bottom and surface dwelling fish

[Adz795]

Q. Values of the total surface area of gills (in arbitrary units) per unit gram body weight of two types of fish are given below:
Fish I: 442
Fish II: 1725
One of them is a bottom dwelling fish while the other is a surface dwelling fish. Identify the two types.

That was the question. I don't understand the relationship between bottom/surface dwelling and distinct requirements for gas exchange. Please explain.

[canalon]

Think about why a fish would need relativley more gill than another? what advantage that would provide? which of those 2 environments would favour such an evolution?
This is also related to the way gas diffuse in water...

[Trevor]

Think about why a fish would need relativley more gill than another? what advantage that would provide? which of those 2 environments would favour such an evolution?
This is also related to the way gas diffuse in water...

I agree. The deeper the water, pressure increases and the oxygen levels will be less than those available to surface-dwellers. Therefore- they would need a greater surface area of gill to extract as much O2 as possible. This is can be seen in humans as well. People who spend most of their lives in higher elevations (Let's say Denver) will have a higher lung capacity than someone from, say New Orleans. Same can be seen with musicians who play a woodwind instrument- an increased lung capacity. So it all relates. Right?
As canalon said, the differnce in environments can cause the difference too.

[JackBean]

LOL, Denver is high?

[Trevor]

LOL, Denver is high?

Generally speaking compared to sea level, why not.

[JackBean]

generally speaking, Netherlands is higher than sea level as well (at least most of it), but we are talking about changes in oxygen level, are we not?

[Trevor]

generally speaking, Netherlands is higher than sea level as well (at least most of it), but we are talking about changes in oxygen level, are we not?

Yes we are. I didn't know that, I've never been to Europe. Or out of the country.

[JackBean]

How is that related?

[Adz795]

Thanks a lot canalon. I do approach situations with questions similar to the ones you suggested. The reason I posted this question was that the answer says that Fish I (442) is bottom dwelling and Fish II (1725) is surface dwelling. That is contradictory to Trevor's logic (and mine too). I don't see any reason for this answer though I can assure you that the answer is correct.

The question was asked in the Indian National Biology Olympiad 2011 and the given options were:

a. Fish I is marine while Fish II is freshwater fish
b. Fish I is bottom dwelling while Fish II is surface dwelling
c. Fish I is a bony fish while Fish II is a cartilagenous fish
d. Fish I has a small body mass while Fish II has a large body mass

I chose d. but the answer was b.
(Well, now I think d. has to be wrong because larger gas exchange area per unit body mass has to be relatively more in a fish with smaller body mass than one with a larger body mass)

Thanks a lot Trevor, we share the same idea =)

[Gavin]

Cold water can hold more oxygen than warm water. Bottom waters tend to be colder than surface waters.

[Adz795]

I've made a fool of myself.

Thank you very much Gavin.

[Gavin]

You're welcome, and I doubt you're a fool.