Evolution

[SamuraiBlue]

There are fishes that "hibernate" and bury themselves in the mud when their watery habitat dries out.
One of the things fish needs to live outside their watery habitat is way to negotiate with dryness and this fish probably gives us a glimpse on how they overcame that hurdle.

Next question concerning eyes, this probably first came very early within evolution when sigle cell organism became light-sensitive.
When organism divided into botanic when they gained chloroplast, predatory single cell organism also developed a light sensitivity organ to seek out botanic single cell organism thriving at a light source. From there on the light sensitive organ evolved and became more sophisticated into eyes of today.

 

[Maurice]

I'm not saying this is how it happen where "feet" are concerned, but one can imagine fishes that spent a lot or all of their time bottom feeding, in which case natural selection might favor limbs that allow them to locomote easily on the sea floor, and thus some fishes already have rudimentary limbs partially pre-adapted for crawling around on land.

 

[Silvercrest]

Christopher said:

As time goes on, their bodies absorb numerous environmental factors (which include bacteria, viruses and everything else ...) that are recorded in the DNA and passed on from generation to generation, which also results in genetic mutations and so forth.

That's not true. The life experience of an individual organism does not alter its genes in the Lamarckian way you suggest, not for the most part...Genes don't "remember" life experience in that way.

Yeah, I've always wondered how much thought Lamarck put into that one. Apparently if you cut off a child's right arm for enough generations, eventually you'll get a generation that's born with no right arm.


How many generations would that take, do you think?

 

[bryce]

Silvercrest said:

Christopher said:

As time goes on, their bodies absorb numerous environmental factors (which include bacteria, viruses and everything else ...) that are recorded in the DNA and passed on from generation to generation, which also results in genetic mutations and so forth.

That's not true. The life experience of an individual organism does not alter its genes in the Lamarckian way you suggest, not for the most part...Genes don't "remember" life experience in that way.

Yeah, I've always wondered how much thought Lamarck put into that one. Apparently if you cut off a child's right arm for enough generations, eventually you'll get a generation that's born with no right arm.


How many generations would that take, do you think?

Lamarck is, of course, total pants, BUT Nova recently had an episode on about "epigenetics", and how environmental factors can alter the eipgenome (how genes express themselves) in ways that can effect offspring for several generations - even in humans.

That's a pretty surprising new idea.

 

[Christopher]

Actually, as I recall, Lamarck's thinking is generally misunderstood and misinterpreted. He's best remembered for the idea of the inheritability of acquired characteristics, but he didn't originate that idea, just incorporated it as part of his broader theory of evolution. And a lot of aspects of that theory were pioneering and laid some of the foundation for Darwin's work.

And according to Wikipedia, Lamarckian inheritance doesn't apply to injury or mutilation, only to beneficial adaptations. He was right that changes that improve an organism's adaptation to its environment get passed on, and he was pretty much the first person to codify that idea. He was just wrong about the mechanism that generated those changes, because Mendelian genetics hadn't been developed yet. So people use his name as a joke, but really he was on the right track and contributed a lot to the development of evolutionary theory.

 

[Silvercrest]

Okay, I guess I'm guilty of misinterpreting him. I'll lay off. :thumbsup: