Transcript Evolution Lecture Part 1

Fig. 22-2
Evolution Unit Lecture Part I Ch 22,23
Theory: fact based
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Wallace (evolution, natural selection)
American Revolution
French Revolution
U.S. Civil War
1800
1900
1750
1850
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his hypothesis of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks.
1844 Darwin writes essay on descent with modification.
1858 Wallace sends his hypothesis to Darwin.
1859 The Origin of Species is published.
Darwin’s proposed mechanism, natural selection,
explained the observable patterns in evolution
* artificial selection
• Observation #1: Members of a
population often vary greatly in
their traits (snails)
• Observation #2: Traits are
inherited from parents to
offspring
• Observation #3: All species
are capable of producing more
offspring than their
environment can support
(puffball fungus)
• Observation #4: Owing to the
lack of food or other resources,
many of these offspring do not
survive.
• Inference #1: Individuals
whose inherited traits give
them a higher probability of
surviving and reproducing in a
given environment tend to
leave more offspring that other
individuals.
• Inference #2 This unequal
ability of individuals to survive
and reproduce will lead to the
accumulation of favorable traits
in the population over
generations.
Fig. 22-10
Fig. 22-11
Spore
cloud
Natural Selection: A Summary
• 1. NS is a process in which individuals that
have certain heritable characteristics
survive and reproduce at a higher rate
than other individuals
• 2. Over time, NS can increase the match
between organisms and their environment
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
• 3. If an environment changes, or if
individuals move to a new environment,
NS may result in adaptation to these new
conditions, sometimes giving rise to new
species in the process
• “INDIVIDUALS DO NOT EVOLVE!”
• POPULATIONS EVOLVE OVER TIME
Fig. 22-13
EXPERIMENT
Predator: Killifish; preys
mainly on juvenile
guppies (which do not
express the color genes)
Experimental
transplant of
guppies
Pools with
killifish,
but no
guppies prior
to transplant
Guppies: Adult males have
brighter colors than those
in “pike-cichlid pools”
Predator: Pike-cichlid; preys mainly on adult guppies
Guppies: Adult males are more drab in color
than those in “killifish pools”
RESULTS
12
Number of
colored spots
12
10
8
6
4
2
0
Source
population
Transplanted
population
10
8
6
4
2
0
Source
population
Transplanted
population
Evidence
• Direct observations of Evolutionary
Change (predation, HIV resistance)
• Fossil record (transition fossils)
• Homology (common ancestry)embryology,
vestigial structures and genetic: hox genes
(gene conservation)
• Biogeography
Fig. 22-15
0
2
4
4
6
4 Bristolia insolens
8
3 Bristolia bristolensis
10
12
3
2 Bristolia harringtoni
14
16
18 1 Bristolia mohavensis
2
1
Latham Shale dig site, San
Bernardino County, California
Fig. 22-16
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)
Fig. 22-17
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Fig. 22-18
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
Fig. 22-19
Branch point
(common ancestor)
Lungfishes
Amphibians
1
Mammals
2
Tetrapod limbs
Amnion
Lizards
and snakes
3
4
Homologous
characteristic
Crocodiles
Ostriches
6
Feathers
Hawks and
other birds
Birds
5
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Flying
squirrel
EVOLUTION OF POPULATIONS
Adapt, Migrate or Die
• Genes Mutate
• Individuals are selected
• Populations Evolve
Fig. 23-3
Geographic variation
Genetic variation
1
2.4
8.11
9.12
3.14
5.18
10.16 13.17
6
7.15
19
XX
1
2.19
3.8
4.16 5.14
9.10 11.12 13.17 15.18
6.7
XX
Fig. 23-4
1.0
CLINE
0.8
0.6
0.4
0.2
0
46
Maine
Cold
(6°C)
44
42
40
38
36
Latitude
(°N)
34
32
30
Georgia
Warm
(21°C)
How do we measure evolution?
• The smallest unit of measure is an allele.
