A variety of nutritional adaptations have resulted from natural selection during the evolutionary development of animals. Diets and feeding mechanisms vary extensively among animals Animals usually ingest other organisms. The food organism may be either dead or alive. The food organism may be ingested whole or in pieces. Animals are categorized based on the kinds of food they usually eat and their adaptations for obtaining and processing food items.
Carnivores eat other animals.
Omnivores eat other animals and autotrophs. The varied diets exhibited by animals are accompanied by a variety of mechanisms used to obtain food. Suspension-feeders sift small food particles from the water. Substrate-feeders live on or in their food source and eat their way through the food. Earthworms ingest soil and their digestive systems extract the organic materials.