Scientific method of grouping animals based on similarities, differences, and evolutionary relationships to study the vast animal diversity systematically.
Animal classification is the scientific method of grouping animals based on similarities and differences in body structure, habits, and habitats. It helps in easy study, identification, and understanding of evolutionary relationships among the vast diversity of animals.
| Basis | Description | Examples/Categories |
|---|---|---|
| Level of organization | How cells are organized in the body | Cellular, tissue, organ, organ system |
| Body symmetry | Arrangement of body parts around a central axis | Asymmetrical, radial, bilateral |
| Type of body cavity | Presence and type of coelom (body cavity) | Acoelomate, pseudocoelomate, coelomate |
| Segmentation | Division of body into repeated segments | Non-segmented, segmented (metamerism) |
| Presence of notochord | Rod-like supporting structure | Non-chordates, chordates |
| Germ layers | Number of embryonic cell layers | Diploblastic, triploblastic |
| Digestive system | Type of digestive tract | Incomplete, complete |
Animal Kingdom
↓
Non-chordates (Without notochord) | Chordates (With notochord)
↓
Vertebrates (With backbone) | Invertebrates (Without backbone)
Animals are broadly divided into two major groups based on the presence or absence of a notochord:
Non-chordates are animals without a notochord at any stage of life. They constitute about 95% of animal species and are mostly invertebrates.
The simplest multicellular animals with porous bodies.
Radially symmetrical animals with stinging cells.
Flatworms with dorsoventrally flattened bodies.
Roundworms with cylindrical bodies.
Segmented worms with true coelom.
The largest animal phylum with jointed appendages.
Soft-bodied animals often with hard shells.
Spiny-skinned marine animals with radial symmetry.
Chordates are animals that possess a notochord at some stage of their life cycle. They are characterized by three main features at some point in development.
Vertebrates are chordates that have a vertebral column (backbone) replacing the notochord in adults. They are the most advanced group of animals.
Aquatic vertebrates with gills and fins.
Animals that live both on land and in water.
Cold-blooded vertebrates with dry, scaly skin.
Warm-blooded vertebrates with feathers and wings.
Warm-blooded vertebrates with mammary glands.