b. Flower color in this species is controlled by two factors: (1) genes and (2)
ID: 20406 • Letter: B
Question
b. Flower color in this species is controlled by two factors: (1) genes and (2) the pH of the soil in which the plant grows. A genetic analysis shows that 30% of the variation in color in this population is due to the soil pH in which each plant grows (plants growing in more acidic soils tend to be more blue, rather than pink). What is the heritability value (H) for flower color in this population of plants? What does this value mean?
c. In addition to what you already know about this population from parts a and b, what else would have to be true to demonstrate natural selection acting on flower color? Your answer should describe how it would work on flower color specifically.
Explanation / Answer
Part A
4 conditions are necessary to demonstrate natural selection:
A. More organisms are born than can survive.
B. Organisms vary in their characteristics, even within a species.
C. Variation is inherited.
D. Differences in reproduction and survival are due to variation among organisms.
This normalized distribution of colors indicates variation in characteristics (B). You don't know if that variation is linked to genes or if it has an impact on survival/reproduction.
Part B
Heritability value (H) = the amount of variability that is determined by genes = genetic variation/total. In this case, since the environmental influence on variation is 30%, the genetic influence is 70% so the H = .7
Part C
As noted above, a demonstration that natural selection impacts flower color would need to demonstrate several things:
-prerequisite demonstration that more individuals are born than can survive (ie some organisms die)
-an inherited link exists between flower colors in plants (e.g. Mendel's pea plants)
-the rate of survival and reproductive success among one or a few colors is higher than others
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