Biscuithead wrote:
We all know the story, these things supposedly grew and changed over billions of years and became everything there is on Earth now. That supposedly happened through evolution by natural selection. Now, I don't have a problem with natural selection: the environment can change, to favor organisms with certain characteristics, and the rest of the population dies. But the theory of evolution relies not on on natural selection, but on this surviving population then becoming more diverse so it can happen again.
This is incorrect. The environment does not change to favor organisms; organisms change to be better suited towards the environment. And no, the theory of evolution relies almost entirely on natural selection. It makes no sense that the changing environment would produce diversity. Organisms that contain traits that allow them to reproduce more often are favored by their environment and can pass these traits to their offspring, eventually forming a more "fit" species.
Biscuithead wrote:
So the population then has to have mutations. Mutations that actually benefit the organism in terms of it's survival. Riiiiiight. So an organism is somehow mutated, and instead of causing cancer or a negative genetic change as usual, the mutagen finds the perfect spot in the DNA sequence to alter a gene to create a new version of that gene. Then the changed organism has offspring that are also altered in a good way. Then, like clockwork, another climate change gets rid of the old type of the species.
Your logic here is flawed. Mutations have very little impact on slowly reproducing organisms, such as ourselves. However, early unicellular organisms would have a reproduction rate exponentially greater than more complex organisms. The bacteria E.coli can reproduce every 20 minutes in a favorable environment; in the human colon, E. Coli can produce 2,000,000,000 offspring every day. The chances of a spontaneous mutation in an E. Coli gene runs at about 1x10^-7 per cell division, meaning 2000 bacteria created each day with a mutation in that gene. Combine this with the fact that there are 4300 E. Coli genes: 2000x4300=8,600,000 mutations per day per human host. The point being that while individually rare, mutations can have an enormous impact on a rapidly producing species.
Now if early organisms reproduced at a fraction of the rate that E. Coli does, mutations would still have a major impact on their development. You're right in claiming that mutations can have detrimental effects; however, a unicellular organism cannot develop cancer, sickle cell, or huntingtons. More than likely, death would be the number one result. If the cell dies, so be it. But if the mutation is beneficial, no matter how unlikely an event, all of its progeny will receive the benefit, become better suited to their environment and reproduce more successfully.
Mutation, however, has little or no benefit towards more complex organisms such as ourselves. For every beneficial mutation in a human, there are millions that cause death or severe handicap. For multicellular organisms, diversity arises through the recombination of chromosomes through sexual intercourse. This recombination produces diversity much, much quicker than mutation. This accounts for the massive diversity in animals and plants.
First post, btw
