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Ecology & Evolution




Ecology Questions;Attachment Preview;Fall 2013 PS2.pdf Download Attachment;Biol 301;Ecology & Evolution;Fall 2013;TH Pendergast;Ecology & Evolution;Predation & Competition Problems;1. You are studying bird immigration to 2 small islands off the coast of San Diego, California, the;islands are similar in size and habitats, but one is substantially further from the mainland. Eight;new bird species immigrate to one island each a year, the other only 3. There are 492 resident bird;species in San Diego.;A. Assuming equilibrium on these islands, draw an appropriately labeled figure (with;correct values) that includes the predicted patterns for the near and far island.;B. How many species do you predict to be on each island? (Note: Im only looking for an;estimation here, a specific pattern of diversity.);2. You are studying a community where smallmouth bass prey on bluegill. At the start of your;study, there are 500 bluegill in the prey population and one year later, the bluegill population size is;525. From previous work, you know that the intrinsic growth rate of bluegill is 0.15 yr-1. One of;your colleagues, a behavioral ecologist, tells you that the smallmouth bass capture efficiency (a.k.a;kill rate) for bluegill is 0.001 bass-1 yr-1. Assume that the bass and bluegill encounter each other;randomly, and that the bass population size is constant.;A. If there were no predation, what will the bluegill population size be after one year?;B. Given the amount of predation that did occur, what is the population size of the bass?;C. If, instead of population growth, the bass had held the bluegill population in equilibrium;what would be the size of the bass population?;Biol 301;Ecology & Evolution;Fall 2013;TH Pendergast;3. In California, garter snakes of the genus Thamnophis are often the only predator on Taricha;newts. This is because the newts produce a poison to which garter snakes are immune. However;both the strength of the poison and the strength of immunity vary, so not every encounter between;snake and newt results in a kill. In fact, for about 95% of the encounters that occur in a year, the;newt will get away for one reason or another. The snakes, in turn, have to be concerned with;becoming prey themselves: many species of birds prey on them, so the snakes have a mortality rate;of about 0.625 per year. Snakes and newts are pretty similar creatures, so the fraction of energy;contained in the prey that is converted into snakes is high, about 15%.;You have just used a mark-recapture technique to estimate the population size of both snakes and;newts. You think that in the forest youre studying, there are 150 newts ha, and 10 snakes ha-1.;-1;A. What is the population growth rate of snakes in your forest?;B. If you came back one year later, how many snakes would you expect to find?;C. You have enough information to solve for the equilibrium isocline of the predator.;Explain what that means, and solve for it.;D. You do not have enough information to solve for the equilibrium isocline of the prey.;What piece of information is missing?;E. Assume that missing number is 0.05. Now solve for the second isocline. (Note: the;equilibrium isoclines are terms for P-hat and H-hat. P-hat is the equilibrium;isocline of the prey, H-hat is the equilibrium isocline of the predator);4. Ibises and jacanas really do coexist in northern Costa Rica, and competition between these;species occurs for food. Here we will focus on the ibises. They have an exponential growth rate of;0.075 yr-1, and at Guanacaste National Park have a carrying capacity of about 15,000 ibises.;Jacanas are smaller, and dont need as much food, so each jacana is the equivalent of 0.63 ibises.;Currently, the population size of ibises at Guanacaste is 8500, and the population size of jacanas is;9000. Will the population size of ibises increase or decrease in the next year, and by how much?


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