Ch 54 Community Ecology

1. Ch 54 Community Ecology

2. Rivet model vs redundancy model • Changing one species numbers affects all organisms vs not affecting all • Interspecies interactions • Competition(-/-), predation/parasitism/herbivory(+/-), mutualism (+/+), commensalism(+/0), facilitation (0/+) • Competitive exclusion principle-when 2 similar species compete for the same resource, one will use the resource more efficiently, survive and reproduce, eliminating other species. • Resource partitioning-when 2 species occupy the same niche, one will become extinct (Com. Exc. Prin.) or evolve to use different niche

3. Prey defenses • Plants produce toxins against herbivores • Cryptic coloration-camouflage • Aposematic coloration-warning color • Batesian Mimicry-harmless species mimics harmfull species • Mullerian mimicry-both species are harmful • Co-evolution-reciprocal evolution of 2 interacting species • Species diversity • Species richness and relative abundance (calculated by Shannon diversity(uses natural logs)) • Dominant vs keystone species • Most abundant vs. most critical to maintain stability of ecosystem • Recognize keystone species by removal experiments

4. Succession-changes in community composition • Primary succession-begins virtually lifeless (volcanic islands) • Volcanic rock erodes, lichen and moss (pioneer species) forms and decomposes to form soil • Secondary succession-existing community has been cleared (soil intact, but erosion occurs). • Some species facilitate biodiversity • Some species inhibit biodiversity • Typically start with small plants, shrubs, pine trees, and then hardwoods. • More habitats and niches form • As producer population increase, consumer population increases • Abiotic changes • Soil quantity, soil quality (nitrogen, phosphorus, and pH) to light availability from taller trees.

5. Disturbance Influences • Nonequilibrium model • communities are constantly changing after a disturbance • Intermediate disturbance hypothesis • Moderate level disturbances foster greater diversity than low or high • Latitudinal gradients • More diversity closer to equator • Island Equilibrium models • Island immigration rate will equal it extinction rate (composition might change though) • Immigration/extinction rates of islands based on size and distance from mainland • Fig 54.27

6. Ch. 55 and 56 Ecosystems

7. Law of conservation of Mass • Mass is conserved (everything in equals everything out) • Don’t forget CO2 has mass • Trophic levels • Primary producers, primary consumers (herbivores), secondary consumers, tertiary consumers, detritivores (decomposers)

8. Energy • Primary production-light energy converted to chemical energy (photosynthesis) • 1% of light energy • Gross primary production-total amount of light converted • Net primary production-gross productivity minus energy used by primary producers for respiration • energy available to consumers • typically 50% of GPP • Net ecosystem productivity-GPP minus respiration of all organisms • Calculated by measuring net influx of CO2 or O2 • Oceans produce most energy (because of mass) • only top 20 meters is photosynthetic • past 20 meters, net is less than 0 (respiration is happening faster than photosynthesis) • typically measure by dissolved oxygen • Rain forest and reefs produce most per area

9. Secondary productivity-Amount of energy in consumers food that gets converted to their growth • Ranges from 1% (birds) to 40% (insect)(think about exothermic vs. endothermic organisms) • Trophic efficiency-percentage of energy transferred to next trophic level • About 10% efficient

10. Biogeochemical cycles-nutrients cycling between biotic and abiotic components (pgs 1228-1229) • Water cycle • Carbon-photosynthesis and respiration/burning • Nitrogen (N2 cannot be used) • Bacteria • Nitrogen fixation-bacteria convert N2 into minerals (which can be used by plants) • Nitrification-bacteria breaking down ammonia (NH3) for energy (making nitrite (NO2-), which can be used by plants) • Denitrification-Bacteria taking O2 from NO2- making N2 • Ammonification-bacteria converting ammonia to N2 • Plants take it in from soil, animals take in plants, animals excrete nitrogen to soil

11. Phosphorus • Weathering of rocks leaves PO43- (phosphate) in soil • Producers absorb phosphate and make nucleic acids • Transferred to consumers • Back in soil by decomposition

12. Human Impact (Ch 55 and 56) • Nitrogen cycle • Grow crops, remove crops no more nitrogen in soil • Solution, use fertilizer, rotate crops, or burn • Soil nitrogen will also run off, causing oceans/rivers to have high nitrogen levels • Could lead to toxic levels • Or could lead to enhanced plant growth • Eutrophication • Leads to higher plant life, kills fish, throws off ecosystem • Can be caused by human impact on the levels of inorganic material in freshwater systems. • Acid rain • Burning causes sulfur and nitrogen oxides to be released forming sulfuric and nitric acid • Affects all lakes and rivers in region (not local)

13. Biological magnification • Toxins becoming more concentrated at higher trophic levels • DDT affecting birds of prey • Climate change • Greenhouse effect-carbon dioxide and water in atmosphere reflecting infrared radiation back to earth • Keeps planet at current temperature • Global Warming-the increasing levels of carbon dioxide in the atmosphere affecting the global temperature • Ozone depletion • Fluctuating hole over Antarctica causing more radiation to reach earth • Most likely caused by chloroflourocarbons

14. Loss of Biodiversity • Types of diversity • Genetic diversity (variation) • Species diversity • Ecosystem diversity • Threats to biodiversity • Habitat destruction • Introduced species • Overexploitation • Food chain disruptions • Rivet model

15. Restoration • Naturally by succession • Bioremediation • Use of living organism (bacteria) to detoxify polluted ecosystems • Genetic engineer can increase efficiency • Commonly used in old mining sites • Biological Augmentation • Uses organisms to add essential nutrients to soil • Used recently in destroyed wet lands