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ECOLOGY

ECOLOGY. TROPHIC CATEGORIES. Producers organic vs. inorganic autotrophs vs. heterotrophs Consumers predators parasites pathogens Detritus Feeders and Decomposers.

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ECOLOGY

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  1. ECOLOGY

  2. TROPHIC CATEGORIES • Producers • organic vs. inorganic • autotrophs vs. heterotrophs • Consumers • predators • parasites • pathogens • Detritus Feeders and Decomposers

  3. climate: description of the average temperature and precipitation (weather) that may be expected on each day throughout the year • patterns… • latitude • elevation

  4. A given climate will support only those species that find the temperature and precipitation levels within their ranges of tolerance. • A species will be excluded from a region where any condition is beyond its limit of tolerance. • Ex. temperature limits forests when it becomes low enough to cause permafrost (permanently frozen subsoil)

  5. microclimate • A specific site with temperature and moisture conditions that are significantly different from the overall, or average, climate of the region. • Ex. south-facing slope in the northern hemisphere

  6. four spheres • biosphere: layer of Earth occupied by living things • lithosphere: Earth’s crust, made up of rocks and minerals • hydrosphere: water; in oceans, rivers, ice, groundwater • atmosphere: thin layer of gases separating Earth from space

  7. key elements of life (C,H,N,O,P,S) • carbon • hydrogen • nitrogen • oxygen • phosphorus • sulfur

  8. PHOTOSYNTHESIS • reactants: light + 6CO2 + 12H2O • products: C6H12O6 + 6O2 + 6H2O • enzymes: promote synthesis or breaking of chemical bonds (biological catalysts)

  9. CELL RESPIRATION • reactants: C6H12O6 + 6O2 + 6H2O • products: 6CO2 + 12H2O + energy

  10. PRIMARY PRODUCTION • in most ecosystems, sunlight (solar energy) is the initial source of energy absorbed by producers through the process of photosynthesis (exception: chemosynthetic bacteria) • only about 2% of light is captured • other 98% is absorbed by atmosphere, oceans, and land, thus heating them in the process

  11. influences on primary productivity • area • light • temperature • water • nutrients

  12. each successive trophic level captures only a fraction of the energy that entered the previous trophic level • transfer efficiency averages 10% (~90% loss of energy between trophic levels) • losses are critical at higher trophic levels, which explains why there are few top carnivores in ecosystems

  13. PHOSPHORUS CYCLE • main reservoir = lithosphere • acts as limiting factor in many ecosystems • impact of fertilizer  eutrophication

  14. NITROGEN CYCLE • main reservoir = atmosphere • acts as limiting factor in many ecosystems • plants take up nitrogen (Nr…reactive nitrogen) as ammonium ions (NH4+) or nitrate ions (NO3-) • incorporate nitrogen into essential organic compounds such as proteins and nucleic acids • nitrogen is passed along food chain from producers to herbivores to carnivores • released at points along the way as ammonium compounds • nitrifying bacteria oxidize the ammonium to nitrate in a process that provides energy for the bacteria

  15. NITROGEN CYCLE • nitrogen fixation • process using nonreactive nitrogen carried out by many bacteria and cyanobacteria • on land, Rhizobium is the most important genus • lives in the root nodules of legumes (beans, peas) • example of mutualism—legume provides food (simple sugars) and a place to live while Rhizobium provides nitrogen • every ecosystem has a representative legume (Ex. clover in grasslands) • also done in 3 other ways • (1) N2 NH4 by lightning • (2) industrial fixation (fertilizer)  NOx • (3) combustion of fossil fuels (N is oxidized)  NOx

  16. NITROGEN CYCLE • denitrification • microbial process that occurs in soils depleted of oxygen • microbes take nitrate (NO3) which is highly oxidized and use it as a substitute for oxygen • during process, N is reduced to nitrogen gas and released to atmosphere • farmers work to avoid process by plowing as early as possible in the spring to restore oxygen to the soil • human impacts • use of N-rich fertilizers • burning of fossil fuels

  17. POPULATION GROWTH • equilibrium = births and deaths are more or less equal over time • exponential growth = increasing population under favorable conditions (minimal limits on resources, predators, etc.); results in J-curve • usually occurs when there are unusual disturbances • increases are usually temporary

  18. biotic potential = ability of populations to increase (# of offspring that a species may produce under ideal conditions) • to have an effect on the size of future generations, young must survive and reproduce • recruitment = survival through early growth stages to become part of breeding population • reproductive strategies • produce massive numbers of offspring • low reproductive rate with high parental care

  19. carrying capacity • upper limit to population size of a particular organism that an ecosystem can support • whether a population grows, remains stable, or decreases depends on interactions between its biotic potential and environmental resistance • density-dependent factors: • density-independent factors:

