(3) You are conducting research on how natural selection, imposed by pollinators
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(3) You are conducting research on how natural selection, imposed by pollinators, affects flower shape and color. You test whether bumblebee pollination can lead to evolutionary change in flower color. In a greenhouse, vou grow a population of snapdragon plants These plants all produce pink flowers, but there is variation in flower color intensity ranging from lighter pink to darker pink with a mean value of 0.8 abs (abs- a measure of color intensity). You bring a box of bumblebees into the greenhouse to pollinate the snapdragon plants and leave them for 2 days. After 2 days you remove the bees and let the snapdragon plants produce seed. Only snapdragon flowers that were visited by bees produce seed, and you find that the mean flower color intensity for the plants that produce seed is 1.2 abs. In a previous study, you found that narrow sense heritability for flower color intensity in snapdragon is 0.6 a) What do you expect the mean value for flower color intensity to be in the next generation? In other words, when you take all the seeds produced as a result of bee visitation in your experiment, grow them up, and measure flower color intensity. (10 points, show your work for full credit, write your final answer as a complete sentence) b) Describe how you your expected response to selection would differ if all other parameters were the same, but narrow sense heritability for flower color intensity were 0.2 instead of 0.6. Note: no calculations required. If you do decide to perform a calculation, be sure to describe how the expected response to selection changes. (8 points)Explanation / Answer
3(a).
After inbreeding the plants for many generations, they were essentially homozygous and genetically identically; VG = 0. Since VP = VG+ VE+ VGE, VGE also equals 0 and VP = VE.
Narrow sense heritability, h2= VA/VP
0.6= VA/ 0.8; VA = 0.48
The initial population exhibited a mean colour intensity, VP =0.8 ; the inbred population exhibited a VP = 1.2. The difference between the two populations' phenotypic variance must be due to genetic/additive variance, therefore VP- VE = VG; 1.2 -0.8= 0.4.
The mean value of flower colour intensity for the next generation is expected to be: 1.2 +0.4= 1.6.
3(b).
If Narrow sense heritability was 0.2, then variation in colour intensity would be lesser.
Narrow sense heritability, h2= VA/VP
0.2= VA/ 0.8; VA = 0.16
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