♻️AP Environmental Science AP Cram Sessions 2021

Key Concepts and Principles

• Ecosystem structure and function includes biotic (living) and abiotic (non-living) components that interact through complex relationships and processes
• Energy flow through ecosystems follows the laws of thermodynamics, with energy being transferred and transformed from one trophic level to another (producers, primary consumers, secondary consumers, tertiary consumers, decomposers)
• Biogeochemical cycles, such as the carbon cycle, nitrogen cycle, and water cycle, involve the movement and exchange of matter between the biosphere, atmosphere, hydrosphere, and geosphere
• Biodiversity encompasses the variety of life at all levels, including genetic diversity, species diversity, and ecosystem diversity, and plays a crucial role in maintaining ecosystem stability and resilience
• Ecological succession is the gradual process of change in an ecosystem's species composition over time, often following a disturbance (primary succession, secondary succession)
• Population dynamics involve factors that influence population size and growth, such as birth rates, death rates, immigration, emigration, and carrying capacity
• Ecological footprint measures the impact of human activities on the environment, considering factors like resource consumption, waste generation, and land use

Environmental Systems and Cycles

• The water cycle (hydrologic cycle) involves the continuous movement of water through evaporation, transpiration, condensation, precipitation, infiltration, and surface runoff
  • Evaporation occurs when water changes from a liquid to a gas, primarily from the surface of oceans, lakes, and rivers
  • Transpiration is the process by which water evaporates from the leaves of plants
• The carbon cycle includes the exchange of carbon among the atmosphere, biosphere, hydrosphere, and geosphere through processes like photosynthesis, respiration, decomposition, and combustion
  • Photosynthesis by plants and other autotrophs converts atmospheric carbon dioxide into organic compounds, storing carbon in biomass
  • Respiration by organisms releases carbon dioxide back into the atmosphere
• The nitrogen cycle involves the transformation of nitrogen through processes like nitrogen fixation, nitrification, denitrification, and ammonification
  • Nitrogen fixation converts atmospheric nitrogen (N2) into forms usable by plants, such as ammonia (NH3) and nitrates (NO3-)
  • Nitrification is the process by which ammonia is converted into nitrites (NO2-) and then nitrates (NO3-) by bacteria
• Phosphorus cycle is a sedimentary cycle, with phosphorus moving between rocks, soil, water, and living organisms through weathering, erosion, and biological processes
• Sulfur cycle involves the movement of sulfur through the environment, with important processes like sulfur dioxide (SO2) emissions from volcanic activity and fossil fuel combustion, and the formation of acid rain

Human Impact on the Environment

• Deforestation, the removal of trees and conversion of forested land to other uses (agriculture, urbanization), leads to habitat loss, biodiversity decline, soil erosion, and climate change
• Urbanization, the growth and expansion of cities, can lead to increased air and water pollution, habitat fragmentation, and the urban heat island effect
• Agriculture practices, such as monoculture farming, pesticide use, and irrigation, can impact soil health, water quality, and biodiversity
  • Monoculture farming involves growing a single crop over a large area, which can deplete soil nutrients and increase vulnerability to pests and diseases
  • Pesticides can have unintended consequences on non-target species and accumulate in food chains through biomagnification
• Fossil fuel combustion releases greenhouse gases (carbon dioxide, methane) into the atmosphere, contributing to global climate change and ocean acidification
  • Greenhouse gases trap heat in the atmosphere, leading to rising global temperatures and changes in weather patterns
  • Ocean acidification occurs when atmospheric carbon dioxide dissolves in seawater, lowering the ocean's pH and impacting marine ecosystems
• Invasive species, introduced intentionally or accidentally to new environments, can outcompete native species, disrupt ecosystem balance, and cause economic damage
• Pollution, the introduction of harmful substances into the environment, can take many forms, including air pollution, water pollution, and soil contamination
  • Air pollution from sources like vehicle emissions and industrial activities can lead to respiratory health issues and contribute to acid rain
  • Water pollution from agricultural runoff, sewage, and industrial waste can degrade aquatic habitats and impact human health

