Study & Topic Discussion – Chapter 17: Species Interactions and Community Structure

Choose one of the questions from the four provided ones: Source Textbook: Ecology: Concepts and Application by Manuel Molles, 7th Edition Requirements for Topic Discussion: Part 1 – Discussion Board Post Review the assigned sections of Chapter 17 (shown below), answer any ONE of the four questions, and post your answer to the Discussion Board. Question 1 – Review 17.1 (pages 374–375): Describe the influence of foundation species on communities. Discuss the pros and cons of emphasizing strong interactions in food web studies. Predict how the community food web associated with Phragmites australis would change if the insect-feeding bird, Cyanistes caeruleus, were removed from the ecosystem (see Fig. 17.5, p. 375). Question 2 – Review 17.2 (pages 376–378): Distinguish between direct interactions and indirect interactions, and between competition and apparent competition. Outline the field experiments that demonstrated that the relationship between Brassica nigra and Nassella polycha is apparent competition. Predict how the results of the experiment summarized in Figure 17.7 (p. 377) would have changed if the interactions between Brassica nigra and Nassella polycha were actually direct competition, with small herbivorous mammals playing no role. Question 3 – Review 17.3 (pages 379–386): Distinguish between keystone species and dominant (or foundation) species. Explain how Lubchenco’s (1978) experiments showed that feeding preferences, population density, and competitive relations among food species all potentially contribute to the influence of keystone consumers on community structure (see Figs. 17.11 and 17.12, p. 382). What refinements did Lubchenco’s work add to the keystone species hypothesis? Question 4 – Review Application (pages 388–390): Explain how human hunting of a relatively small percentage of animal species in tropical rainforests can have a massive impact on the rainforest community (see Fig. 17.21, p. 388). Some paleontologists have proposed that overhunting caused the extinction of many large North American mammals at the end of the Pleistocene (about 11,000 to 10,000 years ago). The hunters implicated were a newly arrived predatory species, Homo sapiens. Offer arguments for and against this hypothesis. Additional Instructions for the Post: The answer must address the subject(s) using facts, data, and/or case studies covered in the assigned textbook. The post must be: Factually correct, reflective, and a substantive contribution. Written in a well-organized essay format. Include correctly written references and in-text citations. Part 2 – Response to Colleague Complete at least one response to a colleague’s post.