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Selection Intensity &
Frequency based Selection
GPB 607 (3+0) - Crop Evolution
Dr. K N Ganeshaiah
Background
Peppered moth
Biston betularia
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Lichens
Not seen under polluted conditions
Background
Industrialization
London / Europe
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Biston betularia F.typica
light-coloured species with dark patches, that
help them to camouflage against the lichens on
the barks of the trees
Biston betularia F.carbonaria
sub species of F.typica mutated into dark
coloured moth with light-coloured patches.
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
The proportion of the
white (Bb) and black (Bb)
after the predation will
be used to re-populate
next generation
Assumptions
Predation rate
The rate at which the
birds prey on the moth
Biston betularia is
constant for all
generations
Repopulation No Death
There will be no decline
in the population of the
Bb in any generation due
to any other factors like
disease or natural
calamities
10% wn:bn::Wn+1:Bn+
1
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
BIRD A
Results of demonstration / experiment conducted by group A
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 1% Frequency
How selection against white (Bb)
increased black (Bb) proportion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
 Population curves (frequency)
remain stable until predation of
Black (Bb)
 Predation of Black (Bb) in
13th generation
 No individual of Black (Bb) to
repopulate the 14th generation
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
 Population curves (frequency)
remain stable until predation of
Black (Bb)
 Predation of Black (Bb) in
13th generation
 No individual of Black (Bb) to
repopulate the 14th generation
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 5%Frequency
How selection against white (Bb)
increased black (Bb) proportion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Faint lines represent the normalized polynomial curve
( to the power of 3) for which the equations are
represented below in the graph
1. White (Bb): Observe the sharp
decline in the population curve
after 10th generation
1. Black (Bb): Observe the sharp
increase in the population
curve after 10th generation
We shall discuss this later - collectively
10th
generation
Study - 10% Frequency
How selection against white (Bb)
increased black (Bb) proportion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Faint lines represent the normalized polynomial curve
( to the power of 2) for which the equations are
represented below in the graph
1. White (Bb): Observe the sharp
decline in the population curve
after 12th generation
1. Black (Bb): Observe the sharp
increase in the population
curve after 12th generation
We shall discuss this later - collectively
12th
generation
Study - 20% Frequency
How selection against white (Bb)
increased black (Bb) proportion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Faint lines represent the normalized polynomial curve
(to 4th degree) for which the equations are
represented below in the graph
1. White (Bb): Observe the
gradual decline in the
population curve
1. Black (Bb): Observe the
gradual increase in the
population curve
We shall discuss this later - collectively
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 50% Frequency
How selection against white (Bb)
increased black (Bb) proportion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Faint lines represent the normalized linear curve for
which the equations are represented below
There is a sharp increase in
selection against the White (Bb)
The Black (Bb) population is
reaching the saturation and stability
from the 14th generation onwards
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Collective discussion
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Trying to explain
SELECTION INTENSITY and
FREQUENCY based SELECTION
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
12
Dif. Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
17 20 31
Difference Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
10
Difference Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
10
Difference Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
10
Difference Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
60
Difference Population White (Bb) Black (Bb)
0 G0 =
(initial population)
90 10
12 G12 =
(12th generation)
80 20
5 G17 =
(17th generation)
70 30
3 G20 =
(20th generation)
60 40
10 G31 =
(31st generation)
1 99
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
60
10
Initially where it took  10 generations (G0-G12)to reduce the population by 10 individuals,
later the 10 generations (G20-G31) reduced the population by 60 individuals (6x increase)
Which means that -
with increasing number of
generations, there is incremental
selection against the White (Bb)
population
i.e ., favouring Black (Bb) population
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
12 17 20 31
This constitutes
SELECTION INTENSITY
This selection intensity is in-turn
dependent on the frequency of the
population of
Whites and Blacks
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
12 17 20 31
Population White (Bb) Selection Intensity
G5 =
(5th generation)
86 -
G6 =
(6th generation)
85 1
G7 =
(7th generation)
84 1
G26 =
(26th generation)
34 -
G27 =
(27th generation)
28 6
G28 =
(28th generation)
22 6
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Therefore, when there is lower frequency of white population, there is higher probability that the white
moths are preyed upon - frequency based selection
FREQUENCY based
SELECTION
{
The selection intensity and frequency
based selection are interdependent
The lower
frequency of the
population
increases the
selection intensity
{
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
BIRD B
Results of demonstration / experiment conducted by group B
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
20% Population frequency
10% Selection intensity
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
40 (White):10 (Black)
I case
White  Chickpea
Black - Horsegram
II case
White  Chickpea
Black - Soybean
40:10 (White: Black)
 Gradual changes till 6th
generation
 After 25:25 changes were
sharp at 6th generation
 By the 15th generation, Black
moths were more than white
moths
 Stability may be achieved
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Selection intensity >>>>> Distinction between moths
I case
- Predominant distinction between moths
- Discrimination also increases
- Selection intensity is more
II case
- Distinction between moths is less
- Discrimination is gradual (The earliest stage of
melanization
- Selection intensity is less
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 1% Frequency
99 (White):1 (Black)
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
99:1 (White : Black)
 Stabilization till the 5th
generation
 Random chance
 Leads to random genetic drift
 Is there any chance of the
occurrence of black moth
again??
