CBSE Class 7 Science Chapter 09 Life Processes In Animals MCQs Set 03

Practice MCQs for Class 7 Science Chapter 09 Life Processes In Animals

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Question: When food reaches the stomach after passing through the oesophagus, what three components are released from the stomach's inner lining to begin breaking down the food further?
A. Bile, pancreatic juice, and saliva
B. Digestive juice, acid, and mucus
C. Starch-breaking enzymes, bile, and water
D. Acid, sugar, and protective oil
Show Answer & Explanation

Answer: (B) Digestive juice, acid, and mucus

Explanation:
The chapter explicitly states that the stomach's secretion contains digestive juice, acid, and mucus. These three components work together to partially digest food—the digestive juice breaks down proteins, the acid kills harmful bacteria, and the mucus protects the stomach lining itself.

Question: Based on the information about how saliva affects starch in the mouth, which of the following would most likely occur if a person could not produce saliva?
A. Starch would turn sweet immediately upon entering the mouth
B. Starch would remain largely undigested in the mouth, requiring more work by the stomach later
C. The person would only be able to digest protein and fats
D. Food would move through the oesophagus more quickly without moisture
Show Answer & Explanation

Answer: (B) Starch would remain largely undigested in the mouth, requiring more work by the stomach later

Explanation:
The chapter demonstrates that saliva contains a digestive juice that breaks down starch into sugar—this is why chapati tastes sweet when chewed for a long time. Without saliva, this initial breakdown would not occur in the mouth, placing greater digestive burden on subsequent organs.

Question: The chapter describes the food pipe as a 'long, flexible tube' that moves food by gentle contractions and relaxations. What is this wave-like movement called?
A. Peristalsis
B. Churning
C. Rumination
D. Mechanical digestion
Show Answer & Explanation

Answer: (A) Peristalsis

Explanation:
Though the chapter does not explicitly name this phenomenon, it describes the walls of the food pipe contracting and relaxing in a wave-like motion to push food down. This movement pattern is peristalsis, which occurs throughout the alimentary canal.

Question: In Activity 9.1, the experiment compared unchewed and chewed rice using iodine solution. What was the underlying principle that made this experiment work?
A. Iodine reacts with saliva to change colour
B. Iodine indicates the presence or absence of starch in food
C. Iodine breaks down carbohydrates into simpler sugars
D. Iodine kills bacteria in the digestive system
Show Answer & Explanation

Answer: (B) Iodine indicates the presence or absence of starch in food

Explanation:
The chapter explains that in Grade 6, students learned iodine gives a blue-black colour when reacting with starch. Blue-black colour in test tube A indicated starch presence; little or no colour in test tube B indicated starch had been broken into sugar by saliva.

Question: Which of the following best describes why the pancreas is considered a vital organ in the small intestine's digestive process?
A. It produces bile to neutralise stomach acids and break down fats
B. It secretes pancreatic juice that is basic in nature and breaks down carbohydrates, proteins, and fats
C. It stores and concentrates digestive juice between meals
D. It absorbs water and salts from undigested food
Show Answer & Explanation

Answer: (B) It secretes pancreatic juice that is basic in nature and breaks down carbohydrates, proteins, and fats

Explanation:
The chapter states that pancreatic juice is basic in nature, helps neutralise acids, and additionally breaks down carbohydrates, proteins, and fats—making it a multi-functional secretion essential for small intestine digestion.

Question: The term 'absorption' in the context of digestion refers to which process?
A. The mixing of food with digestive juices in the stomach
B. The breakdown of complex foods into simpler chemical forms
C. The passage of digested nutrients from the intestine into the blood
D. The removal of waste material from the body through the anus
Show Answer & Explanation

Answer: (C) The passage of digested nutrients from the intestine into the blood

Explanation:
The chapter defines absorption as the process where digested nutrients pass from the small intestine into blood vessels found in the intestinal walls, allowing these nutrients to be transported to different body parts.

