WARM UP 1.Describe why a keystone species is important. 2.Give one example of a top-down keystone species and one example of a bottom-up keystone species.

Biodiversity Patterns

Island Biogeography Study of biodiversity on barren islands –Volcanic –Mangrove

Island Biogeography –Researched by E.O. Wilson and R.H. MacArthur

Island Biogeography Area effect –Larger the size of the island, greater the biodiversity

Island Biogeography Distance effect –Larger distance from a continent or large island meant lower biodiversity

Island Biogeography Species turnover –Smaller islands have a higher loss of species More susceptible to disasters

Implications of Island Biogeography Applies to “islands” of habitats –Forests –Nature preserves One large area is better than many small ones

Latitudinal Biodiversity Gradient Biodiversity decreases as you move toward the poles

Latitudinal Biodiversity Gradient

Hypotheses on Latitudinal Gradient - Abiotic Area hypothesis –Greater area in tropics Productivity hypothesis –More photosynthesis, more resources in tropics Evolutionary time hypothesis –Tropics are “older” because they’ve had fewer disturbances, have more evolution Rapoport’s Rule –Tropics can support both tolerant and weakly tolerant species, while higher latitudes can only have tolerant ones

Hypotheses on Latitudinal Gradient - Biotic Competition hypothesis –More K-selected species at the tropics, so more resource partitioning Predation hypothesis –More predators in the tropics, so prey can’t competitively exclude each other Animal pollinators hypothesis –Little wind in tropics –Plants must coevolve with animals to move pollen and seeds –Many specific adaptations and species

WRAP UP List the 3 conclusions from the studies of island biogeography.

WARM UP “No bird soars too high, if he soars with his own wings.” – William Blake 1.How can you apply this to your own life? 2.How can you apply this to populations and biodiversity?

WRAP UP List 4 hypothesis explaining the latitudinal gradient in biodiversity.