Nutrition In Animals Class 7th Science Lesson 2

 

NOTES PREPARED BY 
ASHAQ HUSSAIN BHAT 
TEACHER SCHOOL 
EDUCATION DEPARTMENT 
JAMMU AND KASHMIR

"NUTRITION IN ANIMALS"

SOME IMPORTANT DEFINITIONS

Digestion Process of breaking down of complex substances of food into simpler form is called digestion.

Digestive system. The digestive tract and associated glands together constitute digestive system.

Ingestion. The process of taking food in the body is called ingestion.

Tooth decay. The process of damaging the tooth by the acids produced by bacteria is called tooth decay.

Absorption. The process of passing digested food into the blood vessels in the wall of small intestine is called absorption.

Assimilation. The process by which absorbed substances are transported to different organs to build complex substances is called assimilation.

Egestion. The process of removal of faecal matter from the body is called egestion.

TEXT BOOK EXERCISES

Q. 1. Fill in the blanks :

(a) The main steps of digestion in humans are........., ............... ,................, ...................  and............. 

(6) The largest gland in human body is............... 

(c) The stomach releases hydrochloric acid and.............. juices which act on food.

(d) The inner wall of small intestine has many finger like outgrowths called................. 

(e) Amoeba digests its food in the.................. 

Answer 

(a) ingestion, digestion, absorption, assimilaton, egestion. 

(b) liver 

(c) digestive 

(d) villi 

(e) food vacuole.

Q. 2. Mark 'T' if the stateme true and 'F' if it is
false.

(a) Digestion of starch starts in the stomach. (T/F)

(6) The tongue helps in mixing food with saliva. (T/F)

(c) The gall bladder temporarily stores bile. (T/F)

(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)

Answer.

(a) Digestion of starch starts in the stomach.(F) 

(6) The tongue helps in mixing food with saliva. (T)

(c) The gall bladder temporarily stores bile. (T)

(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T)

Q. 3. Tick mark (V) the correct answer in each of the following:

(a) Fats are completely digested in the

(i) stomach

(ii) mouth

(iii) small intestine

(iv) large intestine.

(6) Water from the undigested food is absorbed mainly in the:

(i) stomach

(ii) food pipe

(iii) small intestine

(iv) large intestine.

(c) The process of taking food into the body is called :

(i) Digestion X 

(ii) Absorption

(iii) Ingestion

(iv) Assimilation.

(d) Which of the following is the largest gland in human body?

(i) Pancreas

(ii) Liver

(ii) Salivary gland 

(iv) Thyroid.

(e) Finger like projections called villi are present in :

(i) Small intestine 

(ii) Stomach

(iii) Rectum

(iv) Large intestine.

(1) Which of the following is a ruminant :

(i) Amoeba

(ii) Man

(iii) Cow

(iv) Earthworm.

Answer. 

(a) (iii) Small intestine 

(b) (iv) Large intestine

(c) (iii) Ingestion

(d) (ii) Liver

(e) (i) Small intestine

(A) (iii) Cow.

Q. 4. Match the items of Column I with those of

Column II.                           Column I

(Food Components)        (Products of Digestion)

Carbohydrate                  Fatty acids and glycerol

Proteins                            Sugar

Fats                                    Amino acids.

Answer

Column I                                  Column II

(Food Components)            (Products of Digestion)

Carbohydrate                       Sugar

Proteins 2                              Ami no acids

Fats                                     Fatty acids and Glycerol

Q. 5. What are villi ? What is their location and function ?

Ans. The finger like outgrowths present in the inner lining of small intestine are called villi. Villi are present in small intestine. They contain a network of blood vessels near the surface which help in absorption of digested food in them.

Q. 6. Where is the bile produced ? Which component of food does it belp to digest ?

Ans. Bile is produced in liver but is stored in gall bladder. It mixes with food in the small intestine and digests mainly fats.

Q. 7. Name the type of carbohydrates that can be
digested by ruminants but not by humans. Give the reason also.

Ans. Cellulose is digested by ruminants only.

Cellulose is digested by certain bacteria found in rumen, a sac like structure between the small intestine and large intestine of ruminants only. This Sac like structure is called Ruman.

Q. 8. Why do we get instant energy from glucose ?

Ans. Glucose is simple soluble form of  carbohydrate which is easily digested by the body. It assimilates into the blood and release instant energy.

Q. 9. Which part of the digestive canal is involved in :

(i) Absorption of food

(ii) Chewing of food

(iii) Killing of bacteria

(iv) Complete digestion of food

(0) Formation of faeces

Answer. 

(i) Small intestine

(ii) Buccal cavity

(iii) Stomach

(iv) Small intestine

(u) Large intestine.

Q. 10. Write one similarity and one difference between the nutrition in amoeba and human beings.

Ans. Similarity in the nutrition in amoeba and
human beings :

Digestion of food and Release of energy

Difference in nutrition in amoeba and human beings.

 Human beings have a well developed digestive system while amoeba has only food vacuole for digestion.

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

Column I                               Column II

(a) Salivary glands                      (i) Bile juice secretion

(b) Stomach                                  (ii) Storage of undigested food

(c) Liver                                        (iii) Saliva secretion

(d) Rectum                                    (iv) Acid release

(e) Small Intestine                       (v) Digestion is completed

(f) Large Intestine                       (vi) Absorption of water

Answer.

