Beta Diversity Chapter 7

Chapter Seven: The authors job as a Wildlife Conservation Department director changed his focus from extinct species to protecting the living ones. It reminded him of the species richness of the earth. Ecologists have three levels of this diversity. These measurements are the alpha, the beta and the gamma. The alpha diversity tells how many species are in an ecological community. The beta diversity compares that to the nearby communities that have different physical characteristics. Gamma diversity compares communities on a grander scale, including similar places that are separated. Topology variation is important to gamma diversity. Many things can shape biodiversity. The two most important are global distribution of life and …show more content…
The global distribution of life is very uneven. Diversity is highest at the equator and lowest at the poles, slowly decreasing as you get toward them. This is called the “latitudinal species-diversity gradient.” Because of this, destroying the ecosystems near the equator is a big problem. You put many more species at risk by messing up that one area than you would by altering an area in the same way, but farther north or south. This gradient is harder to determine in the oceans. The deep ocean was once thought to be devoid of life, but we now know that the opposite is true. It is thought that the gradient is caused by the amount of light an area gets and its temperature. It is believed that evolution occurs at a higher rate in the tropics and that is why the species diversity is so great there. The species in the tropics can afford to be more picky, so they develop more specific niches. Another hypothesis says that the reasoning behind evolution is instability. Life began in the oceans, so that explains why there are more phyla there. We don’t know how many species are in the world today. The majority of estimates range from five to fifty million. 85% of the species that we know exist are on land. Mammals