Thursday 16 June 2011

Nutrition in Animals : Lesson 2 - NCERT Class VII Science Exercises Solutions

Exercises -  Questions and Answers : 

1. Question : 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 liver.
(c) The stomach releases hydrochloric acid and digestive juices which act on 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. Question : Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) Digestion of starch starts in the stomach. (F)
(b) The tongue helps in mixing food with saliva. (T)
(c) The gall bladder temporarily stores bile. (F)
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T)

3. Question : 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 : (iii) 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 : (iv) large intestine

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

Answer : Matched Items Column wise:-

Column I
Food components
  1. Carbohydrates 
  2. Proteins
  3. Fats
Column II
Product(s) of digestion
  1. Sugar
  2. Amino acids 
  3. Fatty acids and glycerol 
 5.Question : What are villi? What is their location and function?
Answer : Villi are finger-like outgrowths present on the inner walls of the small intestine. They number in thousands. The main functions of villi is to speed up the absorption of the digested food in small intestine by increased surface area for absorption of the digested food.  Each villus (singular of Villi) has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials. 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.
6.Question : Where is the bile produced? Which component of the food does it digest?
Answer : The bile is produced in liver. The liver is a reddish brown gland situated in the upper part of the abdomen on the right side. It is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder .The bile plays an important role in the digestion of fats.
8.Question : Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer : Cellulose,  a  type of carbohydrate which is present in grass can be digested by ruminants but not by humans. Ruminants have a large sac-like structure between the small intestine and large intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
9. Question : Why do we get instant energy from glucose?
Answer : As we know during digestion, carbohydrates which are  complex substances can not be used as such  by body for its energy requirement. They are further broken down into simpler substances such as Glucose, which takes time. Glucose is the end product  and simplest form of carbohydrate, which is readily consumed by blood cells. Blood cells converts this glucose into Energy, Water and carbon dioxide using oxygen from respiration process. Energy so produced is utilized by the body for brain and various other   functions. Therefor direct availability of glucose gives us instant energy  as it surpasses the other time consuming processes involved in digestion of food  and its conversion into usable components.
. 10.Question : Which part of the digestive canal is involved in: (i) absorption of food --small intestine. (ii) chewing of food -- mouth . (iii) killing of bacteria --stomach (iv) complete digestion of food --small intestine. (v) formation of faeces-- large intestine.11. Question : Write one similarity and one difference between the nutrition in amoeba and human beings.
Similarity: For Nutrition requirement, Amoeba  traps food article in a food vacuole. Here digestive juices are secreted into the food vacuole. They act on the food and break it down into simpler substances. Gradually the digested food is absorbed. Similarly, In human being, the inner linings of stomach and the small intestine also secrete the digestive juices. The digestive juices convert complex substances of food to simpler ones. 
Difference: Amoeba feeds on some microscopic organisms. When it senses food, it pushes out finger-like projections, called pseudopodia or false feet around the food particle. The food is trapped in a food vacuole. Where as Human beings consumes different forms of  food through the mouth using real fingers and utilize it for his nutrition and energy requirement through the process of digestion at different level.
12. Question : Match the items of Column I with suitable items in Column II 
Column I
(a) Salivary gland
(b) Stomach 
(c) Liver 
(d) Rectum
(e) small intestine
(f ) Large intestine
Column II
(i) Bile juice secretion
(ii) Storage of undigested food
(iii) Saliva secretion
(iv) Acid release
(v) Digestion is completed
(vi) Absorption of water

Answer : The matched items from Column I and Column II are as given below : -

Column I
(a) Salivary gland
(b) Stomach 
(c) Liver 
(d) Rectum
(e) small intestine
(f ) Large intestine
Column II
(iii) Saliva secretion 
(iv) Acid release
(i) Bile juice secretion
(ii) Storage of undigested food
(v) Digestion is completed
(vi) Absorption of water
13. Question : Label Fig. 2.11 of the digestive system.
Human Digestive System

14. Question : Can we survive only on raw, leafy vegetables/grass? Discuss.
Answer : We know that human being , including all animals, fungi, many bacteria, non-green plants do not possess the ability to synthesize their own food like autotrophs. Hence for food supply ,  they depend upon autotrophs like green plants  either directly or indirectly. The green plants (leafy vegetables / grass) trap solar energy and manufacture their food in the form of glucose. As glucose is the most useful, readily consumable product for energy requirement by human being, therefor  we can  survive only on raw, leafy vegetables/grass. 

 Extended Learning — Activities and Project  
1. Visit a doctor and find out:
(i) Under what conditions does a patient need to be on a drip of glucose?
(ii) Till when does a patient need to be given glucose?
(iii) How does glucose help the patient recover?
Write the answers in your notebook.

2. Find out what vitamins are and get the following information.
(i) Why are vitamins necessary in the diet?
(ii) Which fruits or vegetables should be eaten regularly to get vitamins? Write a one-page note on the information collected by you. You may take help of a doctor, a dietitian, your teacher or any other person, or from any other source.  
3. Collect data from your friends, neighbors and classmates to know more about “milk teeth”. Tabulate your data. One way of doing it is given below:
S. No.Age at which first tooth fellAge at which last tooth fellNo. of teeth lostNo. of teeth replaced
1. - - --
2.- - --
3. - - --
4. - - --
5. - - --
Find out from at least twenty children and find the average age at which children lose the milk teeth. You may take help of your friends.

You can read more on the following website:
Did you know? That fats in goat’s milk are much simpler than those in cow’s milk. Therefore, the goat’s milk is much easier to digest than the cow’s milk.