First of all, could someone more knowledgeable on the subject tell me if my assumptions regarding natural selection are correct, or if Iíve left something out? Iíve always thought that natural selection was due to two factors (if this is true, which has the greater effect? Or do they result in different types of adaptation?)
Survival of the fittest: A few individuals will develop a favorable adaptation, ensuring a higher probability of survival than the general population of the species. This adaptation becomes more prevalent, and eventually universal, as the individuals lacking this adaptation die at a higher rate.
Competition for mates: Individuals will mate with those that they instinctually feel will produce the fittest offspring. Also, in some species (and to a lesser extent humans), the biggest and strongest males will chase off other suitors for available females, ensuring that genes for vigor are passed on.
OK, here's my question: Could a strong argument be made for a more purely adaptive model, in which all members of a species adapt due to environmental pressure? What could be the biological mechanism for relatively widespread and rapid adaptation?