Download Evolution Part 2

EVOLUTION
Part II
Figure 23.5
Ldh-Bb allele frequency
1.0
0.8
0.6
0.4
0.2
0
46
44
42
Maine
Cold (6°C)
40
38
36
Latitude (ºN)
34
32
Georgia
Warm (21ºC)
30
Genetic Drift
• Changes in the frequency of genes of a
population
Figure 23.9-1
CRCR
CRCR
CRCW
CWCW
CRCR
CRCW
CRCR
CRCR
CRCW
CRCW
Generation 1
p (frequency of CR) = 0.7
q (frequency of CW) = 0.3
Figure 23.9-2
CRCR
CRCR
CRCW
CWCW
5
plants
leave
offspring
CRCR
CWCW
CRCW
CRCR
CWCW
CRCR
CRCW
CRCW
CRCR
CRCR
CRCW
CRCW
Generation 1
p (frequency of CR) = 0.7
q (frequency of CW) = 0.3
CWCW
CRCW
CRCR
CRCW
Generation 2
p = 0.5
q = 0.5
Figure 23.9-3
CRCR
CRCR
CRCW
CWCW
5
plants
leave
offspring
CRCR
CWCW
CRCW
CRCR
CWCW
CRCR
CRCW
CRCW
CRCR
CRCR
CRCW
CRCW
Generation 1
p (frequency of CR) = 0.7
q (frequency of CW) = 0.3
CWCW
CRCW
2
plants
leave
offspring
CRCR
CRCR
CRCR
CRCR
CRCR
CRCR
CRCR
CRCW
Generation 2
p = 0.5
q = 0.5
CRCR
CRCR
CRCR
CRCR
Generation 3
p = 1.0
q = 0.0
Figure 23.10-1
Original
population
Figure 23.10-2
Original
population
Bottlenecking
event
Figure 23.10-3
Original
population
Bottlenecking
event
Surviving
population
Figure 23.11
Pre-bottleneck
(Illinois, 1820)
Post-bottleneck
(Illinois, 1993)
Greater prairie chicken
Range
of greater
prairie
chicken
(a)
Location
Illinois
1930–1960s
1993
Population
size
Percentage
Number
of alleles of eggs
per locus hatched
1,000–25,000
<50
5.2
3.7
93
<50
Kansas, 1998
(no bottleneck)
750,000
5.8
99
Nebraska, 1998
(no bottleneck)
75,000–
200,000
5.8
96
(b)
The Hardy Weinberg Principle
• Evolution viewed as a change in the
frequency of alleles in a population
• A and a are alleles for particular gene
• Frequency of possible combinations:
AA, Aa, or aa, is expressed as:
p2 + 2pq + q2 = 1.0
The Hardy Weinberg Principle
•
•
•
•
•
•
p+q=1
p = frequency of dominant allele
q = frequency of recessive allele
p2 = % of homozygous dominant
q2 = % of homozygous recessive
2pq = % of heterozygous
• The five conditions for nonevolving populations
are rarely met in nature:
1. No mutations
2. Random mating
3. No natural selection
4. Extremely large population size
5. No gene flow
© 2011 Pearson Education, Inc.
Frequency of
individuals
Figure 23.13
Original
population
Evolved
population
(a) Directional selection
Original population
Phenotypes (fur color)
(b) Disruptive selection
(c) Stabilizing selection
Figure 23.13a
Original
population
Evolved
population
(a) Directional selection
Figure 23.13b
Original
population
Evolved
population
(b) Disruptive selection
Figure 23.13c
Original
population
Evolved
population
(c) Stabilizing selection
Figure 23.17
Key
Frequencies of the
sickle-cell allele
0–2.5%
2.5–5.0%
Distribution of
malaria caused by
Plasmodium falciparum
(a parasitic unicellular eukaryote)
5.0–7.5%
7.5–10.0%
10.0–12.5%
>12.5%
Figure 24.3_b
Prezygotic barriers
Habitat
Isolation
Temporal
Isolation
Individuals
of
different
species
(a)
MATING
ATTEMPT
(c)
(d)
(b)
Gametic
Isolation
Mechanical
Isolation
Behavioral
Isolation
(e)
(f)
FERTILIZATION
(g)
Figure 24.3_c
Postzygotic barriers
Reduced Hybrid
Viability
Reduced Hybrid
Fertility
Hybrid
Breakdown
VIABLE,
FERTILE
OFFSPRING
FERTILIZATION
(h)
(i)
(j)
(k)
(l)
Figure 24.5
(a) Allopatric speciation.
A population forms a
new species while
geographically isolated
from its parent population.
(b) Sympatric speciation.
A subset of a population
forms a new species
without geographic
separation.
Figure 24.6
A. harrisii
A. leucurus
Figure 24.13
EUROPE
Fire-bellied
toad range
Hybrid zone
Fire-bellied toad, Bombina bombina
Yellow-bellied
toad, Bombina
variegata
Frequency of
B. variegata-specific allele
Yellow-bellied
toad range
0.99
Hybrid
zone
0.9
Yellow-bellied
toad range
0.5
Fire-bellied
toad range
0.1
0.01
40
10
0
20
10
20
30
Distance from hybrid zone center (km)
Figure 24.4
Grizzly bear (U. arctos)
Polar bear (U. maritimus)
Hybrid “grolar bear”
Figure 24.11-4
Species A
2n = 6
Normal
gamete
n=3
Species B
2n = 4
Meiotic error;
chromosome number not
reduced from 2n to n
Unreduced gamete
with 4 chromosomes
Hybrid with
7 chromosomes
Normal
gamete
n=3
Unreduced gamete
with 7 chromosomes
New species:
viable fertile hybrid
(allopolyploid) 2n = 10
Figure 24.17
(a) Punctuated
pattern
Time
(b) Gradual
pattern