Perspectives on Evolution

[TheBeardedDude]

I'm human because I am a Homo. Not because I am a Homo sapiens.

So is Vorls! Not sure if he's human though!

I just think of evolution as change in all living things over time. (Some things die off, some speciate, some remain the same (eg: sharks).
Question? Is it strictly an environmental thing + random mutations? Or is it more complex than that?

There are also a variety of ways that organisms interact with one another that influence the evolution of lineages. Predator-prey interactions (such as the "Red Queen Hypothesis," which was named after the Queen in Alice in Wonderland) and sexual selection are two obvious ones. 

For predator-prey relationships, a trait in one may influence the traits in another. So a fast predator hunting down the slowest among the prey, will be electing against the slower prey and the faster prey will survive and reproduce, resulting in an overall faster subsequent generation. This, in turn, might cause the slowest among the predator species in the next generation to be unable to catch enough food to survive, resulting in an overall faster subsequent predator generation. (we can pick a variety of traits, like camouflage, that this scenario applies to). 

Sexual selection is where one of the genders selects for specific traits in a mate (most commonly it is females selecting males, but some species are reversed. Some birds for instance). Deer are a good example because of their horns. Mature male deer have large horn displays and mate more frequently. So doe select for the more impressive displays and drive selection towards even more elaborate and impressive displays (male peacocks and their plumage is another good example. The female peacock is a drab brown color for more effective camouflage, but males are brightly colored and quite large. They should stand out to predators more easily this way, thus harming their overall survival, but the reproductive advantage outweighs this).

When it comes to stasis in lineages, it means that selection pressures are relatively stable, but this might be a consequence of the organism adapting into an environment where selection pressures are low because the environments are relatively stable through geologic time (like the abyssal ocean), and because the organism has few predators or the predators that preyed upon it have gone extinct. The coelacanth is a great example here