Science Question of the Day
This is an actual question from one of my students. I always like it when the kids are thinking, and the answer is interesting, so I thought I would post it for all to read. Names have been changed and questions edited to protect the students, though nobody is really innocent.
Dear LaBlonde,
Why do some animals reproduce sexually (who have the ability to reproduce asexually) in times of crisis?
The answer
You are referring to 'facultative sexuality': the ability to change from asexual to sexual reproduction in times of environmental crisis. The benefit to this process lies in the fact that, although we've been talking about individual genes in class, in complex organisms a single trait may depend on the actions of several genes. To have the most beneficial phenotype for an environment, you will need to a specific combination of alleles for these genes. In asexual reproduction, individuals pass their allele combinations to their offspring unscathed, allowing the offspring to be just as successful at navigating the environment as the parent was. This is fine as long as the environment is stable- well-adapted parents produce well-adapted offspring. No, I'm serious, although anyone who ever attended Thanksgiving at the boyfriend's relatives might disagree. (Ba dum CHING!) However, when things go badly, the old gene combinations might not be good enough anymore. In fact, in a changed environment, who's to know what will work well and what will drag you out of the gene pool? The best solution is to produce many, variable offspring, with the hopes that one will contain a more idea genotype. The good thing about sexual reproduction is that between crossing over and the random assortment of paternal and maternal chromosomes in the gamete, an individual will not pass their complete genotype to their offspring- it will get mixed up with alleles from the other parent, and potentially produce a more ideal genotype for that environment.
As one can imagine, this sort of free-and-easy switchin'occurs mostly in our low-on-the-food-chain brethren (and sistren), such as microbes, aphids, and some plants. This is a shame, given some of the dates I've been on. Asexuality doesn't sound that bad to me.
Dear LaBlonde,
Why do some animals reproduce sexually (who have the ability to reproduce asexually) in times of crisis?
The answer
You are referring to 'facultative sexuality': the ability to change from asexual to sexual reproduction in times of environmental crisis. The benefit to this process lies in the fact that, although we've been talking about individual genes in class, in complex organisms a single trait may depend on the actions of several genes. To have the most beneficial phenotype for an environment, you will need to a specific combination of alleles for these genes. In asexual reproduction, individuals pass their allele combinations to their offspring unscathed, allowing the offspring to be just as successful at navigating the environment as the parent was. This is fine as long as the environment is stable- well-adapted parents produce well-adapted offspring. No, I'm serious, although anyone who ever attended Thanksgiving at the boyfriend's relatives might disagree. (Ba dum CHING!) However, when things go badly, the old gene combinations might not be good enough anymore. In fact, in a changed environment, who's to know what will work well and what will drag you out of the gene pool? The best solution is to produce many, variable offspring, with the hopes that one will contain a more idea genotype. The good thing about sexual reproduction is that between crossing over and the random assortment of paternal and maternal chromosomes in the gamete, an individual will not pass their complete genotype to their offspring- it will get mixed up with alleles from the other parent, and potentially produce a more ideal genotype for that environment.
As one can imagine, this sort of free-and-easy switchin'occurs mostly in our low-on-the-food-chain brethren (and sistren), such as microbes, aphids, and some plants. This is a shame, given some of the dates I've been on. Asexuality doesn't sound that bad to me.
posted by La Blonde Parisienne at 3:26 PM
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