Ap Environmental Science Unit 1 Review

AP Environmental Science Unit 1 Review: Ecosystems, Biodiversity, and Human Impact

Our planet's intricate web of life, from the tiniest microbe to the largest whale, forms a complex system known as the environment. Understanding this environment, its components, and how we interact with it is the core of environmental science. This AP Environmental Science Unit 1 review will cover the foundational concepts of ecosystems, biodiversity, and human impact, ensuring you're well-prepared for your exams and ready to engage with the world around you.

Introduction to Environmental Science and Ecosystems

Environmental science is an interdisciplinary field that combines biology, chemistry, physics, geology, and social sciences to study the environment and solve environmental problems. It examines how humans interact with the environment and the consequences of those interactions.

• Key Goals of Environmental Science:
  • Understand and mitigate environmental problems.
  • Promote sustainable practices.
  • Conserve natural resources.
  • Protect biodiversity.

Ecosystems: The Foundation of Life

At the heart of environmental science lies the concept of the ecosystem. An ecosystem is a community of living organisms (biotic factors) interacting with their non-living environment (abiotic factors). These interactions create a dynamic system where energy flows and nutrients cycle.

• Biotic Factors: Living components such as plants, animals, fungi, and bacteria.
• Abiotic Factors: Non-living components such as sunlight, water, soil, temperature, and air.

Components of an Ecosystem

Understanding the different roles organisms play within an ecosystem is crucial. These roles are often defined by their trophic level, which indicates their position in the food chain or food web.

• Producers (Autotrophs): These organisms, primarily plants and algae, convert sunlight into chemical energy through photosynthesis. They form the base of the food chain.
• Consumers (Heterotrophs): These organisms obtain energy by consuming other organisms. They can be further classified into:
  • Primary Consumers (Herbivores): Eat producers (e.g., deer, rabbits).
  • Secondary Consumers (Carnivores): Eat primary consumers (e.g., foxes, snakes).
  • Tertiary Consumers (Top Predators): Eat secondary consumers (e.g., lions, eagles).
  • Omnivores: Eat both producers and consumers (e.g., bears, humans).
• Decomposers (Detritivores): These organisms break down dead organic matter, releasing nutrients back into the ecosystem. Examples include bacteria, fungi, and earthworms.

Energy Flow in Ecosystems

Energy flows through an ecosystem in a linear fashion, starting with the sun and moving through the trophic levels.

• The 10% Rule: Only about 10% of the energy stored in one trophic level is converted to biomass in the next trophic level. The remaining 90% is lost as heat during metabolic processes. This explains why food chains rarely have more than four or five trophic levels.
• Food Chains vs. Food Webs:
  • Food Chain: A linear sequence of organisms through which nutrients and energy pass as one organism eats another.
  • Food Web: A more complex network of interconnected food chains, representing the feeding relationships in an ecosystem.

Nutrient Cycles

Unlike energy, nutrients cycle within an ecosystem. Key nutrient cycles include:

• Water Cycle (Hydrologic Cycle): The continuous movement of water on, above, and below the surface of the Earth. Processes include evaporation, transpiration, condensation, precipitation, infiltration, and runoff.
• Carbon Cycle: The movement of carbon through the atmosphere, oceans, land, and living organisms. Processes include photosynthesis, respiration, decomposition, and combustion. Human activities, such as burning fossil fuels and deforestation, have significantly altered the carbon cycle, leading to increased atmospheric CO2 levels and climate change.
• Nitrogen Cycle: The movement of nitrogen through the atmosphere, soil, and living organisms. Nitrogen is essential for building proteins and nucleic acids. Processes include nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. Human activities, such as the use of synthetic fertilizers, have disrupted the nitrogen cycle, leading to water pollution and greenhouse gas emissions.
• Phosphorus Cycle: The movement of phosphorus through rocks, soil, water, and living organisms. Phosphorus is essential for building DNA, RNA, and ATP. Unlike the other cycles, the phosphorus cycle does not have a significant atmospheric component. Phosphorus is often a limiting nutrient in ecosystems. Human activities, such as mining and the use of fertilizers, have altered the phosphorus cycle, leading to water pollution.
• Sulfur Cycle: The movement of sulfur through the atmosphere, oceans, land, and living organisms. Sulfur is a component of many proteins and is released into the atmosphere through volcanic eruptions and the burning of fossil fuels.

Ecosystem Productivity

Ecosystem productivity refers to the rate at which biomass is generated in an ecosystem. It's a measure of how efficiently an ecosystem converts sunlight into organic matter.

