Instructions: Complete all of the tasks listed below. There is no page limit or requirement, but your submission is estimated to be 3-4 pages (including figures). Simply put: write as much or as little as you need to complete each task. You should submit your assignment to the eCollege dropbox in the appropriate basket before the deadline. Be sure to include your last name in the title of the document that you upload. If you have any questions, including needing clarification or a helpful push in the right direction, please contact your instructor. Good luck!
1. (Not included in this sample)
2. Consider a hypothetical study of the number of heterotrophic species in 45 different communities across the globe – 5 from each of the 9 terrestrial biomes covered in the text (pp. 386-390). Using Data Set 1 (see note at the bottom), construct a histogram with 10 intervals. Explain how it was constructed, including a calculation of the range of observations. In a paragraph or two, explain what the histogram shows and discuss where communities from the different biomes are likely to be found within it.
3. Now we’ll zero in on the community that has 15 heterotrophic species. How does this community compare to the average community? Make comparisons using all three of the measures of central tendency – the mean, median, and mode – explaining how each measure is determined and noting any differences between them. Name 2-3 biomes that this community is likely to come from and say why.
4. Data Set 2 (see note at the bottom) shows the results of a more detailed investigation of this community, one in which the populations (in individuals/km2) of the different species were estimated. Describe a procedure one might have used to carry out such an investigation (i.e. in order to obtain data of that kind). Briefly explainwhat would be good about the procedure you suggest as well as what problems with it you foresee.
5. Do the best job you can of characterizing the trophic level of each of the 15 species, explaining the assignments you make. Remember the following:
· There are generally no more than 4 levels of consumers in a community.
· The total population at one level will be roughly 5-20% as large as the total population one level below.
· A species can occupy more than one trophic level simultaneously. (Ask yourself: what would that mean for its relative population size?)
For the purposes of this exercise, also assume the following (which are in fact quite unrealistic):
· Most species occupy a single, unambiguous trophic level.
· Each species at a given trophic level is equally common (i.e. its population size is similar to other species at that level).
6. Make a circle graph showing the relative abundance in this community of organisms categorized by trophic level. Your graph should encompass all 15 species, so include hybrid categories (e.g. primary/secondary consumer) if you found them useful/necessary.
7. Explain the concept of a keystone species. Describe how one might conduct an experiment (or series of experiments) to test whether one of the 15 species in this community is a keystone species. What sort of data would one look for? And if there is a keystone species, what could account for its playing that role? (Feel free to discuss specific examples of keystone species here if you like).
8. (Not included in this sample)