Ch 20 Notes
Ch 20 Notes Bio 260
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This 2 page Class Notes was uploaded by Michaela Humby on Monday March 28, 2016. The Class Notes belongs to Bio 260 at University of Tennessee - Knoxville taught by Charles Price in Spring 2016. Since its upload, it has received 18 views. For similar materials see Ecology in Biology at University of Tennessee - Knoxville.
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Date Created: 03/28/16
Ch 20 Notes The term ecosystem was first used by Tansley (1935) to refer to all the components of an ecological system, biotic and abiotic, that influence the flow of energy and elements. The ecosystem concept integrates ecology with other disciplines such as geochemistry, hydrology, and atmospheric science. Primary production is the chemical energy generated by autotrophs during photosynthesis and chemosynthesis. It is the source of energy for all organisms, from bacteria to humans. Energy assimilated by autotrophs is stored as carbon compounds in plant tissues, thus carbon is the currency used to measure primary production. Primary productivity is the rate of primary production. Gross primary production (GPP)—total amount of carbon fixed by autotrophs. GPP depends on photosynthetic rate. Photosynthetic rate is influenced by climate and leaf area index (LAI)—leaf area per unit of ground area. LAI varies among biomes: Less than 0.1 in Arctic tundra (less than 10% of the ground surface has leaf cover). 12 in boreal and tropical forests (12 layers of leaves between the canopy and the ground, on average). Plants use about half of the carbon fixed in photosynthesis for cellular respiration. Net primary production (NPP) = GPP – Respiration GPP - total amount of carbon fixed by autotrophs Respiration - cells break up sugars into a form that the cell can use as energy. NPP is the amount of energy captured by autotrophs that results in an increase in biomass (living plant matter). Ch 20 Notes NPP is the energy left over for plant growth and for consumption by detritivores and herbivores. NPP can also be estimated from GPP and respiration measurements. Sometimes whole stands of plants are enclosed to study CO exch2nge. The net change in CO i2 GPP minus total respiration: Net ecosystem production or exchange (NEE). Uptake of CO i2 by photosynthesis. Heterotrophic respiration must be subtracted from NEE to get NPP. Thus, NEE is a more refined estimate of ecosystem carbon storage than NPP. Variation in NPP in terrestrial biomes is associated mostly with leaf area index and length of growing season. Variation in NPP in aquatic ecosystems is primarily related to variation in nutrient inputs. Secondary production: Energy derived from consuming organic compounds produced by other organisms. Heterotrophs include archaea, bacteria, fungi, animals, and a few plants. Heterotrophs: Herbivores eat plants and algae. Carnivores eat other live animals. Detritivores eat dead organic matter (detritus). Omnivores eat both plants and animals. Net secondary production = Ingestion – Respiration – Egestion
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