Unit_10.doc

Unit 10: 4 (a). Example of defense response against an avirulent pathogen (model of coevolutionary relationship) Pollinator Factors the pollinator favors Factors that a plant uses to attract the pollinator Bees - Attracted to bright colors, ultraviolet bull?s-eye patterns, and sweet, aromatic or minty odors - active only during the day and usually alight on petal before mving into part of flower containing nectar and pollen - have showy, brightly colored petals, usually blue or yellow, seldom red have a UV bull?s eye, sweet, aromatic or minty fragrance daytime opening or nectar production special protruding lip or suitable landing platform Moths most active at dusk and during the night flowers they pollinate are mostly white and are open only during the late afternoon and night Flowers have heavy fragrances that help guide the night creatures to them Bats most active at dusk and during the night flowers they pollinate are mostly white and are open only during the late afternoon and night Flowers have heavy fragrances that help guide the night creatures to them Hummingbirds See red well, but blue only poorly have weak sense of smell ordinarily do not land on flowers, but hover in front of them while sucking nectar usually red or yellow nearly odorless, lack any protruding landing platform Flies Attracted by rank rather than sweet odors Rely very little on vision in locating food Flower of plants that depend on these flies are usually dull colored and ill smelling - some flowers, like orchids, look like other insects, so the insects try to copulate with them Wind No visual preference Plants lack bright colors no special odors or nectar most have no petals and their sexual parts are freely exposed to the air currents pollen grains produced are particularly small and light, and they can be blown for hundreds of miles 5 (c): Common Trends in succession: The species composition changes continuously during the succession, but change is usually more rapid in the earlier stages than in the later ones. The total number of species represented increases initially, then sometimes declines slightly, and finally becomes more or less stabilized in the older stages This trend applies particularly to the heterotrophs, whose variety is usually much greater in the later stages of the succession Net primary productivity (the amount of energy converted into products of photosynthesis by autotrophs, and available to heterotrophs) increases until it reaches a stable high level. The store of inorganic nutrients held in the organisms and soil of the ecosystem increases, and an increasing proportion of the store is held in the tissue of plants Both the total biomass in the ecosystem and the amount of nonliving organic matter increase during the succession until a more stable stage is reached The height and massiveness of the plants in the community increase and lead to greater differentiation of vertical strata The food Webs become more complex, and the relations between species in them become better defined or more specialized. As a result, the efficiency of resource utilization at various levels usually rises Glacial Succession: As the glacial retreats, it leaves moraines (a mass of rocks and sediment carried down and deposited by a glacier, typically at its ridges or extremities) along the edges of the bay and primary succession occurs on the moraines Primary succession occurs Plant succession occurs: original plants may include alders and cottonwoods, covering the hillsides Then spruce arrives, then Sitka spruce, western hemlock, then sphagnum moss Field Trip Succession: seeing lichens appearing on rocks deposited by glaciers (primary succession following glacial succession) 7 (C): Limits on Food Chain Length: Energetic Hypothesis: suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain Only about 10% of the energy stored in the organic matter of each trophic level is converted to organic matter in the next trophic level Producer level consisting of 100 kg of plant material can support 10 kg of herbivore biomass and 1 kg of carnivore biomass Biomass: the total mass of all individuals in a population Dynamic Stability Hypothesis: long food chains are less table than short chains Population fluctuations at lower trophic levels are magnified at higher levels This causes local extinction of top predators In a variable environment, top predators must be able to recover from environmental shocks that can reduce food supply all the way up the food chain The longer a food chain is, the more slowly top predators can recover from environmental set backs 8 (d) Nitrogen Cycle: 8 (e) The Phosphorus Cycle Biological Importance: Organisms require phosphorus as a major constituent of nucleic acids, phospholipids and ATP and other energy-storing molecules Also, as mineral constituent of bones and teeth Forms available to life: Most biologically important inorganic form of phosphorus is phosphate: PO43- Plants absorb and use it in synthesis of organic compounds Reservoirs: Sedimentary rocks of marine origin ? soils ? oceans ? organisms Key Processes: Weathering of rocks gradually adds phosphate to soil Leaches into groundwater and surface water and may eventually reach sea Phosphate taken up by producers and incorporated into biological molecule s may be eaten by consumers and distributed through food web Phosphate is returned to soil or water through decomposition of biomass or excretion by consumers No significant phosphorous-containing gasses: only relatively small amounts of phosphorous move through the atmosphere Move in forms of dust/sea spray