[Zoo]

If something is thigmotropic, what does it do?

[skenasis]

'tropic' means that it reacts to something...biology from two years ago gives me a nagging suspicion it would be touch, or pressure.

So if something is thigmotropic, it responds to touch/pressure.

[Zoo]

*nods* Although to be nitpicky, tropic means it will react by moving toward the stimulus. Could also be thigmophobic (kinda like photophobic or hydrophobic), where it would move away from the touch.

Your question

[skenasis]

Although to be nitpicky, tropic means it will react by moving toward the stimulus.

Well, my biology teacher worded it as 'reacting positively' to the stimulus, so...meh. And moving towards is reacting to, so nyer

Name one of the theories behind cats' purring.

That is, scientists aren't sure exactly how cats purr, and have developed several theories to that end. Name one of 'em.

[Goto]

No idea about the purring thing, but 'moving toward' and 'reacting to' are certainly not the same thing, Darkie. Not that Zoo shouldn't have given you the point for it, but I do enjoy picking at minor flaws.

[skenasis]

Mister Goto is a nitpicking meanie. And moving towards something is reacting to it.

No answers yet, I see.

*waits for Zoo to notice the topic*

[Neraphym]

Communication.

[Goto]

She said how, not why.

And I agree that moving towards something is reacting to it. What you said was that reacting means moving towards it. That's certainly not the case, 'reacting' is much broader and contains a lot of actions which aren't moving forward.

[Zoo]

Picky, picky!

Anyway. One idea is that they can control some of the laryngeal muscles in a way that they open and close the vocal cords very rapidly, so that air passing through is caused to vibrate to make the purring sound.

Ah, and while I was poking around I found that it's thought that purring might be used for a kind of self-healing, since the frequency of the purr is the right one to stimulate bone growth and other such things. Which would explain why they purr when they're in pain or under stress of some sort. Although that doesn't seem to be the only use.

[skenasis]

Yay for Zoo.

Sometimes I swear Goto's sole purpose in life is to terrorize me.

Anyway, next question to Zoo.

[Zoo]

What is a change in allele frequency over time?

[skenasis]

My first attempt at a post mysteriously disappeared, so I have to post again <_<

A change in allele frequency over time is, in essence, a certain 'trait' (eg brown eye gene) becoming more or less common in a species over time.

And I can't be stuffed elaborating any more, so nyer.

[Zoo]

I was looking for a one word answer ("evolution" - had that beaten into me in a couple different classes). Your answer is approximately correct though, so your turn.

[Ratty]

I was looking for a one word answer ("evolution" - had that beaten into me in a couple different classes). Your answer is approximately correct though, so your turn.

Blah. I was seriously going to say that, but I thought it was too stupid.

Lol... Kicking myself now.

[skenasis]

Blame biology, since that's how I learnt it.

And apparently Zoo's classes and mine were very different, because what was beat into me was that evolution is not change in allele frequency. Evolution is mutation of genes over milennia, and change of allele frequency is adaption. I suppose one could also argue that the two go hand in hand and together make up evolution, but...whatever.

What is the only rock that floats in water?