We take food from the environment by ingesting them.Complete answer:
Ingestion is the consumption of a substance from the environment by an organism. In animals, it normally is done by taking in a substance using the mouth and then into the GI (gastrointestinal) tract. It is done through eating or drinking. In some prokaryotes or single-celled organisms, ingestion occurs by absorbing a substance through their cell membranes.
Ingestion is important because by this process nutritional items are taken into the body. The substances nourish the body and upon breakdown of the food, energy is produced.
Besides nutritional items, some other substances may also be ingested: these include medication (oral administration), drugs, and substances considered inedible, such as foreign bodies or pathogens. Ingestion is a common route taken by pathogenic organisms to enter the body. So, the oral area is protected by one of the immunological barriers- mucous barriers. Mucous in the mouth contains some immunoglobulin which protects the oral region.
There are few parts/organs which help in the ingestion process: tongue is a muscle which pushes the ingested food towards teeth. Teeth mechanically process it and shape the food into smaller rounded pieces to be swallowed. In humans and some other animals, ptyalin from the salivary glands is secreted immediately after ingestion. It helps digesting carbohydrates and in further processing of the food.So, the correct answer is A. ingestion.Note:
After ingestion, the next step is digestion of the ingested items. Digested food particles are assimilated in our system to provide the required nutrition.