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1. Interspecies competition (+/-): two different species compete for the same resource. This often results in one species succeeding over the other Results in competitive exclusion
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COMMUNITY ECOLOGYCH 54
• Community: a group of populations of species interacting
I. Community Interactions
• Classified by whether they help, harm, or have no effect on species involved– Interspecific interactions involve different
species– Intraspecific interactions involve one
species
1. Interspecies competition (+/-):
• two different species compete for the same resource.
• This often results in one species succeeding over the other
• Results in competitive exclusion
2. Resource partitioning (0/0): • when species coexist despite their
competition for the same resources because they live in slightly different niches
3. predation (+/-)
• when one species negatively uses another species for food.
• Evolutionary adaptations that allow predator to capture prey– acute sense of smell – speed – claws, fangs, stingers, poisons
• evolutionary adaptations of prey– defensive adaptations: chemicals to thwart
predator– behavioral adaptations: herding/schooling,
hiding, fleeing
– morphological adaptations:• Camouflage or cryptic coloration allows an animal to
blend into its surroundings
– Aposematic or warning colorations of an animal that warns predators that they should be avoided
– Mimicry: when two species resemble each other •mullarian: animals with the same
mechanism of defense share the same coloration• batesian: one animal with no defenses
resembles another animal with defenses
4. Symbiosis occurs when two species live in close contact • Mutualism (+/+): both species benefit • Commensalism (+/0): one species benefits • Parasitism (+/-): one species benefits and
the other is harmed
• species diversity: the variety of different species on a community. Has 2 components: – species richness: the number of different
species in the community – relative abundance: the amount of each
species in the community
II. Species Diversity and Community Structure
• communities with high diversity are:–more productive and stable–more likely to recover from
environmental stress–more resistant to invasive species
1. Dominant species
• most abundant species in the community • ex: sugar maple is abundant species in
northeast forests and provides shade and good quality soil
• what might happen if the dominant species declined in number?
• How did it become a dominant species?
2. Invasive/introduced species
• Organisms that are introduced to a new community, usually by humans
• Why are they so successful?
3. Keystone species
• Affects community structure not by being abundant but by its role in the community
• Ex: sea otters
III. Ecological Succession and Community Disturbances
• A. Community Disturbances • A change in a community due to the destruction
of resources and death of organisms oNatural disturbances
Fire, hurricane, volcanos oHuman disturbances
Clearing of land, sinking of ships • Community disturbance could be positive or
negative
B. Ecological Succession: Colonization of new species into the disturbed area
• Primary succession: –when a force like a volcano destroys
everything in community even soil –moss and lichen grow on hardened lava
and make soil – small plants like grasses start growing in
soil from blown in seeds – shrubs and trees start to grow
• Secondary succession –When a force like a tornado or an
abandoned farm destroys everything but leaves soil intact –Grasses start to grow then shrubs and
trees
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