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Ch. 45: Community Ecology and Ecosystems Community Structure Species Richness = a listing of the various species found in a community Ex. Tropical Rain Forests have more different types of species that a coniferous forest Species Diversity = includes species richness and species abundance The greater the species richness and the more even the distribution of those species, the greater the species diversity Community Interactions Habitat = a particular place where a species lives and reproduces Ecological Niche = the role a species plays in its community Includes the resources used to meet energy, nutrient, and survival demands Fundamental Niche = all the abiotic conditions under which a species could survive with no adverse biotic conditions (disease, predation, competition) Realized Niche = the resources a species actually uses The fundamental niche is always greater than the realized niche Effect of Competition Competition occurs when members of different species need to use the same resource that is in limited supply Ex. Paramecium species both flourish if grown separately, but if grown together, one thrives and the other does not Competitive Exclusion Principle = no two species can occupy the same niche at the same time One will always out-compete the other To avoid this, organisms use Resource Partitioning = dividing up the use of a limited resource so that both species can survive o Ex. Owls and hawks eat same prey, but owls are nocturnal hunters and hawks are diurnal hunters By specializing niches, more individuals of each species can avoid competition and have a reproductive advantage Character Displacement = when characteristics are more divergent when populations are found in the same community than when they are alone o Ex. Finch beaks on Galapagos Predator-Prey Interactions Predation = when one living organisms (the predator) feeds on another (the prey) Includes Parasitism Predator and prey both affect the population size of the other, sometimes creating a “boom and bust” cycle of their populations Prey Defenses Include: heightened senses, speed, protective armor, spines, thorns, tails and appendages that break off, chemical defenses, and camouflage Cryptic Coloration = ability to blend into background Ex. Flounder, walking sticks, toads, etc. Aposematic (Warning) Coloration = bright colors that stand out to warn of possible danger Ex. Poison arrow frogs or skunks Features to trigger startle responses in predators Ex. South American lantern fly Association with other prey can help protect an individual Includes flocks, schools of fish, herds, and mimicry Batesian Mimicry = when one (harmless) species resembles another that possesses an overt predation defense o Ex. Scarlet kingsnake (harmless) looks like a coral snake (venomous) Mȕllerian Mimicry = when two species that are both harmful resemble each other o Reinforces their strategy with predators o Ex. Many stinging bees look alike Symbiotic Relationships Symbiosis = when two different species live together, affecting each other Three Types: 1) Parasitism = parasite benefits while the host is harmed Host often provides parasite with food and place to live and reproduce o Ex. Heart worm and dogs May only slightly weaken host or may kill them over time 2) Commensalism = one species benefits while the other is unaffected Ex. Clown fish and sea anemones Some debate about whether it really exists 3) Mutualism = both species benefit Ex. Termites need protozoans in their digestive tract to break down wood Ex. Mycorrhizae, root nodules, and lichens are ones you should know COMMUNITY DEVELOPMENT: Ecological Succession Succession = change within a community over time Usually depends on type of dominant plant life Primary Succession occurs in areas where this is no soil formation Ex. After volcanic eruptions or glacial retreats Wind, water, and often lichens begin to break the rock down into soil Secondary Succession occurs in areas where soil is already present Pioneer Species = First species to live there Often small, short-lived seed plants mixed species large, long-lived species of trees o Plant life present determines the animal life that can live there Each group of species prepares the way for the next until you get the climax community Climax Community = succession always leads to the same type of community in a particular area o This community remains until a disturbance happens Ex. Tornado, beaver dams, volcanic eruptions, etc. o Will tend to return to this climax community make-up again (Our climax community is the beech-maple forest) DYNAMICS OF AN ECOSYSTEM Autotrophs (Producers) = produce their own organic food Need only inorganic materials and an energy source Includes cyanobacteria, algae (phytoplankton), and green plants OR chemosynthetic bacteria Heterotrophs (Consumers) = must eat other organisms as food Herbivores = eat plants or algae (producers) Carnivores = eat other animals Omnivores = eat both plants and animals Detritivores = eat detritus (decomposing organic matter) Decomposers = break down dead organic matter, including animal wastes o Critical in nutrient cycling Energy Flow Can be shown with diagrams: Food Chains and Food Webs, or Ecological Pyramids Trophic (feeding) Levels = the level of nutrients within a food web or chain Food chains and food webs diagram the flow of energy amongst organisms Food chains typically follow the pattern: Primary Producers Primary Consumers Secondary Consumers Tertiary Consumers Ex. Leaves Caterpillars Birds Hawks Food Webs = several interconnected food chains You need to be able to analyze a food chain or food web and determine how changes in one population will affect the others. Ecological Pyramids Food chains are typically limited to the tertiary consumer level. This is due to the loss of energy between trophic levels. 10% Rule: Only 10% of energy is passed to the next level. The other 90% is used by the organism to drive its metabolism and is eventually lost as heat. Flow of energy can be shown with an ecological pyramid. <insert picture> Other pyramids reflect this loss of energy by showing that the number of individuals that can be supported by an area decreases as you move through a food chain Numbers Pyramids = # of each type of organism at each trophic level Biomass Pyramids = dry weight of each organism Biogeochemical Cycling = how nutrients are moved from the inorganic world into the organic world and back again Water Cycle Involves: precipitation evaporation OR precipitation transpiration/evaporation Human Impact: Groundwater Mining = when we withdraw more water from aquifers than they can replace Freshwater makes up only 3% of the world’s supply, but is considered a renewable resource (for now) Carbon Cycle Involves: CO2 enters through carbon fixation in plants (part of photosynthesis), then is used by organisms for body functions/parts, then is returned to environment via respiration and more Human Impacts: More CO2 is being added due to burning fossil fuels and less is being removed due to deforestation Greenhouse Effect (N2O and CH4 also play a role) = when these gases trap heat in the Earth’s atmosphere Leads to Global Warming and Climate Change o Glaciers will melt, sea levels will rise, super-storms will develop Phosphorus Cycle Involves: Weathering of rocks, ionizing in soil, being incorporated in plants, move through organisms, decay back to soil Human Impact: Fertilizers and detergents contain lots of phosphates, which then enter the water supply, and result in eutrophication (over-enrichment) of waterways Nitrogen Cycle (see diagram) Human Impacts: 1) Fertilizers contain nitrates, which can run-off into lakes and rivers results in Algal Blooms o Cause a sudden overgrowth in algae o Then they die off and decomposers quickly increase in numbers o They use up all the O2 in the water o Results in massive fish kill 2) Contribute to acid rain when nitrogen oxides from fossil fuels (and SO2) react with water in atmosphere to form acid