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Transcript
CHAPTER 53 COMMUNITY ECOLOGY Introduction What is a Community? Different species living together in an area Individualistic hypothesis - chance assemblage due to similar abiotic requirements Fig. 53.1a An interactive hypothesis - closely linked species locked in by mandatory biotic interactions. Fig. 53.1b •The ecological niche = organism’s use of abiotic/biotic resources in the environment. Habitat = "address" Sir Deciduous Oak Tree, The Oak Forest, England, U.K. •The ecological niche = organism’s use of abiotic/biotic resources in the environment. Habitat = "address" Niche = how organism fits into environment What is the niche of a lizard? Temperature range Where it perches When it is active No two organisms can have the same ecological niche Principle of Competitive Exclusion And Resource Partitioning No two organisms can have the same ecological niche - Competitive Exclusion QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Character Displacement - species living close together differ more in traits than those living far away Interspecific Interactions Realized - max. range that a species has occupied in reality due to competition/other factors Interspecific Interactions Potential/Fundamental Niche - max. range that a I)species Competition (-/-) can occupy Realized and Potential Niche Interspecific Interactions II) Predation Herbivory (+/-) Parasitism Interspecific Interactions Predation -ways to avoid it 1)Cryptic Coloration = camouflage Interspecific Interactions Avoiding Predation 2)Aposematic Coloration= warning coloration Interspecific Interactions Avoiding Predation 3)Batesian Mimicry – harmless species mimics harmful Interspecific Interactions Avoiding Predation 4)Mullerian Mimicry – 2 unpalatable species resemble each other. Why? Interspecific Interactions Predation (+/-) Parasitism is a type of predation “Scientists have discovered a way to kill the malaria parasite - by targeting its sweet tooth.” –BBC News Interspecific Interactions Predation (+/-) Parasitism Interspecific Interactions Predation (+/-) a) Ectoparasite c) ParasitoidismNasonia Parasitism - types: b) Endoparasite Interspecific Interactions III) Mutualism (+/+) Coevolution- change in one species affects evolution of another species Ex. Nitrogen fixing bacteria in the root of legumes, bees and flowers, cellulose digesting bacteria in gut of cows Interspecific Interactions Commensalism (+/0) One benefits, one neithergains/loses: dung beetle, birds on cattle, Nemo and anemone! Symbiosis - term describes ‘living together’ Commensalism (+/0) Predation (+/-) Mutualism (+/+) Trophic Structure Food chain •(V – vegetation; Feeding relationships (trophic levels) herbivores - H; Predators - P) •How change in biomass of one level affects another •N V H P : Bottom-up •N V H P : Top-down How long can a food chain be? •V H: Intermediate -1) Energetic hypothesis 100kg plant = 10kg cow=1kg lion -2) Dynamic stability Long chains less stable Unpredictable envt. = short chain Energetic hypothesis wins!!! - more producers = longer food chains QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Leaf litter amount Biomanipulation-change the ecology through the use of living organisms; Lake Vesivarji – Finland-Top down or bottom up? Pike Roach Increase pike fish, which eventually = decrease in algal blooms; decrease in Eutrophication Trophic Structure Food web interconnected food chains Dominant species - highest biomass (sum of weight of all individuals in a population) Sugar maple - shade out other plants and take in most water What happens if dominant species is removed? Something else takes over usually Can a species be non-dominant and still control the community? Sea star preys on mussels Mussels eat algae/small invertebrates Sea star’s absence results in decrease of algae/invertebrates in the community Keystone species – strongest control over community due to its niche Sea Star -few but ‘powerful’ Keystone species – Sea Otter Disturbances – environmental changes (volcanoes, fires…..!) Density Independent Factor - keeps population size in check; dominant species growth is curbed Non-equilibrium Fig. 53.16 Succession – Transition in Species Composition Over Ecological Time; Predictable order of species (first - easily dispersed species; later - superior competitors) 1980 1981 After Before Primary Succession -soil ‘gonner’ Soil has been removed by volcano 1) Short lived weed growing through the ash Early successional Community Primary Succession 2) Herbaceous plants and grasses Primary Succession 3) Shrubs (willow) and short lived trees (alder) Mid successional Community Primary Succession Climax Community ?????? 4) Long-lived trees (fir, hemlock, pine) Primary Succession A) Glaciation Soil has been removed B) Volcanic Lava Flows C) Volcanic Explosions D) Faulting raising sea floor Secondary Succession- soil ‘Okey dokey’ A) Forest Fires Soil is intact B) Disease C) Climatic Conditions - Hurricane, tornado, drought, windstorms, etc........ D) Human Disturbance – urban development, clearing woods, grazing etc.......... Soil concentrations of nutrients show changes over time. Fig. 53.20 Compare the Kentucky old growth forest and Crater lake National park. What happened in Crater lake national forest? Biodiversity •Species richness, the total number of species in the community. •Relative abundance of the different species. Species richness may be equal, but relative abundance may Fig. 53.21 be different. Species richness generally declines along an equatorialpolar gradient WHY??? Tropical areas -show more speciatio in evolutionary time -no glaciation - are older because th growing season is longer -show more evapotranspiration Evapotranspiration (Climate) Fig. 53.24 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Biodiversity Species richness is more in larger islands Biodiversity Species richness is more in larger islands, closer to the mainland