Copy of Biosphere Homework

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Apr 3, 2024

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ESS 1 Biosphere Homework 2 Ecosystem Modeling Overview With this homework you will learn about the interactions between species by building virtual ecosystems and exploring the effects of those interactions. The Ecology Virtual Lab Procedure The exercise, that is reported below, can be found at the following webpage: https://www.learner.org/series/the-habitable-planet-a-systems-approach-to-environmental-science/ecology-lab/ Make sure the click on the HELP tab to understand how the simulator works. Open the virtual lab: https://www.learner.org/wp-content/interactive/envsci/ecology/ecology.html The producers: Developing a solid food-web base Try to get two plants to happily co–exist. In any given ecosystem, most organisms will carve out a niche for themselves where they can obtain all of the necessities to survive. Often, different species within the ecosystem will compete for the resources that a niche provides. However, certain species live well together—symbiotically, parasitically, or by staying out of each other's way. For example, lichen and moss, often the primary colonizers of a new ecosystem, tend to live fairly harmoniously in each other's vicinity. Let's see what happens in this model. Imagine the ecosystem is newly forming—the previous ecosystem has been destroyed by fire or flood—and the first colonizers of the successive ecosystem are, of course, producers. 1. Predict what will happen in this young system that is only composed of two fictitious species of plants (A and B). Report your prediction in the table below: Use X for "die out," ↑ for "increase in numbers," and ↓ for "decrease in numbers." Lesson 1: Step 1 (X, ↑, or ↓) Plant A Plant B Prediction: starting population ↑ ↑ Prediction: ending population ↓ X 2. Then, in the simulator, check that plant A and plant B are selected and run the simulator to 100 time steps (100 days) and record the population numbers for both plants: Clicking on a line of the graph will give you the number of individuals of the corresponding species. Lesson 1: Step 1 (X, ↑, or ↓) Plant A Plant B Starting population ↑ ↑

ESS 1 Biosphere Homework 2 Ending population ↑ X 3. What assumptions does this model make about co-dominance as well as the general terrain of the ecosystem? This model assumes that the plants can coexist and survive with each other. 4. Do you find one producer to be dominant? Why might one producer be dominant over another? Plant A is more dominant due to its survival, as well as its genetic composition and ability to adapt to the environment. Now you'll introduce an herbivore into the environment. In theory, an herbivore native to the ecosystem should feed primarily on the dominant species. In this system, the herbivore may consume enough of the dominant species to give the non-dominant species a chance for proliferation and survival. 5. Click on herbivore A (the rabbit) and choose "eats plant A." Predict and record what will happen to the population numbers in the ecosystem. Use X for "die out," ↑ for "increase in numbers," and ↓ for "decrease in numbers." Lesson 1: Step 2 Plant A Plant B Herbivore A Prediction: Starting population ↑ ↑ ↑ Prediction: Ending population ↓ ↓ ↑ 6. Then, run the simulator for 100 time steps and record your results: Lesson 1: Step 2 Plant A Plant B Herbivore A Starting population 5000 5000 1000 Ending population 3334 5001 2055 7. Does adding the herbivore establish a more equal field? Is one producer still dominant over the other? Why might one producer be dominant over another? The addition of a herbivore to an ecosystem may influence the balance between producers, potentially leading to a more equal field if the herbivore feeds on a dominant producer. However, factors such as the herbivore's feeding preferences, plant defenses, and resource availability can contribute to the continued dominance of one producer over another. 8. If the simulation included decomposers, how would your current results change? If decomposers were included in the simulation, they would break down dead organic matter, enriching the soil with nutrients that benefit plant growth. This could lead to changes in the abundance and distribution of producers, enhancing overall ecosystem productivity.

ESS 1 Biosphere Homework 2 9. How do producer population numbers with the presence of an herbivore compared to the primary colonizer model? The herbivore's presence can change producer populations, promoting a more diverse mix compared to the primary colonizer model. Investigating a food web Now that you have a sense for the interrelationships between the trophic levels, see how big you can make your food web and still have all of the species you add survive through the end of the simulation run. Keeping the ideas of succession and the competitive exclusion principle in mind, think of the many factors that may go into sustaining an ecosystem. Is there any way we can all get along and live side by side? First you'll run a less than "real-life" scenario. Choose only one organism from each trophic level and make sure that the food chain goes in a straight line from one trophic level to the next, i.e., Herbivore A eats Plant A, Omnivore A eats Herbivore A, and the Top Predator eats Omnivore A. Let Plant B survive on its own and see what happens. 1. Predict whether each species will survive, and whether it will increase or decrease in number, as well as whether Plant B will survive to the end. Record your prediction in the Data Table and then run the simulation twice and record your data. Use X for "die out," ↑ for "increase in numbers," and ↓ for "decrease in numbers." Lesson 2: Step 1 (X, ↑, or ↓) Plant A Plant B Herbivore A Omnivore A Top Predator Prediction ↓ X X ↓ ↑ Starting population ↑ ↓ ↑ ↓ ↑ Ending population ↑ ↑ ↑ 2. Was your prediction correct? How did you arrive at your prediction? What differences were there between your prediction and the simulation? I made a completely random prediction and it was not correct. 3. What would happen to this imaginary ecosystem if the producers were to die out? If the producers were to die out, the entire imaginary ecosystem would collapse as they form the foundation of the food chain, impacting herbivores, carnivores, and decomposers. 4. Did any of the species increase in number? What could account for this increase? Which species decreased in number and what might account for this decrease? The herbivores increased in number, definitely due to a plentiful amount of producers, and the plants decreased in number due to them being eaten by the herbivores. 5. Which populations would benefit the most from the presence of decomposers?

