Ch. 58 BIO Final
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The total number of different species in the community
The proportion each species represents of all individuals in the community
What are the four types of species richness?
Time hypothesis, Area hypothesis, Productivity hypothesis, and Intermediate-disturbance hypothesis
(Hypothesis) Temperate regions have less species rich communities because they are younger- resident species of temperate zones have not yet evolved new forms to exploit vacant niches- has limited applicability to marine organisms
(Hypothesis) Larger areas contain more species because they can support larger populations and a greater range of habitats- does not explain lack of species richness in large biomes such as the open ocean or tundra
(Hypothesis) Greater production by plants results in greater overall species richness- increased plant biomass leads to more herbivores which leads to more predators, etc- influenced by evapotranspiration rate- does not hold for broad comparisons between continents
(Hypothesis) The highest number of species are maintained in communities with intermediate levels of disturbance- high levels of disturbance favor r-selected species, while low levels of disturbance favor K- selected species
An event that changes in a community. It removes organisms from a community and alters resources available
ex. draught, fire, flood, hurricanes
The gradual and continuous change in species composition and community structure over time (2 types)
Succession (Primary and secondary)
(succession) occurs where no soil exists when succession begins
(succession) begins in an area where soil remains after a disturbance
(Mechanisms of succession) Each colonizing species makes the environments a little different so that it becomes more suitable for other species- continues until the most competitively dominant species has colonized- determined by climate and soil conditions
(Mechanism of succession) Early colonizing species prevent colonization by other species- the primary method of succession in the marine intertidal zone, where space is limited
(Mechanism of succession) Any species can start the succession- species that establish and remain do not change the environment in ways that either facilitate or inhibit subsequent species- species have differing tolerances to the intensity of competition
What are the two factors that determine the number of species on an "island" are the rate at which new species immigrate to the island and the rate at which species become extinct on the island- The physical features of the island that affect immigration and extinction are its size and its distance from the "mainland"
Equilibrium model of island biogeography
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