ICA 09 Population Dynamics/Structure Group _____________________Names ___________________ _______________________ ____________________1. Population Cycles A. What are three possible density-dependent factors affecting population cycles? 1. food availability 2. disease 3. predation B. Develop a hypothesis with infections by a parasitic roundworm as the factor causing cycles in grouse. If…infections by roundworms cause populations cycles in grouse, C. Roundworms can be treated by a drug. Develop a prediction to test your hypothesis. then…subpopulation of grouse treated with drugs will stop cycling and have a stable population size, while the subpopulation of grouse untreated will continue to have cycles. What is your independent variable? drug treatment What is your dependent variable? cycling of population size D. Graph your prediction. Label axes and treatments. Put time on X axis. See graph on PPT for this lecture. E. What is the conclusion? Roundworm infections appear to cause the cycling of grouse. Is the hypothesis proven? No Explain. Hypotheses are never proven; they are supported. All possible causes of cycles have not been examined.2. Distribution of Mimulus Individuals from 2 species were transplanted to a range of elevations within and outside of their native range. Individual fitness components (survival, growth, and flowers) were measured. A. Summarize in one concise sentence the main results for: Lowland species: The fitness measures of the lowland species are highest in the lowest elevation and decline with increasing elevation. Highland species: The fitness measures of the highland species are highest in the second highest elevation and decline with both increasing and decreasing elevation. B. What is the main conclusion of the experiment? Individual fitness components are highest when the individual is growing in their native habitat.3. Range (and density) of species A. Summarize in one concise sentence the major pattern in: Fig 1: Most species have very small ranges. Fig 2: Species with greater range have greater (local) abundance. Fig 3: Population density is highest in the center of the range. 4. Spatial Distribution A. Describe in one concise sentence the owl’s spatial pattern. The owls are concentrated in areas of old growth forest. B. Summarize in one concise sentence the pattern for: 1. adults (top 2 graphs): Owl density and pair density increase as % old growth forest increases. 2. offspring (bottom 2 graphs): Number of owls fledged and number offspring per pair increase as % old growth forest increases. C. Taking into account B, what is the explanation for the owl distribution in A? (1 sentence) Owls are found in the highest density in the habitat in which they have high reproductive success, viz. in old growth forest. 5. Dispersion What type of dispersion is shown for: A. eagle: even Provide a hypothesis to explain its dispersion: If…territoriality explains eagle dispersion B. desert plants: even Provide a hypothesis to explain its dispersion: If…competition for limited resources (e.g. water) explains desert plant
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