EVOLUTIONARY PROCESSES AND
PATTERNS
• Theory of Special Creation
– Species unchanged
through time &
independent of one
another
EVOLUTIONARY PROCESSES AND
PATTERNS
• Theory of Spontaneous
Generation
– New organisms (species)
suddenly appear
EVOLUTIONARY PROCESSES AND
PATTERNS
• Prior to Darwin and Wallace Lamarck
EVOLUTIONARY PROCESSES AND
PATTERNS
• Theories of Evolution
• Darwin and Wallace
– Species are related to one another, and they
change over time, thus species existing today
have descended, with modifications, from other
preexisting species
Evolution
•
What is evolution?
•
Microevolution:
•
Macroevolution:
Population Characteristics
• Species
– A group of
organisms
capable of
interbreeding
Population Characteristics
• Species
– A group of
organisms capable
of interbreeding and
producing fertile
offspring.
– Isolated gene pools
• Isolation
–
–
–
–
Temporal
Spatial
Mechanical
Behavioral
Genes go in
but they don’t
Come out!
Evolution
•
Allopatric
Speciation
Evolution
•
Sympatric
Speciation
?
Evolution
•
Parapatric
Speciation
?
Darwinian Selection
• All natural selection results in evolution, but not
all evolution is the product of natural selection.
• What is evolution?
• What is natural selection?
• What is an adaptation?
Darwinian Selection
• All natural selection results in evolution, but not all evolution is
the product of natural selection.
• What is evolution?
Darwinian Selection
• All natural selection results in evolution, but not all
evolution is the product of natural selection.
• What is evolution?
– Evolution is the change in allele frequencies (or traits)
over time.
• What is natural selection?
• What is an adaptation?
Darwinian Selection
• All natural selection results in evolution, but not all
evolution is the product of natural selection.
• What is evolution?
– Evolution is the change in allele frequencies (or traits)
over time.
• What is natural selection?
– Natural selection is the differential reproductive success
resulting from an adaptation.
• What is an adaptation?
Seeds
Ticks off of iguanas etc.
Tools use to get insects
Leaves and fruit
Insects, spiders, nectar
Darwinian Selection
Is there variation about a trait?
Darwinian Selection
Is there an excess of individuals
so that only some animals live
to reproduce?
Are resources limited?
Darwinian Selection
- Drought of 1977 eliminated seed
set by most of the plants
producing small soft seeds.
- Large and hard seeds became
dominant food item.
- Only large birds with deep
beaks could defend resources
and access the resources
Darwinian Selection
Did evolution occur?
- 1983 El Niño produced 1359
mm of rain and lavish seed set by
the small soft seeded plants.
- Birds with shallow beaks
harvest these seeds more
efficiently and thus reproduced
better than birds with deep
beaks, undoing the selection
shown here.
- Fluctuating environmental
conditions maintained both
phenotypes.
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Directional Selection
• Phenotype at one
extreme of population
distribution has
selective advantage.
• Leave more offspring
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Stabilizing Selection
• Intermediate
phenotypes have
selective advantage.
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Disruptive Selection
• Intermediate phenotypes selected against
Darwinian Selection
• The consequences of natural selection are
expressed at the population level.
Genetic drift
• Genetic drift results in a gradual loss
of genetic diversity
• Over time an individual locus and
gene frequency will drift until one
allele becomes fixed
Convergent Evolution
ISOLATION AND
CONVERGENT EVOLUTION
Convergence
–
Myrmecophages
anteaters, aardvark, aardwolf, numbat,
pangolins
ISOLATION AND
CONVERGENT EVOLUTION
Convergence
–
Cursorial herbivores
pronghorn, capybara, guanaco,
kangaroos
digestive tract, dentition, elongated
limbs
Convergent Evolution
• Batesian Mimcry
– Benign species
resembles a noxious
or dangerous species
Convergent Evolution
• Mullerian Mimicry
– Noxious species
resemble each other
Convergent Evolution
• Mullerian Mimicry
– Noxious species
resemble each other
– Pitohui birds in New
Guinea
Convergent Evolution
• Aggressive Mimicry
– Noxious or dangerous
species resembles a
benign one
Coevolution
Association
Parasitism
Effect on
Species A
Positive
Effect on
Species B
Negative
Commensalism
Positive
None
Mutualism
Positive
Positive
Predation
Positive
Negative
Competition
Negative
Negative