Looking for NCERT Solutions? Check out here.
Nutrition: Nutrition is a process of understanding nutrients requirements, and taking food.
Animal nutrition: Animals require food for growth, and energy. The process of by which animals takes their food is called animal nutrition.
The following organs are involved in digestion process:
The process of digestion starts from buccal cavity. The process of taking food through mouth is called ingestion.
In mouth, the food is chewed with the help of teeth – which means that the food in break-down into smaller pieces.
At the same time, the food is mixed with the saliva which is secreted by the salivary gland.
*Milk teeth: The teeth grown during the teenage falls off during the age between 6 to 8 years. These are called milk teeth.
*Permanent teeth: The teeth grown after the milk teeth fall of are called permanent teeth. These teeth last for lifetime or fall of during old age.
There are four types of teeth:
1. Incisors are the front teeth that are used for cutting and biting the food.
2. Canine are the tearing teeth, which help us to tear the food.
3. Premolar and molar are the chewing and grinding teeth that helps to break down the food into smaller pieces.
After the process of chewing, the food is passed from the oesophagus or food pipe. Here the food pipe, pushed down by the walls of food pipe.
From the oesophagus the food reaches the stomach. The stomach is a thick bag like structure. Here, the food is broken down into simpler substance with the help of digestive juices.
Note: The stomach secretes mucus, hydrochloric acid and other digestive juices.
*Mucus protects the lining of the stomach.
The undigested food is transfer into small intestine where carbohydrates is broken into simple sugar such as glucose fats into fatty acid and glycerol and proteins into amino acids.
*The bile juice secreted by the liver plays an important role in the breaking down of fats.
*Absorption: The food digested in the small intestine is taken up by the blood vessels, which is called absorption.
*Villi: The finger like outgrown structures on the wall of small intestine is called villi.
Large intestine is wider but smaller than small intestine. It’s function is to absorb water and salt from the undigested food. The remaining material is passed into rectum.
And from there it is removed from the body from time to time. This process is called egestion.
The grass-eating animals such as cow eat up the grass frequently, which gets stored in a sac like structure called rumen.
The grass is partially digested in the rumen called cud.
When the cow sits, it gets the partially digested grass in the mouth back and chew it properly. This process is called rumination.
*Ruminants: The grass-eating animals such as cow and buffalo are called ruminants.
*Cellulose: It is a type of carbohydrate, which is found in the grass. Animals like cow can digest the cellulose but humans and some other animals can’t digest cellulose.
Amoeba is a single cell microscopic animal, which is usually found in water.
Amoeba has a finger like structure called pseudopodia, which helps in taking of food.
The food taken by the pseudopodia is trapped in the food vacuole. The digestive juices are secreted in the food vacuoles, which breaks down the food into simpler substances.
The undigested food is expelled outside the food vacuole.