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lecture outlines for posting18

lecture outlines for posting18 - Lecture 18 EEB 13-11 March...

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Lecture 18 - EEB 13 -11 March 2008 Dr. Hespenheide REMINDER: The final exam for EEB13 will be given during the lecture and discussion hours (12:30-3:00 pm) this Thursday, March 13th Macroevolution – the patterns produced by the macroevolutionary processes of adaptation, speciation and extinction include [history of life [biogeography ] biodiversity number of species - last Thursday’s lecture ecological diversity - aspects of the environment physical factors determine the amount of living organisms primary productivity = amount of photosynthesis; all organisms depend on plants for energy sun [temperature] CO 2 + H 2 O [rainfall] ( C H 2 O) + O 2 [ C = Carbon “fixed”] primary productivity is directly related to amounts of rainfall and temperature in terrestrial habitats [figures] primary productivity (“fixation” of Carbon as sugar) & habitats; note: productivity is net productivity = (amount made by plants) - (amount used by plants for their own needs) habitat productivity, in gC fixed/m 2 /yr open ocean 125 - limited by low Nitrogen, Phosphorus continental shelf 350 coral reefs 2000* (endangered by global warming) desert 90 grassland 500 [cultivated crops 650] - average - can be much higher tropical rainforest 2200* (endangered by human destruction) marshes 2500* (endangered by human destruction) * = endangered habitat – all of Earth’s most productive habitats are endangered by human activities
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other species - 0rganisms live interacting communities with other organisms community structure in terms of flow of energy ([ = movement of energy, “energy flow”]: “trophic levels” terrestrial communities dominated by [top carnivores (hawk)] eaten by carnivores (birds + insects, other vertebrates) eaten by herbivores (insects + some mammals) eaten by plants (primary producers) (flowering plants) photosynthesis - C “fixed” [sun] [note: much of energy lost as it moves from one trophic level to another, on average about 90%, so little is left for upper levels predator-prey interactions - all organisms require energy major interactions in communities special relationships + evolved adaptations kinds of predation “hunters” - kill individual prey (lion killing a zebra) parasites - smaller than prey, usually don’t kill prey (insect feeding on a plant) - different kinds of predation produce different selection pressures and different adaptations coevolution - two species adapt to each other species 1 species 2 predator prey adaptations favor: more prey less predation - thus, in “arms race”
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example: pollination of plants by insects herbivores bees coevolution bees exploitation ↑↓ outbreeding plants flower flower (pollen) (pollen + “rewards”) mutualism – two species interact and both benefit, usually in a
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