CBSE Class 7 Science Chapter 09 Life Processes In Animals MCQs Set 02

Answer: (B) It is converted into simpler sugar molecules, making the food taste sweet

Explanation:
The chapter explains that saliva contains a digestive juice capable of breaking down starch into sugar. This is why chapati or rice tastes sweet when chewed for an extended time—the starch component is gradually being converted to simpler forms by the enzyme in saliva.

Answer: (B) Pancreas

Explanation:
• The pancreas secretes pancreatic juice, which is basic in nature
• It neutralises acids moving down from the stomach
• It breaks down carbohydrates, proteins, and fats in the small intestine

Answer: (B) Rumination

Explanation:
Ruminants like cows partially chew their grass and swallow it, then bring the partially digested food back to the mouth for more chewing. This process is specifically called rumination, and these animals spend approximately 8 hours daily engaged in this activity.

Answer: (B) A specialised chamber called the gizzard that grinds food with muscular contractions and sometimes grit

Explanation:
Birds possess a chamber known as the gizzard where food is broken down through contraction and relaxation of the walls, often assisted by small stones or grit that birds swallow. This mechanism replaces the function of teeth in these animals.

Answer: (B) Saliva breaks down starch into simpler sugars, so less starch remains in the chewed sample

Explanation:
Iodine produces a blue-black colour when it reacts with starch. Since chewed rice shows little or no colour change while unchewed rice turns blue-black, this demonstrates that saliva has already broken down much of the starch into simpler sugars during the chewing process.

Answer: (B) They increase the surface area available for the absorption of digested nutrients into the bloodstream

Explanation:
The small intestine's inner lining contains thousands of finger-like projections that significantly increase surface area. This enlarged surface allows more efficient absorption of digested nutrients into the blood vessels within these projections.

Answer: (B) It absorbs water and some salts from undigested food, converting it into semi-solid stool

Explanation:
After most nutrients are absorbed in the small intestine, the undigested material moves to the large intestine, which is about 1.5 metres long. Here, water and some salts are absorbed, leaving behind semi-solid waste called stool that is eventually expelled through the anus during egestion.

Answer: (C) Balloons represent the lungs and rubber sheet represents the diaphragm

Explanation:
The model demonstrates the mechanism of breathing. When the rubber sheet is pulled downwards, it increases space inside the bottle, causing the balloons to inflate—just as the diaphragm moving downward increases chest space and allows air to enter the lungs during inhalation.

Answer: (B) The nasal passages have tiny hairs and mucus that trap dust and dirt before air reaches the lungs

Explanation:
Tiny hairs and mucus lining the nasal passages work together to trap dust and dirt from inhaled air, providing a filtering mechanism. This is why breathing through the nose is preferable to mouth-breathing, as the nasal passages offer better protection of the lungs.

Answer: (C) Exhaled air contains more carbon dioxide than inhaled air

Explanation:
Lime water turns milky when it reacts with carbon dioxide. Because only the exhaled air turned the lime water milky in Activity 9.3, this directly indicates that exhaled air contains significantly more carbon dioxide than the inhaled air we breathe in from the atmosphere.

Answer: (A) Inhaled air has about 21% oxygen while exhaled air has about 4–5% oxygen

Explanation:
Figure 9.13 shows that inhaled air contains nearly 21% oxygen while exhaled air contains only about 16–17% oxygen. This difference demonstrates that our body uses a portion of the oxygen from each breath, but not all of it, indicating that some oxygen passes through unused.

Answer: (B) Carbon dioxide, water, and energy are released

Explanation:
The chapter states the respiration equation as: Glucose + Oxygen → Carbon dioxide + Water + Energy. This shows that when oxygen helps break down glucose, it produces carbon dioxide and water as waste products, along with usable energy for the body to perform activities.

Answer: (B) Animals develop different alimentary canal structures based on the types of food they consume and their environment

Explanation:
The chapter demonstrates through examples that ruminants have specialised chambers like the rumen for regurgitation and re-chewing, while birds lack teeth but have a gizzard for grinding food. These variations show how digestive system structure reflects and adapts to an animal's feeding habits and habitat.

