At a Glance

Life on Earth Chapter 18 The Origin of Species
At a Glance

Speciation: Allopatric speciation occurs in populations that are physically separated.
Sympatric speciation occurs in populations that live in the same area.

Maintaining Reproductive Isolation between Species
Premating isolating mechanisms prevent mating between species.
Postmating isolating mechanisms prevent production of vigorous, fertile offspring.

Phyletic and Divergent Speciation

The Genetics of Speciation
One model of speciation stresses gradual accumulation of many small changes.
A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Sympatric speciation occurs in populations that live in the same area.

Maintaining Reproductive Isolation between Species
Premating isolating mechanisms prevent mating between species.
Postmating isolating mechanisms prevent production of vigorous, fertile offspring.

Phyletic and Divergent Speciation

The Genetics of Speciation
One model of speciation stresses gradual accumulation of many small changes.
A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.
Maintaining Reproductive Isolation between Species: Premating isolating mechanisms prevent mating between species.
Postmating isolating mechanisms prevent production of vigorous, fertile offspring.

Phyletic and Divergent Speciation

The Genetics of Speciation
One model of speciation stresses gradual accumulation of many small changes.
A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Postmating isolating mechanisms prevent production of vigorous, fertile offspring.

Phyletic and Divergent Speciation

The Genetics of Speciation
One model of speciation stresses gradual accumulation of many small changes.
A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.
Phyletic and Divergent Speciation
The Genetics of Speciation: One model of speciation stresses gradual accumulation of many small changes.
A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; A second model stresses the sudden appearance of a few major changes.
Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Which model is correct?

Rates of Speciation
During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.
Rates of Speciation: During adaptive radiation, one species gives rise to many under the differing selection pressures of new habitats.

The Pattern of Evolution
Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.
The Pattern of Evolution: Gradualism explains speciation as the slow, steady accumulation of small changes over time.
Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Punctuated equilibrium explains speciation as occurring relatively rapidly amid long periods of little change.
Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Gradualism and punctuated equilibrium models can both be applied to the evolution of the horse.
Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.; Many evolutionary biologists accept a synthesis of gradualism and punctuated equilibrium.

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