AP Environmental Science
Earth's Living Systems

A grassland ecosystem has grass (10,000 kcal), rabbits, foxes, and hawks. (a) Using the 10% rule, calculate the energy available at each trophic level. (b) A drought reduces grass productivity by 40%. Predict the cascading effects through the food web, explaining each step mechanistically. (c) How would removal of foxes affect the rabbit population, the grass, and the hawks? Name the concept and explain.

The Everglades has experienced invasion by Burmese pythons since the 1990s. (a) Explain why Burmese pythons are considered invasive and describe their ecological impact using the HIPPO framework. (b) What ecosystem services does the Everglades provide? Name 3 from different categories. (c) Describe one conservation strategy to manage the python population and explain why you chose it.

In 2024, a country has a population of 8 million, a birth rate of 25/1000, and a death rate of 10/1000. (a) Calculate the population growth rate (%). (b) Using the Rule of 70, estimate when the population will double. (c) The country has an affluence index of 3 and technology index of 2. If the population doubles, calculate the new environmental impact using IPAT (assuming A and T unchanged). (d) The country is in Stage 2 of the demographic transition. Describe what this means for birth rates, death rates, and age structure.

A farming community in the American Southwest relies on an aquifer that has been declining 2 meters per year for 30 years. (a) Explain what causes aquifer depletion mechanistically. (b) The community considers two solutions: drip irrigation (reduces usage 40%) and desalination (provides new water). Compare these using environmental, economic, and social criteria. (c) A dust storm strips topsoil from farms. Explain what soil properties make this region particularly vulnerable and describe TWO conservation tillage strategies.

A developing nation plans to convert 2 million hectares of Amazon rainforest to soybean farms. (a) Explain THREE environmental impacts of this deforestation using specific mechanisms (soil, water cycle, biodiversity, carbon). (b) A fishery off its coast is experiencing decline. The government imposes a maximum sustainable yield cap. Explain what MSY means and predict what would happen if the cap is set 20% above the biological MSY. (c) Compare monoculture soybean farming to polyculture farming using three criteria: yield stability, soil health, and biodiversity.

A coastal city currently gets 80% of its energy from a coal power plant. The city is evaluating switching to offshore wind turbines. (a) Calculate: if the coal plant produces 1000 MW with 35% efficiency, how much energy input is needed? (b) Compare coal and offshore wind using 4 criteria: cost, reliability, environmental impact, and EROI. (c) Identify and explain TWO barriers to the transition to offshore wind. (d) Design a policy package that would accelerate the transition, including economic incentives and regulatory changes.

Los Angeles experiences photochemical smog regularly. (a) Explain the chemical formation of ground-level ozone starting from nitrogen oxides and VOCs. Describe the role of sunlight. (b) A thermal inversion occurs on Tuesday. Draw a labeled diagram and explain how it traps pollutants and worsens air quality. (c) SO₂ emissions from upwind coal plants cause acid deposition in a local lake (pH drops from 7.0 to 4.5). Explain three environmental effects. (d) The city considers restricting traffic during inversions. Argue for this policy using evidence from APES.

Agricultural runoff containing fertilizers enters a lake in Iowa. (a) Describe the step-by-step process of eutrophication, from nutrient input to fish kill. Include the roles of phytoplankton, bacteria, and dissolved oxygen. (b) Pesticides sprayed on the surrounding farmland enter the lake. Explain the difference between bioaccumulation and biomagnification. If grass shrimp have 0.1 ppm of the pesticide, and the biomagnification factor is 10× per trophic level, calculate the concentration in a hawk (4th trophic level above shrimp). (c) Propose TWO strategies to reduce agricultural nonpoint source pollution in this watershed.

Arctic permafrost contains large amounts of organic carbon. As temperatures rise, the permafrost thaws and releases methane (CH₄). (a) Explain the enhanced greenhouse effect and identify the role of CH₄ compared to CO₂. (b) Describe this as a positive feedback loop: draw the loop and label each step. (c) Calculate: if the Arctic currently stores 1,500 Gt of carbon and releases 2% per decade due to warming, how much will be released in 50 years? (d) Design a multi-pronged policy response to reduce global CH₄ emissions from both permafrost and agriculture sources.