Evolution CH 4 flashcards

It is the formation of a new species. Allopatric speciation is when a new species forms due to reproductive isolation. It is a three step process 1. A physical barrier seperates a single population (can also be human caused) Ex: continental drift. 2. Natural selection works on the seperated groups independently ensuring only the fittest survive. 3. Over time the changes become so great that if you were to reunite the seperate populations they would no longer be sexually compatible.

Reproductive isolation means since you can only make viable babies with your species you become so distant from your own species you cannot make babies anymore.. 1. Biochemically - the gametes of both species become chemically different and noncompatible. 2. Physical - You are physically not the same size (elephant and hamster) 3. Behavioural - some species have special mating rituals and if you do not know them they will not mate.

It states that speciation takes place slowly, at a steady pace. There are many transition species throughout evolution, fossil records show evidence of this. The theory of punctuated equilibrium states that speciation can appear abruptly (to paleontolgists this is about every 100 000 years) and then little evolution is seen over a long time. there are 3 main assertions 1. many species evolve rapidly in evolutionary time 2. it occurs in small isolated populations so a fossil record would be rare 3. after an initial burst of evolution, they are adapted to their enviroment so they do not change significantly for a long time.

Diversification means there has been an increase in diversity since life began. There have been several major extinction events during this time which cause widespread evolution right after.

Divergent evolution involves homologous structures and it is the evolution of one species into many different species by developing different traits. Convergent evolution involves analogous structures is the process wherby organisms who are not closely related, independently evolve similar traits as a result of having to adapt to similar enviroments or ecological species