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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)