Biogeography

Previously we’ve focused on local interactions and how they shape diversity, but diversity cannot be explained solely by local phenomena - diversity indeed varies multiple scales and time. The discipline of biogeography considers the geographic distribution of organisms and the abiotic factors that influence their dynamic distribution through time. Background reading for biogeography is listed below.

Succession takes place after major ecological disturbances. We will look at an example of Mt. St. Helens and how the landscape changed over time after the catastrophic eruption. For another example, watch the TED-Ed video talks about why wildfires are necessary for the conifer-rich forest in western North America.

We'll also discuss five important major extinction events that have occurred in earth's history. We'll also learn about the 6th extinction event that we are currently experiencing, and how human activities have contributed in part to this modern extinction event. For more information, read the articles: Sixth mass extinction, and Habitat on the Edges.

Earth’s six major tectonic plates are roughly linked with the six biogeographic regions. The plates are constantly drifting due to the molten rock mantle present below the earth's surface. See related TED-ed videos ; What Happens When Continents Collide,  Why is Mount Everest So Tall? Animated Life: Pangea, Wegener, and Continental Drift.

We'll also explore a long-standing question "why we see more terrestrial diversity in the tropics?", and the theories of latitudinal diversity gradients proposed by numerous scientists. 

Island theory of biogeography developed by Robert. H. MacArthur and Edward. O. Wilson explains how size and distance of an island away from the mainland are related to the number of species present on the island. To understand this theory, try this online biogeography simulation tool. For more information, watch: Why Biodiversity Is Distributed Unevenly?