After watching TedED's "Five Fingers of Evolution", myMy understanding is that the possible mechanisms of evolution are:
- Environmental changes; in the video, I believe this mechanisms is called adaption. Examples include, change in availability of food (including water), shelter, climate, ecological zones, predators, availability of space, etc. Environmental changes
- Mating preferences. Cultural, genetic, etc.
- Population Immigration. Genetic different populaces immigrating into existing populaces./mating preferences
- Genetic Mutation. Population Immigration
- Population shift. Random applied growth or decline in population not based on above mechanisms. That said, it's given that population shifts within a existing populaces are complete random, it's hard to see why the would make a difference. Genetic Mutation
Misc: Am I missing anything? I've heard that population shifts within a existing populaces will effect evolution, but imagining the most simplicity scenario, it's hard to see why the would make a difference.
- As for the meaning of evolution, "Evolution is any change across successive generations in the inherited characteristics of biological populations."
- Re: "availability of reproductive partners", I believe that if the availability reproductive partners was stable, it would not be a factor.