Science STD 7 Chapter 2: Nutrition in Animals - Exercises
1. Fill in the blanks:
- (a) The main steps of nutrition in humans are ............., ............., ............., ............. and .............. .
ingestion, digestion, absorption, assimilation, egestion
- (b) The largest gland in the human body is .............. .
liver
- (c) The stomach releases hydrochloric acid and .............. juices which act on food.
digestive
- (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) Digestion of starch starts in the stomach. (T/F)
F
- (b) The tongue helps in mixing food with saliva. (T/F)
T
- (c) The gall bladder temporarily stores bile. (T/F)
T
- (d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)
T
3. Tick (✓) mark the correct answer in each of the following:
- (a) Fat is completely digested in the
- stomach
- mouth
- small intestine
- large intestine
- (b) Water from the undigested food is absorbed mainly in the
- stomach
- foodpipe
- small intestine
- large intestine
4. Match the items of Column I with those given in Column II:
| Column I | Column II |
|---|---|
| Carbohydrates | Sugar |
| Proteins | Amino acids |
| Fats | Fatty acids and glycerol |
5. What are villi? What is their location and function?
The inner walls of the small intestine have thousands of finger-like outgrowths called villi. The villi are located in the small intestine. Their main function is to increase the surface area for the absorption of digested food. Each villus has a network of thin and small blood vessels close to its surface, which absorbs the digested food materials into the blood vessels.
6. Where is the bile produced? Which component of the food does it help to digest?
Bile is produced by the liver. It is a reddish-brown gland located in the upper part of the abdomen on the right side. The bile juice is stored in a sac called the gall bladder. Bile plays an important role in the digestion of fats.
7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
The carbohydrate that can be digested by ruminants but not by humans is cellulose. The reason is that ruminants like cattle and deer have a large sac-like structure called the caecum between the oesophagus and the small intestine. Certain bacteria that are not present in humans live in the caecum and help in the digestion of cellulose. Humans do not have these specific bacteria, so they cannot digest cellulose.
8. Why do we get instant energy from glucose?
We get instant energy from glucose because it is a simple sugar that does not need to be broken down further. It is easily absorbed into the bloodstream and used by the cells to release energy. In the body's cells, glucose breaks down with the help of oxygen to release carbon dioxide, water, and energy. This is why people are given glucose drips when they are ill or need a quick energy boost.
9. Which part of the digestive canal is involved in:
- (i) absorption of food
Small intestine
- (ii) chewing of food
Buccal cavity
- (iii) 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 the nutrition in amoeba and human beings.
Similarity: Both amoeba and human beings are heterotrophs. The basic process of digestion of food and release of energy is similar in both. Ingestion, digestion, and egestion occur in both organisms.
Difference: Humans have a complex digestive system with specialized organs like the stomach and intestines. Amoeba is a single-celled organism and does not have a digestive system. It ingests food using pseudopodia and digests it in a food vacuole.
11. Match the items of Column I with suitable items in Column II
| Column I | Column II |
|---|---|
| (a) Salivary gland | (iii) Saliva secretion |
| (b) Stomach | (iv) Acid release |
| (c) Liver | (i) Bile juice secretion |
| (d) Rectum | (vi) Storage of undigested food |
| (e) Small intestine | (v) Digestion is completed |
| (f) Large intestine | (vii) Absorption of water |
12. Label Fig. 2.11 of the digestive system.
The image shows the human digestive system. You would label the parts including the buccal cavity, salivary gland, oesophagus, liver, gall bladder, stomach, pancreas, small intestine, large intestine, rectum, and anus.
[Image of the human digestive system with labels]
13. Can we survive only on raw, leafy vegetables/grass? Discuss.
No, we cannot survive only on raw, leafy vegetables and grass. This is because raw grass and leafy vegetables contain a large amount of cellulose, which humans cannot digest. Ruminant animals like cows can digest cellulose because they have specific bacteria in their digestive system (caecum) that help break it down. Humans lack these bacteria, so consuming only raw leafy vegetables would not provide us with enough energy and nutrients for survival.
Suggested Activities and Projects
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.
Outline: This activity involves interviewing a doctor to understand the medical use of glucose drips. You would learn that glucose is administered when a patient is unable to eat, is dehydrated, or needs immediate energy. The doctor would explain that glucose provides instant energy, helping the body function and recover without the need for digestion. The duration of the drip depends on the patient's condition and recovery progress.
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 dietician, your teacher or any other person, or from any other source.
Outline: This activity focuses on researching and understanding the importance of vitamins. You would learn that vitamins are essential organic compounds that the body needs in small amounts for various functions, such as metabolism, growth, and disease prevention. The note would include a list of different vitamins (like A, B, C, D, E, K) and their sources, such as citrus fruits for Vitamin C, leafy greens for Vitamin A and K, etc.
3. Collect data from your friends, neighbours and classmates to know more about "milk teeth". Tabulate your data. One way of doing it is given below: 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.
Outline: This is a data collection activity to study the process of losing milk teeth. You would interview at least twenty children and record information like the age at which they lost their first and last milk teeth and the total number of teeth lost. After collecting the data, you would calculate the average age for losing milk teeth, providing a practical understanding of this developmental stage.