Resource Management and Sustainability

• Renewable resources, such as solar, wind, and hydropower, can be replenished naturally and offer sustainable energy alternatives to fossil fuels
  • Solar energy harnesses the power of the sun through photovoltaic cells or solar thermal collectors
  • Wind energy uses wind turbines to convert kinetic energy into electricity
• Non-renewable resources, like fossil fuels and minerals, are finite and can be depleted over time, requiring careful management and conservation
• Sustainable agriculture practices, such as crop rotation, intercropping, and integrated pest management, aim to maintain soil health, reduce chemical inputs, and promote biodiversity
  • Crop rotation involves planting different crops in succession to prevent soil nutrient depletion and break pest and disease cycles
  • Intercropping is the practice of growing two or more crops together to maximize land use and promote beneficial interactions between plants
• Water conservation measures, like drip irrigation, rainwater harvesting, and low-flow fixtures, help to reduce water waste and improve water use efficiency
• Waste reduction and recycling help to conserve natural resources, reduce pollution, and minimize the environmental impact of waste disposal
  • The "three Rs" of waste management are reduce, reuse, and recycle, prioritizing waste prevention and minimization
  • Composting is the process of converting organic waste into nutrient-rich soil amendment, reducing methane emissions from landfills
• Sustainable forestry practices, such as selective logging and reforestation, aim to balance the economic, social, and environmental values of forests
• Ecosystem services, the benefits provided by ecosystems to humans (clean air, water purification, pollination), highlight the importance of maintaining healthy ecosystems for human well-being

Environmental Policies and Regulations

• The National Environmental Policy Act (NEPA) requires federal agencies to assess the environmental impacts of their proposed actions and consider alternatives
• The Clean Air Act sets national air quality standards and regulates emissions from stationary and mobile sources to protect public health and the environment
  • The act establishes National Ambient Air Quality Standards (NAAQS) for six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide
  • The act also requires the use of best available control technology (BACT) for new or modified major sources of air pollution
• The Clean Water Act regulates the discharge of pollutants into U.S. waters and sets water quality standards to protect aquatic ecosystems and human health
  • The National Pollutant Discharge Elimination System (NPDES) requires permits for point source discharges of pollutants into navigable waters
  • The act also establishes the Total Maximum Daily Load (TMDL) program to identify and address impaired water bodies
• The Endangered Species Act provides protection for threatened and endangered species and their habitats, prohibiting actions that could jeopardize their survival
• The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production and consumption of ozone-depleting substances (chlorofluorocarbons, hydrochlorofluorocarbons)
• The Paris Agreement is a global accord aimed at strengthening the response to climate change by limiting global temperature rise and promoting adaptation and resilience
• Cap-and-trade systems set a limit on total emissions and allow companies to trade emission allowances, creating economic incentives for reducing pollution

Data Analysis and Scientific Methods

• The scientific method is a systematic approach to acquiring knowledge through observation, hypothesis formation, experimentation, data analysis, and conclusion
  • Observations lead to the formulation of a testable hypothesis, which is then evaluated through controlled experiments
  • Data collected from experiments are analyzed and interpreted to draw conclusions and refine or reject the hypothesis
• Sampling techniques, such as random sampling, stratified sampling, and systematic sampling, are used to collect representative data from a population
  • Random sampling ensures that each member of the population has an equal chance of being selected, reducing bias
  • Stratified sampling divides the population into subgroups (strata) based on shared characteristics and then randomly samples within each stratum
• Statistical analysis tools, like mean, median, mode, standard deviation, and correlation, help to summarize and interpret data
  • Mean is the average value of a dataset, calculated by summing all values and dividing by the number of observations
  • Standard deviation measures the spread of data around the mean, indicating the variability of the dataset
• Graphs and charts, such as bar graphs, line graphs, and pie charts, are used to visually represent and communicate data
  • Bar graphs compare categorical data using rectangular bars, with the height or length of each bar representing the value for that category
  • Line graphs show trends and changes over time, with data points connected by lines to illustrate continuity
• Models, both conceptual and mathematical, are used to simplify complex systems, make predictions, and guide decision-making
  • Conceptual models, like food webs and biogeochemical cycle diagrams, represent the key components and interactions within a system
  • Mathematical models, such as population growth models and climate models, use equations to quantify relationships and simulate system behavior
• Uncertainty and error in scientific data can arise from measurement limitations, natural variability, and human factors, requiring careful consideration in data interpretation
  • Measurement error can be reduced through the use of precise instruments, calibration, and multiple measurements
  • Confidence intervals and error bars are used to communicate the uncertainty associated with a reported value or result

