Fluent Essays

These are two documents, the questions are related to evolution, please help me to finish these questions! thank you! keystones20.docx nichewarss20.docx Unformatted Attachment Preview 1 Keystone Predator © 2011 SimBiotic Software for_Teaching and Research Inc. All Rights Reserved. (29 pts) BE SURE TO PAUSE THE VIDEO AS YOU ANSWER EACH QUESTION, ESPECIALLY WHEN ASKED TO MAKE PREDICTIONS. This exercise is based on a series of famous experiments conducted in the 1960’s along the rocky shore of Washington state, in the northwestern United States (Paine, 1966: Am. Nat. 100: 65-75; Paine, 1969: Ecology 50: 950-961). The intertidal community is comprised of organisms living in the area covered by water at high tide and exposed to the air at low tide. The nine species in this laboratory’s simulated rocky intertidal area include three different algae; three stationary (or “sessile”) filter-feeders; and three mobile consumers. The following table provides information on the species that you will encounter in this simulation COMMON NAME OF ORGANISM (GENUS) TYPE OF ORGANISM PRODUCER OR CONSUMER? FILTER FEEDER? (YES / NO) STATIONARY OR MOBILE? Nori Seaweed (Porphyra) Algae Producer NO Stationary Black Pine (Neorhodomela) Algae Producer NO Stationary Coral Weed (Corallina) Algae Producer NO Stationary Mussel (Mytilus) Mollusk Consumer YES Stationary Acorn Barnacle (Balanus) Crustacean Consumer YES Stationary Goose Neck Barnacle (Mitella) Crustacean Consumer YES Stationary Whelk (Nucella) Mollusk Consumer NO Mobile Chiton (Katharina) Mollusk Consumer NO Mobile Starfish (Pisaster) Echinoderm Consumer NO Mobile In this laboratory, you’ll use simulated experiments to elucidate how interactions between species can play a major role in determining community structure. You will apply techniques similar to those used in the original studies. In the competitive dominance hierarchy diagram below, the arrows point from weaker to stronger competitors. For example, the arrow pointing from Nori Seaweed to Black Pine indicates that Black Pine is dominant over (i.e., can displace) Nori Seaweed. Next to each species name, indicate how many arrows point to that species. The highest number indicates the most highly ranked and aggressive, or “best”, competitor. Which species is the dominant competitor? (2 pts) Acorn Barnacle Mussel Goose Neck Barnacle Coral Weed Nori Seaweed Black Pine (Green algae) You will now examine the predator-prey interactions that occur in the rocky intertidal zone. This table provides information on the prey each of the predators consumes. STARFISH Prey Species: Percentage of Diet: Prey Species: Percentage of Diet: Prey Species: Percentage of Diet: WHELK CHITON Mussel Gooseneck Barnacle Black Pine 60\% 50\% 40\% Gooseneck Barnacle Acorn Barnacle Nori Seaweed 40\% 50\% 30\% Coral Weed 30\% Use this data on feeding relationships to construct a food web diagram for the organisms that live in the simulated intertidal zone. Link the species names below with arrows that point from prey to consumer. (3 pts) Based on your studies so far, you know important details about the competitive and feeding relationships among the species in your simulated intertidal community, and these relationships, when integrated, define the role played by each. One way to more fully elucidate the importance of a species to its community structure is to remove it from the environment and observe what happens. In this exercise, you will experimentally determine how removing each of the highest trophic level species (the mobile consumers) affects the rocky intertidal community structure. Before you start your experiments, you will first make some predictions. Refer back to your data to inform your answers. [NOTE: only one species will be removed in each experiment.] [ 1.1 ] In the spaces provided below, predict which other species in the community will be impacted the most by each removal and explain your reasoning. (6 pts) Predicted impact of removing Whelk and explanation: Predicted impact of removing Chiton and explanation: Predicted impact of removing Starfish and explanation: [ 1.2 ] One removal experiment will have a more dramatic impact than the other two. Write down which one you predict this will be, and why: (2 pts) [2] Select “Who Rules the Rock?” from the Select an Exercise menu. [3] Your first step is to record population sizes BEFORE REMOVALS. To make sure the simulation is initialized correctly, click the RESET button. A data table is provided on the next page for recording your results.  