Download Chapters 22-23 Evolution - Seattle Central College

In the 18th century, people became
more mobile
► Why
are there different animals and plants
in different geographic areas?
► How do we explain this diversity?
Evolution
►As
Where do species come from?
fossils were discovered:
► Why
don’t these organisms exist anymore?
► Why do the things living today look totally
different from these fossils?
Slide 1
Slide 2
Until mid 19th
century:
Each species was
individually created
and has remained
unchanged over
time
Different Explanations
Fig. 9.01a
Slide 4
Slide 3
Lamarck was first to propose how
life evolves
► Use
Lamarck proposed
(1809):
Each species is a
unique individual
creation but changes
over time
Slide 5
and Disuse:
Disuse:
Parts of the body that were used became bigger
and stronger, those unused disappeared
► Inheritance
of acquired characteristics:
characteristics:
Organisms passed on
those modifications developed
during the INDIVIDUAL’s
lifetime (WRONG)
Slide 6
1
The Voyage of HMS Beagle
(c) Descent with modification
Darwin and Wallace:
Species descend from
a common ancestor
through changes over
time
Slide 7
Slide 8
Darwin and the theory of evolution
► Descent
with
modification leads to
evolution of new species
process of natural
selection explains how
Credit. Dr. R. Rothman
► The
Slide 9
Slide 10
Figure 22.7 Descent with modification
Slide 11
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2
Darwin’s observations of natural populations
► Evolution:
How Does Evolution Really Work?
► Parents
often produce more offspring
than will replace themselves but OVER
TIME populations remain steady in size.
► Offspring
are similar to their parents
► Variation
within populations exists and is
inherited from the parents
Slide 13
Darwin’s observations of natural populations
► Resources
Slide 14
Natural Selection
► Adaptations
are limited
► In
a population there is a continuous
struggle for existence.
Individuals have different fitness. Fitness is the
ability to survive and reproduce offspring
Slide 15
are the
traits of an organism
that help it to survive
and reproduce in its
environment.
► Individuals that are
best adapted to their
environment will
survive to reproduce.
Slide 16
Figure 22.11b Artificial selection: diverse vegetables derived from wild mustard
Artificial Selection
Slide 17
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3
Evolution = process of change over
time
► Evidence
How do fossils form?
comes from a variety of sources
1) fossils
2) biogeography
3) anatomical similarities
►Homologous
structures
structures
►comparative embryology
►Vestigial
5) Molecular data
Slide 19
Figure 22.2 Fossils of trilobites, animals that lived in the seas
seas hundreds of millions of
years ago
Slide 20
Figure 25.1 A gallery of fossils
Slide 21
Slide 22
Biogeography
(a) Velociraptor
Tail acts as a
counterbalance
► Biogeography
is the study of the geographic
distribution of organisms
(b) Oviraptosaur
Oviraptosaur has finer
vertebrae and a portion similar
to tail feather insertion platform
Organisms of the Galapagos are more similar to
those of mainland South America rather than
other tropical islands.
Related species are found in distant geographic
areas.
(c) Archaeopteryx
of modern birds
Intermediates in
the fossil record
(d) Eagle
Slide 23
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4
Figure 25.4 The history of continental drift
Marsupials and Eutherians
► Continental
Drift
explains some species
distributions
Slide 25
Key: C = Cassowary; E = Emu;
Emu; e = Elephant Bird;
K = Kiwi; m = Moa; O = Ostrich; R = Rhea.
Slide 26
Comparative embryology
► http://www.pbs.org/wgbh/evolution/educat
ors/course/session3/explain_c.html
Slide 27
Comparative embryology
Slide 28
Homologous structures
Slide 29
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5
Biochemical/molecular/genetic evidence
Vestigial Structures
Ribs
Ileum
Femur
Slide 31
Natural Selection in Action
Slide 32
Chapter 23: Evolution of Populations
Slide 33
Individuals are selected, but populations evolve!!!
Slide 34
The Modern Synthesis
► Populations
are the units of evolution
Selection is the most important
mechanism of evolution
► Gradualism explains how large changes
occur as the result of small changes over a
long period of time
► Natural
► Grass
► The
in the foreground is growing on mine tailings
same species is growing in the background
Slide 35
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6
Genetic Variation and Evolution
► Populations
=
localized group
capable of
interbreeding and
producing fertile
offspring
► = basic unit of
evolution
► An
important consequence AND
requirement of evolution is the maintenance
of genetic variation (phenotypic variation)
within a population.
Slide 37
► GENE
POOL – the sum of all alleles found in
a population
► The HARDYHARDY-WEINBERG EQUILIBRIUM
MODEL provides a model based upon
certain assumptions to which real
populations can be compared.
Slide 38
► Allele
frequencies are
maintained over
generations
► This
maintains genetic
variation
Slide 39
The Hardy Weinberg Theorem
Slide 40
► Population
= 500 plants
320 Red, 160 pink, 20 white
► How
► Describes
gene pools that are NOT evolving
► Provides a benchmark for comparison with
evolving populations
► Frequencies of alleles will remain constant
over time if only Mendelian segregation and
recombination are at work.
Slide 41
many TOTAL alleles
are there for flower color
in the population?
1000
► How
many CR and how
many CW ? (think individual
alleles)
800 CR and 200 CW
► If
mating is random, then
the genotype frequencies
will be at HardyHardy-Weinberg
Equilibrium
Slide 42
7
HardyHardy- Weinberg Model Assumptions
► No
mutations
► All matings are random
► No gene flow
► Populations must be very large
► No natural selection
Slide 43
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How is the equation applied?
Mutation
► By
determining and following allele frequencies as
they change within a population.
► There are several things that can affect allele
frequencies.
GENE FLOW
GENETIC DRIFT
bottleneck effect
founder effect
MUTATION
NONRANDOM MATING
► Rates
Slide 45
are low in higher organisms, high in lower
organisms
► 1/100,000 genes/generation
Slide 46
Gene flow does occur
Genetic drift
► The
frequency of alleles increases or decreases
due to random chance
(can also be due to selective forces like habitat loss or
mass overhunting)
overhunting)
Slide 47
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8
Bottleneck Effect
Founder Effect
Slide 49
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Genetic Variation
Natural Selection is the
primary mechanism of
adaptive evolution
► Occurs
in individuals in populations of all
species
► Variation is not always heritable
(a) Map butterflies that
emerge in spring:
orange and brown
Slide 51
Variation within populations
characters
characters
► Polymorphisms
Slide 52
Figure 23.9 A, B
Variation between populations
► Geographic
► Discrete
(b) Map butterflies that
emerge in late summer:
black and white
variation
► Clinal
variation
► Quantitative
Phenotypic – males vs. females
Genetic - height
Slide 53
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Figure 23.12 Modes of selection
How does natural selection
alter gene frequencies?
Slide 55
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Figure 23.16x1 Sexual selection and the evolution of male appearance
appearance
How is genetic variation preserved???
► Diploidy
► Balancing
selection
when natural selection
maintains stable
frequencies of two or
more phenotypic forms
in a population
Heterozygote
Advantage
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Slide 58
Figure 23.16x2 Male peacock
WHY SEX?
► It
is still not well understood why sexual
reproduction continues.
Most accepted hypothesis is disease resistance
► http://www.pbs.org/wgbh/evolution/educat
ors/course/session2/elaborate_b.html
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10
Organisms are not perfect
► Evolution
is limited by historical constraints
► Adaptations are compromises
► Chance and natural selection interact
► Selection can only act on existing variation
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