Chapter 2: Nutrition in Animals - Important Questions & Answers
I. Very Short Answer Type Questions (1-2 Marks)
Define digestion.
Answer:
Digestion is the process of breaking down complex food substances into simpler, soluble forms that can be absorbed by the body.
What are the five steps involved in the process of nutrition in animals?
Answer:
Ingestion, Digestion, Absorption, Assimilation, Egestion.
Name the largest gland in the human body.
Answer:
Liver.
What is the function of bile juice?
Answer:
Bile juice helps in the digestion of fats.
Where is bile juice stored?
Answer:
In the gallbladder.
Name the enzyme present in saliva.
Answer:
Salivary amylase (or ptyalin).
What is the function of hydrochloric acid in the stomach?
Answer:
It kills bacteria that enter with food and makes the medium acidic for the action of digestive juices.
Name the finger-like outgrowths in the inner wall of the small intestine.
Answer:
Villi.
What is the main function of the large intestine?
Answer:
To absorb water and some salts from the undigested food material.
What is rumination?
Answer:
The process by which ruminants (grass-eating animals) chew their food a second time after it returns from the rumen to the mouth.
Name the part of the Amoeba that helps in capturing food.
Answer:
Pseudopodia (false feet).
II. Short Answer Type Questions (2-3 Marks)
Why do we need to chew food thoroughly?
Answer:
Chewing food thoroughly (mastication) breaks down large pieces of food into smaller ones, increasing the surface area for enzymes to act upon. It also mixes food with saliva, initiating carbohydrate digestion and making it easier to swallow.
What is the role of the tongue in digestion?
Answer:
The tongue helps in mixing saliva with food, pushing food around the mouth during chewing, swallowing the food, and tasting food.
Differentiate between milk teeth and permanent teeth.
Answer:
Milk Teeth:
The first set of teeth that grow in infants (around 6-8 months) and fall off between the ages of 6-8 years. There are usually 20 milk teeth.
Permanent Teeth:
The second set of teeth that replace milk teeth. They are typically 32 in number and are meant to last for a lifetime.
What is the significance of villi in the small intestine?
Answer:
Villi are tiny, finger-like projections in the inner wall of the small intestine. They increase the surface area for absorption of digested food tremendously. Each villus has a network of thin and small blood vessels close to the surface, which absorb the digested food and transport it to the bloodstream.
Explain why glucose gives instant energy.
Answer:
Glucose is a simple carbohydrate (sugar) that does not need to be digested. It is directly absorbed into the blood and quickly provides energy to the body's cells through respiration. This is why athletes and sick people are often given glucose.
What is the difference between absorption and assimilation?
Answer:
Absorption:
The process by which digested food (simple, soluble substances) passes into the blood vessels in the wall of the intestine.
Assimilation:
The process by which the absorbed food is transported by the blood to different parts of the body and used for growth, repair, and energy production.
Why do cows and other grass-eating animals chew their food repeatedly (ruminate)?
Answer:
Grass is rich in cellulose, which is a complex carbohydrate. Ruminants have a special four-chambered stomach, with the largest chamber called the rumen. They first quickly swallow the grass into the rumen, where it is partially digested by bacteria. Later, they bring the partially digested food (cud) back to the mouth and chew it thoroughly. This helps in breaking down cellulose and facilitates complete digestion.
III. Long Answer Type Questions (3-5 Marks)
Describe the process of digestion in humans. (Mention the major organs and their roles).
Answer:
The human digestive system consists of the alimentary canal and associated glands.
Mouth/Buccal Cavity:
Food is ingested. Teeth chew (masticate) the food, and the tongue mixes it with saliva. Saliva contains salivary amylase, which begins the digestion of starch.
Oesophagus (Food Pipe):
The chewed food (bolus) passes down the oesophagus to the stomach by peristaltic movements.
Stomach:
A thick-walled bag that churns food. It secretes gastric juices, hydrochloric acid (kills bacteria, provides acidic medium), and digestive enzymes (e.g., pepsin, which begins protein digestion). Food remains here for a few hours.
