(a) Why is nutrition necessary for the human body? (b) What causes movement of food inside the alimentary canal? (c) Why is small intestine in herbivores longer than in carnivores? (d) What will happen if mucus is not secreted by the gastric glands?

Q: (a) Why is nutrition necessary for the human body? (b) What causes movement of food inside the alimentary canal? (c) Why is small intestine in herbivores longer than in carnivores? (d) What will happen if mucus is not secreted by the gastric glands?

**(a)** Nutrition is necessary to provide energy for carrying out vital maintenance and repair processes in the body (even when at rest) and to supply raw materials needed for growth, development, and the synthesis of proteins. **(b)** The rhythmic contraction and relaxation of the muscles in the lining of the alimentary canal (peristaltic movements) push the food forward. **(c)** Herbivores eat cellulose-rich grass, which is difficult to digest and requires a longer small intestine. Carnivores eat meat, which is easier to digest, hence they have a shorter small intestine. **(d)** Without mucus, the strong hydrochloric acid ($HCl$) secreted by the gastric glands will erode and damage the inner lining of the stomach, leading to acidity and gastric ulcers.

Nutrition in Human Beings

Official Answer

(a) Nutrition is necessary to provide energy for carrying out vital maintenance and repair processes in the body (even when at rest) and to supply raw materials needed for growth, development, and the synthesis of proteins.

(b) The rhythmic contraction and relaxation of the muscles in the lining of the alimentary canal (peristaltic movements) push the food forward.

(c) Herbivores eat cellulose-rich grass, which is difficult to digest and requires a longer small intestine. Carnivores eat meat, which is easier to digest, hence they have a shorter small intestine.

(d) Without mucus, the strong hydrochloric acid ( $HCl$ ) secreted by the gastric glands will erode and damage the inner lining of the stomach, leading to acidity and gastric ulcers.

energymaintenanceraw materialsgrowthperistaltic movementsrhythmic contractioncellulosemeat is easier to digestmucushydrochloric acidinner lining of stomachulcers

Marking Scheme

11.5 marks for (a): 0.75 marks for mentioning energy for maintenance/repair, and 0.75 marks for raw materials for growth/protein synthesis.
21 mark for (b): Mentioning rhythmic contraction of muscles in the canal lining / peristaltic movements.
31.5 marks for (c): 0.75 marks for explaining that herbivores need to digest complex cellulose, and 0.75 marks for explaining that meat is easier to digest for carnivores.
41 mark for (d): Explaining that hydrochloric acid ( $HCl$ ) will corrode/damage the inner stomach lining, causing acidity or ulcers.

Hint

Think about: (a) energy and growth, (b) rhythmic muscle contractions, (c) digestion of cellulose vs. meat, and (d) the protective shield against hydrochloric acid ( $HCl$ ).

Quick Oral Answer

Nutrition provides energy and raw materials. Food moves via peristalsis. Herbivores have longer intestines to digest tough cellulose. Mucus protects the stomach lining from being digested by its own hydrochloric acid.

Analysis & Explanation

This question tests multiple core concepts of the human digestive system from the NCERT textbook:

Nutrition necessity: Establishes the link between energy, maintenance of order, and raw materials for growth.
Peristalsis: Explains the mechanical movement of food along the soft lining of the gut.
Comparative anatomy: Highlights how the length of the small intestine is an evolutionary adaptation based on diet (cellulose vs. meat).
Gastric secretions: Explores the physiological balance in the stomach where mucus acts as a chemical shield against self-digestion by hydrochloric acid ( $HCl$ ).

Common Mistakes

1In part (b), students often write 'gravity' instead of 'peristaltic movements' as the cause of food movement.
2In part (c), failing to mention the word 'cellulose' when explaining why herbivores have a longer small intestine.
3In part (d), omitting the mention of hydrochloric acid ( $HCl$ ) as the specific agent that damages the stomach wall in the absence of mucus.

Interesting Facts

Peristalsis is so strong and independent of gravity that you can actually swallow food and have it reach your stomach even if you are standing on your head!

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 5 marks in the CBSE Class 10 Science 2020 examination.

What topic does this question cover in Science?

This question covers the topic "Nutrition in Human Beings" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a Long Answer question from Section C in the CBSE Class 10 Science 2020 paper.