APES Cram Notes

1. Ecosystems & Biomes

• Ecosystem: A biological community of interacting organisms (plants, animals) and their physical environment (soil, water, air).

  • Components:

    • Biotic Factors: Living components (plants, animals).

    • Abiotic Factors: Non-living components (water, temperature, soil, sunlight).

  • Energy Flow: Sunlight → Producers (plants) → Consumers (herbivores, carnivores) → Decomposers (fungi, bacteria). Energy is lost at each level (about 90%).

  • Food Web vs. Food Chain: A food chain shows one path of energy, while a food web shows multiple paths.

• Biomes: Large, geographically distinct areas with specific climates and ecosystems.

  • Tropical Rainforest: Warm, wet year-round, high biodiversity.

  • Desert: Dry, extreme temperature variation, few organisms.

  • Tundra: Cold, little precipitation, low biodiversity, permafrost.

  • Temperate Forest: Four seasons, deciduous trees.

  • Savanna: Grasslands with scattered trees, seasonal rainfall.

  • Grasslands: Flat areas with few trees, moderate rainfall.

2. Biodiversity

• Species Diversity: The variety of different species in an area (important for ecosystem health).

• Genetic Diversity: The variety of genes within a species, which allows for adaptation and resilience.

• Ecosystem Diversity: The variety of ecosystems in a region, from forests to wetlands to deserts.

• Keystone Species: Species whose role in the ecosystem is disproportionately large compared to their abundance (e.g., sea otters control sea urchin populations, which protects kelp forests).

• Biodiversity Loss:

  • Habitat Loss: Destruction or alteration of habitats (e.g., deforestation).

  • Overexploitation: Overhunting, overfishing, or overharvesting.

  • Invasive Species: Non-native species that outcompete local species.

  • Climate Change: Altered habitats or temperature changes affect species survival.

3. Cycles in Nature

• Water Cycle:

  • Evaporation: Water from oceans, rivers, and lakes turns into vapor.

  • Transpiration: Water released by plants into the atmosphere.

  • Condensation: Water vapor cools and forms clouds.

  • Precipitation: Rain, snow, etc., falls back to Earth.

  • Runoff: Water moves across the land back to bodies of water.

• Carbon Cycle:

  • Photosynthesis: Plants absorb CO₂ to make glucose.

  • Respiration: Animals and plants release CO₂ back into the atmosphere.

  • Decomposition: Dead organisms are broken down, releasing carbon into the soil.

  • Fossil Fuels: Burning fossil fuels releases large amounts of CO₂, contributing to climate change.

• Nitrogen Cycle:

  • Nitrogen Fixation: Certain bacteria convert nitrogen gas (N₂) into ammonia (NH₃) or nitrate (NO₃⁻) usable by plants.

  • Nitrification: Bacteria convert ammonia into nitrites and nitrates.

  • Assimilation: Plants take up nitrogen compounds and animals eat the plants.

  • Denitrification: Bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere.

• Phosphorus Cycle:

  • Weathering: Rocks release phosphate (PO₄³⁻) into soil and water.

  • Absorption: Plants take up phosphate; animals eat plants.

  • Decomposition: Decomposers release phosphorus back into the soil.

  • No Atmospheric Component: Unlike carbon and nitrogen, phosphorus does not exist in the atmosphere, making the cycle slower.

4. Pollution

• Air Pollution:

  • Sources: Fossil fuel burning (cars, factories).

  • Pollutants: Carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NOx), particulate matter.

  • Acid Rain: Sulfur dioxide and nitrogen oxides combine with water vapor to form sulfuric and nitric acid, damaging ecosystems.

  • Ozone Depletion: Chlorofluorocarbons (CFCs) damage the ozone layer, which protects us from UV radiation.

• Water Pollution:

  • Nutrient Pollution: Excess nitrogen and phosphorus from agriculture cause algal blooms, depleting oxygen and harming aquatic life.

  • Plastic Pollution: Non-biodegradable plastic accumulates in oceans and harms marine species.

  • Thermal Pollution: Heat from industrial processes raises water temperatures, reducing oxygen levels and harming aquatic life.

• Land Pollution:

  • Deforestation: Large-scale removal of trees disrupts ecosystems and increases CO₂ levels.

  • Waste Disposal: Landfills and illegal dumping of chemicals cause soil contamination.

• Climate Change:

  • Global Warming: Greenhouse gases (CO₂, methane) trap heat in the atmosphere, leading to rising global temperatures.

  • Impacts: Melting ice caps, rising sea levels, extreme weather events, and habitat disruption.

5. Human Impact

• Deforestation: Clearing forests for agriculture or development reduces biodiversity and contributes to carbon emissions.

• Habitat Fragmentation: Breaking large habitats into smaller, isolated patches reduces biodiversity and makes it harder for species to survive.

• Overfishing: Depletes fish populations and harms aquatic ecosystems.

• Pollution: Industrial and agricultural practices contaminate air, water, and soil, harming ecosystems and human health.

• Invasive Species: Non-native species introduced by humans can disrupt local ecosystems by outcompeting or preying on native species.

6. Sustainability

• Sustainable Development: Balancing human needs with the health of the planet, ensuring resources are available for future generations.

• Renewable Resources: Resources that can be replenished naturally (solar, wind, geothermal, biomass).

• Nonrenewable Resources: Resources that cannot be replaced on a human timescale (coal, oil, natural gas).

• Conservation: Protecting ecosystems, conserving resources, and reducing waste (e.g., using less water, recycling).

7. Environmental Policy

• EPA (Environmental Protection Agency): Government agency that works to protect the environment and public health.

• Clean Water Act: Federal law that regulates the discharge of pollutants into U.S. waters to ensure water quality.

• Endangered Species Act: Protects species that are at risk of extinction by preventing their exploitation and conserving their habitats.

• Kyoto Protocol/Paris Agreement: International agreements aimed at reducing global greenhouse gas emissions to combat climate change.