classnotes19 - Community ecology: community - groups of...

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Community ecology: community - groups of organisms living close enough together for interactions to occur. Some features of communities include: Biodiversity - the variety of organisms that make up a community. This is composed of: a) species richness - how many different species are there? b) relative abundance of each species. measures of diversity usually include both features (there are many different ways to measure diversity . For example: # of individuals of each species species A species B species C species D species E community 1: 25 25 25 25 0 community 2: 97 1 1 1 0 community 3: 20 20 20 20 20 Community 1 is obviously more diverse than community 2 (right out of the text), but community 3 is more diverse than community 1. Competition - this is when organisms compete for the same resources. There are two types of competition: - interspecific (between different species) - An example [Fig., not in book (in 5 th ed. on p. 717)]: - two species of barnacle. One is found further up on rocks than the other (it can survive drying out at low tide better than the other). - if the species that lives lower down in the water is removed, the upper species moves down and takes over - it CAN live lower down if the other one isn’t there. - if the species from lower down is put back, then it quickly drives the species from the upper zone to
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extinction in the lower area - it outcompetes the species form the upper area in it’s preferred habitat (the lower area). - this gave rise to the “Competitive exclusion” principle.
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classnotes19 - Community ecology: community - groups of...

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