• Gross Primary Productivity (GPP): The total rate of photosynthesis in an ecosystem.
• Net Primary Productivity (NPP): The rate of energy storage as biomass after accounting for the energy used by producers for respiration. NPP is a key indicator of ecosystem health and is available to consumers.
• Factors Affecting Productivity: Sunlight, water availability, temperature, and nutrient availability.

Biodiversity: The Variety of Life

Biodiversity refers to the variety of life at all levels of biological organization, from genes to ecosystems. It encompasses the diversity of species, genetic diversity within species, and the variety of ecosystems. Biodiversity is essential for ecosystem stability, resilience, and the provision of ecosystem services.

Levels of Biodiversity

• Genetic Diversity: The variation in genes within a species. High genetic diversity allows a population to adapt to changing environmental conditions.
• Species Diversity: The number and abundance of different species in a given area. High species diversity contributes to ecosystem stability and resilience.
• Ecosystem Diversity: The variety of ecosystems within a region. High ecosystem diversity provides a range of habitats and supports a wider array of species.

Importance of Biodiversity

• Ecosystem Services: Biodiversity provides essential ecosystem services, such as pollination, water purification, climate regulation, and nutrient cycling.
• Economic Value: Many industries, such as agriculture, forestry, and tourism, rely on biodiversity.
• Intrinsic Value: Many people believe that biodiversity has intrinsic value, meaning that it is valuable in its own right, regardless of its usefulness to humans.

Threats to Biodiversity

Biodiversity is currently being lost at an unprecedented rate due to human activities. Major threats include:

• Habitat Loss and Degradation: The destruction and fragmentation of habitats due to agriculture, urbanization, and deforestation. This is the leading cause of biodiversity loss.
• Invasive Species: Non-native species that outcompete native species for resources, disrupting ecosystem dynamics.
• Pollution: The contamination of air, water, and soil with pollutants that harm or kill organisms.
• Climate Change: Changes in temperature, precipitation patterns, and sea level that alter habitats and disrupt species distributions.
• Overexploitation: The unsustainable harvesting of resources, such as overfishing and poaching.

Conservation Strategies

Conserving biodiversity requires a multifaceted approach that addresses the underlying causes of biodiversity loss. Strategies include:

• Protected Areas: Establishing national parks, wildlife refuges, and other protected areas to conserve habitats and species.
• Habitat Restoration: Restoring degraded habitats to improve their ability to support biodiversity.
• Sustainable Resource Management: Managing resources in a way that meets the needs of the present without compromising the ability of future generations to meet their own needs.
• Controlling Invasive Species: Preventing the introduction and spread of invasive species.
• Reducing Pollution: Reducing air, water, and soil pollution through regulations and technological innovations.
• Mitigating Climate Change: Reducing greenhouse gas emissions to slow the rate of climate change.

Human Impact on Ecosystems

Humans have a profound impact on ecosystems around the world. Our activities can alter nutrient cycles, disrupt food webs, and lead to habitat loss and biodiversity loss. Understanding these impacts is crucial for developing sustainable practices.

Deforestation

Deforestation is the clearing of forests for other land uses, such as agriculture, urbanization, and logging.

• Impacts of Deforestation:
  • Habitat Loss: Destroys habitats and contributes to biodiversity loss.
  • Soil Erosion: Increases soil erosion, leading to sedimentation of waterways and loss of soil fertility.
  • Climate Change: Reduces carbon sequestration and contributes to greenhouse gas emissions.
  • Water Cycle Disruption: Alters rainfall patterns and reduces water availability.

Agriculture

Agriculture is the cultivation of crops and livestock for human consumption.

• Impacts of Agriculture:
  • Habitat Loss: Converts natural habitats into agricultural land.
  • Water Pollution: Contributes to water pollution through the use of fertilizers, pesticides, and animal waste.
  • Soil Degradation: Leads to soil degradation through erosion, nutrient depletion, and salinization.
  • Greenhouse Gas Emissions: Contributes to greenhouse gas emissions through the use of fossil fuels, fertilizers, and livestock.

Urbanization

Urbanization is the growth of cities and towns.

• Impacts of Urbanization:
  • Habitat Loss: Destroys habitats and fragments ecosystems.
  • Water Pollution: Contributes to water pollution through stormwater runoff, sewage, and industrial waste.
  • Air Pollution: Contributes to air pollution through vehicle emissions, industrial processes, and energy production.
  • Heat Island Effect: Increases temperatures in urban areas, leading to increased energy consumption and health problems.

Pollution

Pollution is the contamination of air, water, and soil with harmful substances.