HELFUL HINT: if you click on the colored bars in the Population Size graph, the numbers (population sizes) that the bars represent will pop up! [ 3.1 ] In the table on the next page, record the population size of each species at ‘Time Elapsed = 0 Weeks’ in the BEFORE REMOVALS column. [4] After recording data BEFORE REMOVALS, you are ready to remove mobile consumers. Find the REMOVE WHELK button (which is round and depicts a Whelk with a slash through it) in the TOOLS PANEL. When you click this button, all Whelk will vanish from the Intertidal Zone. [5] For each removal experiment, you will run the simulation for 200 weeks (in model time, not real time!). To do this, first make sure that the Time Elapsed = 0 weeks (RESET if not), and then click the STEP 200 button in the CONTROL PANEL.. [6] Confirm that the simulation stopped at (or near) 200 weeks. If so, click the bars in the Population Size graph and record the abundance of each species. [ 6.1 ] In the data table, record the population size of each species in the AFTER WHELK REMOVAL column. (1 pt) [7] RESET the simulation and confirm that Time Elapsed = 0 weeks. Then click the REMOVE CHITON button to remove all Chiton from the Intertidal Zone. [8] Click the STEP 200 button to run the simulation for 200 weeks. [ 8.1 ] [9] When Time Elapsed = 200 weeks, record the population size of each species in the AFTER CHITON REMOVAL column. (1 pt) Finally, RESET the simulation and use the REMOVE STARFISH tool and the STEP 200 button to repeat the experiment for Starfish. [ 9.1 ] In the data table, record the population size of each species in the AFTER STARFISH REMOVAL column. (1 pt) Abundance Data for Removal Experiments SPECIES BEFORE REMOVALS AFTER WHELK REMOVAL AFTER CHITON REMOVAL AFTER STARFISH REMOVAL Nori Black Pine Coral Weed Mussel Acorn Barnacle Goose Neck Barnacle Whelk Chiton Starfish 0 0 0 [ 10 ] When your data table is complete, answer the following questions. Try to be as quantitative as possible with your answers, indicating by approximately how much each species increased or decreased in size (e.g., “The Starfish population more than doubled”; “The population of Coral Weed decreased to about half its original size.”). [ 10.1 ] What were the most dramatic changes to the community after Whelk were removed? (2 pts) [ 10.2 ] What were the most dramatic changes to the community after Chiton were removed? (2 pts) [ 10.3 ] What were the most dramatic changes to the community after Starfish were removed? (2 pts) [ 10.4 ] Which removal had the greatest impact upon the rest of the community? (2 pts) [ 10.5 ] Referring back to your competitive dominance hierarchy and food web diagrams, try to explain what happened in the removal experiment that had the greatest impact on community structure. Why was the effect so pronounced? In other words, why was that species a keystone predator? (5 pts) 1 BIOL230 Ecology and Evolution Spring 2020 Names: ___________________________________________ SimBio Virtual Labs®: EcoBeaker® Niche Wars © 2013, SimBio. All Rights Reserved (45 pts) BE SURE TO PAUSE THE VIDEO AS YOU ANSWER EACH QUESTION, ESPECIALLY WHEN ASKED TO MAKE PREDICTIONS. The Ecological Niche The principle of competitive exclusion states that two species cannot persist in the same niche in the same habitat. An organism’s ecological niche is defined by the range of all conditions—biotic and abiotic—that underlie its ability to survive and reproduce (see Figure 1). An organism’s fundamental niche describes the sum total of the organism’s basic (fundamental) ecological properties. Based on the principle of competitive exclusion, two species sharing the same fundamental niche should not coexist. However, when two species’ niches only partially overlap (imagine two partially overlapping squares or cubes in Figures 1a and 1b), the two species could potentially coexist within the same community if one or both restricted its niche to minimize overlap. This restricted version of a species’ niche is called its realized niche. The Niche Wars Simulation Model in SimBio Virtual Labs In this lab you will experiment with the relationship between the ecological niche and competition. Your model organisms will be rabbits raised in a pen and provisioned with food. Every day, food will be added to the rabbit pen. Individual rabbits will hop around looking for and eating food. Rabbits gain energy from eating and use up energy staying alive. If a rabbit’s energy runs out, it dies. If, on the other hand, it acquires more than it needs to survive, it will reproduce. 