Some basics about animals. The vast majority of animals have specialized tissues, and all animals are eukaryotic, multicellular organisms. The majority of animals are mobile, at least at some points in their lives. Animals need nourishment in order to thrive and grow.

Every animal is heterotrophic, meaning they consume both live and dead organic stuff. They differ from autotrophic creatures like most plants, which produce their own nutrition through photosynthesis, and from fungi, which externally digest their food, in that they receive energy in this manner. Animals can be parasitic, herbivorous, carnivorous, or omnivorous. majority of animals sexually reproduce: In contrast to plants, for example, where the precise structure of the body is deterministic, the progeny go through a series of developmental stages that establish a specified body plan.

The sea is where animals first began to evolve. Around 510 to 471 million years ago, during the Late Cambrian or Early Ordovician, lineages of arthropods first colonized the land at the same time as terrestrial plants.

Creatures live in almost every habitat on the planet, including the air, saline water, fresh water, hot springs, swamps, forests, meadows, and deserts. They also live inside of other animals, plants, fungus, and rocks.

The human population engages in extensive animal exploitation for food, primarily at sea through hunting wild species as well as tamed cattle species in animal husbandry. Many different species of marine fish are commercially fished for food. Commercial species farming is limited to a few. More than 90% of the biomass of all terrestrial vertebrates is made up by people and the animals they keep, which is almost as much as all the insects put together.