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Transcript
Community Ecology • Interactions of a community: interactions that affect survival and drive evolution – – – – • Competition - negative effect on both species interspecific competition - 2 species compete for the same resource niche - an organisms use of the abiotic and biotic resources in its environment exclusion principle states that 2 species cannot occupy the same niche Predation - benefits one and has a negative effect on the other – drives evolution - mimicry and other diverse adaptations • Parasitism - parasite benefits while the host is harmed – can exert a substantial influence on a population • • • Disease - similar to parasite Mutualism - benefits both Commensalism - one is benefited while the other is unaffected – very rare in nature • Interspecific interactions and adaptation – drives coevolution and adaptation of species living in close proximity to each other Flow of Energy • Trophic structure - food chains – size is limited to the inefficiency of the transfer of energy – shorter chains are generally more stable than longer ones • bottom up control - producers determine the amount of herbivores which determines the amount of carnivores that can be supported • top down control - predators control herbivores which have an impact on the producers Influence of Species • Species with a large impact on community structure – dominant species - most abundant species – keystone species - exert a strong influence despite small numbers – founding species - exert an influence through changing the physical environment Disturbances influence community structure • moderate levels of disturbances can create more species diversity than a high level of disturbance – Storm, fire, flood • Alters resources and removes members of species • Disturbance is below the threshold for most of the species living in that area • human disturbances usually lead to less species diversity – Reduction and alteration of habitat leading to loss of species Ecological Succession • primary succession begins where there is no soil • after a major disturbance where soil is left...secondary succession is the 1st level – succession continues until a climax community is established • Lichens and mosses create soil from rock through chemical weathering – Autotrophic prokaryotes • Grasses and herbaceous plants add to the litter and humus of the developing soil adding nutrients and water holding capacity – Attract animal species that further add to the fertility of the soil – Early species arrival of shrubs and bushes either add or detract to the arrival of the late species (trees) • The climax community is stable