2 The key niche dimensions in this simulation are habitat (the pen) and food. As you work through the exercises, you will have the opportunity to modify your rabbits’ niches. This lab uses a simulation model of a rabbit pen containing four different “species” of rabbits. The model establishes rules for each species that are based on a number of important characteristics reflecting their ecological niches and their competitive abilities. These characteristics include how far rabbits can see (to find food), how fast they can hop (to acquire food), how much energy they use each day just to stay alive, how much energy they must accumulate before reproducing, and how much energy they absorb from each type of food they eat. As you will see, the simulation model is “parameterized” by assigning values to the variables for the rules. You will have the power to change each of the rules separately for each of the rabbit species, and you will also be able to change the amount of lettuce (and later on carrots) that the rabbits are fed every day. Part 1: Competitive Exclusion Exercise 1. Rabbits and Their Habits: Competitive Exclusion After reading the introduction, start the program by double-clicking the SIMBIO VIRTUAL LABS icon or by selecting it from the Start Menu on your computer. [ 1 ] When SIMBIO VIRTUAL LABS opens, select NICHE WARS from the EcoBeaker suite. You will see several panels on the screen: ––The large panel on the left shows the rabbit pen. It is initially provisioned with lettuce; as the simulation runs, you will also see four different “species” (colors) of rabbits moving around the pen. The rabbits have no predators, and their color differences do not provide them any advantages or any disadvantages. ––The bar graphs on the right show the population sizes of all species in the pen. ––A drop-down menu at the top of the screen lets you select each of the exercises in this lab. Be sure the exercise Rabbits and Their Habits is selected. ––A Control Panel in the bottom left corner on the screen lets you start and stop the simulation. [ 2 ] Click the STEP 100 button. The simulation will stop automatically after running for 100 virtual weeks. Note: speed things up by moving the speed slider to the right. It’s a bit like feeding your rabbits caffeine! [ 2.1 ] Did all four species survive? Briefly describe what happened in the space below. (3 pts) 3 [ 3 ] Click the RESET and then the GO button. This time run the simulation until only one species survives, recording the order of extinctions and surviving “color” in the Run 1 column below. Then run the simulation 2 more times, similarly recording your results in the Run 2 and Run 3 columns. [ 3.1 ] Order of extinctions: (1 pt) [ 3.2 ] What evidence do you have that random chance determines which species will survive? (2 pts) [ 4 ] The competitive exclusion principle (described in the Introduction) applies when two or more species occupy the same niche. To determine whether the rabbits in the simulation occupy the same niche, click on the MODEL SETUP button at the right on the Control Panel. A floating window will appear that lets you see the model settings (parameters) for each of the four “species” of rabbits. Select the tab for the Red rabbit and look at the settings. Then select the tabs for each of the other 3 species and look at their settings. [ 4.1 ] Given what you’ve discovered about each species’ niche and your results from running the simulation, explain how the competitive exclusion principle applies to these species. (3 pts) [ 5 ] Close the MODEL SETUP window. [ 6 ] Competitive exclusion occurs when a critical resource is limited in the environment. You will now modify the simulation to increase the amount of lettuce (the limiting resource) available each day. To the right of the rabbit pen, find the box labeled Lettuce/day. The number is currently set at 4 heads of lettuce. Click inside the box and change the value to 8. [ 6.1 ] With twice as much lettuce available, will multiple species be able to coexist? Explain your reasoning. (3 pts) 4 [ 7 ] Now test your prediction. Click the RESET and GO buttons to run the simulation. As before, run the simulation several times. [ 7.1 ] Did you predict correctly? Explain your results. (3 pts) [ 8 ] As you read in the Introduction, two species requiring the same limiting resource can’t coexist, because one species will inevitably be better adapted to its environment —specifically, better adapted to finding and using that limiting resource—than the other. It will, therefore, outcompete the other species. In your previous experiments, the four species were identical (i.e., they had the same model settings). In your final experiment of this section, you will modify one species to make it a better competitor than the others and see how this affects the outcome of the interactions. Two of the most important characteristics determining how well rabbits can acquire and use food are found in the MODEL SETUP: sight distance (how far away a rabbit can see, and thus detect food) and speed (how fast the rabbit can get to the food once it’s been seen). [ 9.1 ] If one