Class 7 Science Curiosity Chapter 9 MCQ – Life Processes in Animals

Food enters the mouth and passes through the food pipe into the stomach. It then moves through the small and large intestines. Undigested material is stored in the rectum before leaving the body through the anus.

Saliva mixes with food while we chew. It begins breaking down starch into simpler sugars and also moistens the food. This is why a piece of rice or chapati may taste sweeter after being chewed for some time.

Iodine produces a blue-black colour when starch is present. Unchewed rice still contains its starch. In rice chewed well with saliva, some starch breaks down into sugars, so the blue-black colour may be weaker or absent.

The walls of the food pipe contract and relax in a wave-like manner. These movements push swallowed food towards the stomach. The food pipe therefore transports food after the tongue helps us push it back for swallowing.

The stomach releases acid, digestive juices, and mucus. Mucus forms a protective covering over its inner lining. This protection helps the stomach carry out digestion without its own acid and digestive juices damaging the lining during normal functioning.

The stomach churns food and mixes it with its secretions. Its digestive juices begin breaking down proteins. The acid helps these juices work and also kills many bacteria that may have entered the stomach with the food.

The small intestine is about six metres long and is the longest part of the alimentary canal. Its name refers to its smaller

Bile is produced by the liver and enters the small intestine. It is mildly basic, so it helps neutralise acidic food arriving from the stomach. It also breaks fats into smaller droplets, making their digestion easier.

The pancreas sends digestive juice into the small intestine. This juice helps break down carbohydrates, proteins, and fats. It is also basic and helps neutralise acidic food from the stomach, supporting further digestion in the small intestine.

The small intestine has thousands of tiny finger-like projections on its inner lining. These increase the surface area available for absorption. Digested nutrients pass through the thin lining into the blood, which carries them to different body parts.

Undigested material passes from the small intestine into the large intestine. Here, water and some salts are absorbed. The remaining material becomes stool, which moves to the rectum and is later removed from the body through the anus.

Not all material in food is digested and absorbed. The remaining undigested material is stored in the rectum and passes out through the anus. This removal is called egestion and is a different step from absorption of nutrients.

Cows and buffaloes swallow partly chewed food, which undergoes partial digestion in the stomach. Later, this food returns to the mouth for more chewing. This process is called rumination and helps these animals process the plant material they eat.

Birds do not have teeth for chewing food. Their gizzard has strong muscular walls that grind the food. Small stones or grit swallowed by some birds assist this grinding, helping break food into smaller pieces for digestion.

Alveoli are tiny balloon-like air sacs in the lungs. Their thin walls and surrounding blood vessels allow gas exchange. Oxygen passes from the air into the blood, while carbon dioxide passes from the blood into the alveoli.

During inhalation, the ribs move upwards and outwards while the diaphragm moves downwards. These movements increase the space inside the chest. As the lungs expand, air enters them through the air passages, bringing oxygen into the body.

Carbon dioxide makes limewater turn milky. Exhaled air has a higher proportion of carbon dioxide than ordinary room air, so the change happens faster. Room air also contains some carbon dioxide, but its proportion is much smaller.

During respiration, glucose combines with oxygen and breaks down to form carbon dioxide and water. Energy is released in this process. The body uses this energy for its activities, including movement, growth, repair, and other life processes.

Breathing is the physical process of taking air into the lungs and pushing it out. Respiration is a chemical process in which food is broken down to release energy. Breathing supplies oxygen needed for this process in humans.

Fish use gills to obtain oxygen dissolved in the surrounding water. This is different from humans, who take oxygen from air through their lungs. Animals have different breathing structures suited to the environments in which they live.

Teeth carry out the mechanical breaking of food into smaller pieces during chewing. Saliva moistens the food and begins breaking starch down into sugars. Both help digestion in the mouth, but they perform different jobs rather than doing exactly the same thing.

Iodine turns blue-black when starch is present. If the rice sample shows this colour, some starch remains, even if saliva has broken down part of it. The observation therefore does not support the claim that all starch has disappeared.

The projections provide a large surface through which digested nutrients enter the blood. Having fewer projections would reduce the available surface for absorption. Their role is different from chewing food, filtering inhaled air, or storing undigested material.

Fibre is useful even though much of it is not digested by our digestive system. It helps the movement and removal of undigested material. The chapter also explains that some bacteria in the large intestine break down fibre.

The nose does more than allow air to enter. Nasal hairs and mucus trap dust and other particles in inhaled air. This filtering helps protect deeper air passages, although it does not make dusty air completely harmless.

The rubber sheet represents the diaphragm, and the balloons represent the lungs. Pulling the sheet down increases the space inside the bottle. This models how downward movement of the diaphragm increases chest space and helps air enter the lungs.

he chapter states that inhaled air contains about 21% oxygen, while exhaled air still contains about 16–17%. The body uses only part of the oxygen taken in. Therefore, exhaled air is not completely free of oxygen.

adpoles live in water and use gills for breathing. Adult frogs can breathe using lungs on land and their skin in water. This example shows that breathing structures can change as an animal develops into its adult form.

Earthworms breathe through their moist skin rather than through lungs or gills. Gases pass across this surface during breathing. Keeping the skin moist is therefore closely connected with obtaining oxygen and removing carbon dioxide from the body.

The circulatory system includes the heart, blood, and blood vessels. Blood transports absorbed nutrients and oxygen to different body parts. This connects digestion and breathing with the needs of the body, including obtaining energy and supporting growth and repair.