Ecology and Environmental Science Comprehensive Review: Comprehensive Units 1-9 Study Guide

Unit 1: Introduction to Ecosystems

• Definition of Ecosystems: Communities of living (biotic) organisms interacting with non-living (abiotic) components such as sunlight, water, and soil.

• Symbiosis: Close and long-term biological interactions between different biological species. Categories include:     * Mutualism ($+/+$): Both species benefit from the interaction.     * Commensalism ($+/0$): One species benefits while the other is neither helped nor harmed.     * Parasitism ($+/-$): One species benefits (parasite) at the expense of the other (host).

• Resource Partitioning: The process where species using the same limited resource evolve to use it in different ways to reduce competition. This can occur through differences in:     * Time: For example, one species hunts at night while another hunts during the day.     * Location: For example, different bird species nesting in different parts of the same tree.     * Type: For example, different species eating different parts of the same plant.

• Terrestrial and Aquatic Biomes: Large regions characterized by specific climates and vegetation.     * Terrestrial Biomes: Determined primarily by temperature and precipitation. Key examples include:         * Tropical Rainforests: Characterized by high biodiversity and high rainfall.         * Tundras: High-latitude or high-altitude regions characterized by permafrost.         * Deserts: Regions with extremely low rainfall levels.     * Aquatic Biomes: Characterized by salinity (salt content) and depth. They are divided into:         * Freshwater: Includes lakes and rivers.         * Marine: Includes oceans and coral reefs.

Biogeochemical Cycles and Energy Flow

• Biogeochemical Cycles: Describe the movement of essential elements through the biosphere, atmosphere, hydrosphere, and geosphere.

• The Carbon Cycle: Driven by two primary processes:     * Photosynthesis: Takes in $CO_2$ to produce glucose.     * Respiration: Releases $CO_2$ back into the atmosphere.     * Carbon Sinks: The ocean is identified as a massive sink for carbon.

• The Phosphorus Cycle: Considered the slowest cycle because it lacks a significant atmospheric phase. It is primarily driven by the weathering of rocks.

• The Nitrogen Cycle: Nitrogen gas ($N_2$) must be "fixed" into usable forms like ammonia ($NH_3$) or nitrates ($NO_3$) by bacteria. The key stages are:     1. Fixation     2. Nitrification     3. Assimilation     4. Ammonification     5. Denitrification

• Energy Flow and Trophic Levels: Energy moves from producers (autotrophs) up through consumer levels.     * The 10% Rule: In an ecosystem, only about $10\%$ of the energy is transferred from one trophic level to the next; the remaining $90\%$ is lost as heat.

• Primary Productivity: Measures the rate at which solar energy is converted into organic compounds.     * Gross Primary Productivity (GPP): The total amount of energy captured by producers in a given area over a specific time.     * Net Primary Productivity (NPP): The energy remaining after producers use some for their own respiration. Formula: $NPP = GPP - R$.

Unit 2: Biodiversity

• Levels of Biodiversity:     * Genetic Diversity: The variety of genes within a population, which helps species adapt to environmental changes.     * Species Diversity: The number of different species in a region. This is measured by Species Richness (total number of species) and Species Evenness (the relative abundance of each species).     * Ecosystem Diversity: The variety of habitats or biomes within a geographical region.

• Ecosystem Services: The free benefits humans receive from healthy, functioning ecosystems, categorized into four types:     * Provisioning: Physical goods provided by nature, such as food, water, timber, and medicine.     * Regulating: Services that control environmental conditions, including pollination, climate regulation, and water filtration.     * Cultural: Non-material benefits, such as aesthetic beauty, recreation, and tourism.     * Supporting: Basic processes necessary for all other services, like nutrient cycling, photosynthesis, and soil formation.

• Island Biogeography: A theory predicting species richness on "islands" (including actual islands or fragmented habitats like national parks).     * Size: Larger islands support higher biodiversity because they offer more resources and diverse niches.     * Distance: Islands closer to the mainland have higher biodiversity due to the ease of migration for new species.

• Ecological Tolerance: The range of environmental conditions (e.g., temperature, salinity, sunlight) a species can survive.     * Optimal Range: Conditions where organisms survive, grow, and reproduce most effectively.     * Zone of Physiological Stress: Conditions where organisms survive but experience stress, leading to reduced growth or reproduction.     * Zone of Intolerance: Conditions too extreme for survival; the organism dies.

