Question: How would evolution explain mimicry? Did the plants and animals develop mimicry by chance, by their intelligent choice, or by design? And how did photosynthosis evolve?

Ceri-Wyn Thomas answered on 24 Jun 2010:

This is a great question! Mimicry in animals did not develop by chance, choice OR design I’m afraid Evolution is far more complex than that- mimicry is a type of adaptation that results in animals being much better adapted to their environment since they’re so effectively concealed from prey. It may seem staggering to think that an insect could evolve to look like a leaf or another type of insect- but here is a quick explanation of how it might happen: Firstly, mimicry is considered a positive adaptation- this means that it is usually very beneficial to the mimic. Adaptations arise through a chance mutation to a gene or number of genes over time. These genes may cause a change in an organism’s appearance- some changes may make an organism more conspicuous and vulnerable to prey, but some would be highly advantageous- for example- a butterfly living off green leaves developing more green pigments in their wings through a mutation. These advantageous mutations generally mean that the organism will live longer and perhaps produce more offspring who will inherit this mutation simply because their parents were able to live long enough to reproduce. The parents would have had an advantage over other parents without this mutation. (Parents without the advantageous mutation might not be as successful at producing offspring if they’re being gobbled up by prey for looking too conspicuous.) This is what natural selection is!

So- now that our good mutation is in the gene pool- lots of organisms within the species will eventually end up with it through sexual reproduction. Where mimicry is involved- when animals mimic other animals or plants they often inhabit the same environment- so they face the same challenges and may even be competing for the same resources! Over time smaller mutations to the mimic’s genome may fine tune its appearance to look like another insect or plant that’s already very successful in that environment- (Insects do this when they mimic other nasty tasting poisonous species) It’s not doing this through choice or design though- Natural selection works on adaptations rather than the animals themselves- if an adaptation for bright poisonous looking colouration is a very successful adaptation in one environment then another completely different organism could evolve this adaptation too- it depends on competition within that environment- not on the animal itself! Natural selection is blind to animals- it selects for adaptations! So though it may seem amazing that an insect could so closely resemble a twig or a flower- they’ve just evolved similar structures according to the constraints of their environments.

Photosynthesis was also a rather successful adaptation for green plants- the chlorophyll molecule was probably evolved in a similar way- through natural selection! 🙂