NCERT Class 7th Science Nutrition in Animals, NCERT Free solution, Nutirion in Animals, solution of NCERT 7th class, UPSC, CTET CTET TGT, CTET Paper-II, Science content

Chapter 2

Nutrition in Animals

Animals obtain their food from plants, either directly by eating plants or indirectly by eating animals that eat plants. Some animals eat both plants and animals 

Digestion
Animals take food and that have carbohydrate, proteins, fats, and other nutrients and these complex compound are going to be breakdown into smaller compounds and this is called digestion.

Different organisms take food by different mean like Humming bird takes food by sucking nectar from the flower, snake swallow the whole organism, baby take milk by sucking, some aquatic animals take food by filtering small particles through their gills and some eat flesh.

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Different Animals and Their Mode of Nutrition

Digestive System

The main purpose of the digestive system to breakdown the complex particles into simpler compounds for example, proteins break down into amino acids, carbohydrates into glucose, and fat into fatty acids.


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Digestive System

Teeth
The functions of the teeth are to breakdown the food into smaller chunks so that they can be easily digested by the digestive system. We have different types of teeth for different types of work like cutting, tearing, piercing and biting and for grinding and chewing the food. Each tooth is rooted in a separate socket in gums. 
  • The damaging of teeth is caused by the acid and called as tooth decay. Tooth Decay is caused by sweet food, carbonated drinks, chocolates, etc that's why brushing the teeth two times is good for our oral health.
  • We have two types of teeth milk teeth in childhood which replaced by permanent teeth.
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Teeth and Tooth Root

Salivary Glands
Exocrine glands, which secrete saliva that helps to digest starch and breaks down into smaller sugars.
The tongue is the strongest muscle in the body and helps in the mixing of the food, cleans the teeth, swallowing of the food and also help to detect the taste with the help of the presence of taste buds and these are of 4 following types:
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Salivary Glands

Food Pipe or Oesophagus
Stomach is a thick-walled bag, the shape of the stomach is like a flattened U and is the widest part of the alimentary canal.
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  • The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices which helps in the digestion of the food. The mucous protects the lining of the stomach.
  • The acid in the stomach kills many bacteria that enter along with the food and makes the medium in the stomach acid. The digestive juices break down the proteins into simpler substances.
Small Intestines (Duodenum)
 It is about 7.5 meters long and receives secretions from the pancreas and liver. Small intestines have three parts:

  1. Duodenum
  2. Jejunum
  3. Ileum

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Esophagus and Small Intestine

Liver
  • The liver is a reddish-brown organ situated in the upper part of the abdomen at the right side.
  • The liver is the largest gland in the body situated right side of the abdomen.
  • Gall bladder stores bile juice and secretes in the duodenum, fat is digested with the help of bile.
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Liver

Pancreas
  • Pancreas is the cream-colored organ, located just below the stomach.
  • Pancreatic juice help to digest carbohydrate and proteins and breaks down into smaller compounds.

Now the food reaches the lower part of the small intestine and intestinal juices complete the digestion of carbohydrates, fat and protein.  

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Pancreas

Absorption in the small intestine
  • Absorption is the process when the digested food passes into the blood vessels in the wall of the intestine.
  •  Inner walls of the small intestine have thousands of finger-like projections called villi. The villi increase the surface area for absorption of the digested food.
  • The surface of the villi absorbs the digested food materials and digested food transported to the needed organs via blood vessels. This process is called Assimilation.
  • In the cells, glucose breaks down with the help of oxygen into carbon dioxide and water, and energy is released.
  • Undigested and unabsorbed food enters into the large intestine.
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Microvilli in the small intestine

Large intestine
  • It is wider and shorter than small intestine.
  • It is about 1.5 meters in length and its function is to absorb water and some salts from the undigested food material.
  • The remaining waste passes into the rectum and remains there as semi-solid feces. The fecal matter is removed through the anus from time-to-time. This is called as egestion.
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Large Intestine

Digestion in Grass eating Animals
As we observed cows, buffaloes and other grass-eating animals chewing continuously even when they are not eating grass? They quickly swallow the grass and store it in a separate part of the stomach called Rumen. The partially digested food here is called as Cud.  
And later this cud returns to the mouth of these animals in forms of small lumps this process is called as Rumination that’s why these animals are called Ruminants.
The grass is rich in Cellulose, the cellulose of the food is digested in rumen by the action of certain bacteria that are absent in humans.

