Copy_of_Island_Biogeo_Lab_Inquiry_2020 - Name Khloeu2019...

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Name: Khloe’ Couey_____________ Period: 5_____ Island Biogeography Inquiry Lab Read the introduction below: Biogeography explores global patterns in species diversity. Two major factors that influence the number of species that are found in a given place are the amount of available habitat and distance among communities. The Equilibrium Theory of Island Biogeography explores these concepts by focusing on diversity on islands. You will use a simulation to investigate and explain this theory. One of the first global patterns of diversity that early scientists observed was the relationship between area/size and the number of species that a space holds. This relationship was easy to describe on islands where species richness of multiple groups of animals or plants (taxa) had been described. For example, Figure 1 demonstrates this species- area relationship . For example, Cuba is the largest island in the Caribbean, and Redonda is one of the smallest. If you look at the number of species found on each island (y-axis), Cuba has far more species than Saba does. Ecologists noted that species richness did not just increase with size; it tended to increase at a regular rate. In general, we find that an area that is 10 times larger has about twice as many species. (Note this relationship appears linear in the figure due to the use of log scales on both axes!) While studying patterns of species richness on islands, two ecologists, Robert H. MacArthur and Edward O. Wilson (a super famous ecology dude!), noted some exceptions to the rule. For example, some large islands had fewer species than expected due to their size, while some small islands tended to be more species- rich than expected. To explain these global patterns they proposed the Equilibrium Theory of Island Biogeography. It focuses on how size and distance from a "mainland", or source of species, influences island richness. To understand the Island Theory of Biogeography, let's first consider Figure 2 to the right. Imagine there are two islands located off the coast of the mainland. Although the two islands are about the same size, the second island is located much farther away than the first island. If you are a bird that lives on the mainland, which island are you most likely to end up on? The answer is generally the first island. This means immigration (or colonization) is influenced by the distance of an island from the mainland (a source of colonists). Therefore, islands that are closer to the mainland are more likely to receive immigrants than islands that are further away. Once a species manages to reach and colonize an island, the rate of extinction is largely influenced by the size of the island. This is because smaller islands tend to hold smaller populations (which are more likely to experience extinction due to chance negative effects like genetic drift!). Larger habitat size reduces the probability of extinction of the colonized species due to chance events. Smaller islands are also likely to hold fewer populations in general because they have less resources and less diversity of resources.

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