Small Intestine:
A highly coiled, long tube (about 7.5 m). It receives secretions from the liver (bile for fat digestion) and pancreas (pancreatic juice for carbohydrate, fat, and protein digestion). The intestinal wall also secretes intestinal juice, which completes the digestion of all food components. Digested food is absorbed through villi.
Large Intestine:
Wider and shorter than the small intestine (about 1.5 m). It absorbs water and some salts from the undigested food material.
Rectum:
The remaining undigested waste is stored here as semi-solid faeces.
Anus:
The faecal matter is expelled from the body through the anus (egestion).
Explain the feeding and digestion in Amoeba.
Answer:
Amoeba is a microscopic, single-celled organism found in pond water. It has a flexible cell membrane and constantly changes its shape.
Ingestion:
When Amoeba senses food (e.g., microscopic organisms), it extends one or more finger-like projections called
pseudopodia
(false feet) around the food particle. The pseudopodia engulf the food, forming a small cavity called a
food vacuole
.
Digestion:
Digestive juices are secreted into the food vacuole. These juices break down the food into simpler, soluble substances.
Absorption:
The digested food is then absorbed directly into the cytoplasm of the Amoeba.
Assimilation:
The absorbed substances are used for growth, maintenance, and multiplication.
Egestion:
The undigested waste material remains in the food vacuole. The food vacuole then moves to the surface of the cell, ruptures, and the undigested waste is expelled out of the body.
Draw a neat
labeled
diagram of the human digestive system.
Answer:
(Students should draw a diagram showing the following
labeled
parts):
Buccal cavity (mouth)
Salivary glands
Oesophagus (food pipe)
Stomach
Liver
Gallbladder
Pancreas
Small intestine
Large intestine
Rectum
Anus
IV. Higher Order Thinking Skills (HOTS) Questions
Why can't humans digest cellulose, while cows can?
Answer:
Humans lack the specific enzymes (like cellulase) and the specialized digestive system (like the rumen with cellulose-digesting bacteria) required to break down cellulose. Cows, being ruminants, have a large chamber in their stomach called the rumen, where cellulose-digesting bacteria are present. These bacteria ferment the cellulose, converting it into simpler substances that the cow can absorb and utilize for energy.
What would happen if the small intestine was not highly coiled and long?
Answer:
If the small intestine was not highly coiled and long (approx. 7.5 m), its surface area for absorption would be significantly reduced. The digestion and absorption of nutrients would be incomplete, leading to nutritional deficiencies as the body would not be able to efficiently absorb all the necessary digested food components.
Why is it advisable to rinse your mouth after eating sweets or chocolates?
Answer:
Bacteria present in our mouth feed on the sugar (carbohydrates) remaining in our mouth after eating sweets. These bacteria produce acids. These acids gradually damage the tooth enamel and cause tooth decay (cavities). Rinsing the mouth after eating sweets helps remove sugar particles, thus reducing the food source for bacteria and preventing acid formation and tooth decay.
V. Multiple Choice Questions (MCQs)
Which of the following is NOT a part of the human digestive system? a) Stomach b) Heart c) Small Intestine d) Liver
Answer:
b) Heart
The process of taking food into the body is called: a) Digestion b) Absorption c) Ingestion d) Egestion
Answer:
c) Ingestion
The part of the digestive system where no digestion takes place is the: a) Oesophagus b) Stomach c) Small Intestine d) Large Intestine
Answer:
a) Oesophagus
The largest gland in the human body is: a) Pancreas b) Salivary gland c) Liver d) Gallbladder
Answer:
c) Liver
The acid present in the stomach is: a) Sulphuric acid b) Nitric acid c) Hydrochloric acid d) Citric acid
Answer:
c) Hydrochloric acid
Grass-eating animals are called: a) Carnivores b) Omnivores c) Ruminants d) Parasites
Answer:
c) Ruminants
The false feet of Amoeba are called: a) Cilia b) Flagella c) Pseudopodia d) Tentacles
Answer:
c) Pseudopodia
The final product of carbohydrate digestion is: a) Fatty acids b) Amino acids c) Glucose d) Glycerol
Answer:
c) Glucose
