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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