  20. predator-prey dynamics • Ex. Isle Royale (moose and wolves) • predation: + / - • density-dependent • other factors may influence the observed fluctuations in population density • vegetation shortage • vulnerability to parasites and disease • density-independent factors may also play a role (Ex. weather)

  21. parasites • parasitism: + / - • Ex. tapeworm • density-dependent • parasite can work in conjunction with a predator to control an herbivore population • relationships between a prey population and several natural enemies (predators and parasites) is generally very stable • different enemies come into play at different prey densities

  22. plant-herbivore dynamics • herbivory (predation on plants): + / - • overgrazing • Ex. reindeer on St. Matthew Island • in ~20 years, herd grew from 19 to 6000 • lichens were overgrazed and replaced by unpalatable grasses and sedges • consequences of overgrazing are not only related to herbivores • predator removal • upsets plant-herbivore relationships

  23. keystone species • Ex. sea star, Pisaster ochraceus • feeds on mussels • allows barnacles, limpets, anemones, and others to colonize • keystone species = plays crucial role in maintaining ecosystem structure (originates from architectural term)

  24. KEYSTONE

  25. competition: - / - • form of bottom-up regulation (occurs only when resource is in limited supply) • interspecific • intraspecific • territoriality = individuals or groups defending a territory against the encroachment of others of the same species • restricts breeding to individuals capable of claiming and defending territory • self-thinning • can lead to short-term density-dependent regulation of population, but also long-term improvements thanks to natural selection

  26. competition • interspecific • plants • landscapes are far from uniform as a result of microclimates • specific abiotic conditions of moisture, temperature, and light differ between locations • Ex. tree species • single species generally does not use all available resources • Ex. grassland plants • epiphytes

  27. competition • interspecific • animals • competitive exclusion

  28. competition • interspecific • animals • resource partitioning

  29. introduced species • rabbits • American chestnut • pests • plants

  30. adaptation through natural selection • selective pressures = environmental resistance factors (predators, parasites, drought, etc.) • natural selection = constant selection and consequent modification of a species’ gene pool toward features that enhance survival and reproduction • evolution = modification of the gene pool of a species by natural selection over the course of many generations

  31. adaptations to the environment • under selective pressures exerted by the factors of environmental resistance, the gene pool of each population is continually tested • fitness = measure of traits that adapt an organism for survival and reproduction

  32. adaptations to the environment • coping with climate and other abiotic factors • obtaining food and water (animals) or nutrients, energy, and water (plants) • escaping from or protecting against predators • resistance to disease or parasites • finding or attracting mates (animals) or pollinating (plants) • migrating (animals) or dispersing seeds (plants)

  33. 4.4 Ecosystem Responses to Disturbance • ecological succession = transition from one biotic community to another • occurs because the physical environment may be gradually modified by the growth of the biotic community • may cause the area to become more favorable for another group of species • pioneer species are the first to colonize an opening • final stage is a climax ecosystem

  34. succession • primary succession = occurs in area that has not been previously occupied • species gradually prepare soil • bacteria  lichens, mosses  grasses  shrubstrees • Ex. bare rock after glacial recedes • Ex. volcanic island • secondary succession = occurs as a result of the disturbance of an ecosystem • starts with existing soil • Ex. fire • Ex. tornado • Ex. abandoned farm field

  35. BIODIVERSITY

  36. Chapter 10: Wild Species and Biodiversity • biological wealth • about 2 million species identified • likely between 5 and 30 million • comprised of species and ecosystems; sustains human life and economic activity with goods and services

  37. Two kinds of value • 1. instrumental value • existence or use benefits some other entity • anthropocentric • 2. intrinsic value • value for its own sake • philosophical question based on moral reasoning

  38. general values of natural species • value as sources for agriculture, forestry, and animal husbandry • value as sources of medicine • recreational, aesthetic, and scientific value • intrinsic value

  39. medicine • Ex. rosy periwinkle on Madagascar • vincristine = leukemia treatment • vinblastine = Hodgkin’s treatment • Ex. Chinese star anise  shikimic acid • raw material for Tamiflu • Ex. Pacific yew  taxol • treatment for breast and ovarian cancers

  40. protecting endangered species • Lacey Act (1900) • forbid interstate commerce in illegally killed wildlife • U.S. FWS can bring federal charges against individuals violating wildlife laws • Ex. airline passenger from Ivory Coast with 500 pounds of bush meat • Ex. civil charges against men accused of killing first wolf seen in Nebraska in 93 years • Ex. men in Alaska prosecuted for killing 16 black bears for their gall bladders • Ex. FWS agent purchased leopard skin and frozen stillborn cub on eBay, which led to prosecution

  41. protecting endangered species • Endangered Species Act (1973, 1988) • endangered = in imminent danger of becoming extinct if no protection is provided • threatened = in jeopardy, but not yet on the brink of extinction • administered by FWS for terrestrial and freshwater species • administered by National Oceanic and Atmospheric Association (NOAA) for marine species

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