Question

1. individuals with tolerant alleles have (click to select) growth rates on unpolluted soil and (click to select) growth rates on mined soils.
2. therefore, we would expect copper tolerance to be (click to select) % on mine sites and (click to select) % on unpolluted sites if natural selection is acting alone.
3. however, the index of copper tolerance (click to select) decreases from the downwind side of the mine.
4. this is an example where (click to select) constrains selection.

Explanation:

To solve this problem, we analyze each part based on the concept of natural selection and genetic tolerance:

1. Growth Rates

• On unpolluted soil, individuals with tolerant alleles (adapted to high copper) will have lower growth rates because the tolerant alleles are not beneficial here (unpolluted soil has low copper, so the tolerance trait is not advantageous and may even be costly).
• On mined soils (high copper), individuals with tolerant alleles will have higher growth rates because the tolerance trait helps them survive and reproduce in the polluted environment.

2. Expected Copper Tolerance Percentages

• On mine sites (where copper is present), natural selection favors copper-tolerant alleles, so we expect copper tolerance to be high (e.g., 100% or a high percentage).
• On unpolluted sites, copper tolerance is not favored, so we expect it to be low (e.g., 0% or a low percentage).

3. Index of Copper Tolerance

The index of copper tolerance gradually decreases from the downwind side of the mine. This is because as distance from the mine increases, the concentration of copper in the soil decreases, so the selective pressure for copper tolerance also decreases.

4. Constraint on Selection

This is an example where gene flow constrains selection. Gene flow (movement of genes between populations) can introduce non - tolerant alleles into the mine - adjacent population from the unpolluted - soil population, reducing the frequency of tolerant alleles even in areas where selection would favor them.

Answer:

s:

1. lower; higher
2. high; low (specific numbers may vary, but the trend is high on mine sites, low on unpolluted)
3. gradually
4. gene flow