 Column I                           Column II

(a) Salivary glands (iii) Saliva secretion

(6) Stomach                                  (iv) Acid release

(c) Liver                                        (i) Bile juice secretion

(d) Rectum                                   (ii) Storage of undigested food

(e) Small Intestine                      (v) Digestion is completed

(f) Large Intestine                      (vi) Absorption of water

Q. 12. Label Fig. of the digestive system.

Answer.

Q. 13. Can we survive on raw, leafy vegetables/grass ? Discuss.

Ans. Raw, leafy vegetables are source of minerals, cellulose, water and vitamins. But besides these, body need carbohydrates, proteins also. So 'survival on raw, leafy vegetables is not possible.

ADDITIONAL SHORT ANSWER QUESTIONS

Q. 1. How do star fishes take their food ?

Ans. The starfishes open the hand shell of the prey. Then their stomach pops out its mouth to eat the soft animal in the shell. Then stomach goes back into the body to digest the food slowly.

Q. 2. Why do hiccups or choking sensation occur ?

Ans. When food is taken in hurry some food particles may enter the wind pipe, thus causing a choking sensation.

Q. 3. Describe stomach in brief.

Ans. Stomach. It is a thick walled bag. Its shape is like flattened-U. It receives food from food pipe and passed absorbed food into the intestine.

Its lining secrete mucous, hydrochloric acid and digestive juices.

Q. 4. How does pancreatic juice help in digestion ?

Ans. Pancreatic juice acts on carbohydrates and proteins and convert them in simpler forms.

Q. 5. What is function of large intestine ?

Ans. Function of Large Intestine. It absorbs water and some salts from the undigested food material.

Q. 6. Describe structure of Amoeba in brief.

Ans. Amoeba. It has a irregular shape surrounded by cell membrane, a rounded dense nucleus is present in its cytoplasm along with many bubble like vacuoles.

ADDITIONAL LONG ANSWER QUESTIONS

Q. 1. What are functions of food ?

Ans. Functions of food are as under :

(1) It provides energy. All the activities carried out by body require energy. It is provided by oxidation of food substances,

(2) It provides building materials for growth and development

(3) Food helps in repairing damaged parts of cells and tissues.

(4) It helps in keeping the body healthy as it provides resistance to diseases by production of many antibodies, antitoxins etc. and regulating body temperature.

(5) It provides basic components of protoplasm.

Q. 2. (a) What is the main function of the digestion process ? (b) Do cells in our body use the food that we consume in their original form ?

Ans. (a) Digestion. The process of conversion of non- diffusible form of food into the simple and diffusible form by chemical and mechanical processes in the alimentary canal, is called digestion.

Digestion is necessary because :

(1) Large molecules must be broken down into molecules small enough to pass through living membranes.

(2) Insoluble substances must be changed into substances which can be carried in solution around body.

(3) Complex molecules must be converted into molecules simple enough to be used by cells during assimilation.

(b) The assimilation of only digested food takes place in the cells. For example, the proteins consumed as food ara simplified into amino acids. These amino acids are used to synthesize new types of only required proteins in the cells.

Q. 3. Explain digestive glands.

Ans. Digestive glands. A gland that secretes digestive juice which is helpful in the digestion of food is called digestive gland

Digestive glands of Man

(1) Salivary glands. There are three pairs of salivary glands which open into buccal cavity. The salivary glands secrete a digestive juice called saliva which lubricates food and help in partial digestion of starch.

(2) Gastric glands. These are microscopic glands presents in inner wall of stomach. They secrete gastric juice which contain hydrochloric acid, pepsin and prorennin.

(3) Liver is a large, dark-red gland has gall bladder in a groove. Liver secrete bile that is stored in gall bladder.

(4) Pancreas is an elongated creamish gland lying below the stomach. It secretes pancreatic juice from its exocrine part and hormones from its endocrine part.

Q. 4. Explain the process of nutrition in amoeba.

Ans. Amoeba is omnivorous i. e. it feed on smaller animals, plants, micro-organisms and fragments of larger organisms. 

Nutrition is holozoic. Ingestion can occur at any place on the surface since a regular mouth is absent. Ingestion occurs through phagocytosis or engulfing the food particle in an  invagination of the body. The engulfed food particle comes to lie inside a food vacuole. The latter is surrounded by a membrane.

The food vacuoles circulate in the endoplasm by the streaming movements of the latter. The enzymes bring about digestion or conversion of non-diffusible part of food into  diffusible state inside the food vacuole. The disfusible substances are absorbed and utilised for synthesis of more protoplasm, reserve food and respiratory substrate. The undigested materials remain in the vacuoles. The latter decrease in size, become heavy and sink. After coming in contact with the cell membrane, the food vacuoles burst to eliminate the undigested matter. The process is called egestion.

Q. 5. Describe the digestive system of man.

Ans. The digestive system of man includes the following organs.

(1) Mouth: The mouth is first part of food pipe. It contains tongue, teeth and salivary glands. The tongue tastes the food. The salivary glands secrete saliva which lubricates the food. The teeth break the solid food into smaller fragments.

(2) Oesophagus : It is a tubular structure from mouth to stomach. It takes the food from mouth to stomach. 

(3) Small intestine : It is a coiled tube and is the longest part of food pipe. The digestion of food is completed here with the help of enzymes present in the secretions of liver and pancreas

(4) Large intestine: It absorbs the water. The undigested food or faecal matter is stored temporarily and finally removed from the body through anus.

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