Animal

Animal (Latin: Animalia) is a kingdom within the major groups of living organisms. Animals are multicellular organisms whose cells lack a rigid cell wall, unlike plants. Animals cannot produce food from sunlight; they depend on consuming food from outside their bodies and break it down internally.

Most animals have muscles and nerve cells, which enable movement and response to environmental stimuli. Some lack these structures, such as sponges. Reproduction in most species involves the fusion of male and female gametes, although some reproduce asexually.

Major divisions

Animals are classified by divisions called phyla. The most familiar include Chordata (organisms with backbones and related forms), Arthropoda (insects, arachnids, and marine creatures such as crustaceans), Mollusca (snails and related forms), Annelida (segmented worms), and Cnidaria (jellyfish and corals). Arthropoda contains the largest number of species.

Vertebrates are divided into: fish, amphibians (such as frogs), reptiles, birds, and mammals. Humans are a type of mammal, and thus are classified as animals within the biological classification system.

Habitat and way of life

Animals live in oceans, freshwater, on land, and in the air. Their natural habitats serve different roles: some eat plants (herbivores), some eat meat (carnivores), some eat both, and some live on decaying matter or parasitically on other organisms. They therefore participate in nutrient cycles and are part of food chains.

Relationship with humans

Humans use animals for food, clothing, labor, and transportation. Livestock—such as camels, cattle, sheep, and goats—form the basis of the economy in much of Somalia. There are also animals kept as household pets. On the other hand, habitat loss, overexploitation, and climate change threaten many species with extinction.