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Ecology
Your share in the biosphere
Levels of Organization
• Biosphere
– Earth & its atmosphere that supports life
• Ecosystem
– Organisms & abiotic materials in 1 place
• Community
– Different species of an ecosystem
• Population
– Members of single species of an ecosystem
• Organism
Interdependence
• All organisms interact with other organisms
– Plant, animal, bacteria, fungi, protists, & archaea
• All organisms interact with their surroundings
– Food, shelter, air, moisture, temperature, etc…
• Abiotic environment is changed by organisms
– Erosion, fertilization, pH, mineral cycles, etc…
Ecosystem’s Components
• Biotic factors
– Living organisms
• Abiotic factors
– Nonliving materials, conditions, energy
• Tolerance curve
– Survival range for given condition
– Acclimation: organisms’ ability to adjust tolerance
• Niche
– Species’ specific role within its environment
Species Interaction
• Predation
– Herbivores : eats plants
– Carnivores : eats meat
• Competition
– Interspecific competition: > 2 species, 1 resources
– Competitive exclusion:2 species,1 resource, 1 wins
• Fundamental niche vs. realized niche
• Character displacement (competition-driven evolution)
Species Interaction, continued
• Symbiosis
– Parasitism
• Similar to predation but death of host is not immediate
• Either external (ectoparasites) or inside (endoparasite)
– Mutualism
• Mutually beneficial
• Ants & Acacia plants; pollinators & nectar/ food
– Commensalism
• One benefits & other is unaffected
• Cattle egrets & cape buffaloes
Ecological Succession
• Primary Succession
– New life on previously barren land (no soil)
– Bare rock, sand dune, new island/ lava flow
– Pioneer species predominate early in succession
• Secondary Succession
– Replacement following disruption of existing life
– Soil present after forest fire, flood, storm, humans
– Weeds/ wild flowers->perennials-> shrubs-> trees
• ***Climax community = stable end point ***
Conservation of Energy
• Sun is Earth’s ultimate source of energy
• Autotrophs = Producers of biomass
– Photosynthesis & chemosynthesis
• Heterotrophs = Consumers
– Herbivores, Carnivores, Omnivores, Detritivores
• Energy flows through trophic levels
– Food chains & food webs
– Only ~ 10% of energy is transferred to next troph
Ecosystem Recycling
• Water cycle
Surface H2Oevaporationcloudsprecipitation
runoff  surfaceH2O  percolation groundH2O
plants  transpiration  clouds
• Carbon cycle
– Atmospheric CO2  photosynthesis  plant life
 animal life  respiration  Atmospheric CO2
 animal/plant death  Atmospheric CO2
 fossil fuel  combustion  Atmospheric CO2
Ecosystem Recycling, continued
• Nitrogen cycle
Atmospheric N2 N-fixation by bacteria (root &
soil)  NH3 & NH4+  Nitrification (via bacteria)
 NO3  Denitrifying soil bacteria  N2 in air OR
 NO3  Assimilation into plants  herbivores
 urine/ feces/ plant or animal death/ decay 
decomposers  Ammonification  NH3 & NH4+
• Phosphorous cycle
Rock erosion  PO43-  soil & water plant
absorption herbivores  carnivores/omnivores
 waste/ death/ decay  soil & water