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 5% Frequency
95 (White):5 (Black)
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
95:5 (White : Black)
 Gradual changes
 22nd generation >>> sharp
changes
 Converge at 50:50
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 10% Frequency
90 (White):10 (Black)
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
90:10 (White : Black)
 Sharp decrease and increase
in white moths and black moths
population
 Converge at 50:50
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Study - 50% Frequency
50(White):50 (Black)
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
50:50 (White : Black)
 Initial sharp changes in both
the populations
 Later the changes were gradual
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
 The rate of reproduction is more
when white moths is 90 and the
rate of elimination of white
moths when it is 10 is lesser due
to the reproduction
 But when both white and black
moths are at the same
population composition (50: 50)
the chance of elimination and
chance of reproduction will be
equal then there will sharp/
exponential change.
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Generations No. of generations White Black
G1  G8 8 90 - 80 10- 20
G8- G18 10 80-60 20-40
G-18  G21 3 60-50 40-50
>>>G-21 - 50 50
Generations No. of generations White Black
G1-G4 4 50-40 50-60
G4-G6 3 40-30 60-70
G6-G9 3 30-20 70-80
G9-G12 3 20-10 80-90
G12-G21 10 10-0 90-100
90:10 50:50
The black moths
population rate will be
sharp as the number of
black moths in the initial
population increases
THANK YOU
Department of Genetics and Plant Breeding
GPB 607 (3+0) - Dr. K N Ganeshaiah
Brahmesh Reddy B R
Aishwarya G
Sinchana K
PhD Scholars
UAS,GKVK, Bangalore

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Selection Intensity & Frequency based Selection in evolution

  • 1. Selection Intensity & Frequency based Selection GPB 607 (3+0) - Crop Evolution Dr. K N Ganeshaiah
  • 2. Background Peppered moth Biston betularia Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 3. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Lichens Not seen under polluted conditions
  • 4. Background Industrialization London / Europe Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 5. Biston betularia F.typica light-coloured species with dark patches, that help them to camouflage against the lichens on the barks of the trees Biston betularia F.carbonaria sub species of F.typica mutated into dark coloured moth with light-coloured patches. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 6. The proportion of the white (Bb) and black (Bb) after the predation will be used to re-populate next generation Assumptions Predation rate The rate at which the birds prey on the moth Biston betularia is constant for all generations Repopulation No Death There will be no decline in the population of the Bb in any generation due to any other factors like disease or natural calamities 10% wn:bn::Wn+1:Bn+ 1 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 7. BIRD A Results of demonstration / experiment conducted by group A Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 8. Study - 1% Frequency How selection against white (Bb) increased black (Bb) proportion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 9. Population curves (frequency) remain stable until predation of Black (Bb) Predation of Black (Bb) in 13th generation No individual of Black (Bb) to repopulate the 14th generation Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 10. Population curves (frequency) remain stable until predation of Black (Bb) Predation of Black (Bb) in 13th generation No individual of Black (Bb) to repopulate the 14th generation Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 11. Study - 5%Frequency How selection against white (Bb) increased black (Bb) proportion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 12. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Faint lines represent the normalized polynomial curve ( to the power of 3) for which the equations are represented below in the graph 1. White (Bb): Observe the sharp decline in the population curve after 10th generation 1. Black (Bb): Observe the sharp increase in the population curve after 10th generation We shall discuss this later - collectively 10th generation
  • 13. Study - 10% Frequency How selection against white (Bb) increased black (Bb) proportion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 14. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Faint lines represent the normalized polynomial curve ( to the power of 2) for which the equations are represented below in the graph 1. White (Bb): Observe the sharp decline in the population curve after 12th generation 1. Black (Bb): Observe the sharp increase in the population curve after 12th generation We shall discuss this later - collectively 12th generation
  • 15. Study - 20% Frequency How selection against white (Bb) increased black (Bb) proportion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 16. Faint lines represent the normalized polynomial curve (to 4th degree) for which the equations are represented below in the graph 1. White (Bb): Observe the gradual decline in the population curve 1. Black (Bb): Observe the gradual increase in the population curve We shall discuss this later - collectively Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 17. Study - 50% Frequency How selection against white (Bb) increased black (Bb) proportion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 18. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Faint lines represent the normalized linear curve for which the equations are represented below There is a sharp increase in selection against the White (Bb) The Black (Bb) population is reaching the saturation and stability from the 14th generation onwards
