10

Q1. Which one of the following respiratory organs is not described correctly?

• Nasal cavity - Passage behind the nostrils
• Trachea - Wind pipe
• Larynx - Voice box
• Bronchi - Tiny air sacs 

Solution

The tiny air sacs present at the ends of the smallest bronchioles are called alveoli.

Q2. When we take deep breaths, we tend to

• Inhale more water vapour
• Exhale more water vapour
• Inhale more carbon dioxide
• Inhale more oxygen

Solution

We inhale more oxygen-rich air while taking deep breaths.

Q3. The outer surface of plant roots has a thin layer of cells called

• Stroma
• Epiblema
• Sclera
• Epidermis

Solution

The outer surface of plant roots has a thin layer of cells called epiblema.

Q4. Tracheoles are small branches present in the respiratory system of 

• Mammals
• Insects
• Reptiles
• Amphibians

Solution

Tracheoles are fine tubes that are a part of the respiratory system of insects. Air enters the insect's body through the spiracles and then enters the trachea. From the trachea, the air moves to the small tracheoles.

Q5. Snakes do not have

• Wind pipe
• Diaphragm
• Lungs
• Muscles

Solution

Snakes do not have a diaphragm. Therefore, air enters and leaves the lungs due to the action of body muscles and movement of the ribs.

Q6. Glucose partially breaks down into lactic acid in

• Yeasts
• Muscle cells
• Bacteria
• Plant cells

Solution

During anaerobic respiration in muscle cells, glucose partially breaks down into lactic acid and releases energy.

Q7. Plants lose water through the 

• Stems
• Stomata
• Roots
• Flowers

Solution

In plants, water vapour is released through the stomata.

Q8. Which of the following is broken down into energy during cellular respiration?

• Glucose
• Water
• Alcohol
• Oxygen

Solution

Energy-rich food such as glucose is broken down to release energy during cellular respiration.

Q9. Which of the following is involved in the process of respiration as well as transpiration?

• Leucoplasts
• Stomata
• Trichomes
• Midribs

Solution

Stomata play a major role in respiration as well as transpiration. In respiration, they are responsible for the exchange of gases while in case of transpiration, excess water is released in the form of water vapour through the stomata.

Q10. Oxygen is present in air as well as in water. Then, why do fishes die when taken out of water?

• Because the fish need to swim continuously to take in oxygen
• Because the gills cannot utilise dissolved oxygen when fish are outside water
• Because gills dry up and stick to each other in air and gaseous exchange cannot occur
• Because oxygen is in an ionic state in air which cannot be absorbed by gills

Solution

Fishes take in the dissolved oxygen from water for respiration. So, there must be a constant flow of water over gills. If the fishes are taken out of water, they suffocate and die because of lack of dissolved oxygen. Without water, the gills dry and stick to each other, and gaseous exchange cannot take place.

Q11. Breathing takes place with the help of

• Respiratory organs
• Digestive organs
• Excretory organs
• Reproductive organs

Solution

The process of breathing involves organs of the respiratory system.

Q12. Continuous supply of oxygen is necessary to produce

• Alcohol
• Energy
• Lactic acid
• Glucose

Solution

Breakdown of food to release energy takes place under the continuous supply of oxygen in the body. 

Q13. What happens if we hold our breath for some time?

• Level of oxygen decreases in our body
• Level of alcohol increases in our body
• Level of lactic acid increases in our body
• Level of carbon dioxide decreases in our body

Solution

If we hold our breath for some time, the level of oxygen decreases and the level of carbon dioxide increases in our blood. As a result, we feel suffocated.

Q14. Each part of the body carries out respiration independently in case of

• Crabs
• Plants
• Earthworms
• Goats

Solution

In plants, each part can independently take in oxygen from the air and utilise it to obtain energy and give out carbon dioxide.

Q15. Exhaled air is warmer than inhaled air because

• Energy is released in the form of heat during respiration.
• Exhaled air has less carbon dioxide and water vapour than inhaled air.
• Exhaled air has less oxygen than inhaled air.
• Exhaled air carries large amount of dirt and impurities.

Solution

Exhaled air is warmer than inhaled air because when we exhale, energy is released in the form of heat during respiration.

Q16. The amount of carbon dioxide present in inhaled air is approximately

• 20%
•  0.04%
• 1%
• 5%

Solution

Approximately, 0.04% of carbon dioxide is present in inhaled air.

Q17. Breathing is a part of the process of 

• Digestion
• Excretion
• Reproduction
• Respiration

Solution

Breathing is a part of the process of respiration.

Q18. Diaphragm is present above the

• Lungs
• Abdomen
• Wind pipe
• Pharynx

Solution

Diaphragm is a curved sheet of muscle present below the lungs and above the abdomen.

Q19. Mammals respire through their

• Spiracles
• Lungs
• Tracheae
• Gills

Solution

Mammals respire through their lungs.

Q20. In which of the following situations will the level of carbon dioxide in our body be low?

• Eating
• Sleeping
• Running
• Jumping

Solution

The breathing rate of a person is the slowest while sleeping as compared to the rate while eating, running and jumping. As a result, the level of oxygen used and the level of carbon dioxide released is also very low. 

