Question

3. A mouse has approximately 1,400 olfactory genes. Provide an evolutionary explanation. [2]

4. A nose also functions as a humidifier. Explain the relationship between noses and people who live on the shores of the Mediterranean sea, compared to those further north, or further south. [2]

Answer 1

3. Answer- A mouse contains 1400 olfactory genes which are far grater then human olfactory genes. One study suggests that, mice have ≈2.7 times as many Olfactory Recepters (ORs) as humans, and 1.4 times as many OR subfamilies.

The mouse and humans both are evolutionary related to each other because both of them are mammals and have common evolutionary ancestors. But mouse have evolved greater number of olfactory genes due to its burrowing habit. The burrowing habit of mice lead to greater demand of more adative olfactory organs. Because under the ground, the mice can't rely on vision and it gets the sense of direction by sense of touch and smell.

4. Answer- Humidifier is an instrument which adds moisture in the air. Our nose functions as natural humidifier by adding mositure to the air coming in respiratory passage.

When we talk about the people living on Shores of Mediterranean sea, its not needed for their nose to function more for humidification because air is naturally very moist in these areas.

But when we talk about people away from shores (either in North or South), there noses are more adapted for the purpose of humidification because moisture level is low in those areas.