some members of a photosynthetic plant species are geneticallyresistant to an he
ID: 1243 • Letter: S
Question
some members of a photosynthetic plant species are geneticallyresistant to an herbicide, while other members of the same speciesare resistant to the herbicide. Maintaining resistance against theherbicide is metabolically metabolically expensive for the plants.Which combination of events should cause the most effectivereplacement of the non-herbicide-resistant strain of plants by theresistant strain?1. an abundance of sunny weather
2. an abundance of cloudy weather
3. the presence of the herbicide in the environment
4. the absence of the herbicide from the environment
5. the maintenance of the proper conditions for one generation
6. the maintenance of the proper conditions for manygenerations
a.2, 4, and 5
b.2, 3, and 5
c.1, 4, and 6
d.1, 3, and 6
e.2, 3, and 6
Explanation / Answer
The resistant plants experience a fitness penalty--they are not ashealthy as susceptible plants under normal conditions. Thus, theresistant plants need sunny weather to stand a chance. 2nd, we need herbicide in the environment. Otherwise, thesusceptible plants will always win, as they are healthier than arethe resistant plants (EXCEPT in the presence of the herbicide, inwhich case the resistant plants actually have the advantage). 3rd, to replace the susceptible plants with resistant plants, weneed many generations of selection with the herbicide as well asother proper conditions. So the answer is 1, 3, and 6
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