Case Studies and Real-World Applications

• The Chesapeake Bay watershed restoration efforts involve a multi-state partnership to reduce nutrient pollution, restore habitats, and improve water quality in the largest estuary in the United States
  • Agricultural best management practices (BMPs), such as cover crops and nutrient management plans, are being implemented to reduce nutrient runoff from farms
  • Urban stormwater management, including green infrastructure (rain gardens, permeable pavement), helps to reduce polluted runoff from cities and suburbs
• The Yellowstone wolf reintroduction in 1995 demonstrates the concept of trophic cascades and the importance of keystone species in maintaining ecosystem balance
  • The reintroduction of wolves, a top predator, has led to changes in elk behavior and population dynamics, allowing for the recovery of riparian vegetation and benefiting other species
  • This case study highlights the complex interactions within ecosystems and the potential for species reintroductions to restore ecological processes
• The Great Pacific Garbage Patch, a vast accumulation of plastic debris in the North Pacific Ocean, illustrates the global scale of marine pollution and the need for waste reduction and management strategies
  • Ocean currents and gyres concentrate floating plastic waste, which can entangle and be ingested by marine life, leading to injury, starvation, and death
  • Microplastics, tiny plastic fragments derived from the breakdown of larger debris, can enter food webs and potentially impact human health through seafood consumption
• The Flint, Michigan water crisis, caused by the contamination of the city's water supply with lead, underscores the importance of safe drinking water and environmental justice
  • The decision to switch the city's water source without proper corrosion control led to the leaching of lead from aging pipes into the water supply
  • This case study highlights the disproportionate impact of environmental hazards on low-income and minority communities and the need for equitable access to clean water
• The Paris Agreement and the Intergovernmental Panel on Climate Change (IPCC) reports demonstrate the global effort to address climate change through international cooperation and scientific assessment
  • The Paris Agreement, adopted in 2015, sets a goal to limit global temperature rise to well below 2°C above pre-industrial levels and pursue efforts to limit the increase to 1.5°C
  • The IPCC, a United Nations body, assesses the scientific, technical, and socio-economic information relevant to climate change, providing policymakers with regular reports and projections

Exam Prep Strategies

• Review key concepts and principles regularly, using flashcards, mind maps, or summary sheets to reinforce your understanding
  • Focus on the relationships between concepts and how they apply to real-world scenarios
  • Identify areas where you need more clarification or practice and prioritize these topics in your study plan
• Practice applying your knowledge to multiple-choice questions, free-response questions, and data analysis problems
  • Analyze the question stems and answer choices carefully, eliminating incorrect options and selecting the best answer based on the information provided
  • For free-response questions, outline your answer before writing to ensure a clear and organized response that addresses all parts of the question
• Utilize released exams and practice questions from reliable sources, such as the College Board and your textbook, to familiarize yourself with the exam format and question types
  • Time yourself when completing practice exams to develop pacing strategies and identify areas where you may need to work more efficiently
  • Review your answers and explanations, focusing on understanding the reasoning behind correct answers and identifying patterns in your mistakes
• Collaborate with classmates through study groups or peer tutoring to share knowledge, discuss complex topics, and provide mutual support
  • Engage in active discussions and debates to deepen your understanding of the material and expose yourself to different perspectives
  • Take turns teaching concepts to one another, as explaining ideas to others can help solidify your own comprehension
• Develop effective test-taking strategies, such as reading questions carefully, managing your time, and revisiting challenging questions
  • Preview the entire exam before starting to answer questions, noting the number of questions, their point values, and any special instructions
  • If you encounter a difficult question, mark it and move on, returning to it later if time allows
• Stay mentally and physically prepared by maintaining a balanced lifestyle leading up to the exam
  • Get sufficient sleep, eat nutritious meals, and engage in regular physical activity to manage stress and optimize your cognitive performance
  • Practice relaxation techniques, such as deep breathing or meditation, to help you stay focused and calm during the exam