AP Environmental Science Review: Everything You Need to Know

AP Environmental Science (APES) is a interdisciplinary course that combines biology, chemistry, geology, and social science to study the environment and human impacts on it. The course covers topics ranging from ecology and biodiversity to pollution and resource management. Success on the APES exam requires understanding scientific concepts, applying them to real-world scenarios, and analyzing data. In this review, we will cover the most important topics and provide strategies for exam success.

The Exam Format

The APES exam has two sections: Section I includes 80 multiple-choice questions (90 minutes) and Section II includes 3 free-response questions (70 minutes). The multiple-choice section includes sets of questions based on graphs, data sets, and scenarios. The free-response questions require you to analyze environmental problems, propose solutions, and design experiments. Understanding the exam format helps you prepare effectively.

Unit 1: The Living World - Ecosystems

This unit covers the structure and function of ecosystems. Key concepts include energy flow through ecosystems (food chains, food webs, trophic levels), biogeochemical cycles (carbon, nitrogen, phosphorus, water), and ecosystem services. Understand how energy is transferred between organisms, how nutrients cycle through ecosystems, and the role of ecosystems in providing services to humans.

The carbon cycle is particularly important. Understand the sources and sinks of carbon, how human activities (burning fossil fuels, deforestation) have disrupted the carbon cycle, and the consequences of increased atmospheric CO2 (climate change, ocean acidification). The nitrogen cycle is also critical, especially the impacts of agricultural nitrogen fixation and fertilizer runoff.

Unit 2: The Living World - Biodiversity

This unit covers the variety of life on Earth and the factors that affect biodiversity. Key concepts include species diversity, genetic diversity, ecosystem diversity, island biogeography, ecological tolerance, and biodiversity hotspots. Understand the ecological and economic value of biodiversity, the causes of biodiversity loss (habitat destruction, invasive species, pollution, overexploitation, climate change), and conservation strategies.

Island biogeography is a frequently tested topic. The theory states that species richness on an island is determined by the balance between immigration (from the mainland) and extinction (on the island). Larger islands closer to the mainland have more species. This theory also applies to habitat fragments on the mainland.

Units 3-6: Population, Earth Systems, and Resources

These units cover population ecology (growth models, carrying capacity, demographic transition), earth systems (plate tectonics, soil formation, atmospheric structure), and natural resources (renewable vs. nonrenewable, mineral resources, fossil fuels, alternative energy). Understand the difference between exponential and logistic growth, the factors that affect population size, and the environmental impacts of resource extraction and use.

The demographic transition model describes how populations change as societies industrialize. It has five stages: high birth and death rates, declining death rates, declining birth rates, low birth and death rates, and potentially declining population. Understanding this model is essential for analyzing global population trends.

Units 7-9: Pollution and Global Change

These units cover air pollution (smog, acid rain, ozone depletion), water pollution (point source, nonpoint source, wastewater treatment), land pollution (solid waste, hazardous waste, recycling), and global change (climate change, ozone depletion, loss of biodiversity). Understand the causes, effects, and solutions for each type of pollution and global change.

Climate change is one of the most important topics on the APES exam. Understand the greenhouse effect, the difference between weather and climate, the evidence for climate change (rising temperatures, melting ice, sea level rise), and the potential impacts (more extreme weather, ecosystem disruption, sea level rise, food insecurity). Know the major international agreements (Kyoto Protocol, Paris Agreement) and their goals.

Free-Response Strategies

The free-response questions require you to apply your knowledge to real-world scenarios. They often ask you to identify an environmental problem, explain its causes and effects, and propose solutions. Structure your answers clearly: identify the problem, explain the science behind it, discuss the impacts, and propose specific, actionable solutions.

Many free-response questions include data analysis. Practice interpreting graphs, tables, and maps. Identify trends, calculate rates of change, and draw conclusions from data. Design experiments: identify the independent and dependent variables, describe the control group, and explain how you would collect and analyze data.

Study Tips for APES

APES is a content-heavy course, but understanding concepts is more important than memorizing facts. Focus on understanding how systems work and how human activities affect them. Use visual aids like diagrams, flow charts, and concept maps to organize your knowledge. Practice with released exams and sample questions. Stay current with environmental news, as the exam often includes questions about recent environmental events.