Look up an image:
Explore by theme
evolution of life The history of the Earth is divided into geological eras characterized by the formation of minerals and the appearance of animal and plant species, and humans.
insects and arachnids Highly diversified grouping of all animal invertebrates, (over 1 million species of insects and 50,000 species of arachnids); they are more numerous than all other animal or plant species.
mollusks Land and aquatic invertebrates (more than 100,000 species) with soft nonsegmented bodies; they usually secrete a calcareous shell.
crustaceans Usually aquatic invertebrates (over 40,000 species) whose segmented bodies have articulated appendages and often carapaces.
fishes Cold-blooded aquatic vertebrates (about 30,000 species) having motor fins and bodies that are usually covered in scales.
amphibians Four-limbed vertebrates with soft smooth moist skin, usually found in water in the larval stage and on land in the adult stage.
reptiles Cold-blooded vertebrates covered with scales (about 6,000 species) found mainly in warm countries; their four limbs are sometimes atrophied or absent.
birds Vertebrates (about 9,000 species) with feather-covered bodies, a bill, two legs and two wings that are usually adapted for flight.
insectivorous mammals Vertebrates (about 370 species) with four limbs and a body almost entirely covered with hairs and sometimes barbs; they feed on insects.
rodents and lagomorphs Rodents have one pair of constantly growing sharp incisors used for feeding; lagomorphs have two pairs.
ungulate mammals Herbivorous vertebrates covered with hair, having four limbs bearing a varying number of digits ending in a corneous sheath (nail or hoof).
carnivorous mammals Vertebrates with four limbs, covered with hair and having carnassial teeth to tear meat apart; they feed mainly on the flesh of animals.
marine mammals Carnivorous aquatic vertebrates (about 116 species) with limbs evolved into fins, skin that is smooth or covered in short hairs, and sometimes a dorsal fin.
primate mammals Vertebrates (about 200 species) with prehensile hands and feet, with five digits ending in a nail; they live mainly in trees and can stand erect.
flying mammal Vertebrate covered with hair, with forelimbs converted into wings by means of a membrane connecting the fingers, allowing it to fly.
marsupial mammals Four-legged vertebrates covered with hair; the female usually has a ventral pouch in which the embryo develops after birth.