Evolution is the process by which all living organisms constantly
change, in the big picture towards better suiting their environment.
Not only is it a past change, the process is ongoing, it's just so slow
that we don't notice it.
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It is much easier to see if you look into the past. Most organisms
have
two eyes, two ears, five toes and five fingers. Slowly, over millions
and millions of years, all the organisms have evolved, starting from
bacteria, molluscs, then fish, and slowly to more developed animals.
And on every
level, as well as within species, evolution has created plenty of
diversity.
It happens by a random mutation happening every so often within
inherited characteristics. If the mutation does not suit the
environment, obviously the individual is disadvantaged compared to
other individuals, the individual is less likely to reproduce so the
characteristic is less likely to survive. If the mutation suits the
environment better than the original inherited characteristics would
have been, it has good chances to be passed on to future generations
and start a 'new trend'.
That is what Charles Darwin means by the 'survival of the fittest' in
his theory
of evolution.
There are some things that get mistaken with what is evolution:
* Evolution only works over a long enough time. That time is different
for each species. Insects for example have really short life time and a
quick generation turnover. They adapt to new conditions quickly (which
is a big evolutionary advanatge), so evolution works on them in quite a
short time. Humans, on the other hand, have a slow generation turnover,
so a couple of hundreds or even a thousand of years is not a long
enough
time for evolution to affect us. We need more like a ten thousand of
years at the very least.
* Evolution strives to perfection but is not always perfect. Evolution
hasn't stopped, (and will never, because the mutations will always
happen and the conditions in our environment will always change, so
there will always be room for improvement), so you cannot look at a
characteristic and say, what is this good for - it has to be good for
something? Not necessarily. We have rudimentary organs, we have
characteristics that are not exactly good for something. If a
characteristic is neither exactly good or exactly bad it can be carried
on through generations. It has to be bad, it has to be of a direct
disadvantage,
for the evolution to 'get rid of it'.
Note:
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correct in the language used in Australia.
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