The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms. Give reason. State the pathway of air from nostrils to the lungs in human beings.

Life Processes

Respiration

Official Answer

The rate of breathing in aquatic organisms is much faster than in terrestrial organisms because the amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air. To meet their oxygen requirements, aquatic organisms must breathe rapidly.

The sequential pathway of air from the nostrils to the lungs in human beings is:

Nostrils $\rightarrow$ Nasal passage $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli (Lungs).

dissolved oxygenlow concentrationnostrilsnasal passagetracheabronchibronchiolesalveoli

Marking Scheme

11.5 Marks: Explaining that dissolved oxygen in water is low compared to atmospheric oxygen, requiring faster breathing in aquatic organisms.
21.5 Marks: Correctly listing the sequential pathway of air from nostrils to alveoli/lungs.

Hint

Compare the concentration of oxygen in water versus air, and trace the anatomical route of inhaled air.

Quick Oral Answer

Aquatic organisms breathe faster because dissolved oxygen in water is much lower than in air. The pathway of air in humans is: Nostrils $\rightarrow$ Nasal passage $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.

Analysis & Explanation

Terrestrial organisms breathe atmospheric oxygen, which is abundant (about 21% of air). Aquatic organisms rely on oxygen dissolved in water, which is present in very low concentrations. Consequently, aquatic animals like fish must continuously and rapidly pump water over their respiratory organs (gills) to extract sufficient oxygen. In humans, the respiratory system is highly structured to filter, warm, and moisten air as it passes through the nasal cavity, pharynx, larynx, and trachea, before branching into bronchi and bronchioles to reach the alveoli where gas exchange occurs.

Common Mistakes

1Forgetting to mention that the concentration of dissolved oxygen in water is low.
2Scrambling the order of the respiratory pathway (e.g., placing trachea before pharynx or bronchioles before bronchi).

Interesting Facts

While humans breathe about 12 to 20 times per minute at rest, a fish may open and close its mouth to breathe up to 100 times per minute to extract enough dissolved oxygen!

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2014?

This question carries 3 marks in the CBSE Class 10 Science 2014 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Life Processes" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Respiration" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2014 paper?

This is a Short Answer question from Section SECTION-A in the CBSE Class 10 Science 2014 paper.