SSS 2008-11-06

（单词翻译）

This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

Why bother with sex? It’s a question that’s bugged¹ biologists since they first noticed that some critters do it and some don’t. The answer they’ve come up with is that sex generates genetic² diversity, which could allow a species to better adapt to changing environments. That’s because sex mixes together the genes³ from mom and dad. And, like shuffling⁴ a deck of cards and dealing⁵ new hands, sometimes the kids will get a better combination of genes than their parents had.

So how do species that reproduce by cloning weather change? It turns out not all clones are alike. Scientists from Melbourne were studying a kind of mite⁶ that reproduces asexually. In the process, sometimes rare mutations occur, so a clone might be a little different from its parent, and from the rest of the population.

What the scientists found is that sometimes these rare mutants are favored by natural selection. Maybe they’re a little better at hiding from predators⁷. So they leave behind more offspring, and eventually come to dominate the population. When circumstances change, another rare mutant might gain favor, results that appear in the current issue of the Proceedings⁸ of the National Academy of Sciences. So sex isn’t necessary, as long as you’re willing to back somebody different when it’s time for a change.

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.