CBSE Class 7 Science Chapter 10: Respiration in Organisms NCERT Solutions

Solution: During strenuous physical activity like running a race, an athlete's body requires a significantly larger amount of energy. To meet this increased energy demand, the body needs more oxygen to facilitate the breakdown of food (glucose) through cellular respiration. Breathing faster and deeper allows for a greater intake of oxygen into the lungs and subsequently into the bloodstream. This increased oxygen supply to the muscles speeds up the process of cellular respiration, leading to the release of more energy required for the athlete's performance and recovery.

Solution:

Similarities:

• Both aerobic and anaerobic respiration involve the breakdown of food (like glucose) to release energy.
• Both processes are essential for the survival of living organisms.

Differences:

Feature	Aerobic Respiration	Anaerobic Respiration
Oxygen Requirement	Requires oxygen	Does not require oxygen
Location	Occurs in cytoplasm and mitochondria	Occurs only in cytoplasm
Food Breakdown	Complete breakdown of glucose	Incomplete breakdown of glucose
End Products	Carbon dioxide and water	Alcohol and carbon dioxide (in yeast); Lactic acid (in muscles)
Energy Released	Releases a large amount of energy	Releases a small amount of energy

Solution: When air containing dust particles enters our nasal passages, these foreign particles can irritate the lining of the nose. This irritation triggers nerve endings in the nasal mucosa, sending a signal to the brain. The brain then initiates a powerful, involuntary reflex action – sneezing. Sneezing forcefully expels the inhaled air along with the irritant particles, helping to clear the nasal passages and prevent the dust from reaching the lungs. It is a vital defense mechanism of the respiratory system.

Solution:

Test-tube A will have the highest concentration of CO₂.

Reasoning:

• Test-tube A (Snail only): The snail is a living organism and respires. Respiration releases carbon dioxide (CO₂) as a waste product. Since there is no plant to consume the CO₂, its concentration will increase over time.

  $Snail\; \backslash rightarrow\; CO\_2\; +\; Energy$

• Test-tube B (Water plant only): The water plant performs photosynthesis, a process that consumes carbon dioxide (CO₂) and releases oxygen. While the plant also respires, its rate of photosynthesis is likely to be higher during the day, leading to a net decrease or stable level of CO₂.

  $CO\_2\; +\; Water\; \backslash xrightarrow\{Light\}\; Glucose\; +\; O\_2$

• Test-tube C (Snail and plant): In this test-tube, the snail releases CO₂ through respiration, but the water plant utilizes this CO₂ for photosynthesis. This consumption of CO₂ by the plant will keep its concentration lower than in test-tube A, where no CO₂ is being consumed.

  $Snail\; \backslash rightarrow\; CO\_2$

  $CO\_2\; +\; Plant\; \backslash rightarrow\; Photosynthesis$

Therefore, test-tube A, containing only the respiring snail, will show the highest concentration of carbon dioxide.

Solution:

1. The correct answer is (iii) spiracles. Cockroaches, like most insects, breathe through a system of tiny pores called spiracles located along their body, which connect to a network of tubes (tracheae).
2. The correct answer is (ii) lactic acid. During intense exercise, when the body's demand for oxygen exceeds supply, muscle cells resort to anaerobic respiration, producing lactic acid. The accumulation of lactic acid causes muscle fatigue and cramps.
3. The correct answer is (ii) 15–18. The normal breathing rate for an average adult at rest is typically between 15 to 18 breaths per minute.
4. The correct answer is (ii) move downwards. During exhalation, the diaphragm relaxes and moves upwards, and the rib muscles relax, causing the ribs to move downwards and inwards. This decreases the volume of the chest cavity, forcing air out of the lungs.

Solution:

Here is the correct matching of items from Column I with Column II:

Column I | Column II

1. Yeast | (Anaerobic respiration, produces alcohol) - *Implied, not directly listed in options but contextually correct for yeast's respiration.*
2. Diaphragm | (Lungs) - *The diaphragm is a muscle involved in breathing for lungs.*
3. Skin | (Frog) - *Frogs use their skin for respiration.*
4. Leaves | (Stomata) - *Implied, stomata on leaves facilitate gas exchange.*
5. Fish | (Gills) - *Fish respire using gills.*
6. Frog | (Skin and Lungs) - *Frogs respire using both skin and lungs.*

Note: The provided options in Column II seem incomplete or not perfectly aligned for all items in Column I. The matching above is based on biological functions. If we strictly use the provided options, a more direct match would be:

Column I | Column II

1. Yeast | (No direct match in options, performs anaerobic respiration)
2. Diaphragm | (Lungs)
3. Skin | (No direct match in options, but frogs use skin)
4. Leaves | (No direct match in options, gas exchange via stomata)
5. Fish | (Gills)
6. Frog | (Lungs)

Assuming the intention was to match organisms with their primary respiratory organs or related structures:

Corrected Matching based on typical NCERT context:

1. Yeast → Anaerobic Respiration (produces alcohol)
2. Diaphragm → Lungs (involved in human breathing)
3. Skin → Frog (cutaneous respiration)
4. Leaves → Stomata (gas exchange in plants)
5. Fish → Gills
6. Frog → Lungs (pulmonary respiration)

Given the options provided in the source, the most direct matches are:

1. Yeast - *No direct match from options*
2. Diaphragm - (ii) Lungs
3. Skin - *No direct match from options*
4. Leaves - *No direct match from options*
5. Fish - (ii) Gills
6. Frog - (iii) Lungs

The source's provided answer format is confusing. Reinterpreting the question and options for clarity:

Column I | Column II

1. Yeast
2. Diaphragm
3. Skin
4. Leaves
5. Fish
6. Frog

Column II Options: (i) Tracheae, (ii) Gills, (iii) Lungs, (iv) Spiracles

Matching:

1. Yeast → Anaerobic respiration (no direct option)
2. Diaphragm → (iii) Lungs (works with lungs)
3. Skin → (Used by frogs, no direct option)
4. Leaves → (Gas exchange via stomata, no direct option)
5. Fish → (ii) Gills
6. Frog → (iii) Lungs (also skin)

The provided answer in the source seems to be incomplete or incorrectly formatted. Based on standard biological knowledge:

Final Answer based on likely intent:

1. Yeast - (No option provided, performs anaerobic respiration)
2. Diaphragm - (iii) Lungs
3. Skin - (No option provided, used by frogs)
4. Leaves - (No option provided, gas exchange via stomata)
5. Fish - (ii) Gills
6. Frog - (iii) Lungs (and skin)