Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: BreakBeatPoet on 17/08/2010 06:20:48
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Was hoping someone, much more qualified in this topic than myself, can help me solve/understand some questions I had about the evolution of senses.
If evolution is random mutations... why do so many species(seemingly vastly different in stages of evolution) carry such similar traits such as eyes to see and ears to hear? and often they are symmetrical and in pairs?
It must have taken quite a few generations of "random mutations" to develop complex(or even simple) sensory systems like eyes and ears. I doubt these changes all happened at once to produce a single generation suddenly possessing ears or eyes. So how did mother nature know to keep certain "random" changes and add to or modify them in order to create ears or eyes without ever initially knowing that such a thing as sound waves and light exist to be interpreted?
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If evolution is random mutations... why do so many species(seemingly vastly different in stages of evolution) carry such similar traits such as eyes to see and ears to hear? and often they are symmetrical and in pairs?
common ancestor species way back in history and simplest solutions to problems. humans and domestic cats both have eyes; and that's because all mammals have evolved from common ancestor species in the triassic which we presume had similar eyes to both humans and cats. humans and octopuses both have eyes; but they come from almost totally different genetic pathways; ie they have developed separately (we can see differences in the eyes that show disparate basic evolutionary steps) as a cool mechanism for gaining an advantage over competitors.
It must have taken quite a few generations of "random mutations" to develop complex(or even simple) sensory systems like eyes and ears. I doubt these changes all happened at once to produce a single generation suddenly possessing ears or eyes. So how did mother nature know to keep certain "random" changes and add to or modify them in order to create ears or eyes without ever initially knowing that such a thing as sound waves and light exist to be interpreted?
evolution is the pairing of two mechanisms - the random variation of the genome through mutation and increased survival and breeding of animals with beneficial mutations; that is all, there is no plan or end. because most of us grew up with creation stories we find it very hard to avoid making a 'goal' for evolution; ie how did evolution create us (in all our awful splendour [:D] ). the eye is a case in point, it is hard (but not impossible) to rationalise the piecemeal mutations (because you are correct it wasn't instantaneous) that create such a organism. however, many of the steps have now been found, in the fossil record and in other species. so mother nature didnt know to keep the eye, there was no decision at any point in any species' evolution; those animals with a slight mutation bred favourable, the mutation persisted and in time other mutations built upon it.
Matthew
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But like we said, a slight mutation could not lead to having a working eye. They developed over time and over many generations, right? So how would that slight mutation still be bred "favorable" if it were not yet a working eye and served no benefit to a species survival until further improved? I'm using the eye as an example here but I suppose the same goes for the ear and many other byproducts of evolution.
common ancestor species way back in history and simplest solutions to problems. humans and domestic cats both have eyes; and that's because all mammals have evolved from common ancestor species in the triassic which we presume had similar eyes to both humans and cats. humans and octopuses both have eyes; but they come from almost totally different genetic pathways; ie they have developed separately (we can see differences in the eyes that show disparate basic evolutionary steps) as a cool mechanism for gaining an advantage over competitors.
If evolution is random, how did sensory systems even develop in more than one species at all? how could true randomness lead to such similarities? I understand that most other mutations that were not as beneficial died off and we are left with the species that have sensory systems BECAUSE they have sensory systems and it was an advantage. But I don't see how it all began? What are the chances of the same random mutation occurring to even form ANY type of eye (out of the infinite number of random mutations) in multiple gene pools?
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If evolution is random mutations... why do so many species(seemingly vastly different in stages of evolution) carry such similar traits
see parallel evolution. (http://en.wikipedia.org/wiki/Parallel_evolution)
why ... symmetrical and in pairs?
two ears or forked tongue enable the creature to tell which direction the stimulus is coming from.
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Just as a guess here is how just one light-sensitive cell (ie the far precursor of an eye) could be an advantage; perhaps many of the creatures near the top of the ocean had developed ways to realise that night had fallen and they should move to different levels in the ocean to get the best nutrients, when one mutation changed a cell that previously sensed the slow heat change in the ocean to being light sensitive (much quicker). for the next n generations all the progeny of this one mutated animal that relied on their one light-sensitive cell rather than the slow heat-sensitive cell bred like rabbits and ate up all the nutrients before their slow cousins could arrive. two cells turned out to be better than one, three better than two etc and suddenly you have basis of external eye. All supposition of course, but does provide a pathway that doesnt involve jumping from no-eye to eye.
Matthew
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Each stage in the evolution of the eye would have offered some advantage to it's owner. Same for ears etc.
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It's probably worth having a read of the wikipedia article about the evolution of the eye as an example of how sensory organs developed.
http://en.wikipedia.org/wiki/Evolution_of_the_eye (http://en.wikipedia.org/wiki/Evolution_of_the_eye)
Specifically with regard to eyes, several different types of eye exist, in different types of animal, and although these different types of eye have essentially developed independently, implying parallel evolution, they have all developed from the same set of initial building blocks, which would have limited the scope of variation between the separate developments: From the article above...
Certain components of the eye, such as the visual pigments, appear to have a common ancestry – that is, they evolved once, before the animals radiated. However, complex, image-forming eyes evolved some 50 to 100 times – using many of the same proteins and genetic toolkits in their construction.