Download Community Ecology

Community Ecology
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Interactions of a community: interactions that affect survival and drive evolution
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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
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Parasitism - parasite benefits while the host is harmed
– can exert a substantial influence on a population
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Disease - similar to parasite
Mutualism - benefits both
Commensalism - one is benefited while the other is unaffected
– very rare in nature
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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