Ecology Fundamentals

Cheatsheet Content

### How to Memorize this Cheatsheet #### 1. Active Recall & Spaced Repetition - **Read a section, then close your eyes and recall everything you remember.** If you get stuck, look back and repeat. - **Use flashcards** for key terms, definitions, and formulas. Test yourself daily, gradually increasing the time between successful recalls. - **Explain concepts aloud** to an imaginary friend or pet. If you can teach it, you understand it. #### 2. Chunking & Association - **Group related information together.** This cheatsheet is already "chunked" into logical sections. - **Create mental images or stories** to link concepts. The more vivid and unusual, the better. - **Draw diagrams or concept maps** to visualize relationships between different ecological components. #### 3. Practice & Application - **Work through example problems** if applicable (e.g., population growth calculations). - **Think of real-world examples** for each concept. How does it apply to local ecosystems or global issues? ### 1. Introduction to Ecology #### 1.1 What is Ecology? - **Definition:** Scientific study of interactions among organisms and between organisms and their environment. - **Levels of Organization (Hierarchy):** 1. **Individual:** Single organism. 2. **Population:** Group of individuals of the same species in the same area. 3. **Community:** All populations of different species in a given area. 4. **Ecosystem:** Community + abiotic (non-living) environment. 5. **Biome:** Large-scale ecosystems characterized by dominant vegetation and climate. 6. **Biosphere:** All living parts of Earth. #### 1.2 Key Ecological Concepts - **Habitat:** Place where an organism lives. - **Niche:** Organism's role/position in the environment (its "job"). Includes resources used, interactions, and conditions tolerated. - **Biotic Factors:** Living components (e.g., predators, prey, competitors). - **Abiotic Factors:** Non-living components (e.g., temperature, water, sunlight, soil pH). - **Limiting Factor:** Any factor that restricts population growth or distribution. ### 2. Population Ecology #### 2.1 Population Characteristics - **Population Density:** Number of individuals per unit area/volume. - **Dispersion:** Spatial arrangement of individuals (clumped, uniform, random). - **Demographics:** Study of vital statistics (birth rates, death rates, migration). - **Life Tables:** Summarize survival and reproduction rates by age. - **Survivorship Curves:** Plot proportion of individuals surviving at each age. - Type I: High survival early/mid-life (humans). - Type II: Constant death rate (squirrels). - Type III: High mortality early life (fish, insects). #### 2.2 Population Growth Models - **Exponential Growth:** $dN/dt = rN$ - Occurs under ideal conditions with unlimited resources. - "J-shaped" curve. - $r$: intrinsic rate of increase. - **Logistic Growth:** $dN/dt = rN(K-N)/K$ - Growth slows as population approaches carrying capacity. - "S-shaped" curve. - **Carrying Capacity (K):** Maximum population size an environment can sustain. #### 2.3 Life History Strategies - **r-selected species:** - High growth rate ($r$). - Many small offspring. - Early maturity. - Little parental care. - Often in unstable environments. (e.g., insects, weeds) - **K-selected species:** - Near carrying capacity ($K$). - Few large offspring. - Late maturity. - Extensive parental care. - Often in stable environments. (e.g., humans, elephants) #### 2.4 Population Regulation - **Density-Dependent Factors:** Effect intensifies with population density (e.g., competition, predation, disease). - **Density-Independent Factors:** Affect population regardless of density (e.g., natural disasters, extreme weather). ### 3. Community Ecology #### 3.1 Interspecific Interactions - **Competition (-/-):** Both species negatively affected by competing for same limited resource. - **Competitive Exclusion Principle:** Two species cannot coexist indefinitely if they occupy the exact same niche. - **Resource Partitioning:** Species divide resources to minimize competition and coexist. - **Predation (+/-):** One species (predator) kills and eats another (prey). - **Adaptations:** Camouflage, mimicry (Batesian, Müllerian), warning coloration. - **Herbivory (+/-):** An organism eats parts of a plant or algae. - **Symbiosis:** Close, long-term interactions between species. - **Parasitism (+/-):** One organism (parasite) benefits at expense of host. - **Mutualism (+/+):** Both species benefit (e.g., clownfish and anemone). - **Commensalism (+/0):** One species benefits, other is unaffected (e.g., barnacles on whales). #### 3.2 Community Structure - **Species Diversity:** - **Species Richness:** Number of different species. - **Relative Abundance:** Proportion of each species in the community. - **Trophic Structure:** Feeding relationships. - **Food Chains:** Linear transfer of energy. - **Food Webs:** Interconnected food chains. - **Trophic Levels:** - **Producers (Autotrophs):** Photosynthesis/chemosynthesis (plants, algae). - **Primary Consumers (Herbivores):** Eat producers. - **Secondary Consumers (Carnivores):** Eat primary consumers. - **Tertiary Consumers (Carnivores):** Eat secondary consumers. - **Decomposers (Detritivores):** Break down dead organic matter (bacteria, fungi). - **Energy Transfer:** ~10% of energy transferred to next trophic level (90% lost as heat). #### 3.3 Succession - **Ecological Succession:** Gradual process of change in species composition over time. - **Primary Succession:** Begins in lifeless areas (no soil) (e.g., new volcanic rock). - Pioneer species (lichens, mosses) $\rightarrow$ grasses $\rightarrow$ shrubs $\rightarrow$ trees. - **Secondary Succession:** Occurs where an existing community has been removed but soil remains (e.g., after fire, logging). Faster than primary. - **Climax Community:** Historic idea of a stable, mature community, though communities are dynamic. #### 3.4 Keystone Species - **Keystone Species:** A species whose impact on its community is larger and disproportionate to its biomass or abundance. Its removal can cause a trophic cascade or ecosystem collapse (e.g., sea otters, wolves). ### 4. Ecosystem Ecology #### 4.1 Energy Flow - **Primary Production:** Rate at which light energy is converted to chemical energy by autotrophs. - **Gross Primary Production (GPP):** Total energy assimilated. - **Net Primary Production (NPP):** GPP - energy used by producers for respiration (R). NPP = GPP - R. - NPP represents energy available to higher trophic levels. - Highest NPP in tropical rainforests, estuaries, coral reefs. - **Secondary Production:** Amount of chemical energy in consumers' food converted to their own new biomass. #### 4.2 Biogeochemical Cycles - **Water Cycle:** Evaporation, condensation, precipitation, runoff, infiltration, transpiration. - **Carbon Cycle:** - **Reservoirs:** Atmosphere (CO2), oceans (dissolved CO2, carbonates), fossil fuels, biomass. - **Processes:** Photosynthesis (removes CO2), respiration (releases CO2), combustion (releases CO2), decomposition. - **Nitrogen Cycle:** - **Reservoirs:** Atmosphere (N2, 78%), soil, biomass. - **Processes:** - **Nitrogen Fixation:** N2 to NH3/NH4+ (bacteria). - **Nitrification:** NH4+ to NO2- to NO3- (bacteria). - **Assimilation:** Plants take up NO3-/NH4+. - **Ammonification:** Organic N to NH4+ (decomposers). - **Denitrification:** NO3- to N2 (bacteria). - **Phosphorus Cycle:** - **Reservoirs:** Rocks, soil, oceans, biomass. No significant atmospheric component. - **Processes:** Weathering of rocks releases phosphate, uptake by plants, consumption by animals, decomposition. ### 5. Biomes #### 5.1 Terrestrial Biomes - Characterized by climate (temperature, precipitation) and dominant vegetation. - **Tropical Rainforest:** High temp, high rain, highest biodiversity, rapid decomposition. - **Desert:** Low rain, extreme temps, sparse vegetation (cacti, succulents), nocturnal animals. - **Savanna:** Warm, seasonal rain, grasslands with scattered trees, large herbivores. - **Temperate Grassland:** Moderate rain, cold winters, fertile soil, prairies. - **Temperate Deciduous Forest:** Moderate rain, distinct seasons, broadleaf trees lose leaves. - **Coniferous Forest (Taiga/Boreal):** Cold winters, moderate rain, conifers (pines, spruces). - **Tundra:** Permafrost, low growing vegetation, very cold, low precipitation. #### 5.2 Aquatic Biomes - Characterized by salinity, depth, water flow. - **Freshwater:** - **Lakes/Ponds:** - **Littoral Zone:** Shallow, near shore, rooted plants. - **Limnetic Zone:** Open water, phytoplankton. - **Profundal Zone:** Deep, aphotic, low O2. - **Benthic Zone:** Bottom substrate. - **Rivers/Streams:** Flowing water, often cold, high O2 near source. - **Wetlands:** Saturated soils, high productivity (marshes, swamps, bogs). - **Marine:** - **Estuaries:** Where freshwater meets saltwater, highly productive, nurseries. - **Intertidal Zone:** Area exposed at low tide, submerged at high tide. - **Oceanic Pelagic Zone:** Open ocean water column. - **Coral Reefs:** Warm, shallow, highly diverse, threatened. - **Marine Benthic Zone:** Ocean floor. - **Abyssal Zone:** Deep ocean, dark, cold, high pressure. ### 6. Conservation Ecology & Human Impact #### 6.1 Threats to Biodiversity - **Habitat Loss/Degradation:** Primary driver (deforestation, urbanization, pollution). - **Introduced (Invasive) Species:** Non-native species outcompeting natives, lacking natural predators. - **Overexploitation:** Harvesting at unsustainable rates (fishing, hunting, logging). - **Pollution:** Toxins, nutrients (eutrophication), plastics. - **Climate Change:** Alters habitats, species ranges, phenology. #### 6.2 Consequences of Biodiversity Loss - Loss of ecosystem services (e.g., pollination, water purification). - Reduced ecosystem stability and resilience. - Loss of potential medicines, food sources. #### 6.3 Conservation Strategies - **Protected Areas:** National parks, reserves. - **Habitat Restoration:** Rebuilding degraded ecosystems. - **Sustainable Resource Use:** Managing resources for long-term availability. - **Captive Breeding/Reintroduction:** For endangered species. - **Policy & Legislation:** CITES, Endangered Species Act. #### 6.4 Human Population Growth - **Ecological Footprint:** Amount of land and water needed to supply resources and absorb waste. - **Sustainability:** Meeting present needs without compromising future generations' ability to meet their own needs.