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Alex Nold, Jared Dicioco, Alec Sequeira, Colin Fox, Dominic Globa
22.1 The Nature of Species and the Biological Species Concept
Sympathetic species inhabit the same locale but remain distant. Populations of a
species exhibit geographic variation. The biological species concept focuses on the ability to
exchange genes. Prezygotic isolating mechanisms prevent the formation of a zygote.
Postzygotic isolating mechanisms prevent normal development into reproducing adults. The
biological species concept does not explain all observations.
22.2 Natural Selection and Reproductive Isolation
Among the factors that separate populations and species are geographical ecological
behavioral temporal and mechanical isolation as well as factors that inhibit fusion of gametes
are the normal development of the hybrid organisms. Some isolating mechanisms prezygotic
prevent hybrid formation others postzygotic prevent hybrids from surviving and reproducing.
22.3 The Role of Genetic Drift and Natural Selection in Speciation
In small populations, genetic drift may cause populations to diverge; the differences that
evolve may cause the populations to become reproductively isolated.
Adaptation can lead to speciation: adaptation to different situations or environments may
incidentally lead to reproductive isolation. In contrast to reinforcement these differences are not
directly favored by natural selection because they prevent hybridization.
Natural selection can directly select for traits that increase reproductive isolation.
22.4 The Geography of Speciation
Speciation is a two-part process
1.
Initially identical populations must diverge
2.
Reproductive Isolation must occur to preserve these differences
Allopatric (geographically separated) populations appear much more likely to have substantial
differences leading\to speciation
Polyploidy- produces individuals that have more than two sets of chromosomes
Autopolyploidy- all chromosomes derive from a single species
Allopolyploidy- happens when two species hybridize
22.5 Adaptive Radiation and Biological Diversity
-Adaptive radiation occurs when a species finds itself in a new or suddenly changed
environment with many resources and few competing species.
-One example of adaptive radiation is the Galapagos islands
-Adaptive radiation can also result when key innovation evolves within a species allowing it to
use previously inaccessible resources
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True or False. Geographical is a factor to populations and animal species.
True or False. Habituation is a factor to populations and species.
True or False. Mechanical Isolation is a factor to populations and species.
True or False. Ecological and behavioral are not factors to populations and species.
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True or False. Temporal is a factor to populations and species.
What prevents hybrids?
a a.Prezygotic
b b.Postzygotic
c c.Gyzotic
d d.a and b only