Nutrition in animals depends upon the feeding habits of the animals. The process of taking in food is called ingestion. The method of ingestion is different in different animals. For example-Bees and hummingbirds suck nectar from plants, python swallows its prey and cattle feed on grass.
Different feeding habits of animals are the result of evolution. Among the terrestrial animals, the earliest forms were large amphibians that ate fish. While amphibians like frogs fed on small fish and insects, the reptiles began feeding on other animals and plants.
The specialization of organisms towards specific food sources and of course specific ways of eating is one of the major causes of the evolution form and function. For example, the differences in the parts of mouth and shape of the teeth in whales, mosquitos, tigers and sharks or distinct forms of beaks in birds, such as in hawks, woodpeckers, pelicans, hummingbirds, and parrots are the results of adaptation to different types of eating by these animals.
Animals can be divided into the following groups depending upon their food habits:
Herbivores: Herbivores are animals that depend upon plants and fruits for their nutrition. Cows, goats, sheep, buffaloes, etc. are herbivores.
Carnivores: Carnivores are animals that depend upon other animals for food. Lion, tigers, wolfs are some examples of carnivores.
Omnivores: These include organisms that eat both plants and animals. Humans, bear, dogs, crow are omnivores.
 
Source: https://byjus.com/biology/nutrition-animals/