Question: Why does the chapter specifically mention that earthworms use their moist skin for gas exchange rather than having specialised respiratory organs?
A. Because earthworms have no need for oxygen due to their simple bodies
B. Because their habitat and body structure allow them to exchange oxygen and carbon dioxide directly across their skin membrane
C. Because they absorb oxygen only through their digestive system
D. Because their small size makes dedicated respiratory organs unnecessary
Show Answer & Explanation

Answer: (B) Because their habitat and body structure allow them to exchange oxygen and carbon dioxide directly across their skin membrane

Explanation:
The chapter lists earthworms as an example of animals with different breathing mechanisms adapted to their unique habitats and environments. Their moist skin provides sufficient surface area for direct gas exchange with the environment.

Question: In the breathing model demonstrated in Activity 9.2, when the rubber sheet is pulled downwards, the balloons inflate. What does this model reveal about the mechanism of breathing?
A. Pressure changes in the chest cavity cause air to move in and out of lungs
B. The lungs actively pull air into themselves through muscular contractions
C. Air is forced into the lungs by external pressure from the atmosphere
D. The diaphragm relaxes to allow air to escape from the lungs
Show Answer & Explanation

Answer: (A) Pressure changes in the chest cavity cause air to move in and out of lungs

Explanation:
The chapter explains that pulling the rubber sheet downwards increases space in the bottle, causing the balloons to inflate—mirroring how the diaphragm's downward movement during inhalation increases chest space, allowing air to enter the lungs naturally.

Question: The chapter states that in test tube B of Activity 9.3, exhaled air turns lime water milky while inhaled air in test tube A does not. What does this observation demonstrate about gas exchange in the lungs?
A. The lungs remove oxygen from the blood and release it into the air
B. The lungs absorb carbon dioxide from the blood and expel it through exhalation
C. Exhaled air contains no oxygen while inhaled air is pure oxygen
D. The body produces carbon dioxide during digestion, which is then exhaled
Show Answer & Explanation

Answer: (B) The lungs absorb carbon dioxide from the blood and expel it through exhalation

Explanation:
The chapter explains that lime water turning milky indicates carbon dioxide presence. Since exhaled air turns lime water milky but inhaled air does not, this shows the lungs have absorbed carbon dioxide from blood and are expelling it through breathing.

Question: According to the chapter's description of the respiratory system's components, which structure serves the primary purpose of protecting the lungs from physical damage?
A. The diaphragm
B. The ribcage
C. The nasal passages
D. The windpipe
Show Answer & Explanation

Answer: (B) The ribcage

Explanation:
The chapter explicitly states that 'our lungs are protected by the rib cage,' identifying the ribs as the protective skeletal structure surrounding the lungs.

Question: The chapter presents the word equation for respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy. What does this equation reveal about the relationship between food digestion and cellular energy production?
A. Digestion and respiration are the same process occurring in different locations
B. Digested food alone cannot provide energy; oxygen is required to release usable energy from glucose
C. Energy is produced during digestion and then stored for later use during respiration
D. Respiration converts water into energy while digestion breaks down glucose
Show Answer & Explanation

Answer: (B) Digested food alone cannot provide energy; oxygen is required to release usable energy from glucose

Explanation:
• The equation shows glucose (from digested food) requires oxygen to release energy
• Oxygen from breathing enables the conversion of food into usable energy
• Neither process alone is sufficient; both digestion and respiration are essential for life

Question: In the chapter's discussion of ruminant digestion, partially digested food is brought back to the mouth from the stomach for additional chewing. What advantage does this process provide for an animal like a cow?
A. It allows the cow to digest plant fibres more thoroughly than single-pass digestion would allow
B. It prevents the cow from consuming too much food at once
C. It eliminates the need for a functional stomach altogether
D. It helps the cow produce milk more efficiently
Show Answer & Explanation

Answer: (A) It allows the cow to digest plant fibres more thoroughly than single-pass digestion would allow

Explanation:
The chapter explains that rumination involves bringing partially digested food back to the mouth for gradual, thorough chewing before final passage through the alimentary canal. This extended breakdown is particularly beneficial for grass-eating animals processing tough plant fibres.