• Natural Disruptions: Ecosystems change due to natural events categorized by frequency:     * Periodic: Occur at regular intervals (e.g., tides).     * Episodic: Occur at irregular intervals (e.g., El Ni\u00f1o, forest fires).     * Random: Unpredictable events (e.g., meteor strikes, volcanic eruptions).

• Adaptations: Specific traits or behaviors (nature's "solutions") that help an organism survive and reproduce in its environment.

• Ecological Succession: The gradual change in an ecosystem over time.     * Primary Succession: Occurs on bare rock with no existing soil (e.g., after volcanic eruptions or glacier retreats). Pioneer species like lichens and mosses break down rock to create soil.     * Secondary Succession: Occurs in areas where soil already exists after a disturbance (e.g., after a forest fire or hurricane). It reaches a climax community much faster than primary succession.

• Key Vocabulary:     * Indicator Species: Species that reflect the health of an ecosystem (e.g., amphibians).     * Keystone Species: Species that have a disproportionately large effect on their environment relative to their abundance (e.g., sea otters, wolves).

Unit 3: Populations

• Generalist vs. Specialist Species:     * Generalists: Thrive in wide environmental conditions and use a variety of resources (e.g., raccoons). They win in unstable environments.     * Specialists: Have narrow niches and are highly sensitive to changes (e.g., pandas, orchids). They are prone to extinction but win in stable, resource-rich environments.

• Survivorship Curves: Graphs showing the number of survivors at each age.     * Type I (K-selected): High survival throughout life; mortality increases in old age (e.g., humans, elephants).     * Type II: Constant mortality rate throughout the lifespan (e.g., birds, some lizards).     * Type III (r-selected): High early mortality; few reach adulthood, but survivors live long (e.g., trees, fish, frogs).

• Ecological Strategies:     * r-Selected Species: Many small offspring, fast maturation, short lifespan, low parental care, unstable environments (e.g., mosquitoes, dandelions, bacteria).     * K-Selected Species: Few large offspring, slow maturation, long lifespan, high parental care, stable environments (e.g., African elephants, bald eagles, whales, humans).

• Population Growth Models:     * Exponential Growth (J-Curve): Growth without limits; occurs with abundant resources.     * Logistic Growth (S-Curve): Growth that levels off as the population reaches the Carrying Capacity ($K$).     * Overshoot and Die-off: When a population exceeds $K$, it experiences a sharp decline due to resource depletion.

• Age Structure Diagrams:     * Wide Base: High proportion of pre-reproductive individuals; indicates rapid future growth (e.g., Nigeria).     * Column/Stable: Balanced birth and death rates; Indicates slow or zero growth (e.g., USA).     * Inverted/Narrow Base: High proportion of post-reproductive individuals; indicates a declining population (e.g., Japan).

• Demographic Transition Model (DTM):     1. Stage 1 (Pre-industrial): High birth/death rates; stable growth.     2. Stage 2 (Transitional): Death rates drop (medicine/sanitation); birth rates remain high; rapid growth.     3. Stage 3 (Industrializing): Birth rates fall (education/family planning); growth slows.     4. Stage 4 (Post-industrial): Low birth/death rates; population stabilizes or declines.

• Population Mathematics:     * Rule of 70 (Doubling Time): $\text{Doubling Time} = \frac{70}{r}$, where $r$ is the growth rate in percentage.     * Growth Rate (%): $\frac{(\text{Birth Rate} + \text{Immigration}) - (\text{Death Rate} + \text{Emigration})}{\text{Population}} \times 100$     * Crude Birth Rate (CBR): $\frac{\text{Number of births}}{\text{Total population}} \times 1000$     * Crude Death Rate (CDR): $\frac{\text{Number of deaths}}{\text{Total population}} \times 1000$     * Net Growth Rate (Simplified): $\frac{CBR - CDR}{10}$

Unit 4: Earth Systems and Resources

• Plate Boundaries: Driven by mantle convection currents.     * Convergent: Plates move toward each other. Causes subduction (volcanoes/trenches) or mountain building (Himalayas).     * Divergent: Plates move apart. Creates seafloor spreading and rift valleys (Mid-Atlantic Ridge).     * Transform: Plates slide past each other. Causes seismic activity (San Andreas Fault).

