1. Patterns and Processes of Evolution
Macroevolutionary Patterns
Large-scale (more than a single species)
Occurs over long periods of time
Microevolution
Small-scale (within a single species)
Forms variations in populations
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2. Speciation – Isolating Mechanism
Species – group of organisms that interbreed to
produce fertile offspring under normal conditions –
share a common gene pool
Speciation – formation of a new species
Requires reproductive isolation – organisms
do not interbreed; gene pools become separate
Behavioral
Geographic
Temporal
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3. Patterns of Extinction
Background Extinction – “business as
usual” extinction – slow and steady
Mass Extinction – many species become
extinct over a short period of time
Causes:
Asteroid
Volcanic eruptions
Moving continents
Changing sea levels 3

4. Rates of Evolution
Gradualism – change in species is slow and
steady
Punctuated Equilibrium – long periods of
stability followed by short periods of rapid change
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5. Patterns of Macroevolution:
Adaptive Radiation
A single species evolves into many species
Often occurs when a niche opens up
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6. Patterns of Macroevolution:
Convergent
Evolution
Organisms come to
resemble one another
but evolved
differently
Source of analogous
structures!
Examples:
Dolphins and sharks
Marsupials and mammals
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7. Coevolution
Organisms with close ecological relationships
evolve together
Pollinators and flowers
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8. The Role of Genes in Evolution
In terms of genetics, evolution is the change in
the frequency of alleles in a population’s
gene pool
Natural selection leads to that change
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9. Genetic Drift
Random change in allele frequency – changes in
the gene pool of a small population due to chance
Types of Genetic Drift:
Bottleneck Effect – change in allele
frequency following dramatic reduction in
population size
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10. Genetic Drift
Founder Effect – small group colonizes a
new habitat
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11. Molecular Evolution
Molecular Clocks – use mutation rates
in DNA to estimate time two species have
been evolving independently
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12. Molecular Evolution: Hox Genes
Genes which control an organism’s basic body plan
Anterior/posterior ends
Limbs, wings
small sequence changes during embryological
development can cause large changes in adults
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