• Question: what selective advantages drove the development of sexual reproduction, and how did it develop?

    Asked by mcfaceface49 to Andrew, Ash, Gem, Paige, SJ on 29 Jun 2012.
    • Photo: Paige Brown

      Paige Brown answered on 29 Jun 2012:

      Very good question!!!

      It’s all about DNA. Have you learned about DNA and how it copies itself each time a cell divides into more cells? DNA, the hereditary material in our bodies, is always best when it is DIVERSE. The more diverse the DNA of a population of people or animals is, the better that population is suited to survive many different environmental conditions. For example, populations with genetic diversity can adapt to new environmental conditions via natural selections and genetic mutations that make the animal or person better able to survive. Without lots of different DNA sequences, it is hard to adapt, because you aren’t working with much diversity in the first place!! Does that make sense?!

      So sexual reproduction, unlike the straight cloning that happens in certain types of single cell organisms like bacteria, produces more diversity by taking genetic material from both a male and female and combining it in new ways. This genetic diversity is very good for the animal! In fact, scientists have actually found that although bacteria do not have sex, they exchange DNA through tubes that like one bacteria to the other sometimes, and thus diversify their gene pool! All this makes the organisms better able to adapt to new environments, and ensures that a quick environmental change will not wipe out the animal and make the population go extinct.

    • Photo: SarahJayne Boulton

      SarahJayne Boulton answered on 1 Jul 2012:

      I went to answer this question but Paige looks like she’s covered most of the bases!

      The first things to proliferate using sexually reproductive means were a thing called ‘protists’ (a really old and basic kind of single cells) the main driving force behind it was the fact that it produced offspring that were ‘viable’ (capable of themselves reproducing) and that were ‘selectable’ (as in natural selection).

      This mode of reproduction probably emerged as a refinement of the previous evolution of sperm and egg like organelles, like Paige mentioned with DNA ‘plasmids’ being swapped from bacteria to bacteria or like the reproductive spores of fungi. The cells found a way to make self contained packages of DNA that could intermix with DNA packages from other members of the same species. And thus: an new kind of reproduction was born! Happy days!

      Sexual reproduction creates greater variability in a population due to the notoriously high mutation rate of DNA in making eggs and sperm compared to cloning, where you just make another copy of your self. Added to the fact that you mix two organisms DNA together to make an offspring you’re bound to get some funky results.

      The offspring that do best get to procreate some more, the ones that are no good don’t. That’s the brutal simplicity of ‘raw selection’.

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