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Ecology (BIO 47) Review for Final Exam Community Dynamics Define community In what way are communities dynamic? How does a disturbance affect a community? Succession Self-thinning Early successional traits (list) Late successional traits (list) Trade-offs in life history traits ex grow longer or reproduce early Primary vs Secondary Succession Facilitation Inhibition Tolerance Climax community – endpoint of succession Effect of disturbance *Intermediate disturbance hypothesis Food chains & food webs Trophic levels Primary producer (photosynthesizers, autotrophs) Herbivores Carnivores Omnivores Decomposers Top down control of community structure (sea urchin example) Trophic cascade Ecosystem engineers (beavers) Bottom up control Limits to food chain length Productivity Ecosystem size Both Community stability Resistance Return time Resilience Persistence Alternative stable strategies Why are some communities more stable than others? Diversity stability hypothesis Food web theory (increased connectance) **Keystone species (sea star, otter examples) Dominant species (numerically dominant) Biogeography Species richness – number of species in an area Latitudinal gradient – more species at the equator / fewer at the poles Ecological vs historical perspective on why species live where they do Sampling species richness – species accumulation curve Rates of speciation & extinction Competition Turnover – change identity of species in the community Generalists vs specialists Why protect biodiversity Genetic library (food, medicines etc) Ecosystem services (water purification, climate regulation, pollination etc) Aesthetics Ecological Biogeography Species-area curves (bigger islands – more species) Island species richness is influenced by immigration, extinction & evolution **MacArthur & Wilson – Equilibrium Theory of Island Biogeography Immigration & extinction Size of island Distance from mainland How to find the equilibrium number of species Rate of Turnover Dispersal Types of barriers to dispersal Modes of crossing barriers Historical biogeography Evidence of major changes in geology (shark fossils in Kansas indicate presence of large inland sea) Plate tectonics Allopatric speciation Vicariance event Founder event Sympatric speciation Land bridges – great American biotic interchange Human accelerated dispersal (ex rats) Impacts of introduced species Latitudinal gradients Hotspots Global patterns created by: Differential energy input from sun (poles vs equator) Tilt & orbit of the earth creates seasons Atmospheric circulation – result in bands of wet & dry Terrestrial Biomes Tropical rain forest Deciduous temperate forest Coniferous forest Savannah Temperate grassland (prairie) Chaparral Taiga Tundra Desert Ecosystem Ecology Sustainable practices Ecological footprint (humans in general, yours specifically) Energy flows through ecosystems Nutrients are cycled within ecosystems Define ecosystem Biotic vs abiotic factors Spatial scale Autotrophs (photosynthetic & chemosynthetic) make own food Heterotrophs eat other organisms Primary producers (autotrophs) Gross primary production (all photosynthetic product) Net primary production (GPP – respiration) what’s left for herbivore Aquatic ecosystems Light is reduced with depth Nutrients important for phytoplankton to grow N, P, Fe, Si Terrestrial ecosystems Limiting nutrients: N, P, K Temperature and Precipitation Trophic levels Autotrophs – primary production Heterotrophs – secondary production Energy transfer is very inefficient Nitrogen fixers can pull nitrogen from air – lowers C:N ratio – better for herbivores Use nitrogen to build proteins Cost of thermoregulation – higher metabolism Ecosystem energetics Detrital food chain Eltonian pyramids – more produces, fewer herbivores, even fewer carnivores Ecosystem services Humankind’s ecological footprint is growing Types of ecosystem services Supportive Provisioning Regulating Cultural Service valuation – how can we attach a value to ecosystem services? Tragedy of the Commons – describe & give example Nutrient Cycling What is a nutrient? Macro vs micronutrients Nitrogen, Phosphorous, Carbon cycles Limiting nutrients (often N & P) What happens when N &/or P is added to an aquatic system? Describe the process of Eutrophication Nutrient pools (ex a tree or the soil act as nitrogen pools) Flux – movement Components of biogeochemical cycles (atmosphere, hydrosphere, lithosphere, biosphere) Abiotic vs biotic Nitrogen cycling Biggest pool is in the atmosphere Important component of proteins Nitrogen fixation Immobilization Mineralization Nitrification Denitrification Problems associated with leaching and disturbance (Hubbard Brook experiment) Human impacts: eutrophication, acid rain, greenhouse effect Phosphorous cycling Biggest pool is rocks & soil Important component of DNA & ATP Anthropogenic sources – phosphate mining for agriculture fertilizers, sewage Carbon Cycling Biggest pools are atmosphere and rocks (limestone) Long term cycles involving lithosphere Short term cycles involving atmosphere & biosphere Human impacts: burning fossil fuels releases huge quantities of CO2 Climate Change Temperature affects organisms on many levels: Enzymes: too cold & they work slowly, too hot & they change shape/stop working. Individual: ectotherms are more active when it gets warmer – to a point. Population: reproductive rates can vary with temperature. Global: species richness increases with temperature Detecting Climate Change: Weather vs. climate Separate signal from noise Components of climate system: atmosphere, hydrosphere, lithosphere, cryosphere, biosphere Atmosphere: measure air temperature over time Biosphere: organism features (growth rings in trees, coral, etc) provide info about temperature Cryosphere: air bubbles trapped in ice can give info regarding temp & CO2 – Ice cores from glaciers can provide info from long ago. Extent of ice coverage declines with increasing temperature Hydrosphere: Amount, intensity, frequency and type of precipitation changes with climate Rise in sea level result of increasing temperatures Climate Models Models are more accurate when they include more variables. Must be tested with data from the past before they can reliably be used to predict the future. Describe how the greenhouse effect works Greenhouse effect necessary for life on Earth – humans are increasing the effect. List greenhouse gases Models include the following: Solar output Distance from the sun Albedo Greenhouse gases Attribution of climate change Natural causes - variations in earth’s orbit or solar output, volcanic eruptions Anthropogenic (human) causes – release of greenhouse gases, changes in land use, aerosols, jet exhaust Consequences Biological Consequences Organisms could move, acclimate, evolve (adapt) (recall acclimation vs adaptation) Changes in phenology (timing): ex caterpillars have come & gone by the time baby birds hatch Fitness varies with temperature - ex? Range shifts – organisms will shift ranges poleward to find appropriate temperatures Changes to communities will result – ex pine bark beetle