Question

 1) Take 5 red, 5 black beans, and 10 white beans and place them, mixed, on the table. Imagine that these are sexually reproducing organisms. Females have two morphs-red and black. Males have one morph-white. Record the starting phenotype # and frequencies (% of your total population) of your starting population in the table provided (generation 0).

 2) Males have a slight preference for mating with black females. Seven times out of ten, a male will choose a black female as a mate. Allow each male to pair once with a female and produce two offspring-one male and one female. Seven of them pair with a black female and each produces two offspring with her-one white male and one black female. The other three males mate with a red female and produce two offspring with her-one white male and one red female. Some red females will be unmated and will not reproduce. (Note: females can mate more than once.) Multiply your organisms accordingly and allow them to mix on the table. Calculate and record the phenotype # and frequencies (% of your total population) of generation 1 in the table.

 3) Repeat the reproduction event with 7 out of 10 males choosing black females as mates to determine generation 2.

 4) Repeat the reproduction event with 7 out of 10 males choosing black females as mates to determine generation 3.

 Summarize how the final population looks different from the starting population. Which evolutionary mechanism is being simulated?

Answer 1

* For ease of understanding, the subjects are taken as birds. White male birds, red and black female birds in a closed population.

*This is a case of sexual selection , sexual selection is a type of natural selection, in which the selection of a particular trait in the opposite sex by the other sex plays a crucial role in evolution.

Here white male birds prefer black female birds.

So naturally over a period of time, as the generation passes the percentage of black female birds will gradually increase and percentage of red female birds will gradually decrease.  

* The G0 generation is the given generation, 5 red fm, 5 black female, 10 white Male

Their percentage ( number of a particular kind ÷ total members in that population)

Red fm = 5/20 = 0.25

Black fm = 5/20 = 0.25

White male = 10/20 = 0.5

* G1

Here 7 black females mate with 7 white Males and produce 7 black daughters and 7 white sons. 3 red females mate with 3 white males and produce 3 red daughters and 3 white sons.

Now take G0 and G1 as the total population and find out percentage

Red fm = (5 +3) / 40 = 0.2

Black fm = (5+7) / 40 = 0.3

White Male = 20/ 40 = 0.5

* G2 - From the total 20 males now present in the population, 14 will mate with 14 black females and produce 14 black females and 14 white males.

6 males will mate with 6 red females and produce same number of males and females.

Thus 6 red fm, 14 black fm and 20 white males produced only in G2, adding to the total population, it will turn out to be 14 red fm, 26 black females, 40 white males

Percentage

Red fm = 14/80 = 0.175

Black fm = 26/80 = 0.325

White male = 40/ 80 = 0.5

* G3 - From 40 white males in the population, 28 will mate with black females producing 28 black females and 28 white males

12 males mate with 12 red females and produce 12 red daughters and 12 white sons.

Thus considering birds fromG2 also , total red females in population is 26, black females are 54, white males are 80. Total population size is 160.

Percentage

Red fm = 26/160 = 0.1625

Black fm = 54/160= 0.3375

White males = 80/160 = 0.5

Thus analysing each generation, we can understand that the percentage of red females are slowly decreasing and that of black females is slowly increasing , percentage of males remains constant.

Thus due to sexual selection, a particular gene allele frequency is increasing in a population and another is decreasing.