  • 19. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 20. Collective discussion Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Trying to explain SELECTION INTENSITY and FREQUENCY based SELECTION
  • 21. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 12 Dif. Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 17 20 31
  • 22. Difference Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 10
  • 23. Difference Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 10
  • 24. Difference Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 10
  • 25. Difference Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 60
  • 26. Difference Population White (Bb) Black (Bb) 0 G0 = (initial population) 90 10 12 G12 = (12th generation) 80 20 5 G17 = (17th generation) 70 30 3 G20 = (20th generation) 60 40 10 G31 = (31st generation) 1 99 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 60 10 Initially where it took 10 generations (G0-G12)to reduce the population by 10 individuals, later the 10 generations (G20-G31) reduced the population by 60 individuals (6x increase)
  • 27. Which means that - with increasing number of generations, there is incremental selection against the White (Bb) population i.e ., favouring Black (Bb) population Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 12 17 20 31 This constitutes SELECTION INTENSITY
  • 28. This selection intensity is in-turn dependent on the frequency of the population of Whites and Blacks Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 12 17 20 31
  • 29. Population White (Bb) Selection Intensity G5 = (5th generation) 86 - G6 = (6th generation) 85 1 G7 = (7th generation) 84 1 G26 = (26th generation) 34 - G27 = (27th generation) 28 6 G28 = (28th generation) 22 6 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Therefore, when there is lower frequency of white population, there is higher probability that the white moths are preyed upon - frequency based selection
  • 30. FREQUENCY based SELECTION { The selection intensity and frequency based selection are interdependent The lower frequency of the population increases the selection intensity { Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 31. BIRD B Results of demonstration / experiment conducted by group B Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 32. 20% Population frequency 10% Selection intensity Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah 40 (White):10 (Black) I case White Chickpea Black - Horsegram II case White Chickpea Black - Soybean
  • 33. 40:10 (White: Black) Gradual changes till 6th generation After 25:25 changes were sharp at 6th generation By the 15th generation, Black moths were more than white moths Stability may be achieved Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 34. Selection intensity >>>>> Distinction between moths I case - Predominant distinction between moths - Discrimination also increases - Selection intensity is more II case - Distinction between moths is less - Discrimination is gradual (The earliest stage of melanization - Selection intensity is less Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 35. Study - 1% Frequency 99 (White):1 (Black) Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 36. 99:1 (White : Black) Stabilization till the 5th generation Random chance Leads to random genetic drift Is there any chance of the occurrence of black moth again?? Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 37. Study - 5% Frequency 95 (White):5 (Black) Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 38. 95:5 (White : Black) Gradual changes 22nd generation >>> sharp changes Converge at 50:50 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 39. Study - 10% Frequency 90 (White):10 (Black) Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 40. 90:10 (White : Black) Sharp decrease and increase in white moths and black moths population Converge at 50:50 Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 41. Study - 50% Frequency 50(White):50 (Black) Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 42. 50:50 (White : Black) Initial sharp changes in both the populations Later the changes were gradual Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah
  • 43. The rate of reproduction is more when white moths is 90 and the rate of elimination of white moths when it is 10 is lesser due to the reproduction But when both white and black moths are at the same population composition (50: 50) the chance of elimination and chance of reproduction will be equal then there will sharp/ exponential change. Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Generations No. of generations White Black G1 G8 8 90 - 80 10- 20 G8- G18 10 80-60 20-40 G-18 G21 3 60-50 40-50 >>>G-21 - 50 50 Generations No. of generations White Black G1-G4 4 50-40 50-60 G4-G6 3 40-30 60-70 G6-G9 3 30-20 70-80 G9-G12 3 20-10 80-90 G12-G21 10 10-0 90-100 90:10 50:50
  • 44. The black moths population rate will be sharp as the number of black moths in the initial population increases
  • 45. THANK YOU Department of Genetics and Plant Breeding GPB 607 (3+0) - Dr. K N Ganeshaiah Brahmesh Reddy B R Aishwarya G Sinchana K PhD Scholars UAS,GKVK, Bangalore