Ecosystems & Restoration Ecology

Ecosystems & Restoration Ecology Chapter 55

Learning Targets • I can explain how energy regulates the amount and sizes of trophic levels. • I can describe the fundamental relationship between autotrophs, heterotrophs and decomposers in an ecosystem. • I can explain how decomposition connects all trophic levels in an ecosystem. • I can explain why the amount of energy used in photosynthesis is so much less than the amount of solar energy that reaches the Earth. • I can summarize the 10% rule. • I can explain why worldwide agriculture could feed more people if all humans consumed only plant material. • I can explain how limiting factors affect ecosystem dynamics. • I can explain how nitrogen and phosphorous limit the structure of an ecosystem. • I can explain how cultural eutrophication can alter freshwater ecosystems. • I can explain how it is that eutrophic bodies of water are both nutrient rich and oxygen poor. • I can use my understanding of photosynthesis to explain how light limits ecosystems. • I can explain how primary productivity impacts the ecosystem structure. • I can describe how to calculate gross and net productivity. • I can compare gross to net productivity • I can explain the influence of cellular respiration on net productivity. • I can design a lab that measures gross and net productivity. • I can explain how nutrients cycle through an ecosystem. • I can describe how water, nitrogen, carbon, and phosphorous cycle. • I can identify the reservoirs of nitrogen, phosphorous and carbon. • I can describe how living organisms assimilate and release the different nutrients in each cycle. • I can explain the role of bacteria in the nitrogen cycle. • I can explain how the phosphorous cycle is local. • I can describe the role of photosynthesis, and cellular respiration in the carbon cycle.

Energy in Ecosystems • Trophic efficiencies:10% rule • Generally, only 10% of energy is transferred between trophic levels • Remaining 90% is lost as heat from metabolism

Limiting Factors • If there is not enough of a resource available, the organisms in the ecosystem are impacted • Nitrogen, phosphorus deficiencies • Used by plants in photosynthesis • Reduced PS = reduced plants = reduced animals • If there is too much of a resource available, the organisms in the ecosystem are impacted • Eutrophication – addition of sewage, fertilizer run off to aquatic ecosystems • Boom in algae, cyanobacteria = less dissolved oxygen for other organisms (fish) = death of fish

Primary productivity Gross Primary Productivity Net Primary Productivity Rate at which plants convert sunlight energy into chemical energy Rate at which plant produces organic material through photosynthesis Net gain of dried mass stored in plant after respiration Key Terms

Net = gross - respiratory Production production losses NPP = GPP - R MUST KNOW….

Biogeochemical Cycles of Matter Biotic factors are made up of matter (CHNOPS) This matter cyclesin our biosphere

4 Cycles Water cycle Carbon cycle Nitrogen cycle Phosphorus cycle Nicely reviewed on pages 1228-1229!

Water cycle • Key processes: • Transpiration • Evaporative loss of water through leaves • Condensation • Water vapor forms clouds • Precipitation • Returns water to land

Carbon Cycle • Key processes: • Photosynthesis • Removes atmospheric CO2 • Cellular respiration • Returns CO2 to atmosphere • Burning of fossil fuels • Adds significant CO2 to atmosphere

Nitrogen Cycle • Key processes: • Nitrogen fixation • Conversion of atmospheric N2 to usable forms by bacteria • Ammonification • Decomposes organic nitrogen to NH4+ • Nitrification • NH4+ is converted to NO3- by nitrifying bacteria • Denitrification • Anaerobic bacteria convert NO3- to N2

Phoshorus Cycle • Key processes: • Weathering of rocks • Adds phosphorus to soil • Uptake by producers • Producers eaten by consumers • Decomposers return phosphorus to soil

Ecosystems & Restoration Ecology