Transcript ECOSYSTEMS
Ecosystems Chapter 54 • Ecosystem involves all abiotic and biotic factors in area. • Trophic levels - groups in which organisms are placed according to eating patterns. • Ecosystems - involve nutrient cycles. http://www.oahunaturetours.com/pelagic/images/sbbfoodchain1.GIF • Autotrophs - self-feeders (usually photosynthesize) -primary producers • They use light to make sugars, other chemicals necessary for life. http://static.howstuffworks.com/gif/irrigation-photosynthesis.gif • Heterotrophs - rely on organisms for food. • Herbivores – eat primary producers (primary consumers) • Carnivores - eat primary consumers (secondary consumers) • Tertiary consumers - eat secondary consumers. • Detritivores - decomposers - break down detritus (dead organic matter left after organism dies) • Organic matter must be recycled in ecosystem. • Biggest decomposers - fungi and prokaryotes (secrete enzymes to break down dead material) • Primary production - amount of light that can be converted to energy in a given time. • All contributes to energy budget in an area (determines how much energy available to ecosystem) http://adaptation.nrcan.gc.ca/posters/images/pr_02_01_e.gif • Gross primary productivity amount of light energy converted to chemical energy. • Net primary productivity - gross productivity minus amount of energy used by primary producers for respiration (amount of energy left over) http://eostc.umt.edu/forestry/Products/Production/Forest%20Production/first_modis_gpp.g • Primary production - expressed in terms of biomass (amount of vegetation added to ecosystem per unit area per unit time) • Each ecosystem different amount of biomass. • Oceans - amount of light to hit ocean floor contributes biomass. • Light can only go to certain level; primary productivity of area may be lower in deeper oceans. Primary Productivity Map • Nutrients also contribute to biomass in aquatic areas. • Nitrogen - plant growth (can be limited in water) • Water pollution adds nutrients to water (eutrophication) • Shifts organisms living in water and is a negative impact of humans. Eutrophication of lake • Land areas - temperature and water availability also determines primary productivity. • Minerals in soil can affect production as well. http://www.usf.uni-osnabrueck.de/~hlieth/npp/npp.gif • Efficiency between trophic levels is about 20%. • Transfer from one level to next is only 20% of energy from level before. • Biomass pyramids show transformations between trophic levels. • Differ dramatically between ecosystems. • Nutrient cycling involves abiotic and biotic factors (biogeochemical cycling) • Water cycling physical cycle and not chemical; not considered biogeochemical cycle, but still essential to ecosystem. Carbon cycle is a biogeochemical cycle. • Nitrogen enters an ecosystem in 2 ways. • Added to soil in usable form. • Can also enter through nitrogen fixation - prokaryotes convert nitrogen into usable organic compounds like amino acids. • Product of nitrogen fixation is ammonia. • Ammonia picks up H+ in soil to become ammonium (ammonification) • Plants can use this nitrogen. • Aerobic bacteria can turn ammonium into a nitrate (nitrification) • Nitrates - used by plants. • In final step, other bacteria use oxygen from nitrates and release N2 back into atmosphere (denitrification) • Phosphorus occurs only in phosphate - plants absorb and use to make organic nutrients. • Does not come from atmosphere. • Recycling of phosphorus is usually confined to specific areas. • Rate of decomposition determines rate of chemical cycling. • Tundra - decomposition can take years; rain forest - decomposition takes much less time. • Humans affect rate of chemical cycling due to habits. • Farmers - disturb crop areas by removing nutrients in soil. • Humans - add fertilizers to soil which disrupt chemical balances. • Chemicals can enter water, disrupting animals that live there. • Burning of fossil fuels - major contributors to nutrients in atmosphere. • Sulfur and nitrogen placed into atmosphere change into acid precipitation. Acid precipitation • Acid precipitation can alter pH of soil and alter the vegetation that lives there. • Poisonous materials also added to our soils and water. • Further up food chain, more organism is affected by chemicals. • DDT (a pesticide) damaged birds and fish when it met with water. • Amount of carbon dioxide in atmosphere has been rising for decades. • Carbon dioxide helps to keep in heat that would normally escape atmosphere (greenhouse effect) • Ozone layer is thinning as a result of fossil fuels. • Ozone protects humans from UV rays.