Answer: (C) Tadpoles use gills while adults use lungs on land and skin for gas exchange in water

Explanation:
• Tadpoles breathe through gills in water
• Adult frogs use lungs for breathing on land
• Adult frogs also use skin for gas exchange when in water
• This flexibility allows them to survive in both environments throughout different life stages

Answer: (C) Bile is basic in nature and neutralises acids while breaking down fats into droplets for easier digestion

Explanation:
The chapter explains that the liver secretes bile, which is mildly basic in nature. Bile serves two critical functions: it neutralises acids present in food coming from the stomach through a neutralisation reaction, and it breaks down fats into tiny droplets, making fat digestion more efficient.

Answer: (C) The process of expelling undigested food waste through the anus

Explanation:
Egestion is the process by which the body removes waste materials it does not need. After the large intestine absorbs water and salts from undigested material, the resulting semi-solid stool is expelled through the anus in a process specifically called egestion, keeping the body healthy.

Answer: (B) Breathing is the mechanical movement of air in and out of lungs, while respiration is the chemical breakdown of glucose using oxygen to release energy

Explanation:
The chapter explicitly states that breathing is a physical process involving inhalation and exhalation of air, whereas respiration is a chemical process occurring inside the body where oxygen breaks down glucose to produce energy, carbon dioxide, and water. Both are essential for survival but operate through different mechanisms.

Answer: (A) Starch is broken down into simpler sugars, making the food taste sweet

Explanation:
The chapter explains that saliva contains a digestive juice that breaks down starch into sugar. This is why chewing chapati or rice for an extended period causes the initially bland starchy food to develop a sweet taste—the starch has been partially digested into simpler sugars by the enzyme in saliva.

Answer: (B) Stomach

Explanation:
According to the chapter, the stomach's walls contract and relax to churn the food, then mix it with secretions containing digestive juice, acid, and mucus. This process transforms the food into a semi-liquid mass in preparation for further digestion in the small intestine. The oesophagus merely transports food; the pancreas secretes juice but does not churn; and the small intestine completes digestion and absorption.

Answer: (B) To neutralise acids from the stomach and break down fats into droplets

Explanation:
• The chapter notes that bile is mildly basic and neutralises acidic conditions from the stomach
• It breaks down fats into tiny droplets, making fat digestion easier
• This creates the proper environment for further digestion by pancreatic juice and intestinal secretions

Answer: (C) The exhaled air still contains approximately 16–17% oxygen, showing some is unused

Explanation:
The chapter presents data showing that inhaled air contains nearly 21% oxygen while exhaled air contains 16–17% oxygen. This difference demonstrates that while respiration consumes some oxygen, a significant fraction remains unused and is expelled. The text notes that some other animals can use a larger fraction of the oxygen available.

Answer: (B) The gizzard contracts and relaxes to break down food, often aided by swallowed grit

Explanation:
The chapter states that birds lack teeth but have a gizzard chamber where food is broken down by contraction and relaxation of the walls, often assisted by grit (small stones) the birds swallow. This mechanical breakdown substitutes for the crushing and chewing action that teeth provide in mammals like humans.

Answer: (B) They use their moist skin directly for gas exchange

Explanation:
The chapter explicitly states that earthworms use their moist skin for the exchange of oxygen and carbon dioxide. This adaptation demonstrates how animals exhibit variations suited to their specific habitats and lifestyles—in this case, a terrestrial animal living in soil where moisture allows cutaneous respiration.

Answer: (B) Exhaled air contains more carbon dioxide because it is a waste product of breaking down glucose

Explanation:
The respiration equation—Glucose + Oxygen → Carbon dioxide + Water + Energy—shows that carbon dioxide is produced when glucose is broken down with oxygen. The chapter's experimental data (Activity 9.3) confirms this: exhaled air turns lime water milky, indicating higher carbon dioxide content, while the composition shift from 21% to 16–17% oxygen demonstrates consumption of oxygen during respiration.

Answer: (B) Blood transports nutrients from digestion and oxygen from respiration to all body parts while removing waste

Explanation:
The chapter describes the circulatory system as transporting nutrients (from digestion) and oxygen (from respiration) to all parts of the body while also carrying away waste products. This dual function links the two processes—digestion provides nutrients that require oxygen for respiration to convert them into usable energy, and the circulatory system is the transport mechanism enabling both processes to work together.