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ESS 1 Biosphere Homework 2 The populations of producers would benefit the most from the presence of decomposers, as decomposers break down organic matter, releasing nutrients that enrich the soil and support plant growth Now try a more "real-life" scenario and experiment with what might happen in an ecosystem that is more like a web. 6. This time click the "all on" button. The model shows who eats whom and the paths by which energy is transferred. Predict which populations will die out, increase in numbers, or decrease in numbers and record your predictions. Run the simulation twice and record the results in your Data Table. Then try to modify who eats whom in order to ensure the survival of all species and record what was changed in your chart. Finally, answer the following: Lesson 2: Step 2 (X, ↑, or ↓) Plant A Plan t B Plant C Herbivore A Herbivore B Herbivore C Omnivore A Omnivore B Top Predator Prediction down dow n down down down down down down Up Starting population Dow n↑ Dow n Dow n Down down down X X Up Ending population Down X down down down down X X Up Modifications made dow n down X down down X X up 7. Was your prediction correct? How did you arrive at your prediction? What differences were there between your prediction and the simulation? I arrived at my prediction by thinking that all of the food was going to be eaten level by level until the top predator ate them all. 8. Were you able to modify the parameters so that each species survived? Explain how you decided what changes to make. I was not able to configure a parameter where each species survived 9. Which way does energy flow and how does eating an organism result in energy transfer? Energy flows towards the top and eating an organism results in energy transfer through the producers getting energy from the sun. Earth works: Energy transfer

ESS 1 Biosphere Homework 2 Directions The image below is a representation of the food webs in the temperate forest (such as Sierra Nevada) 1. Using textboxes, write the name (use text box tool) of all the organisms that are shown in the image below in the pyramid according with the trophic level that they belong.

ESS 1 Biosphere Homework 2 Red-Tailed Hawk Rattlesnake, Elf owl woodpecker, lizard mouse, mantid squirrel, rat, grasshopper, ants cacti, bush, grass, mesquite 2. The rule of thumb is only 10% is transfer to the next level. If 28,000 kcal/m2/yr of energy is stored as biomass from your primary producers, calculate how much energy would be passed on to each of your trophic levels. Write the energy that is available on each trophic level in your pyramid. Primary Producers: 28,000 kcal/m2/yr Herbivores (Primary Consumers): 10% of 28,000 kcal/m2/yr = 2,800 kcal/m2/yr Carnivores (Secondary Consumers): 10% of 2,800 kcal/m2/yr = 280 kcal/m2/yr Top Carnivores (Tertiary Consumers): 10% of 280 kcal/m2/yr = 28 kcal/m2/yr 3. Where does the other 90% of the energy go? It’s lost in growth, movement, waste, or respiration. You learn during the simulation, that the 10% of energy transfer is not precisely what happens in nature. The energy transfer varies greatly from a few percent in large herbivores to a much higher percentage in for example fish or chickens.

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ESS 1 Biosphere Homework 2 The measurement of energy transfer efficiency between two successive trophic levels is termed the trophic level transfer efficiency (TLTE) and is defined by the formula: 𝑇𝐿𝑇𝐸 = ???????𝑖?? 𝑎? ??????? ????ℎ𝑖? 𝑙???𝑙 ???????𝑖?? 𝑎? ?ℎ? ????𝑖??? ????ℎ𝑖? 𝑙???𝑙 𝑥 100 According with your pyramid make an estimation about the biomass for each level. You will start with a biomass of 9,000 (kcal/m 2 /yr) for a primary producer with an energy transfer of 13.5%. Write in the Table the Productivity available according with the organisms that you have in your pyramid per each trophic level. Large herbivores ± 300 (kcal/m 2 /yr) Small herbivores ± 200 (kcal/m 2 /yr) Large carnivores ± 100 (kcal/m 2 /yr) Small carnivores ± 50 (kcal/m 2 /yr) Omnivores ± 175 (kcal/m 2 /yr) Trophic level Productivity (kcal/m 2 /yr) TLTE Producers Primary (example) Large herbivores + small herbivores = 800 + 1000 = 1800 1800/9000 x 100% = 20% Secondary Tertiary Apex predator 1. Which trophic levels are more efficient transferring energy? The lower producer and herbivore levels. 2. Explain why most food chains rarely have more than 4 trophic levels? With approximately 90% of energy lost as heat at each transfer, the amount of energy available for sustaining higher trophic levels is limited. 3. Look at the type of organisms that you have in your different trophic levels. What kind of animals that you have at the top 2 trophic levels (invertebrates, fish, mammals, amphibians, reptiles or birds)? There are birds and reptiles 4. According with your previous answer. Explain, why these animals’ losses more energy, compared with the animals in lower trophic levels? Birds and reptiles lose more energy due to inefficiencies in energy transfer at higher trophic levels, with about 90% lost as heat in each step.

ESS 1 Biosphere Homework 2 5. Human are becoming the apex predator for many food webs in almost all the ecosystems in the planet. Today, the human population is 7.8 billion. How do you think this large number of apex predator will affect your food web? Many of our tertiary predators’ food will be eaten by humans leading to a decrease in their population.