• Key Features:     * Mid-Ocean Ridge: New crust formed at divergent boundaries.     * Non-Volcanic Mountains: Formed by continental-continental collision (Himalayas).     * Volcanic Hotspots: Magma plumes far from boundaries (Hawaii).     * Ring of Fire: Zone around the Pacific Ocean with high earthquake/volcanic activity.     * Island Arcs: Chains of islands from ocean-ocean subduction (Aleutian Islands).     * Andes Mountains: Volcanic range from ocean-continental subduction.

• Soil Properties:     * Horizons: O (Organic/Leaf litter), A (Topsoil/Nutrients), B (Subsoil/Minerals), C (Weathered parent material).     * Texture: Based on particle size.         * Sand (> 0.05\,mm): High permeability, low water-holding.         * Silt ($0.002 - 0.05\,mm$): Medium properties.         * Clay (< 0.002\,mm): Low permeability, high nutrient retention (CEC).         * Loam: Ideal agricultural mix of sand, silt, and clay.

• Atmosphere and Wind Patterns:     * Layers: Troposphere (weather), Stratosphere (ozone layer), Mesosphere, Thermosphere, Exosphere. Temperature increases in the Stratosphere and Thermosphere; decreases in the Troposphere and Mesosphere.     * Global Wind: Driven by solar radiation and the Coriolis Effect.     * Hadley Cells: Air rises at the equator ($0^{\circ}$) and sinks at $30^{\circ}$.     * Trade Winds: Move East to West toward the equator.

• Insolation: The amount of solar radiation. The Earth's tilt of $23.5^{\circ}$ causes seasonal variation.

• ENSO (El Ni\u00f1o-Southern Oscillation):     * El Ni\u00f1o: Trade winds weaken; warm water moves toward South America. Suppresses upwelling; Southern US becomes wetter/cooler; SE Asia/Australia experience drought.     * La Ni\u00f1o: Stronger trade winds; intense upwelling; cooler waters in the eastern Pacific. Southern US becomes dry/warm.

Unit 5: Land and Water Use

• Tragedy of the Commons: Depletion of shared, unregulated resources (e.g., overfishing, overgrazing) for personal gain. Fixes include regulation or privatization.

• Clearcutting: Removing all trees in an area. Results in soil erosion, increased stream temperature, and albedo changes.

• The Green Revolution: Shift to industrial agriculture using mechanization, synthetic fertilizers, pesticides, and GMOs. Increased yields but caused soil degradation.

• Agricultural Impacts:     * Tilling: Plowing soil; leads to erosion and organic matter loss.     * Slash-and-Burn: Cutting and burning forests; provides temporary nutrients but leads to deforestation and high emissions.

• Irrigation Methods:     * Furrow/Flood: Cheap; $35-50\%$ water loss; causes waterlogging.     * Spray: Efficient but suffers evaporation loss.     * Drip: > 95\% efficient; very expensive.     * Salinization: Salt buildup in soil from evaporated irrigation water; makes soil toxic.

• Pest Control:     * Pesticide Treadmill: Pests evolve resistance, requiring stronger chemicals.     * IPM (Integrated Pest Management): Uses biological, physical, and cultural methods before chemicals.

• Meat Production:     * CAFOs (Concentrated Animal Feeding Operations): Efficient but produce manure lagoons leading to eutrophication. Beef requires significantly more land/water than grain.

• Mining Impacts:     * Surface Mining: Strips "overburden"; total habitat loss.     * Acid Mine Drainage: Rainwater reacts with sulfur in tailings to create sulfuric acid.

• Urbanization:     * Impermeable Surfaces: Concrete prevents infiltration, causing flooding.     * Urban Heat Island (UHI): Cities are $2-10^{\circ}C$ warmer due to heat absorption by dark surfaces (low albedo) and lack of vegetation.

• Sustainability:     * Ecological Footprint: Land/water area needed to support a lifestyle.     * MSY (Maximum Sustainable Yield): Maximum harvest without depleting future resources.     * Aquaculture: Fish farming; protects wild stocks but can spread disease and pollution.

