Speciation-allopatric/Rate of Evolution/Macroevolution

Speciation-Allopatric

When term for when new species are formed is called speciation. There is also something called allopatric speciation. This is "speciation by reproductive isolation" and has three main steps.
1) In a single interbreeding population, a physical barrier such as mountains or a dam helps turn a population of species into two or more groups by separating them. If mutations occur in any of these groups, they are not shared with the other isolated groups.
2) Because the two groups are isolated, 'the populations will evolve independently' through natural selection.
3) Over time, these two groups end up becoming two different species because of physical and/or behavioral differences that came between them.
This is how new species are formed. Over periods of time, organisms have been separated to become two or more different species. This is why we infer that many different species might have the same evolutionary origin.

Rate of Evolution

The process of finding changes in species over a long period of time through evidence such as fossils is the theory of gradualism. Niles Eldridge and Stephen Jay Gould concluded a theory of punctuated equilibrium that has three main points:
1) "Many species evolve very rapidly in evolutionary time"
2) When speciation occurs, it happens in isolated populations that are small
3) "After an initial burst of evolution", species do not change rapidly anymore because they have already adapted to their own environment.
From these theories we can conclude that either species take a long time to change or the change is done very rapidly.

Macroevolution

Since the beginning of time, Earth has experienced many events that may have caused species to go extinct or for the whole Earth to environmentally change. The fact that there are more than 120 different species is evidence of something called divergent evolution. Divergent evolution is just the "evolution into many different species."Earth has gone through many eras and in each era, many species were created and some were extinct.

Bibliography:
Ritter, Bob, K.L. Burley, and Douglas Fraser. "Evidence of a Changing Earth."
     Biology. 2007. Print.


"Allopatric Speciation." TutorVista. N.p., n.d. Web. 28 Apr. 2011.
     <http://www.tutorvista.com/content/science/science-ii/heredity-evolution/
     speciation.php>.


Wells, Jonathan. "Why Microevolution Obligates Macroevolution." Xanga. N.p.,
     n.d. Web. 28 Apr. 2011. <http://godlessliberal.xanga.com/705109567/
     why-microevolution-obligates-macroevolution/>.