Ecology.Ecology Ecosystem dynamics involve two processes: energy flow and chemical cycling. We will Quickly follow the flow of energy by grouping species.
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Ecology.Ecology Ecosystem dynamics involve two processes: energy flow and chemical cycling. We will Quickly follow the flow of energy by grouping species into trophic levels of feeding relationships. CHAPTER 41 ECOSYSTEMS
Food Webs & Food Chains Food chains follow who eats whom: sun -> grass -> cow -> man sun -> oats -> mice -> cat. Food webs show interactions in a community, i.e. cows eat grass & oats, cats eat mice & cows, man eats oats, cows, etc. Simple food chain shown here.
The autotrophs, primary producers, are photosynthetic (green plants, algae, microbes). Use light energy to synthesize sugars & other molecules, obtaining chemical nutrients fr/ soil/water. A few chemosynthetic autotrophs use chemicals instead of light to make sugar (bacteria, sea vents). Heterotrophs, consumers, depend on producers to obtain their energy/food & chemicals (animals, decomposers, microbes). An ecosystem’s energy flow & chemical cycling derive from trophic relationships.
Primary consumers are herbivores that eat primary producers. Secondary consumers are carnivores that eat herbivores. Tertiary consumers eat secondary consumers; higher order consumers possible but rare (carnivores). Another important group of heterotrophs are the detritivores and decomposers. They get energy from detritus (dead matter) and are important in chemical recycling in the ecosystem. They return chemical nutrients in dead matter back to the soil for use by primary producers.
Primary production -the amount of light energy converted to chemical energy (sugar) by primary producers. Only ~1% of sunlight reaching the Earth is converted to chemical energy. The rest is reflected back or converted to heat. Although only a small amount of the total, primary production makes about 170 billion tons of organic material/year. Primary Production In Ecosystems
Energy Conversions in Ecosystems (Quick) Plants convert light energy into chemical energy (sugar) and sugar into new biomass. Consumers convert the chemical energy in food to make their new biomass. In these conversions, most energy is lost as heat. The efficiency of energy transfer between trophic levels is usually about 10%.
Ecological Pyramids -represent the percentage of production transferred from one trophic level to the next. Energy is shown here and is lost at each trophic level.
Student Presentations The next 7-9 slides, student individuals or groups will present: First, understand the topic of the slide by doing your reading Present the slide(s) to the class. Do not make more slides.
Nutrients recirculate in ecosystems; three cycles of importance: 1.The carbon cycle. 2.The nitrogen cycle. 3.The water cycle. The rates of nutrient recycling in ecosystems depends on the rates of decomposition. May be 50+ years in the tundra or desert. May be 2 years in a tropical rainforest. The Cycling of Chemical Nutrients
Disrupting nutrient cycles by removing nutrients from one part of the biosphere, adding them to another. Especially from agriculture. Doubled the worldwide supply of fixed nitrogen from the use of fertilizers, growing legumes, and burning. May increase nitrogen oxides in the atmosphere, contribute to atmospheric warming, depletion of ozone, and acid rain. Deforestation link: Deforest.Deforest Human disruption of chemical cycles