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 cycleSurface H2Oevaporationcloudsprecipitation

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 cycleRock erosion PO4

3- soil & water plant absorption herbivores carnivores/omnivores waste/ death/ decay soil & water