An Introduction to Evolution
March 18th, 2008I have to give a speech on evolution…help? – Yahoo! Answers
My nephew would tell you that a shark doesn’t turn into a chair.
Darwin and Wallace were the first guys to write about evolution.
Darwin got his ideas while traveling around the world and seeing all kinds of animals. The ship was called the “Beagle.” You’ll want to talk about Galapagos Island, where he saw different species of birds in a place so far from the continent that they had to have all come from one ancestor. He thought that their beaks were shaped by what food their ancestors ate. Seeds vs. berries vs. bugs, etc. Don’t forget the tortoises.
There are different theories of how evolution occurs.
**Lamarck** said that species evolve because acquired traits are passed down through the generations. Like giraffes stretching their necks up to get leaves makes their offspring have longer necks. (not true)
Darwin believed that evolution was a slow process of population drifting in response to the environment. The average height of a giraffe changes each generation because the short ones all died. (closer, but not quite)
Basically, evolution occurs when something in the environment – Nature – kills off certain animals and let others live. So if the short-necked giraffes always died there would only be taller giraffes left to reproduce. But the next valley over the trees might be really short so the tall giraffes have trouble reaching down and after a couple of generations only short giraffes are left. So now there are two different animals. This is called “Natural Selection.”
Darwin, like most people of his time, believed that offspring were a blend of their parents traits, like a black cat and a white cat have grey kittens and after that all kittens are grey. (not true) He had trouble believing his own theory, and waited many years to publish it. Actually, he published it only after he found out that Wallace had the same ideas.
**Mendel** came up with modern genetics, where there are dominant and recessive genes. So black cats can have white kittens, orange tabby kittens, and black kittens.
Another theory is that small mutations – like birth defects – might make an animal better suited. Maybe a horse had a long-necked colt that could eat from taller trees so it survived. After enough generations the mutations add up until the horse looks like a giraffe. Obviously some mutations don’t help at all, or even kill. It’s random. Some folks can’t handle randomness – everything has to be planned in advance or they freak out.
Still another theory is that small changes aren’t good enough – there had to be a miracle to change one species to another. They always say that the eye had to be a miracle because it’s so complex, but they forget to tell you about lizards with light-sensing patches in their skin instead of eyeballs, or about lower mammals whose species can’t see colors yet. ANY eye is an evolutionary advantage over no eyes at all, even if it’s only a light-sensing patch.
The main thing is that to be scientific, you have to be willing to change your theory to match what you observe. It’s not enough for some scientist to tell you “THIS IS TRUE.” You get to go out and prove it for yourself – or even disprove it! Anybody who doesn’t let you question their theory is trying to control your mind. And that, my young friend, is politics.
Darwin loves you, man.
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