• Types of Pollution:
  • Air Pollution: Includes particulate matter, ozone, sulfur dioxide, and nitrogen oxides. Sources include vehicle emissions, industrial processes, and power plants.
  • Water Pollution: Includes nutrients, pathogens, toxic chemicals, and sediment. Sources include agricultural runoff, sewage, industrial discharge, and mining.
  • Soil Pollution: Includes heavy metals, pesticides, and industrial waste. Sources include mining, industrial processes, and agriculture.
• Impacts of Pollution:
  • Harms human health: Causes respiratory problems, cancer, and other diseases.
  • Damages ecosystems: Disrupts food webs, reduces biodiversity, and harms wildlife.
  • Contaminates water supplies: Makes water unsafe for drinking and recreation.

Climate Change

Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates.

• Causes of Climate Change: Primarily caused by the increase in greenhouse gas concentrations in the atmosphere due to human activities, such as burning fossil fuels and deforestation.
• Impacts of Climate Change:
  • Rising Temperatures: Leads to heat waves, droughts, and increased energy consumption.
  • Changes in Precipitation Patterns: Leads to floods, droughts, and water scarcity.
  • Sea Level Rise: Leads to coastal erosion, flooding, and displacement of populations.
  • Ocean Acidification: Threatens marine ecosystems, particularly coral reefs.
  • Species Extinctions: Alters habitats and disrupts species distributions, leading to extinctions.

Overexploitation of Resources

Overexploitation is the unsustainable harvesting of resources, such as overfishing, deforestation, and mining.

• Impacts of Overexploitation:
  • Depletion of resources: Leads to the depletion of natural resources, such as fish stocks, forests, and minerals.
  • Habitat destruction: Destroys habitats and contributes to biodiversity loss.
  • Ecosystem disruption: Disrupts food webs and alters ecosystem dynamics.

Case Studies

To further illustrate the concepts discussed, let's examine a few case studies:

• The Amazon Rainforest: Deforestation in the Amazon Rainforest is driven by agriculture, logging, and mining. This has led to habitat loss, soil erosion, climate change, and biodiversity loss.
• The Chesapeake Bay: The Chesapeake Bay is a large estuary that has been heavily polluted by agricultural runoff, sewage, and industrial discharge. This has led to nutrient pollution, algal blooms, dead zones, and loss of fisheries.
• The Aral Sea: The Aral Sea was once the fourth-largest lake in the world, but it has shrunk dramatically due to the diversion of water for irrigation. This has led to desertification, salt storms, and health problems.

Sustainable Practices

Sustainable practices are practices that meet the needs of the present without compromising the ability of future generations to meet their own needs. Embracing sustainable practices is essential for mitigating human impacts on ecosystems and ensuring a healthy planet for future generations.

• Renewable Energy: Transitioning from fossil fuels to renewable energy sources, such as solar, wind, and hydropower, can reduce greenhouse gas emissions and air pollution.
• Sustainable Agriculture: Using sustainable agricultural practices, such as crop rotation, no-till farming, and integrated pest management, can reduce soil erosion, water pollution, and pesticide use.
• Water Conservation: Conserving water through efficient irrigation, rainwater harvesting, and water-saving appliances can reduce water scarcity and protect aquatic ecosystems.
• Waste Reduction: Reducing waste through recycling, composting, and reducing consumption can reduce pollution and conserve resources.
• Sustainable Forestry: Practicing sustainable forestry, such as selective logging and reforestation, can maintain forest health, conserve biodiversity, and sequester carbon.

Frequently Asked Questions (FAQ)

• What is the difference between weather and climate? Weather refers to the short-term atmospheric conditions in a specific location, while climate refers to the long-term average weather patterns in a region.
• What is the greenhouse effect? The greenhouse effect is the warming of the Earth's surface due to the presence of greenhouse gases in the atmosphere, which trap heat.
• What are the major greenhouse gases? The major greenhouse gases are carbon dioxide, methane, nitrous oxide, and fluorinated gases.
• What is an invasive species? An invasive species is a non-native species that outcompetes native species for resources, disrupting ecosystem dynamics.
• What is sustainability? Sustainability is the ability to meet the needs of the present without compromising the ability of future generations to meet their own needs.

Conclusion

This AP Environmental Science Unit 1 review has covered the fundamental concepts of ecosystems, biodiversity, and human impact. Understanding these concepts is crucial for tackling the environmental challenges facing our planet and promoting sustainable practices. By studying these topics, you are taking the first step towards becoming an informed and engaged environmental steward. Remember to continue exploring these topics in greater depth and to stay informed about current environmental issues. The future of our planet depends on our collective knowledge and action. Good luck with your studies!