species has an advantage in either sight distance or speed, what outcome do you expect? Explain your reasoning. (3 pts) [ 9 ] Now you get to test your prediction. Click the MODEL SETUP button and select the tab for one of the rabbit species. Increase the value for either speed or sight distance (up to a maximum value of 10). If you make a mistake, click the RESET DEFAULTS button at the bottom of the window. RESET the simulation [be sure to return the Lettuce/day to 4 too], and click GO to run. As before, repeat the simulation several times. [ 9.1 ] Did you predict correctly? Describe your results and explain them in terms of competitive exclusion. (3 pts) 5 [ 10 ] In this exercise, you observed that only one species of rabbit can survive in the pen when all rabbits require the same food source. This was true when all species were identical in every characteristic, and when one species was better adapted to find and acquire food. [ 10.1 ] When all four species were biologically identical, were you able to correctly predict which species would survive competition? (1 pts) [ 10.2 ] What about when one was given an advantage? (1 pt) Part 2: When Can Species Coexist? Exercise 2. Shoots and Roots: Niche Divergence and Overlap Thinking about competitive exclusion becomes particularly interesting when species have niches that do not overlap completely and/or when species reduce their fundamental niches as a result of competition. In this section, you will explore how species can coexist within the same community. To do this, you will focus on the extent to which your rabbits require the same food resource. [ 1 ] What would happen if your rabbits were provided with two food resources; lettuce and carrots? To explore this question, select the Shoots and Roots exercise from the drop-down menu on the top toolbar. Note that you now have two boxes at the bottom of the pen for controlling food: one for Lettuce/day and one for Carrots/day. The default value for each is 2, for a total of 4 food items per day. [ 1.1 ] Will adding carrots as a food source allow more than one species to persist in the pen? Explain your reasoning. (3 pts) [ 2 ] Test your prediction by running the simulation several times (clicking the RESET and GO buttons). Remember to increase the speed slider if you find yourself wishing the rabbits would hop faster. [ 2.1 ] Did you predict correctly? Describe your results below. (3 pts) [ 3 ] You can change what a rabbit species eats in the MODEL SETUP window. Click the MODEL SETUP 6 button and select the tab of one of the species. Changing energy gain from lettuce to 0 and the energy gain from carrots to 4 will result in the selected species eating carrots instead of lettuce. [ 3.1 ] Should changing one species’ food niche allow multiple species to coexist for extended periods of time? Why or why not? (3 pts) [ 4 ] We will now conduct an experiment to test your prediction in 3.1. We will change the Red rabbit species so it consumes only carrots. For the sake of this experiment, multiple species surviving for >100 weeks can be considered coexistence. [ 4.1 ] Describe your experiment. Explain your results in terms of niches and competition. (5 pts) [ 5 ] Hopefully, you have now seen that two species can coexist in the same community when their niches are very different. Next, you will examine what happens when two or more species’ niches overlap, but are not identical. You will accomplish this by modifying the species so that their diets will include the same foods, but the foods will differ in their value to different species. Specifically, all four species will eat both lettuce and carrots, but two will acquire more energy from carrots, and two will acquire more energy from lettuce. [Important note: If a rabbit sees two different food items, it will move towards the one that provides the most energy.] [ 5.1 ] Do you think this modification will affect competition between the rabbits? Do you predict that one species will take over, or that multiple species will coexist? If so, which species? (3 pts) 7 [ 6 ] To perform the experiment, open the Model Setup window, click on the RESET DEFAULTS button, and select the Red rabbit. Set the Energy Gain value of lettuce to 1 and of carrots to 10. Then select the Brown rabbit and make the same changes. Do the opposite for the White and Black rabbits: set the Energy gain value of lettuce to 10 and of carrots to 1. Click through each species to make sure your settings are correct. [ 7 ] As before, click RESET and GO to run the simulation several times. [ 7.1 ] Did you predict correctly? Describe what happened to the four populations, explaining your results in terms of niches and competition. (5 pts) ... Purchase answer to see full attachment