Any biology experts out there?

Question

Can somebody help me answer question number 2 from this college board link?


http://www.collegeboard.com/prod_downloads/ap/students/biology/biology_frq_01.pdf

Answer 1

Alright, to answer these questions, you need to understand in full what natural selection is.

So, let's go on to question 1.

Natural selection is a process in which natural events favor traits of one species over the other. The best way to explain it is through this example:

Let's say there is a small colony of beetles. In this colony, 90% of them are bright red in color as 10% of them are black. Now, every morning, a huge flock of birds flies by the colony and eats all the red beetles they can find (because, for this example, red beetles are easier for the birds to find--while black is almost impossible). Eventually, as time passes, the colony will continue to reproduce--losing more and more red beetles over time. Now, as the colony loses more and more red beetles, the chances of a new generation of beetles with 90% red and 10% black is less and less possible. Soon, the flocks eliminate all of the beetles with red, and can no longer see the new colony of all black beetles. As you can see, natural selection has opted for darker beetles, to help them survive and continue the species. Natural selection is a way for nature to keep things interesting.

Another example--did you know that giraffes once existed in both long and short-necked forms? But, because the leaves were accessable by the long-necked giraffes only, they competed and eliminated their short-neck cousins. Nature SELECTED long necks.

Question 2.i.
Convergent evolution occurs when two different species APPEAR similar, though they have evolved in different ENVIRONMENTS. You can link this to natural selection by saying nature "favored" their appearances. For example, a flying squirrel (a placebal mammal) and sugar glider (a marsupial) are two distinct species, one in North America and the other in Australia. Now, they appear identical--because, for their environment, nature selected their appearance and ability to glide. You can feel free to use this example.

Question 2, ii.
Looking back on my beetle example, pretend that the birds were antibiotics and that the beetles were bacteria. When you use medicine, you are killing off the bacteria who are vulnerable to it. However, some remain. Those immune bacteria then multiply, as their offspring also display the immunity. If you continue to use the same medicine, you will eliminate bacteria who are vulnerable, while those who have an immunity continue to reproduce. So, you see, bacteria do NOT get "stronger" over time, it's just that the surviving bacteria multiply and pass on their immunities.

For the final three questions, I'll let you try them on your own, and I hope I've helped you out a bit. But still, feel free to e-mail me if you need further elaboration. I hope I was clear.

Answer 2

Both are definitely true. This is why the National Institutes of Health (NIH) have recombinant DNA guidelines for all rDNA research.