Edexcel GCE Biology Unit 5 6BI05 June 2013

Thanks Hdizzle - those are really useful. I am bit stuck on:

"Many features of the skin of the naked mole-rat, such as the lack of an insulating layer and the loosely folded morphological arrangement contribute to poikilothermic responses to changing temperatures of this mammal. Further evidence for poikilothermy in the naked mole-rat is indicated by the presence of pigment containing cells in the dermis, rather than the epidermis, as commonly occurs in homeotherms. Lack of fur is compensated by a thicker epidermal layer and a marked reduction in sweat glands."

Namely:

1. Why does the lack of ins. layer and the folded morph CONTRIBUTE to poikilothermic response.

2. Why is the presence of pigment in the dermis EVIDENCE for poikilothermy? I don't really understand that at all. Why would a pigment being lower down prove it is an ectotherm?

3. Lack of fur is compensated by a thicker epidermal layer and a marked reduction in sweat glands. This seems to be more straightforward - they don't want to get too cold without fur, so they have thick skin and sweat less. But that doesn't seem to explain much about them being poikilothermic / ectotherms.

Any help much appreciated!

Got given questions today in school we'll be given answers I think next week
I'll take pictures and upload later today
although I think everyone will get them at some point..?

Questions:

Did you get your hands on the answers for these yet?

I did say the following week I would

Ah right, sorry! I was going through the article right now, and was just wondering. Thanks for the questions, though.

Actually, I don't see how this could be anatomical adaptation?
They did not develop lungs to help them withstand oxygen deprivation.

Also, did you read this:

41. All mammal fetuses live in a low-oxygen environment in the womb, and human infants continue to show brain resistance to oxygen deprivation for a brief time into early childhood. But naked mole rats, unlike other mammals, retain this ability into adulthood.

This paragraph proves it's not anatomical adaptation. It's either physiological or behavioural.

From Wikipedia: The naked mole rat is well adapted for the limited availability of oxygen within the tunnels that are its habitat: its lungs are very small and its blood has a very strong affinity for oxygen, increasing the efficiency of oxygen uptake.

Is this not anatomical?

Edit: as in the small lungs

As you've said before, it could be all 3 of them.
Plus, they never mentioned anything about their lungs being small in the article. Also, I've checked wikipedia; the part you've quoted is not cited and therefore you can't rely on it.

Hey,
You're right but Nooby Potato only quoted this from wikipedia to prove that the article does imply that there is anatomical adaptation in the naked mole rats for oxygen deprivation. He didn't quote it as reference and he did not suggest that we should write our answers in the exam based on what is written on wikipedia.

Could anyone just ask his teacher?

If they quote paragraph 41 or 42 (or both) and ask the following question:
What kind of adaptation is that? Give a reason for your answer.

What would you write? If anatomical, what's the reason?

I will ask my teacher about this tomorrow.
I'm not sure but I think they would give us more details or 'hints' in the question itself if they expect us to explain why the lungs are an example of anatomical adaptation. for example they might tell us certain features of the lungs of the naked mole rats and ask us to suggest how these features enable naked mole rats to survive in their environment.

Sorry for the late response

1. Lack of insulating layer means that their body temperature is more likely to be dependent on the surroundings.

2.the purpose of the pigment in the dermis is to either absorb heat or reflect (dependent on what type of habitat they live in). So that shows that their body temperature is controlled by the temp in their surroundings.
In humans we have the pigment in the epidermis for purposes of protection from uv light rather than as a method of retaining or reflecting heat.

Hope that clears it up a bit?

That's possible but wouldn't they mention something like that in the article?
They mentioned lungs once in paragraph 38.

Please tell us what your teacher says tomorrow. Thanks.

So I asked my teacher today and he said that we can classify the lung adaptations as a form of anatomical adaptation. However, he emphasised that unless the examiners give us more information about the lungs in the question or unless they ask us to make logical suggestions about how they might enable the rats to cope with oxygen deprivation, the questions won't probably focus on the lungs. The examiners are more likely to ask questions about the physiological adaptations of the naked mole rats as they are described in more details in the article.

- Channel proteins/gates allow sodium and potassium ions to move across the membrane and alter the membrane potential
- These proteins are across the whole membrane
- The sodium/potassium pump actively pumps ions across the membrane
- The phospholipid bilayer of the membrane means that ions cannot freely diffuse across the membrane.