Long summary of chapter - Nutrition us animals
class - 7
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Explanation:
Nutrition in Animals
All animals require food for obtaining energy, growth, repair of damaged parts and functioning of the body. The process of taking food by an animal and its utilisation in the body is called animal nutrition.
Plants can prepare their own food by the process of photosynthesis but animals get their food from plants, either directly by eating plants or indirectly by eating other animals that eat plants. Some animals eat both plants and other animals.
Animal nutrition includes nutrient requirements mode of intake of food and its utilisation in the body.
The components of food such as carbohydrates are complex substances which cannot be utilised by the body. So, they are broken down into simpler substances. The process of breakdown of complex components of food into simpler substances is called digestion. There are two methods of digesting food, i.e. physical method (including chewing and grinding of food in mouth) and chemical method (addition of digestive juices to the food by the body itself).
Different Ways of Taking Food
Different types of animals show different modes of nutrition. Some animals filter tiny food particles and feed upon them, while some swollen the animals they prey upon. The mode of nutrition in different animals depends upon the special structure or organ for taking food inside the body.
Various modes of feeding in different Animals
Name of the animalKinds of foodModes of feedingSnailAlgaeScraping from rocksAntPlant material and other animalsBiting and chewingEagleFlesh of preyTearingHumming BirdNectar from flowerSuckingLiceBlood from the skin of scalpSuckingMosquitoBlood from animalsSuckingButterflyNectar from flowerSyphoningHouseflyFilth and refusesSuckingAmoebaTiny aquatic animalsCapturing and SwallowingSnake (Python)Animal as a wholeSwallowing
Starfish
It is a marine animal which is covered by hard shells of calcium carbonate. It has a unique mode of nutrition. It opens the shell of its prey and pops out its stomach through its mouth surrounding the soft body of its prey. The starfish after capturing its prey brings bach its stomach inside its own body. This food is then digested slowly by starfish.
Digestion in Humans
The food components pass through a continuous canal and get digested in each compartment. This is called an alimentary canal, it is ‘the tract or canal running from mouth to anus of human being where digestion and absorption of food take place.’
The alimentary canal can be divided into various compartments:
The buccal cavity
Food pipe or oesophagus
Stomach
Small intestine
Large intestine ending in the rectum
The anus
The main digestive glands which secrete digestive juices are
salivary gland
liver
pancreas
Various processes involved in utilisation of food in humans are
The process of taking food into the body is called ingestion.
The process by which the food containing large insoluble substances is broken down into small water-soluble substances is called digestion. There are two methods of digesting food, i.e. physical method (including chewing and grinding of food in mouth) and chemical method (addition of digestive juices to the food by the body itself).
The process by which the digested food passes through the intestinal wall into the bloodstream is called absorption.
The process by which the absorbed food is taken in body cells and used for energy, growth and repair is called assimilation.
The process by which the undigested food is removed from the body is called egestion.
Carbohydrates, fats and proteins are large insoluble substances which cannot pass through the walls of our intestine and get absorbed in that form. Therefore, these substances are broken down into small water-soluble substances. This is done by the process of digestion.
The carbohydrates get broken down into simple sugar called glucose, while fats in fatty acid and glycerol and proteins get broken down into amino acids during digestion. These simpler compounds are easily absorbed by the walls of small intestine into the blood.
Human Digestive System
The system that consists of the digestive tract along with glands is called the digestive system. Now, let us know what happens to the food in different parts of the digestive tract.
1. Mouth and Buccal Cavity
The process of ingestion starts from the mouth or buccal cavity. As we ingest, food the salivary glands present in the mouth start its digestion. The teeth present in the buccal cavity cut the food into small pieces by chewing and grinding it. Salivary glands secrete a watery liquid, saliva. This saliva contains digestive enzymes which help in partial digestion of food (starch). The tongue helps in mixing saliva with food. This partially digested food is swallowed by the tongue and passed down to oesophagus or food pipe.

Teeth
The food is cut by the teeth inside the mouth. Teeth mechanically break the food into small pieces. These teeth vary in appearance. Each tooth is rooted in a separate socket in the gums.