Q21. Fishes respire through their

• Lungs
• Gills
• Book lungs
• Spiracles

Solution

Fishes respire through gills which are projections of the skin.

Q22. The inhaled air also contains some unwanted impurities which enter the nose. Which of the following is one of them? 

• Nitrogen gas
• Water vapour
• Carbon dioxide gas
• Pollen

Solution

The inhaled air also contains some unwanted impurities such as dust, pollen or smoke which enter the nose and irritate the lining of the nasal passage. 

Q23. How do roots of a plant respire?

• Through guard cells
• Through stomata
• Through root hair
• Through lenticels

Solution

The roots of a plant have a large number of tiny hair called root hair on their surface. The root hair are in contact with the air in the soil particles. Exchange of gases takes place through the root hair.

Q24. Food is broken down inside the body to release

• Oxygen
• Energy
• Alcohol
• Glucose

Solution

Breakdown of food inside the body releases energy along with carbon dioxide and water.

Q25. Which special body feature in dolphins helps them to breathe in water?

• Gills
• Blowholes
• Lungs
• Spiracles

Solution

Dolphins breathe in air with the help of blowholes which are located on the upper parts of their heads.

Q26. Which of the following will occur in case of more supply of oxygen to our body? 

• Increased sneezing
• Release of more energy
• Slow breathing
• Increased sleep

Solution

More energy is released if the supply of oxygen to the body is increased.

Q27. Spiracles are found in

• Birds
• Mammals
• Amphibians
• Insects

Solution

Breathing in insects takes place through tiny holes called spiracles.

Q28. Plants break down food during the process of

• Photosynthesis
• Excretion
• Transpiration
• Respiration

Solution

In plants, food is broken down to obtain energy during respiration.

Q29. The inhaled air enters our body first through the

• Trachea
• Ribs
• Lungs
• Nostrils

Solution

Air enters our body first through the nostrils.

Q30. We tend to feel more hungry after

• Standing
• Exercising
• Resting
• Sleeping

Solution

When we do any heavy physical activity or exercise, we tend to breathe faster than usual. As a result, food gets broken down very rapidly and makes us feel hungry.

Q31. Which of the following uses lungs for respiration?

• Crabs
• Lizards
• Fishes
• Earthworms

Solution

All reptiles including lizards have lungs for respiration.

Q32. Which of the following correctly points out the difference between breathing and respiration?

• Breathing takes place in every cell, whereas respiration takes place in our lungs.
• Respiration is a process of release of energy from food whereas breathing involves gaseous exchange.
• Breathing utilises the oxygen absorbed during breathing whereas respiration removes the carbon dioxide produced during respiration.
• Inhalation and exhalation are the two phases of respiration, whereas breathing does not involve any phases.

Solution

Respiration is a process of release of energy from food whereas breathing involves gaseous exchange. There is no release of energy during breathing.

Q33. Given below are the events that occur during inhalation and exhalation. Which of the following events occur only during exhalation?  (A) Muscles between the ribs relax. (B) Diaphragm relaxes and moves upwards. (C) Rib cage moves upwards and outwards. (D) Chest cavity becomes larger.

• (A) and (B) 
• (B) and (C) 
• (C) and (D) 
• (A) and (D) 

Solution

The rib cage moves upwards and outwards and the chest cavity becomes larger only during inhalation and not exhalation.

Q34. Which of the following acts as a direct source of respiration in submerged aquatic plants?

• Carbon dioxide released by land plants
• Oxygen dissolved in water
• Atmospheric oxygen
• Oxygen released by land plants

Solution

Submerged aquatic plants use the oxygen dissolved in water for respiration.

Q35. Under anaerobic conditions, muscle cells produce

• Glucose
• Lactic acid
• Oxygen
• Alcohol

Solution

Anaerobic respiration in the muscle cells during any vigorous physical activity produces lactic acid.

Q36. The layer present between the chest and the abdominal cavity is called

• Nasal cavity
• Diaphragm
• Trachea
• Rib cage

Solution

Diaphragm is a curved sheet of muscle which separates the chest cavity and the abdominal cavity.

Q37. After a heavy physical activity

• We do not feel hungry.
• We breathe faster.
• We breathe slower.
• We feel short of breath.

Solution

We tend to breathe faster after a heavy exercise because our body needs extra energy. Due to faster breathing, oxygen is supplied to our body cells at a faster rate.

Q38. Each part of the plant respires independently. How does respiration in green stems of certain plants occur?

• Through cork cells
• Through lignified cells
• Through vacuoles
• Through stomata

Solution

Plants with hard and woody stems and mature roots respire through lenticels. However, in certain plants green stems use stomata for gaseous exchange.

Q39. What will you comment on the breathing rate of a normal person at rest and that a sick person?

• A normal person breathes faster as compared to a sick person.
• A sick person breathes faster as compared to a normal person.
• The breathing rates of a normal person and a sick person are the same.
• A normal person tends to breathe more frequently as compared to a sick person.

Solution

A sick person has high energy demands for speedy recovery than a normal person. Therefore, he has a higher breathing rate than a normal person at rest.

Q40. Which organ is not involved in breathing in humans?

• Larynx
• Diaphragm
• Heart
• Lungs