Unit 6: Energy Resources and Consumption

• Math Shortcuts:     * Prefixes: Kilo ($10^3$), Mega ($10^6$), Giga ($10^9$).     * Percent Change: $\frac{\text{New} - \text{Old}}{\text{Old}} \times 100$     * Electrical Energy: $\text{Energy (kWh)} = \text{Power (kW)} \times \text{Time (hours)}$

• Energy Laws:     * 1st Law of Thermodynamics: Energy is not created or destroyed, only transformed.     * 2nd Law of Thermodynamics: Conversions are inefficient; energy is lost as heat.

• Nonrenewable Sources:     * Coal: Cheap, abundant; produces $CO_2$, $SO_2$, mercury, and acid rain.     * Oil: High energy density; oil spills and $CO_2$.     * Natural Gas ($CH_4$): "Bridge fuel"; cleaner than coal but prone to methane leaks.     * Nuclear (U-235 Fission): No $CO_2$; radioactive waste and high accident impact (meltdown).

• Renewable Sources:     * Solar: PV cells; weather dependent.     * Wind: Cheap long-term; intermittent; wildlife impact.     * Hydroelectric: Reliable; disrupts ecosystems/flooding. Use fish ladders to mitigate.     * Geothermal: Stable; releases $H_2S$.     * Biomass: Uses waste; deforestation risk.

• Global Energy Mix: Fossil fuels dominate ($\approx 80\%$).

Unit 7 & 8: Atmospheric, Water, and Soil Pollution

• Air Pollutants:     * Primary: Directly emitted ($CO$, $CO_2$, $SO_x$, $NO_x$, PM, VOCs).     * Secondary: Formed in the atmosphere ($O_3$, acid rain $H_2SO_4).     * Photochemical Smog: NO_x + VOCs + sunlight \rightarrow O_3 + PANs.     * Thermal Inversion: Warm air traps cool, polluted air near the ground.

• Indoor Air Pollution: Radon-222, VOCs, asbestos (developed); biomass burning/smoke (developing).

• Control Technologies:     * Catalytic Converter: Converts CO$and$NO_x$to$CO_2$and$N_2.     * Electrostatic Precipitator: Removes particulates using electric charge.     * Scrubber: Uses chemical/water spray to remove SO_2 and particulates.

• Water Pollution:     * Point Source: Identifiable (pipe).     * Non-Point Source: Diffuse (agricultural runoff).     * Eutrophication Process: Nutrient (N, P) runoff \rightarrow $Algal bloom$ \rightarrow $Blocked sunlight$ \rightarrow $Algae die$ \rightarrow $Decomposition consumes$O_2$$ \rightarrow Dead zone (fish die).

• Toxicity:     * Bioaccumulation: Toxin buildup in one organism over time.     * Biomagnification: Toxin concentration increases up the food chain (e.g., Mercury, POPs).     * LD50: The dose that causes death in 50\% of the test population.     * Endocrine Disruptors: Mimic or block hormones (e.g., BPA, Atrazine).

• Waste and Sewage:     * Landfills: Lined to prevent leachate.     * Sewage Treatment: Primary (physical/solids), Secondary (biological/bacteria), Tertiary (nutrient removal), Disinfection (UV, chlorine, ozone).

• Major Environmental Laws:     * Clean Air Act (CAA): Air quality standards, criteria pollutants.     * Clean Water Act (CWA): Fishable/swimmable waters, point source pollution.     * Safe Drinking Water Act (SDWA): Protects groundwater/drinking water.     * RCRA: "Cradle to Grave" hazardous waste tracking.     * CERCLA (Superfund): Cleanup of abandoned sites, "Polluter Pays".     * ESA: Protects endangered species and habitats.     * Montreal Protocol: Phases out CFCs to save the ozone layer.

Unit 9: Global Change

• Ozone Depletion: Occurs in the Stratosphere due to CFCs. The Montreal Protocol (1987) led to the use of HFC substitutes.

• Climate Change: Greenhouse effect driven by CO_2$(fossil fuels) and$CH_4 (landfills, agriculture). Results in melting glaciers, rising sea levels, and extreme weather.

• Ocean Impacts:     * Warming: Causes fish migration and coral bleaching.     * Acidification: CO_2 + H_2O \rightarrow \text{Carbonic Acid}$$. Lowers pH, harming shelled organisms (oysters, pteropods).

• Biodiversity Loss (HIPPCO):     * H: Habitat Loss     * I: Invasive Species (e.g., Zebra mussels, Kudzu vining)     * P: Population Growth (human)     * P: Pollution     * C: Climate Change     * O: Overexploitation