Question of the Week Podcast

Question of the Week episode

Wed, 11th Dec 2013

Is size important?

A quarter-inch-long parasitic wasp, Peristenus digoneutis, prepares to lay an egg in a tarnished plant bug nymph. (c) Photo by Scott Bauer.

Does a fly evolve faster than a toad? A whale slower than a barnacle? And if so, how does our bodies immune system keep up with bugs?

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My thoughts as a non-scientist...

I would have thought lifespan would have more impact than size. Specifically, the time taken for an organsim to reach sexual maturity. If something could go through fifty generations in the time it takes for us to go through one, it increases the amount of beneficial mutations possible.

Also, if a species has a shorter lifespan and is quicker to die, that species will be faster at weeding out the genetic material that doesn't do so well, and the ones that breed will drive the evolutionary process. bizerl, Mon, 16th Dec 2013

Evolution being a result of individual change expressed in a herd, it's much easier to detect among species that reproduce quickly, reproduce in large numbers, and are relatively simple so that a small genetic variation produces a significant change in appearance or behaviour.

A genetic variant that makes a bacterium resistant to an antibiotic will express itself very quickly (in days if not hours) as the descendants of "normal" bacteria are killed off in vast numbers by their bactericidal environment whilst the daughters of the variant are free from competition for nutrition. But a variant that renders humans immune to, say, peanut allergy, will take millennia to express as a change in herd characteristics because (1) very few humans are allergic to peanuts (2) we are not regularly attacked by hordes of peanuts and (3) it takes around 20 years to produce a new generation of humans. There is evidence of human evolution to cope with dairy products and alcohol, but these traits are not universal throughout the species as they are only essential for survival in a primitive, cold, urban society - environmental conditions that only lasted for a few generations before the gene pool became stirred by travel.          alancalverd, Tue, 24th Dec 2013

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