tbr test 2 bio questions

[2010premed]

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1. The temperature at which a fluid membrane becomes a rigid crystal is called the phase transition temperature. If one bilayer has a higher degree of fluidity than a second bilayer, the phase transition temperature of the first bilayer is:
Answer: less than that of the second bilayer.
</SPAN>Wrong answer: greater than that of the second bilayer.
</SPAN>According to the question, the phase transition temperature = when fluidà rigid.
So if the first bilayer is more fluid, then that means sat at 10 degreed, the second fluid alreadybecame rigid, while the first bilayer is still fluid, and we need to lower the temperature for fluid 1 to be solid. Is this why the phase transition temperature is lower? It’s a little werid to think about because it seems like the lower the phase transition temperature, then the lower the temperature required to become rigid, and thus the easier it is to become rigid… a little clarity is needed here.
Also, would the answer have been the opposite if the phase change was from liquid to gas?

2. In New England, there exists a species of silverfish that shows different population genetics, depending on the temperature. When a population at 25°C initially has 90% female silverfish, it requires more generations to reach equal population distribution of males and females than when the temperature is 30°C. How can this be explained?
A. The silverfish do not mate as readily at warmer temperatures
</SPAN>B. The males have a greater rate of attrition at higher temperatures.
</SPAN>C. A silverfish is able to change its sex in adult life.</SPAN>
D. The silverfish population for this species produces more males at lower temperatures.
</SPAN>How would you do this question? Also, what does attrition mean in this context (chocie B)

 

[fizzgig]

bilayer 1 has HIGH fluidity. it likes being fluid. it will be HARDER to freeze/solidify, and so the temp at which it has a phase transition should be lower.

go back to your sentence 'the lower the temperature required' and reread, bc that is the point i think your thoughts deviated ... yes, a more fluid membrane means a lower temperature required to become rigid - your words were correct. the lower temp is REQUIRED, meaning if you don't get down to that temp you don't solidify. mp/fp can be more of a pain in my brain too bc we usually talk about what makes stuff hard/easy to boil (one direction) but we talk about what makes things easy/hard to freeze AND melt, and 'harder to freeze' and 'harder to melt' move the phase transition in opposite directions...

for the second question, A seems irrelevant bc they mention num of generations in the question. if the generations take longer to happen, so what - they still state that one situation requires more generations vs the other. B, males die off more quickly at high temps. that seems to be the opposite of what happens. D. again, opposite of that they're saying they observed. C. if one gender could turn into the other, and that decision to switch gender vs stay the same was governed by an environmental trigger, sure, this could in theory change how fast you could bring a population to fifty fifty.

 

[2010premed]

k, thanks. Yeah for the 2nd one I automatically crossed out C cus I thought it was so out there, but I guess if all the others are definitely not the answer then it will do