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Title: The Origin of Species
Description: These notes are from an AP Biology course using Campbell's Biology textbook 10th edition. The notes cover topics such as the Biological Species Concept, reproductive isolation, speciation, and hybrid zones.
Description: These notes are from an AP Biology course using Campbell's Biology textbook 10th edition. The notes cover topics such as the Biological Species Concept, reproductive isolation, speciation, and hybrid zones.
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Chapter 24
The Origin of Species
Speciation: the origin of new species; is at the focal point of evolutionary theory
Microevolution consists of changes in allele frequency in a population over time
Macroevolution refers to broad patters of evolutionary change above the species level
24
...
2 Speciation can take place with or without geographic separation
• Speciation can occur in two ways:
• Allopatric
• Sympatric
• Allopatric “Other Country” Speciation
• Gene flow is interrupted or reduced when a population is divided into geographically
subpopulations
• One or both populations may undergo evolutionary change during the period of separation,
resulting in the establishment of pre or post zygotic barriers to reproduction
• Evidence:
• Regions with many geographic barriers typically have more species than do regions with
fewer barriers
• Reproductive isolation between populations generally increases as the distance between
them increases
• Sympatric “Same Country” Speciation
• Speciation takes place in geographically overlapping populations
• Polyploidy is the presence of extra sets of chromosomes due to accidents during cell
division
• An autopolyploid is an individual with more than two chromosome sets, derived from one
species
• An allopolyploid is a species with multiple sets of chromosomes derived from different
species
• Sexual selection can drive sympatric speciation
24
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4 Speciation can occur rapidly or slowly and can result from changes in few or many
genes
• Niles Eldredge and Stephen Jay Gould coined the term punctuated equilibria to describe
periods of apparent stasis punctuated by sudden change
• The Time Course of Speciation
• New species can form rapidly once divergence begins—but it can take millions of years
• The time interval between speciation events varies considerably, from a few thousand to tens
of millions of years
Studying the Genetics of Speciation
•
• New developments in genetics have enabled researchers to identify specific genes involved
in some cases of speciation
• Results show that speciation can be driven by few or many genes
• From Speciation to Macroevolution
• Due to repeated events, small difference between organisms can accumulate, leading to the
formation of new groups of organisms
Title: The Origin of Species
Description: These notes are from an AP Biology course using Campbell's Biology textbook 10th edition. The notes cover topics such as the Biological Species Concept, reproductive isolation, speciation, and hybrid zones.
Description: These notes are from an AP Biology course using Campbell's Biology textbook 10th edition. The notes cover topics such as the Biological Species Concept, reproductive isolation, speciation, and hybrid zones.