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Biology
202
14
Biology
Undergraduate 3
12/13/2006

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Term
Species
Definition
A group of populations whose evolutionary history is distinct and independent from that of other goups.

a distinct and independent path is achieved by the group's reproductive isolation from other groups.
Term
Succession
Definition
Pattern of community development.
Term
Primary Succession
Definition
Development of a community "new" to the area.
Term
Secondary Succession
Definition
Recovery of a community after a disturbance.
Term
Selection in Polygenic Phenotypes
Definition
Polygenic Phenotypes display continuous variation.

Often the phenotypic frequency will approximate a normal distribution.

Selection will involve a portion of the phenotypic range having a higher fitness.
Term
Stabilizing Selection
Definition
Phenotypes too far from the phenotypic norm have a reduced fitness.
Term
Directional Selection
Definition
Phenotypes at one end of the phenotypic range have a higher fitness.
Term
Disruptive Selection
Definition
The environment varies in space or time and different portions of the phenotypic range have a higher fitness under the varying environmental conditions.
Term
Speciation Scenarios
Definition
Allopatric, Parapatric, Sympatric, VIA Founder Effect
Term
Allopatric Speciation
Definition
Speciation is initiated via a barrier to gene flow.

Differentiation is due to selection and/or drift.
Term
Speciation VIA Founder Effect
Definition
Speciation initiated via a unique colonization event.

The event itself causes some differentiation and subsequent isolation facilitates it.
Term
Parapatric Speciaton
Definition
There is no specific extrinsic barrier to gene flow.

Species is subjected to differing selecting pressures across its range.

Selection and limited dispersal lead to interdemic differentiation.
Term
Sympatric Speciation
Definition
Speciation without any geographical component; reproductive isolation develops in spite of potentially high levels of gene flow.
Term
Intermediate Disturbance
Definition
A density-dependent factor may stabilize otherwise unstable competitive relationship by keeping population sizes at levels low enough to permit coexistence.
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