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The Origin of The Origin of Species and Species and SpeciationSpeciation
SpeciesSpecies
�� Characteristics used to distinguish speciesCharacteristics used to distinguish species�� Appearance, biochemistry, genetic makeAppearance, biochemistry, genetic make--up, up,
behaviorbehavior
�� SpeciationSpeciation
Figure 24.1 Two patterns of speciationFigure 24.1 Two patterns of speciation
The Biological Species ConceptThe Biological Species Concept
�� There can be a lot of There can be a lot of variation within the variation within the speciesspecies
�� Different species can Different species can look a lot alikelook a lot alike
Figure 24.4 Reproductive BarriersFigure 24.4 Reproductive BarriersPrezygotic barriers impede mating or hinder fertilization if mating does occur
Individualsof differentspecies
Matingattempt
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION
(b)
(a)(c)
(d)
(e)
(f)
(g)
Viablefertile
offspring
Reducehybrid
viability
Reducehybridfertility
Hybridbreakdown
Fertilization
Gameticisolation
GAMETIC ISOLATION REDUCED HYBRIDVIABILITY
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(h) (i)
(j)
(k)
(l)
(m)
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Figure 24.3 Courtship ritual as a behavioral barrier between spFigure 24.3 Courtship ritual as a behavioral barrier between speciesecies
Morphological speciesMorphological species
Coral Snake Scarlet King Snake
Yellowjacket Clearwing moth
Other species conceptsOther species concepts
�� PaleontologicalPaleontological
�� EcologicalEcological
�� Phylogenetic Phylogenetic
Figure 24.5 Two main modes of speciationFigure 24.5 Two main modes of speciation
(a)
Allopatric speciation
(b)Sympatric speciation.
Figure 24.7 Figure 24.7 AllopatricAllopatric speciation of squirrels in the Grand Canyonspeciation of squirrels in the Grand Canyon
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Figure 24.8 Has speciation occurred during geographic isolationFigure 24.8 Has speciation occurred during geographic isolation??
AutopolyploidyAutopolyploidy
AllopolyploidyAllopolyploidyFigure 24.14b The new primrose species of botanist Hugo de Figure 24.14b The new primrose species of botanist Hugo de VriesVries
Habitat and Mate choice in two species of Lake Victoria cichlidHabitat and Mate choice in two species of Lake Victoria cichlidss
Adaptive Adaptive RadiationRadiation
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�� In Lake Victoria alone there are 300 species of cichlids that In Lake Victoria alone there are 300 species of cichlids that differ in color, size, shape, behavior and parental care.differ in color, size, shape, behavior and parental care.
Today more Today more than 100 of than 100 of
these are extinct these are extinct due to various due to various pressures such pressures such
as the as the introduction of introduction of the Nile Perch a the Nile Perch a
highly highly predatory predatory
animal and high animal and high levels of water levels of water
pollutionpollution
Figure 24.13 Two models for the tempo of speciationFigure 24.13 Two models for the tempo of speciation
Gradualism model. Species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations.
Time
(a) Punctuated equilibrium model. A new species changes most as it buds from a parent species and then changes little for the rest of its existence.
(b)
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