Question: The chapter distinguishes between breathing and respiration by stating that breathing is physical while respiration is chemical. Which of the following best illustrates this distinction?
A. Breathing involves movement of air; respiration involves breakdown of glucose molecules
B. Breathing occurs only in the lungs while respiration occurs throughout the body
C. Breathing requires oxygen while respiration produces carbon dioxide
D. Breathing is voluntary while respiration is automatic
Show Answer & Explanation

Answer: (A) Breathing involves movement of air; respiration involves breakdown of glucose molecules

Explanation:
The chapter explicitly states: 'Breathing is a physical process, while respiration is a chemical process that occurs inside the body.' Breathing involves mechanical movement of air in and out of lungs, while respiration is the chemical breakdown of glucose to release energy.

Question: According to the chapter's description of the small intestine's structure, the thousands of finger-like projections serve what primary function?
A. They produce digestive enzymes that break down remaining food particles
B. They increase the inner surface area to maximize the absorption of digested nutrients into the bloodstream
C. They secrete mucus to protect the intestinal lining from digestive acids
D. They contract to mix the food with additional digestive juices
Show Answer & Explanation

Answer: (B) They increase the inner surface area to maximize the absorption of digested nutrients into the bloodstream

Explanation:
The chapter states that these finger-like projections 'increase the surface area for efficient nutrient absorption' and 'allow the digested nutrients to pass into the blood, which carries them to different parts of the body.'

Question: Considering the chapter's explanation of how different animals breathe, which characteristic of amphibians like frogs demonstrates their remarkable adaptation to variable environments?
A. They can hold their breath underwater indefinitely by storing oxygen in special sacs
B. They transition from gill breathing as tadpoles to lung and skin breathing as adults, allowing survival in both aquatic and terrestrial habitats
C. They have lungs that can extract oxygen directly from water without the need for gills
D. They develop a gizzard similar to birds that allows them to process aquatic plants
Show Answer & Explanation

Answer: (B) They transition from gill breathing as tadpoles to lung and skin breathing as adults, allowing survival in both aquatic and terrestrial habitats

Explanation:
The chapter explains that tadpoles use gills for aquatic life, while adult frogs use lungs on land and skin for gas exchange in water. This physiological flexibility across life stages demonstrates adaptation to changing environmental conditions.

Question: The chapter presents data showing inhaled air contains approximately 21% oxygen while exhaled air contains approximately 16-17% oxygen. Why is this difference significant for understanding how respiration works?
A. It proves that humans only need 4-5% oxygen to survive
B. It demonstrates that the body uses some of the oxygen during respiration to release energy, with the remainder being exhaled
C. It shows that breathing is more efficient than respiration in providing energy
D. It indicates that the lungs produce additional oxygen during the breathing process
Show Answer & Explanation

Answer: (B) It demonstrates that the body uses some of the oxygen during respiration to release energy, with the remainder being exhaled

Explanation:
The chapter notes that 'not all the oxygen is used up,' and presents this data to show the body consumes a portion of inhaled oxygen during respiration to break down glucose and release energy, with unused oxygen being exhaled back into the atmosphere.

Question: When you chew starchy food like chapati for an extended period, the food begins to taste sweet. Which digestive component is responsible for breaking down the starch into simpler sugars in your mouth?
A. Stomach acid
B. Saliva
C. Pancreatic juice
D. Bile
Show Answer & Explanation

Answer: (B) Saliva

Explanation:
Saliva contains a digestive enzyme that breaks down starch into sugar, which is why prolonged chewing of starchy foods results in a sweet taste. This enzymatic action starts the digestion process right in the mouth.

Question: In the experiment where boiled rice was chewed for 30-60 seconds before being tested with iodine solution, the result differed from unchewed rice. What principle allows this experiment to detect whether starch has been broken down?
A. Iodine turns blue-black only in the presence of complex proteins
B. Iodine changes colour when it encounters glucose molecules
C. Iodine produces a blue-black colour specifically when reacting with starch
D. Iodine neutralises acids present in food
Show Answer & Explanation

Answer: (C) Iodine produces a blue-black colour specifically when reacting with starch

Explanation:
Iodine has a distinctive reaction with starch, producing a blue-black colour. When saliva breaks down starch into sugars during chewing, the iodine test shows little to no colour change because starch is no longer present.

