered hearts and most closely related to dinosaurs in terms of evolutionary history; many even consider birds the first flying creatures!

Although the exact origins and development of birds is still under debate, most experts agree they first emerged during the Early Cretaceous period as offshoots from lizard-hipped dinosaurs. What separates birds from other vertebrates are their feathers – these enable them to trap air in their wings, helping them fly, maneuver and land more successfully than other vertebrates.

Animal classification can be a complex task, which requires identifying distinct traits and understanding how they have developed over time. That is why studying the anatomy of specimens is so crucial. For instance, most animal embryonic germ layers develop into organs during gastrulation stage of development due to genetic material contained within their embryo. Complex organisms such as humans have three embryonic germ layers known as endoderm, ectoderm, and mesoderm which contribute significantly to organ development during gestation.


Class Amphibians is comprised of cold-blooded vertebrates such as frogs, toads, salamanders, newts, and caecilians (wormlike animals with poor eyes). These cold-blooded creatures spend part of their lives both underwater and terrestrially, giving rise to its name from Greek words amphi- – meaning both and bios – life.

All amphibians reproduce via external egg fertilization and are oviparous, laying eggs which hatch into tiny jellylike larvae that look nothing like the adult animal. Most use vocalizations to attract mates and communicate between individuals; some such as lungless salamander family Plethodontidae and some caecilians have even developed direct development techniques to give birth directly (vivipary).

Amphibians, like reptiles, are ectotherms that must adapt their body temperatures according to environmental temperatures in order to stay alive. Their permeable skin makes them vulnerable to environmental toxins like pollution or elevated temperatures that threaten them.

Amphibians stand out among all animals by spending significant portions of their lives both underwater and terrestrially – thus earning them the name “two-legged fish.” As larvae, sea stars begin their lives equipped with gills for breathing underwater; when they develop into adults, however, they gain the ability to breath both underwater and terrestrially through lungs that enable them to do both simultaneously. Furthermore, sea stars develop four legs but unlike their reptilian cousins they lack scales on them. Like reptiles, amphibians are carnivorous animals that feed off anything they can catch, making them excellent indicators of environmental health. Their distinct diet makes them standouts among their environment’s other inhabitants; many refer to amphibians as “canaries in the coalmine”, since their presence or absence tells us much about a habitat’s condition.


Invertebrates are animals without backbones; this group includes jellyfish, spiders and snails. Although invertebrates often appear simple or nonintelligent to humans, many species possess great intelligence – sponges, flatworms and roundworms are great examples; there are also cnidarians (jellyfish and sea anemones), mollusks, crustaceans and arachnids to add diversity.

Mammals make up another group of animals; these warm-blooded mammals tend to give birth live while eating both plants and meat for sustenance. Mammals come in many shapes and sizes from tiny shrews and bats up to whales as their species can span vast distances.

Reptiles make up roughly half of terrestrial vertebrates and represent another important group of animals, accounting for half the terrestrial vertebrate population. Cold-blooded, they rely on sunlight for fuel, and lay hard-shelled eggs. There are four classes of reptiles: crocodiles/alligators/alligators; turtles/tortoises; snakes; and lizards.

These groups can further be divided into subgroups such as omnivores, herbivores and carnivores. Omnivores consume both plant matter and meat while herbivores only eat plants; carnivores eat only meat while predators hunt other animals for sustenance; finally phagors feed on decaying flesh, some being beneficial such as ants or bees while others such as scorpions or beetles may become pests if allowed too close; further subdiving takes place within each of these three main animal subcategories –