Energy Flow and Nutrient Cycles Principles of Ecology

Energy Flow in an Ecosystem Learning Targets Describe the different niches organisms occupy in food chains and diagram a model of a food web that includes several food chains. Compare and contrast how matter and energy move through ecosystems and explain how each process relates to the laws of conservation of mass and energy. Discuss the potential ecological, environmental, and social impacts of a primary plant-based or primary meat-based diet in a human society. Identify how living organisms influence global and local cycles of matter (ex. Carbon, nitrogen, phosphorus, and water cycles)

Energy flows through an ecosystem from producers to consumers Energy flows through an ecosystem from producers to consumers. Energy flows from one trophic level to the next. (troph = feeding) Nutrients (matter) cycle in an ecosystem. The processes of photosynthesis and aerobic respiration are important in nutrient cycling and energy flow.

Trophic Levels Primary Producers – plants, algae, photosynthetic bacteria, some archaea cells. Most are photoautotrophs. Some are chemoautotrophs (use chemicals in the environment instead of sunlight to produce food)

Energy Flow in an Ecosystem Food Chains – show the trophic relationship between organisms in an ecosystem. A single food chain is just one link in a food web Primary Producer Primary Consumer Secondary Consumer Primary Producer Tertiary Consumer Primary Consumer Secondary Consumer Tertiary Consumer Secondary Consumer Primary Producer Primary Consumer Quaternary Consumer

Energy Flow in an Ecosystem Food Webs show all the interacting food chains in an ecosystem.

Energy and Biomass Pyramids Energy flow in an ecosystem is not efficient between trophic levels, which can be seen in an energy pyramid. Only about 10% of all energy is passed from one trophic level to the next The 10% rule Biomass pyramids also decline as the trophic level increases. Why? Energy lost in the form of heat. Energy used for metabolic purposes. Indigestible material

Humans and Trophic Ecology The dynamics of energy flow through ecosystems have important implications for the human population. Consider the resources needed to grow, feed, process, and transport beef. Using your knowledge of energy transfer and biomass transfer in an ecosystem, explain how using space to grow plants that will feed people is more energy efficient than using the same amount of space to grow animals that will feed people.

Humans and Trophic Ecology Discussion Question: As human populations continue to grow, will humans be able to sustain a diet that relies on animals for protein? Trophic level Secondary consumers Primary producers What evidence supports this argument? What evidence contradicts this argument?

Nutrient Cycling Decomposers and Detritivores play an important role in recycling nutrients in an ecosystem.

Nutrient Cycling The chemical cycling in an ecosystem is an essential component of ecosystem function. Also called Biogeochemical Cycles CO2 in atmosphere Photosynthesis Cellular respiration Burning of fossil fuels and wood Higher-level consumers Primary Detritus Carbon compounds in water Decomposition THE CARBON CYCLE N2 in atmosphere Denitrifying bacteria Nitrifying Nitrification Nitrogen-fixing soil bacteria bacteria in root nodules of legumes Decomposers Ammonification Assimilation NH3 NH4+ NO3 NO2  Rain Plants Consumption Decomposition Geologic uplift Weathering of rocks Runoff Sedimentation Plant uptake of PO43 Soil Leaching THE NITROGEN CYCLE THE PHOSPHORUS CYCLE

Carbon Cycle The Carbon Cycle is a global biogeochemical cycle What are some living and non-living reservoirs of carbon? What are some of the processes that occur that change carbon from one form to another? In what form(s) is carbon utilized by living things? Classroom discussion questions

Nitrogen Cycle The nitrogen cycle is a global biogeochemical cycle What sort of organisms convert nitrogen from one form to another? Why are each of these processes essential for an ecosystem food web? Classroom Discussion Questions