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Patterns of Evolution
Chapter 17
Section 4
Macroevolution/Microevolution
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Macroevolution- One genus or family
evolves into another….due to large
scale changes that take place over
long periods of time.
Microevolution- Small scale changes
within a species to produce new
varieties or species in a relatively short
amount of time.
Macroevolution/Microevolution
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Both involve changes in allele
frequencies in gene pools
The difference is largely one of
approach and scale
Each offers different insights into the
evolution process
Macroevolution/Microevolution
Macroevolution
Microevolution
1. Large-scale changes in gene
frequencies
2. Occurs over a longer
(geological) time period
3. Occurs at or above the level
of species in separated gene
pools
4. Consists of extended
microevolution
1. Small-scale changes in
gene frequencies
2. Occurs over a few
generations
3. Occurs within a species
or population in same
gene pool
4. Refers to smaller
evolutionary changes
Macroevolution/Microevolution
Macroevolution
Microevolution
5. Observable
5. Has not been
directly observed
6. Evidence produced
6. Evidence based on
by experimentation
remnants of the past
7. Example: Bacterial
7. Example: Birds from reptiles
resistance to
antibiotics
Macroevolution/Microevolution
Macroevolution/Microevolution
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Dog Variability When bred for
certain traits, dogs become
different and distinctive. This is a
common example of
microevolution—changes in size,
shape, and color—or minor
genetic alterations. It is not
macroevolution: an upward,
beneficial increase in complexity.
Patterns of Macroevolution
These are theories/models of evolution
A.
B.
C.
D.
E.
F.
G.
Mass Extinctions
Adaptive Radiation
Convergent Evolution
Coevolution
Gradualism
Punctuated Equilibrium
Developmental Genes
Mass Extinctions
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Many types of living things
became extinct at the same time.
Disrupted energy flow caused
food webs to collapse
Species disappeared.
Left habitats/niches open
Resulted in burst of evolution of
new species in new habitat
Mass Extinctions
 Possible
causes
Asteroids hitting earth
– Volcanic eruptions
– Continental drift
– Sea levels changing
–
Adaptive Radiation
(divergent evolution)
The evolution of an ancestral
species, into many diverse
species, each adapted to a
different habitat
 Many new species diversify from a
common ancestor .
 The new species live in different
ways than the original species did.

Adaptive Radiation
Adaptive Radiation
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
Hawaiian
honeycreepers
Variation in
color and bill
shape is related
to their habitat
and diet
Convergent Evolution
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Opposite of divergent evolution (adaptive
radiation)
Unrelated organisms independently evolve
similarities when adapting to similar
environments, or ecological niches
Analogous structures are a result of this
process
Example: penguin limb/whale flipper/fish fin
The wings of insects, birds, and bats all serve
the same function and are similar in structure,
but each evolved independently
Convergent Evolution
Convergent Evolution
Convergent Evolution
Hummingbird Hawkmoth
Convergent Evolution
Similar body
shapes and
structures have
evolved in the
North American
cacti...and in the
euphorbias in
Southern Africa
Coevolution
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The mutual evolutionary influence between two
species
When two species evolve in response to changes
in each other
They are closely connected to one another by
ecological interactions (have a symbiotic
relationship) including:
– Predator/prey
– Parasite/host
– Plant/pollinator
Each party exerts selective pressures on the
other, thereby affecting each others' evolution
Coevolution
Coevolution
A fly and an orchid--can
influence each other's evolution
Coevolution
Bumblebees and the flowers the they pollinate have coevolved so that both have become dependent on each
other for survival.
Coevolution
Clown Fish and Sea anemone
Coevolution
Praying Mantis simulates plant to protect
itself from predators and eats pests that
are attracted to and feed on the plant, so
it protects the plant.
Gradualism
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The evolution of new species by
gradual accumulation of small genetic
changes over long periods of time
Emphasizing slow and steady change
in an organism
Occurs at a slow but constant rate
Over a short period of time it is hard to
notice
Gradualism
Punctuated Equilibrium
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Stable periods of no change (genetic
equilibrium) interrupted by rapid changes
involving many different lines of descent
Opposite of gradualism
Rapid events of branching speciation
Gradualism or
Punctuated Equilibrium
Developmental Genes
Development is a progressive
process
 There are a variety of certain
developmental
genes that
regulate the
timing of
certain events

Developmental Genes
Hox genes – are master control
genes
 Some alter the position of an
organ
 Others alter
when things
happen

Lamb born with seven legs
Hox Genes
Determine body plans
 Function in patterning the
body axis
 Provide the
identity of
particular
body regions

Hox Genes
Determine where
limbs and other
body segments
will grow in a
developing fetus
or larva
Hox Genes
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They are general purpose in the
sense that they are similar in many
organisms
It doesn’t matter if it’s a mouse’s head
or a fly’s head that is being built, the
same gene directs the process
Hox Genes
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Most insects have two pairs of wings
However, flies have one set of flying
wings and one set of small balancing
wings
A single mutation in the gene will
result in a fly with two complete
sets of flying
wings
This mutation
results in an
organ appearing
in the wrong place.
Hox Genes
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Hox Genes control
development and are
common to most organisms.
Four groups of similar Hox
Genes, shown in color,
appear to control related
regions of the human body
and the fly.
Each box represents a
single Hox Gene.
Illustration by Lydia Kibiuk, Copyright © 1994 Lydia Kibiuk.
Hox Genes
Hox genes
determine the
form, number, and
evolution of
repeating parts,
such as the
number and type
of vertebrae in
animals with
backbones.
In the developing chick (left), the Hoxc-6 gene controls the pattern
of the seven thoracic vertebrae (highlighted in purple), all of which
develop ribs. In the garter snake (right), the region controlled by the
Hoxc-6 gene (purple) is expanded dramatically forward to the head
and rearward to the cloaca.
Patterns of Macroevolution
Flow Chart
Species
that are
Unrelated
form
Related
in
under
under
Interrelationships
Similar
environments
Intense
environmental
pressure
can undergo
can undergo
can undergo
Coevolution
Convergent
evolution
Extinction
in
Small
populations
in
Different
environments
can undergo
can undergo
Punctuated
equilibrium
Adaptive
radiation