focuses on adaptations of indivduals within a population
focuses on demography and simple interactions (within a population or between two populations)
- focuses on complex species interactions.
- (eg. indirect effects of food webs and succession)
- focus on complex interactions among all species and physical environment
- -according to pathways of energy, matter, and information.
- -traces pathway of matter and energy flow
- -principles of feedback dynamics to understand regulatory pathways and state in the system
major energy transformations majorly depend on photosynthesis or respiration.
photosynthesis and plant growth turns carbon dioxide and water into organic carbon. stores energy
by plants and animals, organic carbon is broken down into carbon dioxide and water. releases energy that does work and degrades into heat.
energy transformations based on trophic levels.
- energy flows thru paths in food web, cuz energy is stored and transferred in biomass.
- -energy is lost at each transfer
ecosystem functions and nutrients.
- P - phosphorous
- C - carbon
- N - nitrogen.
- -required for growth, maintenance, and reproduction of organisms.
- -cycling of each element is a major functions of ecosystems.
- occurs in mineral deposits and marine sediments
- -released thru weathering of rock
- -assimilate thru plants and recycled thru ecosystem
- -unassimilated P washed into oceans, where remains dissolved till deposited into sediments
nitrogen. cycle of this summarized by 4 chemical transformations.
- 1. fixation.
- 2. ammonification
- 3. nitrificaton.
- 4. denitrification.
fixation of nitrogen.
speclized bacteria reduce atmospheric nitrogen to biologically useful forms with enzyme nitrogenase either ammonium or as nitrate.
organic nitrogen compounds used by plants to construct proteins. proteins eventually metabolized and excess nitrogen is excreted to environment as waste.
ammonia excreted as waste can further metabolized by microbes in soil. the oxidation of ammonia to nitrite, from mitrite to nitrate.
in soil under anaerobic conditions, microbes convert nitrates back to N gas.
foundation of all organic molecules. atmospheric C compounds such as carbon dioxide and methane influence global climate.
3 classes of processes cause carbon to cycle thru ecosystems.
- 1. photosynthesis/respiration
- 2. exchange of CO2 between atmosphere and oceans.
- 3. precipitation of carbonate sediments in oceans
links between N and C cycles.
- dependent on global distribution of land cover:
- -photosynthesis requires N.
- -N limiting in most ecosystems.
- -fixation and storage of C closely linked to N cycle
as vegetation develops..
soil nitrogen content tends to increase, organic carbon content increase, fraction of phosphorous available decreases
distrubance increases.. and...
nutrient losses from ecosystems
effects of excess nutrients.
- disrupt ecosystem function and structure.
- -terrestrial ecosystems, lead to reduced species richness, simplified community structure
- -favor few competitively dominant species
- -aquatic evironment: can come from human and natural sources.
effects of excess of nutrients in aquatic environments..
- population booms and death of primary producers = huge detritus inputs. decomposition of dead organisms strips waters of oxgyen.
- -extreme: water can become hypoxic