aljana said:
I learned at university that most of the mutation which occur are either repaired by cell mechanism and never show up, or they are lethal, or almost insignificant.
Why there are some that make that big diffence, I do not know.
Let's take some arbitrary figures.
0.1 mutations per generation (0.3 according to one site I checked, but let's use 0.1).
90% of mutations are corrected immediately by internal mechanisms.
60% of mutations are immediately fatal.
80% of non-fatal mutations weaken the organism and thus gradually die out.
40% of the rest do some good.
0.00000001% of those do huge amounts of good, like allowing it to see in 3D or fly.
Let's take a hypothetical example of a small early animal that reproduces once per day and exists in fairly small numbers in a very limited area, like maybe only one million of them in total.
That's 0.00003232 beneficial mutations per generation, or 11804 per year across the whole population. Clearly I was too generous with my figures, so ...
0.01 mutations per generation
99% of mutations are corrected immediately by internal mechanisms.
99% of mutations are immediately fatal.
99% of non-fatal mutations weaken the organism and thus gradually die out.
1% of the rest do some good.
0.00000001% of those do huge amounts of good, like allowing it to see in 3D or fly.
0.0000000001 beneficial mutations per generation.
One every 10,000,000,000 generations.
One every 27.4 years, across the population, and actually 3D vision or flight would take 2.7 billion years by those figures.
Given that the Earth has room for rather more than one million amoebae and has been around for a bit more than four billion years ...
As for big changes, take the example of birds. Feathers are freaky, to be sure, but the first coelurosaur [http://www.ucmp.berkeley.edu/diapsids/avians.html] to grow feathers probably got a really big advantage out of it, like staying a fair bit warmer after sunset and being able to catch the endothermic mammals and/or stop them stealing its eggs. There's been a video about the evolution of flight posted already, so I'll defer to that for now, but feathers of suitable lengths make for a really nice aerofoil with shape adjustment for steering and speed control, which is probably why birds tend to be doing better than bats.
Bats? Oh, hey, sonar! Hearing's handy. Really good hearing's better, so once something randomly got the ability to detect sound it had a huge advantage and every refinement helped, and once things could hear vocal communication became useful so things that could deliberately make sounds and found ways to use that ability were more successful, and that made hearing all the more valuable to everything else ... and then something realised it could use the echoes of its own sounds to find its way in the dark, and DUDE I CAN FIND MY WAY IN THE DARK! Interesting note: birds all recognise each other's alarm calls, and we recognise them too. Even though they've been separate species for a very long time and we evolved from a different branch of the tree going back much further than that, we know an alarm call when we hear it. Did anyone have to tell you what it was? Did you have to see a bird flying away in fear and hear it making that sound to know it was an alarm call, or did it just
sound alarmed? Blue tits and coal tits have so much in common they're natural rivals in a lot of ways, but neither benefits from the predators getting the other as much as they do from the predators being unable to feed their own chicks this year.