Vertebrate and arthropod groups

Characteristics and classification of living organisms · Features of organisms · note 2 of 5

Spec 1.3.2, 1.3.3Download all Features of organisms notes (PDF)Download all notes (PDF)8 pages

Vertebrate and arthropod groupsSpec 1.3.2, 1.3.3

The animal kingdom is split into smaller groups. You need the five groups of vertebrates (animals with a backbone) and four groups of arthropods (animals with jointed legs).

Vertebrates

Main features of the vertebrate groups
Group	Main features
Mammals	Body covered with hair or fur; young develop in the mother and are fed on milk from mammary glands; external ears (pinnae)
Birds	Body covered with feathers; two wings and two scaly legs; a beak; lay eggs with hard shells
Reptiles	Dry skin covered with scales; lay eggs with soft, leathery shells; most live on land
Amphibians	Moist, smooth skin without scales; lay jelly-covered eggs in water; larvae (tadpoles) live in water; adults often live on land
Fish	Body covered with wet scales; fins; gills for gas exchange; lay soft eggs in water

Arthropods

All arthropods have a hard exoskeleton, a body made of segments, and jointed legs. They are split into four groups by the number of legs and body parts.

Main features of the arthropod groups
Group	Main features	Example
Myriapods	Long body made of many similar segments; many pairs of legs, one or two pairs on each segment; one pair of antennae	Centipede
Insects	Body in three parts (head, thorax, abdomen); three pairs of legs; one pair of antennae; usually two pairs of wings	Housefly
Arachnids	Body in two parts (cephalothorax and abdomen); four pairs of legs; no antennae and no wings	Spider
Crustaceans	More than four pairs of legs; two pairs of antennae; breathe using gills; most live in water	Crab

Classification chart: the animal kingdom splits into vertebrates (mammals, birds, reptiles, amphibians, fish) and arthropods (myriapods, insects, arachnids, crustaceans), each with an outline drawing and one identifying feature. — The five vertebrate groups and four arthropod groups, with a key feature of each.

Classifying an organism

To classify an organism, first decide its kingdom using the animal and plant features. Then match its features to the group descriptions. An animal with a backbone, feathers and a beak is a bird. An animal with a hard exoskeleton, eight legs and two body parts is an arachnid.

Exam tip:

Do not name a group from one feature alone. Many groups lay eggs, but only birds have feathers and only mammals have fur and mammary glands.