An ecosystem undergoes a sudden drastic change that now favors organisms with an extreme phenotype. This is an example of
A. genetic drift
B. founder effect
C. artificial selection
D. disruptive selection
E. directional selection
According to cracksat the correct answer is E but for some reason i cant seem to understand why D is wrong i mean they both favor the extreme but D favors two extremes and E favors one.
@goldy1121, echinoderms have an endoskeleton. Often, descriptions mislead you to think that echinoderms have exoskeletons, but actually have calcified plates within to support its body. Also, I think that that centrifugation question isn’t well worded; you’re right.
are we going to discuss answers in this thread or is there a different thread just for that?
Since this will be my first sat, whats the general advice for skipping questions?
Yes, we’ll discuss answers in this thread. blargenshmargen, if you don’t know the answer to a question at all, then you should omit it. If you get a question wrong, that’s a quarter of a point penalty and it would be more favorable to skip 4 questions than to do all of them and get 4 wrong. Idk about this SAT Biology tho…I’m a little worried about it. :-S
An ecosystem undergoes a sudden drastic change that now favors organisms with an extreme phenotype. This is an example of
A. genetic drift
B. founder effect
C. artificial selection
D. disruptive selection
E. directional selection
According to cracksat the correct answer is E but for some reason i cant seem to understand why is D wrong? i mean they both favor the extreme but D favors two extremes and E favors one.
Because the extreme phenotypes are favored suddenly and drastically. See wikipedia page on disruptive and directional selection.
Well, I hope you guys for the best tomorrow. I’m going to start cramming now. 
I still have another 110 pages to read in the barron’s book… Gg sleep
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I did terrible with the barrons, I psyched myself out with preparing too much lol so i’m retaking it tomorrow using princeton and so far i feel better! I’ve been scoring 700-720ish though so i’m kinda mad about that but hopefully all goes well!
Anyone else staying up till 3am to finish studying or am I the only one?
I am too. Doing physics, math 2, and bio D:
Lol…unfortunately for me I’m probably pulling an all nighter…super unhealthy I know,but I have another subject test and I want to make sure my handle on the topics is strong. But from 10:45am-6am(Sunday) I will probably be sleeping.
so how did it go everyone? 
What did you say for the A1 A2 A3 allele question? I said 75 percent.
i cant remember that question to be honest. was it with punnett square maybe?
There wasn’t a Punnet Square in the exam. A1 A2 A3 were codominant. It said at what percent will the offsprings of the cross A2A3 X A1A2 will exhibit allele A2?
so u need to make a punnet square that what i meant and u are right
What is the max number of wrongs for an 800?