BIOL 1004 Lecture Notes - Lecture 19: Ecological Pyramid
8 Dec 2017
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Ecosystem: consists of all organisms living in community, as well as abiotic factors with which they interact. In terrestrial ecosystems temperature and moisture affect primary production. Soil nutrient often limiting factor in primary production. Nitrogen most common limiting nutrients but phosphorus can also be limiting. Bacteria are only organisms capable of fixing atmospheric nitrogen. Adaptations help plants access limiting nutrients from soil. Some plants from mutualisms with nitrogen fixing bacteria. Many plants from mutualisms with mycorrhizal fungi (supplying phosphorus and other limiting elements) Roots have root hairs increasing surface area. Many plants release enzymes that increase availability of limiting nutrients. Humans have dramatically increased terrestrial primary productivity with the industrial fixation of n by haber-bosch process. Estimated to be responsible for 40% of human population. When caterpillar feeds on leaf only about (cid:1005)7% of leaf"s e(cid:374)ergy used for seco(cid:374)dary production. Birds and mammals have efficiencies 1-3% because of high cost of endotherm.
