CBSE Class 7 Science Chapter 2 Notes Nutrition in Animals
Nutrition in Animals Class 7 Notes Understanding the Lesson
1. All organisms including humans require food for growth, repair and functioning of the body.
2. Animal nutrition includes:
- nutrient requirement,
- mode of intake of food and,
- its utilisation in the body.
3. Different organisms have different ways of taking food. For example, snakes swallow their prey, bees and hummingbirds suck nectar from the flowers, etc.
4. The human digestive system consists of the alimentary canal and secretory glands. The canal can be divided into various compartments
- the buccal cavity,
- food pipe or oesophagus,
- stomach,
- small intestine,
- large intestine ending in the rectum and
- the anus.
5. These parts together from the digestive tract.
6. The digestive tract and the associated glands (like salivary gland, liver, pancreas) together constitute the digestive system.
7. Nutrition is a complex process involving
- ingestion,
- digestion,
- absorption,
- assimilation and
- egestion.
The process of taking food into the body is called
8. Digestion is the breakdown of complex components of food into simpler substances.
9. Digestion of food begins in the buccal cavity. Carbohydrate, like starch is digested in buccal cavity. Digestion of protein starts in the stomach.
10. The bile secreted from the liver, pancreatic juice from the pancreas and digestive juice from intestinal wall of small intestine complete the digestion of all components of food in the small intestine.
11. The digested food now passes into the blood vessels in the wall of the intestine. This process is called absorption.
12. The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This is called
13. The removal of faecal matter through the anus time to time is called
14. Grass-eating animals quickly swallow grass which gets stored in the This partially digested food is called cud. This later returns to the mouth of animals in small lumps, and they chew it. This is called rumination and these animals are known as ruminants.
15. Amoeba ingests its food with the help of finger-like projections, called The food is digested in the food vacuole.
Class 7 Science Chapter 2 Notes Important Terms
Absorption: The passage of the digested food into the blood vessels in the wall of intestine is called absorption.
Amino acid: It is the basic building block of proteins.
Amoeba: It is a single-celled microscopic organism found in pond water.
Assimilation: It is the process in which the absorbed food is used for producing complex substances required by the body.
Bile: Bile juice is a kind of juice secreted by the liver.
Buccal cavity: The cavity of mouth, with all its internal parts like cheeks, teeth, tongue and salivary glands, is called buccal cavity.
Canines: These are two teeth one on each side of the incisors, which help in tearing the food materials.
Cellulose: It is a type of carbohydrate which is present chiefly in all plant tissues and fibres.
Digestion: The breakdown of complex components of food into simpler substances is called digestion.
Egestion: The removal of faeces through the anus from time to time is called egestion.
Fatty acid: It is an organic compound consisting of a long hydrocarbon chain and a terminal carboxylic acid.
Food vacuole: A membrane-bound vacuole (as in an Amoeba) in which ingested food is digested.
Gall bladder: It is a pear-shaped sac, which stores bile juice, and is attached to the undersurface of the right lobe of liver.
Glycerol: It is a colourless, sweet-tasting, viscous liquid, formed as a byproduct when fat is broken down.
Incisors: The front four teeth in each jaw adopted for cutting are called incisors.
Ingestion: The process of intake of food inside the mouth cavity is called ingestion.
Liver: It is a reddish-brown gland located on the upper right side of the abdomen. It secretes bile juice which helps in the digestion of fat.
Milk teeth: The first set of twenty teeth that appears by the age of two is called the set of milk teeth.
Molar: There are six teeth, three on each side of the jaw and just behind the premolars which help in grinding the food materials.
Permanent teeth: Milk teeth are replaced by a set of new teeth, which are thirty two in number, and are called permanent teeth.
Oesophagus: Oesophagus, or food pipe, is a tube-like structure that connect the mouth to the stomach.
Pancreas: It is a large cream-coloured gland located just below the stomach.
Premolar: There are four teeth, two on each side of the jaw which help in crushing the chewed food.
Pseudopodia: One or more finger-like projections in Amoeba which help in movement and ingestion of food is called pseudopodia.
Rumen: Rumen is the first stomach in grass-eating animals, which receives food or cud from the oesophagus immediately after being swallowed.
Ruminant: Animal, that digest food by the process of rumination is called a ruminant.
Rumination: A process by which partially digested food by ruminants returns to their mouth and are again chewed properly, is called rumination.
Salivary glands: Salivary glands are a pair of small and branched structures situated in the mouth cavity. They secrete saliva.
Villi: The inner walls of the small intestine have thousands of finger-like outgrowths called villi.
Saliva: It is a secretion from salivary gland which contains starch splitting enzyme, amylase, for breaking starch into sugar.