MeDeFe wrote:Mr_Adams wrote:MeDeFe wrote:And no, evolution is not "the changing of one species into an other", evolution is every species changing a little all the time in response to a myriad of factors in their environments (including other species). If you take what a species looks like now, and what descendants of this species looks like in 100000 years, they might be different enough that one would call them different species, but there is no line which divides them into species 1 and species 2 (or species 27).
2 animals are the same species if they can mate, producing fertile offspring.
Aah, to be so young and naive again, how wonderful that would be... So you're saying that lions and tigers are the same species, got it, many biologists will disagree with you however. Female Ligers and Tigons are for the most part fertile.
Wolves and Coyotes can also produce offspring and they're counted as different species, the resulting Coywolves are as fertile as any coyote or wolf.
McDeFe is technically correct, but most people learned what Mr Adams said in school. The definition has changed and been revised somewhat.
The real definition is that they are seperate species if they generally do not mate and produce fertile offspring ... sometimes the reason is just space and habitat (Tigers and lions generally are not found together outside of zoos. Coyotes and wolves have been moved around and have migrated on their own) plus some other technical stuff.
MeDeFe wrote:And no, evolution is not "the changing of one species into an other", evolution is every species changing a little all the time in response to a myriad of factors in their environments (including other species). If you take what a species looks like now, and what descendants of this species looks like in 100000 years, they might be different enough that one would call them different species, but there is no line which divides them into species 1 and species 2 (or species 27
This is not the full truth, though. In some ways it is almost backwards. That is, small changes absolutely do change species over time. However, that does not account for the vast numbers of species.
Catostrophic events stear this a lot. Something happens. It could be a change in the overall environment (a massive meteor maybe, a huge fire or volcanic eruption, even "smaller" events like tidal waves and such) or a disease or some other factor cause huge numbers of individuals to die off. Those left will almost always have far narrower genetic attributes. In some cases, the individuals die because they are less resistant to the change (classic "survival of the fittest"), but often it is simply chance (or design, if one believes in a higher power directing things). All the blue-tailed flickers just happen to be in the valley that gets inundated with lava, so no more blue-tailed flickers.
Now, after this die-off a few things have most likely happened. First, those that survive don't necessarily have it easy, so classic natural selection kicks in in full force. In many cases, pockets of populations will exist in isolation. Often they will no longer have predators or other controls. The species will expand and expand to fill the territory. In other areas the predators will dominate and quickly "eat up" all the prey ... and then not do so well themselves. Think of any combination of examples and it likely happened. IN fact, at some level all of the above will happen. If a species is isolated from predators, it will tend to overeat food stocks, then be subject to diseases ...e tc. Even if the only "predator" is another plant. Competition occurs, change occurs until the situation "settles down" and more or less stabilizes in a kind of equilibrium, we call an ecosystem.
Sometimes this actually happens quickly by our standards. Some changes in fish and plants have been seen, for example, within the past 50 years. (even well aside from our many intentional changes to livestock and other species). Usually, it happens in a span we would consider "slow", but which, geologically is
phenomenally fast. ( a few hundred or thousand years)