Community Ecology

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Community

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-group of populations of different species that live close enough to interact

-community & physical environment make up an ecosystem

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Niche

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-sum of how a species uses the biotic & abiotic resources in its environment

-"habitat is an organism's address, the niche is it profession"

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Niches

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-Fundamental Niche: the ecological niche occupied by a species when competitors are absent

-Realized Niche: the ecological niche occupied by a species when that species' competitors are present

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Interactions

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-interspecific interactions: interactions of individuals of different species. Includes:

-competition

-predation

-herbivory

-symbiosis

-facilitation

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Competition

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-Interspecific Competition: competition between individuals of diff. secies for a limiting resource needed for their growth & survival
-Competitive Exclusion Principle: two species competing for the same limiting resources cannot both survive

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Competition

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-Resource Partitioning: the division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors
-Character Displacement: the tendency of characteristics to be more divergent in populations of two species that live together, rather than in those populations that live apart

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Predation

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-an interaction b/w species in which one species, the predator, eats the other, the prey

-predator adaptations: acute senses, claws, sharp canines, stingers, poisons, speed & agility, lures & baits

-prey adapatations: alarm calls, large groups, ability to hide, flee, etc., defensive coloration

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Defensice Coloration

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-Cryptic: camouflage

-Aposematic: warning of dangerous chemicals

-Batesian mimicry: a palatable or hamrless spcies mimics one that is not

-Mullerian mimicry: two or more unpalatable species resemble each other

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Herbivory

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-organism eats part of aplant or algae

-herbivore adaptations: long digestive tract, extensive molars

-plant adaptations: spines & thorns, poisons

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Symbiosis

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-species who live in close contact have a symbiotic relationship

-can be: helpful (mutualism), harmful (parasitism), neutral (commensalism))

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Mutualism

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-symbiotic relationship where both parites benefit

+/+

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Parasitism

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-symbiotic relationship where one part benefits, and the other experiences harm

+/-

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Commensalism

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-symbiotic relationship where one aprty benefits, and the other is neither helped nor harmed

+/0

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Faciliation

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-an interaction where one species has a positive effect on the survival or reproduction of nother species, without the intimacy of a symbiotic relationship

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Biodiversity

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ent

-interactions dictate the species present

-species composition: a measure of divrsity that includes the species richness (# of species), their relative abundance (proportion of each species), and their feeding relationships (can be shown in food chains/webs)

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Trophic Structure

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-Food chain: linear pathway along which energy fro food is transferred

-Food wed: complex interconnected feeding relationships in an ecosystem

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Trophic Structure

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-species can also be characterized based on other roles they play

-Dominant species: very abundant w/ a large biomass

-Keystone species: species that are not abundant, but exert a key role

-Ecosystem engineers: species that dramatically change the physical environment, which can benefit or harm other species

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Trophic Cascade

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-the abundance of biomass at each trophic level can be dictated from either the amount of food (bottom-up) or the amount predation (top-down)

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Equilibrium

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-non-equilibrium model: a model that describes communities as structures that change constantly after being buffeted by distrubances

-this model argues that communites can never be stable b/c disturbances will always be present

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Disturbances

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-change the composition of comunites

-Natural Distrubances: fire, flood, drought, earthquake

-Human Disturbanes: urban development, agriculture, pollution

-Intermediate Disturbance Hypothesis: states that moderate levels of distrubances lead to the greatest diversity

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Ecological Succesion

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-transition in the species compsition of a community over time

-primary succession: ecological succesion in an area that was void of life and soil

-seconadry succession: in an area that experienced a distrubance which removed many life forms, but kept the soil intact