Holozoic nutrition is a type of nutrition in which animals obtain their food by ingesting other organisms or their parts. This type of nutrition is characteristic of heterotrophic animals, which are unable to produce their own food through photosynthesis like plants. Instead, they rely on consuming other organisms to obtain the necessary nutrients for their survival.

Holozoic nutrition involves the following processes:

1. Ingestion: Animals with holozoic nutrition are capable of ingesting their food. They have specialized structures such as mouths, beaks, or proboscises that allow them to capture and consume their prey or plant material. Ingestion can occur through various methods, such as biting, sucking, or filter feeding.

2. Digestion: Once the food is ingested, it undergoes digestion. Digestion involves the breakdown of complex food molecules into smaller, simpler forms that can be absorbed and utilized by the animal's body. This process is facilitated by enzymes that are secreted by the animal's digestive system.

3. Absorption: After digestion, the nutrients are absorbed into the animal's body through the walls of the digestive tract. The absorbed nutrients are then transported to the cells where they are used for various metabolic processes.

4. Assimilation: Assimilation refers to the incorporation of the absorbed nutrients into the animal's cells and tissues. The nutrients are utilized for energy production, growth, repair, and maintenance of the animal's body.

Why are nutrition in animals holozoic?

The correct answer is option D, which states that nutrition in animals is holozoic because they depend on plants for food, they are heterotrophs, and they can swallow food. Let's break down each part of the answer:

a) Animals depend on plants for food: Many animals feed directly on plants or consume other animals that have consumed plants. Plants are the primary producers in most ecosystems and convert sunlight energy into organic compounds through photosynthesis. Animals obtain these organic compounds by consuming plants or plant-eating animals.

b) Animals are heterotrophs: Heterotrophs are organisms that cannot produce their own food and rely on consuming other organisms for nutrition. Animals are heterotrophs because they lack the ability to synthesize organic compounds from inorganic sources.

c) Animals can swallow food: Swallowing is a characteristic feature of animals with holozoic nutrition. They have specialized structures such as mouths and digestive systems that allow them to ingest and process food. Swallowing enables efficient intake and digestion of food.

In conclusion, animals have holozoic nutrition because they depend on plants for food, they are heterotrophs, and they have the ability to swallow food. These characteristics enable animals to obtain the necessary nutrients for their survival and growth.