Exercise Answers
1. Fill in the blanks: (a) The main steps of nutrition 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. 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. (T)
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T)
3. Tick () mark the correct answer in each of the following:
(a) Fat is completely digested in the
(iii) small intestine
(b) Water from the undigested food is absorbed mainly in the
(iv) 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?
Villi are tiny, finger-like projections present in the inner walls of the small intestine. Their function is to increase the surface area for the absorption of nutrients from digested food into the blood vessels.
6. Where is the bile produced? Which component of the food does it help to digest?
Bile is produced in the liver. It helps 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 type of carbohydrate is cellulose. Ruminants can digest cellulose because they have specific bacteria in their rumen that help break down cellulose, whereas humans lack these bacteria.
8. Why do we get instant energy from glucose?
Glucose is a simple sugar that is quickly absorbed into the bloodstream and transported to cells where it is used immediately to produce energy.
9. 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
10. Write one similarity and one difference between the nutrition in amoeba and human beings.
Similarity: Both amoeba and humans digest food to release energy and absorb nutrients.
Difference: Amoeba digests food in a food vacuole with the help of digestive enzymes, while humans digest food through a complex digestive system with organs like the stomach and small intestine.
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 | (vii) Release of faeces |
| (e) Small intestine | (vi) Digestion is completed |
| (f) Large intestine | (v) Absorption of water |
12. Label Fig. 2.11 of the digestive system.
(Since I don’t have access to Fig. 2.11, I would recommend you to label the parts of the digestive system according to the image in your textbook.)
13. Can we survive only on raw, leafy vegetables/grass? Discuss.
No, we cannot survive only on raw, leafy vegetables/grass. Humans are omnivores and require a balanced diet consisting of proteins, fats, vitamins, and carbohydrates. Leafy vegetables can provide some of these nutrients, but a variety of foods is necessary for proper growth and maintenance.
Extended Learning — Activities and Project
- 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?You can conduct this activity and write the answers based on your findings.
- Find out what vitamins are and get the following information:
(i) Why are vitamins necessary in the diet?
Vitamins are essential for various body functions such as immunity, energy production, and cell repair. They also help in metabolizing carbohydrates, proteins, and fats.(ii) Which fruits or vegetables should be eaten regularly to get vitamins?
Citrus fruits (for Vitamin C), leafy greens (for Vitamin K), carrots and sweet potatoes (for Vitamin A), and bananas (for Vitamin B6) are good sources of vitamins.Write a one-page note on the information collected by you.
What is animal nutrition?
Answer: Animal nutrition includes the nutrient requirements, mode of food intake, and how the food is utilized in the body for growth, repair, and functioning.
2. Why can animals not prepare their own food?
Answer: Animals cannot prepare their own food because they do not have the ability to perform photosynthesis, unlike plants.
3. How do animals get their food?
Answer: Animals get their food either directly from plants (herbivores) or indirectly by eating other animals (carnivores) that consume plants. Some animals are omnivores, consuming both plants and animals.
4. What is digestion?
Answer: Digestion is the process of breaking down complex food substances into simpler ones so that they can be absorbed and used by the body.
5. What is the mode of feeding in a hummingbird?
Answer: The mode of feeding in a hummingbird is sucking nectar from flowers.
6. What are the components of food?
Answer: The components of food include carbohydrates, proteins, fats, vitamins, minerals, and water.
7. What is the function of the salivary glands?
Answer: The salivary glands secrete saliva, which contains enzymes that help break down starch into simpler sugars.
8. What are the different types of teeth in humans?
Answer: The different types of teeth in humans are incisors (for cutting), canines (for tearing), premolars (for grinding), and molars (for crushing).
9. What happens to the food in the stomach?
Answer: In the stomach, food is mixed with digestive juices, including hydrochloric acid and enzymes, which help break down proteins into simpler substances.
10. How does the food move through the alimentary canal?
Answer: The food moves through the alimentary canal by peristalsis, a series of wave-like muscle contractions.
11. What is the role of bile in digestion?
Answer: Bile, produced by the liver and stored in the gall bladder, helps in the digestion of fats by emulsifying them.
12. What are villi and what role do they play in digestion?
Answer: Villi are tiny finger-like projections in the small intestine that increase the surface area for absorption of digested food into the blood.
13. What is absorption in the context of digestion?
Answer: Absorption is the process by which digested food passes through the walls of the small intestine into the bloodstream.
14. What is assimilation in digestion?
Answer: Assimilation is the process where absorbed food is transported to different organs and used for building complex substances like proteins.
15. What happens to undigested food in the large intestine?
Answer: The undigested food passes into the large intestine, where water and some salts are absorbed, and the remaining waste is excreted as feces.
16. What is rumination?
Answer: Rumination is the process by which ruminant animals like cows chew their food multiple times, after initially swallowing it, to aid in digestion.
17. Why do ruminants need to chew their food multiple times?
Answer: Ruminants chew their food multiple times to break down the cellulose in grass, which is difficult to digest.
18. Why can’t humans digest cellulose like cows?
Answer: Humans lack the necessary bacteria in their digestive system to break down cellulose, unlike ruminants that have specialized bacteria in their rumen.
19. What is the function of the pancreas in digestion?
Answer: The pancreas secretes pancreatic juices that help digest carbohydrates, fats, and proteins, breaking them into simpler substances.
20. What happens in the small intestine after the food leaves the stomach?
Answer: In the small intestine, digestive juices from the pancreas, liver, and intestinal glands further break down food, and nutrients are absorbed through the villi.
21. What is the function of the large intestine?
Answer: The large intestine absorbs water and some salts from the remaining undigested food material, and prepares the waste for egestion.
22. What is egestion?
Answer: Egestion is the removal of undigested and unabsorbed food from the body in the form of feces through the anus.
23. How does amoeba digest food?
Answer: Amoeba engulfs food by extending pseudopodia (false feet) to surround and trap the food particle, which then enters a food vacuole. Digestive enzymes break down the food inside the vacuole.
24. What are pseudopodia in amoeba?
Answer: Pseudopodia are temporary, finger-like projections used by amoeba for movement and capturing food.
25. What is the function of the food vacuole in amoeba?
Answer: The food vacuole in amoeba is where the food is digested by enzymes, and the digested nutrients are absorbed.
26. What role do the teeth play in digestion?
Answer: The teeth break down food mechanically into smaller pieces, which makes it easier for digestive enzymes to act on the food.
27. How does the tongue help in digestion?
Answer: The tongue helps in mixing saliva with food, aids in swallowing, and helps taste food with its taste buds.
28. What is the role of hydrochloric acid in the stomach?
Answer: The hydrochloric acid in the stomach helps kill bacteria, activates digestive enzymes, and creates an acidic environment for protein digestion.
29. What is the function of the gall bladder?
Answer: The gall bladder stores bile produced by the liver and releases it into the small intestine to help in the digestion of fats.
30. What happens when food enters the windpipe instead of the foodpipe?
Answer: If food enters the windpipe, it can cause choking, coughing, or hiccups. The windpipe is meant for air, and a flap-like valve called the epiglottis prevents food from entering it.
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