Question

What do animals eat?

Answer 1

Hint: There are two main types of mode of nutrition, Autotrophic and Heterotrophic nutrition. In Autotrophic nutrition, the organism has to synthesize its own food whereas in a heterotrophic nutrition, the organism utilizes or gains its food from the food synthesized by the autotrophs.

Complete answer:
The Kingdom Animalia is characterized by heterotrophic eukaryotic organisms that are multicellular and their cells lack cell walls.
All animals are heterotrophs. They directly or indirectly depend on plants for food because plants are autotrophic organisms. As we know animals can be herbivores, carnivores or omnivores on the basis of their nutritional requirements. Those animals which are herbivores depend directly on plants as they eat only plant products like fruits, vegetables, cereals, pulses, etc. Whereas the animals which are carnivorous or omnivores eat other animals which obtained their nutrition from either plants or other animals.. For example, Lions eat deers and deers eat grass. Hence, lions indirectly depend on grass.. Here, lions are carnivores and deers are herbivores. Hence, all animals are dependent on plants for food and cannot survive without them.
Nutrition involving engulfment of the whole or part of a plant or an animal either solid or in liquid state is called as animal –like or holozoic nutrition. Holozoic mode of nutrition involves ingestion, digestion, absorption, and assimilation to properly utilize the food. This food ‘taken in’ then is stored in the body in the form of food reserves. Glycogen and fat are the common food reserves in the body of animals.
The digestive system of animals can be of two types on the basis of complexity:
Incomplete digestive system- When the digestive system has only a single opening to the outside of the body that serves as both mouth and anus, it is called an incomplete digestive system. Coelenterates, Ctenophores and Platyhelminthes possess incomplete digestive systems.
Complete digestive system- When the digestive system has two openings; mouth and anus, it is called complete digestive system. Hence the entry of food and exit of waste takes place from separate openings. Aschelminthes to chordates, all possess a complete digestive system.

Note:
The sum total of all the chemical reactions occurring in the body of living organisms is known as metabolism. The metabolic processes which involve the synthesis of molecules are called anabolism, e.g., synthesis of proteins from amino acids. The metabolic processes in which large molecules are broken down into smaller ones are known as catabolism, e.g., sugars broken down into molecules of water, carbon dioxide, to liberate energy.