9/27 Biodiversity Lab

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6 questions

Healthy ecosystems, such as a salt marsh, temperate forest, and tropical rainforests, are complex webs of living and nonliving elements. An important measure of an ecosystem’s health is its biodiversity. The term "biodiversity" is defined in diverse ways. It may be "all living things within a given geographical area and the interrelationships among them (Audesirk & Audesirk 1996). E.O. Wilson - a brilliant man with a lot to say about diversity calls it "all of the variety of life - from the different genes at the same chromosome position within populations, up through different species of organisms, on up to different aggregations of species in ecosystems." Familiarity with the term has increased in the last couple of decades as extinction rates, driven by human activities, have reached a crisis level.

For our purposes, we will define and use this biodiversity definition. “Biodiversity is the variety of life that occurs within an ecosystem (commit this to memory)”. A population is "a group of one species that live in a particular geographic area (Campbell's, 1996)". Although it is important to view life at all structural levels, many ecologists use the "species" level of taxa (short for taxonomy) to determine the biodiversity of the system being studied. Two simple methods for describing the biodiversity are richness and abundance. Richness is defined as "the number of unique taxa (species/organisms) present". It does not give you an indication of how the population (# of each species) is distributed. In other words, a system with 100 grackles, 1 red-wing blackbird, and 1 American crow has the same biodiversity (richness value 3) as a system with 34 grackles, 34 red-wing blackbirds, and 34 American crows. Abundance (sometimes called "relative abundance") is "the number of individuals present in each taxonomic group relative to the total number of individuals" (# of individuals in each taxonomic group, population/total # of individuals from all taxonomic groups being studied X 100). It is expressed in percent. For example: # of red wing blackbirds/total # of birds in the study area X 100. Okay, lets practice.

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Compare the two samples.

Identify which species are more dominant in each community? Explain why do you think this is the case?

Identify which group, if any, is more diverse? Explain why do you think this is the case?

If you conducted this lab in a forest, predict whether the diversity would be high or low, and how it would compare to the pocket prairie.

If you conducted this lab at a butterfly preserve, predict whether the diversity index would be high or low, and how it would compare to the pocket prairie.