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Ruminants (Source: NCERT)

Digestion in organism which do not have a mouth or digestive system

Feeding and Digestion in amoeba

  • Amoeba is a microscopic single-celled organism normally found in pond water.
  • It has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm.
  • Amoeba can change its shape and position. It has one or more finger-like projections, called pseudopodia or false feet for movement and capture of food.
  • Food is ingested with the help of pseudopodia movement Digestive juices are secreted into the food vacuole and help in digestion.
  • Digested food is absorbed and undigested food is expelled from body process called as egestion.

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Amoeba (Source: NCERT)

Exercise

1. Fill in the blanks:
(a) The main steps of digestion in humans are Ingestion, Digestion,
Absorption, Assimilation and Egestion.
(b) The largest gland in the human body is the Liver.
(c) The stomach releases hydrochloric acid and Gastric/digestive juices which act on the food.
(d) The inner wall of the small intestine has many finger-like outgrowths called villi.
(e) Amoeba digests its food in the food vacuole.

2. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) The digestion of starch starts in the stomach. (False)
(b) The tongue helps in mixing food with saliva. (True)
(c) The gall bladder temporarily stores bile. (True)
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (True)

3. Tick () mark the correct answer in each of the following:
(a) Fat is completely digested in the
(i) Stomach (ii) mouth (iii) small intestine (iv) large intestine
Answer: Small Intestine

(b) Water from the undigested food is absorbed mainly in the
(i) Stomach (ii) food pipe (iii) small intestine (iv) large intestine
Answer: Large intestine

4. Match the items of Column I with those given in Column II:
Column I
Column II
Food Components
Product(s) of digestion
Carbohydrates
Sugar
Proteins
Amino acids
Fats
Fatty acids and glycerol

5. What are villi? What are their location and function?
Answer: Villi are the finger-like outgrowth or projection present in the intestine and increase the surface area so the food can digest easily and completely.

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6. Where is the bile produced? Which component of the food does it digest?
Answer: Bile is produced in the liver and it helps in the digestion of the fat in the small intestine.

7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer: Animals can digest the cellulose because they have cellulase enzymes for the digestion of the cellulose and humans do not have enzymes for the digestion of the cellulose.

8. Why do we get instant energy from glucose?
Answer: Glucose is the simplest sugar and easily absorbed by the blood, other food items require breakdown into other sugars then they have to be converted into glucose.

9. Which part of the digestive canal is involved in?
(i) Absorption of food Small Intestine.
(ii) Chewing of food buccal cavity.
(iii) The killing of bacteria Stomach.
(iv) Complete digestion of food Small Intestine.
(v) Formation of faeces Large Intestine.

10. Write one similarity and one difference between nutrition in amoeba and human beings.
Answer:
Similarities: Both human and amoeba takes food for the energy and to do work.
Difference: Amoeba take food through pseudopodia and humans take food through the buccal cavity.

11. Match the items of Column I with suitable items in Column II

Column I
Column II
Salivary gland
Saliva secretion
Stomach
Acid release
Liver
Bile juice secretion
Rectum
Storage of undigested food
Small intestine
Digestion is completed
Large intestine
Absorption of water





Keywords: Absorption, Amino acid, Amoeba, Assimilation, Bile, Buccal cavity, Canine, Cellulose, Digestion, Egestion, Fatty acid, Food vacuole, Gall bladder, Glycerol, Incisor, Ingestion, Liver, Milk teeth, Molar, Permanent teeth, Oesophagus, Pancreas, Premolar, Pseudopodia, Rumen, Ruminant, Rumination, Salivary glands, Villi, Saliva, CTET Paper-II, CTET TGT, CTET, KVS.


Pic Sources: Pixabay, NCERT, Recreation work done by Anil Kashyap

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