Question: The liver secretes bile, which is described as having a mildly basic nature. What is the primary purpose of this basic secretion in the small intestine?
A. To break down proteins into amino acids
B. To neutralise the acids coming from the stomach and break down fats
C. To absorb water and salts from undigested food
D. To produce energy directly for the body
Show Answer & Explanation

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

Explanation:
Bile neutralises the acidic food from the stomach through its basic properties and breaks down fats into tiny droplets to make their digestion easier.

Question: During inhalation, your diaphragm moves downward and your ribs move outward, causing air to enter the lungs. What does this movement accomplish in terms of the space inside your chest?
A. It decreases the space, forcing air out
B. It maintains constant space to prevent injury
C. It increases the space, allowing air to be drawn in
D. It has no effect on space but filters the air
Show Answer & Explanation

Answer: (C) It increases the space, allowing air to be drawn in

Explanation:
The downward movement of the diaphragm and outward movement of the ribs increase the volume inside the chest cavity, which lowers the air pressure and causes air to flow into the lungs.

Question: In Activity 9.3, lime water was used to test both inhaled and exhaled air. The exhaled air turned the lime water milky while the inhaled air did not. What does this observation indicate?
A. Inhaled air contains more oxygen than exhaled air
B. Exhaled air contains significantly more carbon dioxide than inhaled air
C. Both inhaled and exhaled air contain equal amounts of all gases
D. The lungs produce carbon dioxide during breathing
Show Answer & Explanation

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

Explanation:
Lime water turns milky when it reacts with carbon dioxide. Since only the exhaled air produced this reaction, it demonstrates that exhaled air contains a much higher percentage of carbon dioxide (4-5%) compared to inhaled air (0.04%).

Question: Grass-eating animals like cows engage in a process where they partially chew their food, swallow it, and then bring it back to their mouth for more thorough chewing. What is this specific adaptation called?
A. Mechanical digestion
B. Rumination
C. Peristalsis
D. Fermentation
Show Answer & Explanation

Answer: (B) Rumination

Explanation:
• Rumination is the process where ruminant animals regurgitate and re-chew partially digested food
• It allows cows and similar animals to more efficiently break down tough plant materials
• This adaptation is crucial for herbivores that feed on grasses and fibrous plants

Question: Birds lack teeth for chewing food, yet they are still able to break down their food effectively. Which structure in a bird's digestive system provides a functional replacement for teeth?
A. The stomach lining
B. The gizzard
C. The intestinal walls
D. The liver
Show Answer & Explanation

Answer: (B) The gizzard

Explanation:
The gizzard is a muscular chamber where food is broken down through muscular contractions and relaxations, often aided by grit (small stones) that birds swallow. This mechanical action replaces the function that teeth serve in other animals.

Question: The chapter states that breathing is a physical process while respiration is a chemical process. Which statement best explains this distinction?
A. Breathing involves the exchange of gases, while respiration involves moving muscles
B. Breathing is the movement of air in and out of lungs, while respiration is the breakdown of glucose using oxygen to release energy
C. Breathing produces energy, while respiration produces carbon dioxide
D. Breathing occurs only in lungs, while respiration occurs throughout the body
Show Answer & Explanation

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

Explanation:
Breathing is simply the mechanical movement of air into and out of the respiratory system, but respiration is the chemical process where oxygen is used to break down glucose (from food) to produce usable energy for the body.

Question: Amphibians like frogs demonstrate a remarkable ability to survive in both aquatic and terrestrial environments. How do they accomplish this feat in terms of respiration at different life stages?
A. They use only lungs throughout their entire life
B. Tadpoles breathe through gills while adult frogs use lungs on land and their skin for gas exchange in water
C. They develop gills as adults to breathe in water
D. They switch between lungs and skin based on the season
Show Answer & Explanation

Answer: (B) Tadpoles breathe through gills while adult frogs use lungs on land and their skin for gas exchange in water

Explanation:
• Tadpoles rely on gills for respiration in aquatic environments
• Adult frogs transition to lungs for breathing on land
• Adult frogs can also exchange gases through their moist skin when in water
• This dual respiratory capability allows frogs to thrive in both habitats

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