BIO 311D 2nd Edition Lecture 38 Outline of Last Lecture I. Revisit Yellowstone wolvesII. Biotic interactionsIII. In-class exercise: your example community Outline of Current Lecture I. Community Dynamics, Ecological SuccessionII. Trophic Interactions and energy flowCurrent LectureI. Community Dynamics, Ecological SuccessionA. Parasitism: one benefits, other is harmeda. How can host and parasite evolve by co-evolution? (4-21)b. What’s a “good” parasite? – One that doesn’t kill its host, so it could reproduce. c. Leeches: attachment disks, suck the blood of their host. Has an anti-coagulant in their saliva to prevent blood clotting from cutting off their blood supply from the host. Humans could have receptors.B. Mutualism: Tropical communities with high species diverse complex community interactions. Mutualisms: plant- pollinator; coral dinoflagellatea. Which do you think affects the success of the organisms’ there more – abioticfactors or community biotic interactions?1. Deserts and the artic – major abiotic factors2. Places with less severe climate changes, tropics – major biotic factors (escaping from predator, competition)b. Both organisms benefit from the interaction1. Legume roots and nitrogen-fixing bacteria (turning N2 to ammonia NH3)2. Termites and symbiotic protists and bacteria that digest cellulose [termites eat wood, symbiotic microbes has the enzymes to digest the wood] 3. Acacia trees and ants that defend them4. Leaf cutter ants and fungiC. For one case of mutualism, tell how it evolved by mutualism? a. For example, most flowering plants have adaptations such as nectar or fruit that attract animals that function in pollination or seed dispersal. In turn, manyanimals have adaptations that help them find and consume nectar.D. What happens to a population when its mutualistic partner goes extinct? a. Population may decrease in size. May lose its ability to survive.E. Temporal Changes in communitiesa. Ecological succession: progressive changes in species composition over timeb. Early Colonist species (“pioneers”) change conditions for later-arriving speciesc. Primary succession on bare rock, soil develops graduallyd. Secondary succession, after disturbance; forest grows back after clearing or after a fire e. Some ecosystems are maintained by pericarp fires. This is an example of “intermediate” disturbance, community held at intermediate stage of succession. f. Succession of decomposers on a dead body [“CSI succession] g. Succession in your mouth! (Bacteria on teeth- dental plaque community)1. Clean surface- sugar protein deposits2. Primary colonizes, Streptococcus, lock onto surface coatings3. After 1-3 days new species accumulate, biofilm growth on dextran polymer4. After 1 week, new bacteria species grow h. Which of the following is true of primary succession but NOT secondary succession?1. Initial species change habitat to facilitate the success of later species (True for both)2. Succession begins on bare rock II. Trophic Interactions and energy flowA. Ecosystem = biotic and abiotic components: The organisms in a particular area and the physical environment with which they interact constitute an ecosystem a. Energy flows through ecosystemsb. Nutrients cycle within ecosystems B. Primary producers trap sunlight (What’s the general equation for photosynthesis?)a. The annual productivity of an area is determined primarily by temperature and moisture C. What ecosystems have the greatest productivity per area?a. Primary productivity is most often limited by what two factors? – Temperature and water D. Energy distribution in one link of the food chain. How much of the plant mass consumed by the caterpillar becomes new caterpillar mass (growth)? a. 2nd law of thermodynamics: because of entropy there is a progressive loss of useful energy along the food chainb. At each step of the food chain, there is a loss of usable energy for biomass production; based on 10% trophic
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