55.1-55.4: Ecosystem EcologyEcosystem Ecology: focuses on different aspects of an ecosystem interact to move energy around. Movement of matter and energy throughout an ecosystem: -all natural energy comes from the sun, therefore, energy enters ecosystems primarily at the producer (plants) trophic level. *only about 1% of the sunlight reaching the earth is taken up by producers, the rest is reflected back into space or absorbed by air, water, or soil as heat. The 1% taken up by producers is the GPP (gross primary production)-Some energy is lost through heat or organisms using the energy to walk etc. -Some matter is lost in respiration through CO2, but plants/producers bringit back through photosynthesis. Global Patterns of productivity: Higher GPP in rainforest (warm/wet) Lower GPP in dry/airy areasGross Primary Productivity (GPP): total energy input into ecosystem (energy taken up through photosynthesis) Net Primary Productivity (NPP)= GPP – Energy used in cellular respiration by producers. Actual amount of new energy used in new biomass. Standing crop: amount of biomass in the system at any given point in time. (Not necessarily linked to GPP, we would need to know standing crop before and after to be able to figure any actual calculations out.)example if… GPP= 535 g/m2 and respiration uses 255 g/m2 then…. NPP= 535 – 255= 280 g/m2 Limiting Nutrient: the needed nutrient that is in lowest supply and will determineor “limit” the size of the population. -If you add more of the limiting nutrient, you would see a drastic increase in population growth (this is how you prove that something is the limiting nutrient)when an organism eats, most of the food is NOT converted into biomass. -Most energy goes to respiration, and is then lost as CO2-some of it gets lost as waste-and the least amount goes into turning the food into growth (the organism actually growing in size)10% of food taken up is converted into biomass in the next trophic level. The higher up in the trophic level you eat, the more energy it takes. Therefore, it generally isn’t efficient to eat the top predators (for example, we don’t eat tigers….) Biomass and trophic levels in aquatic versus terrestrial ecosystems: TERRESTRIAL: plant (producer) turnover is slow, so it builds up over time-So most of the standing crop, or biomass, is in the producer level. AQUATIC: Algae (producers) turnover is fast, but they are also consumed as fast as the are produced, so in the ocean producers do not make up a large amount of the biomass, and we see more of the higher trophic levels present. *Matter circles around within an ecosystem through cycles etc. For example: the water cycle (water from oceans, rivers etc. evaporates then precipitates/ rains, which keeps constant supply of fresh water on planet) - There is also the carbon and nitrogen
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