• Variation in a population
– measured at the nucleotide level or gene level
Hardy Weinberg equation
• * can be used to test whether a population
is evolving
• * 2 independent mathematicians
Fig. 23-6
Alleles in the population
Frequencies of alleles
p = frequency of
CR allele
= 0.8
q = frequency of
CW allele
= 0.2
Gametes produced
Each egg:
Each sperm:
80%
20%
chance chance
80%
20%
chance chance
Fig. 23-7-1
80% CR (p = 0.8)
20% CW (q = 0.2)
Sperm
CR
(80%)
CW
(20%)
64% (p2)
CRCR
16% (pq)
CRCW
16% (qp)
CRCW
4% (q2)
CW CW
Fig. 23-7-2
64% CRCR, 32% CRCW, and 4% CWCW
Gametes of this generation:
64% CR + 16% CR
= 80% CR = 0.8 = p
4% CW + 16% CW = 20% CW = 0.2 = q
Fig. 23-7-3
64% CRCR, 32% CRCW, and 4% CWCW
Gametes of this generation:
64% CR + 16% CR
= 80% CR = 0.8 = p
4% CW + 16% CW = 20% CW = 0.2 = q
Genotypes in the next generation:
64% CRCR, 32% CRCW, and 4% CWCW plants
Fig. 23-7-4
20% CW (q = 0.2)
80% CR ( p = 0.8)
Sperm
(80%)
CW
(20%)
64% ( p2)
CR CR
16% ( pq)
CR CW
CR
16% (qp)
CR CW
4% (q2)
CW CW
64% CR CR, 32% CR CW, and 4% CW CW
Gametes of this generation:
64% CR + 16% CR
= 80% CR = 0.8 = p
4% CW
= 20% CW = 0.2 = q
+ 16% CW
Genotypes in the next generation:
64% CR CR, 32% CR CW, and 4% CW CW plants
HW continued
• Significant change = allele frequency shift =
evolving population
• Consider PKU 1 in 10000 in the US
• If all assumptions hold for PKU then the
frequency of individuals in the population born
with PKU will correspond to q2
• PKU demonstrates that harmful recessive alleles
can be concealed in a pop due to heterozygotes
• PKU cannot breakdown phenylalanine
5 conditions for HW
•
•
•
•
•
1. No mutations:
2. Random mating
3. No natural selection
4. Extremely large population size
5. No gene flow
Fig. 23-8-3
Natural selection, genetic drift and gene flow can alter allele
frequencies in a pop
CR CR
CR CR
CW CW
CR CW
CR CW
CR CR
CW CW
CR CR
CR CW
CR CR
CR CW
CR CW
Generation 1
p (frequency of CR) = 0.7
q (frequency of CW ) = 0.3
CW CW
CR CW
CR CR
CR CR
CR CR
CW CW
CR CR
CR CW
CR CR
CR CR
CR CR
CR CR
CR CR
CR CR
CR CR
CR CW
Generation 2
p = 0.5
q = 0.5
CR CR
CR CR
Generation 3
p = 1.0
q = 0.0
Genetic drift
• Chance events can cause allele
frequencies to fluctuate unpredictably from
one generation to the next especially in
small population
Founder’s Effect
• When a few individuals become isolated
from a larger population, this smaller
group may establish a new population
whose gene pools differs from the source
population
Fig. 23-9
Original
population
Bottlenecking
event
Surviving
population
Fig. 23-10
Pre-bottleneck Post-bottleneck
(Illinois, 1820) (Illinois, 1993)
Range
of greater
prairie
chicken
(a)
Location
Population
size
Percentage
Number
of alleles of eggs
per locus hatched
Illinois
1,000–25,000
5.2
93
<50
3.7
<50
Kansas, 1998
(no bottleneck)
750,000
5.8
99
Nebraska, 1998
(no bottleneck)
75,000–
200,000
5.8
96
Minnesota, 1998
(no bottleneck)
4,000
5.3
85
1930–1960s
1993
(b)
Effects of Genetic Drift
• 1. Significant in small populations
• 2. Can Cause allele frequencies to change
at random
• 3. can lead to a loss of genetic variation
within populations
• 4. can cause harmful alleles to become
fixed
Fig. 23-11
Gene Flow
• The transfer of alleles into or out of a
population due to the movement of fertile
individuals or their gametes
• Gene flow tends to reduce the genetic
differences between populations
• Single population with a common gene
pool