Question

The residues ("tailings") of mines often contain such high concentrations of toxic metals (e.g., copper, lead) that most plants are unable to grow on them. However, some hardy species (e.g. certain grasses) are able to spread from the surrounding uncontaminated soil into such areas. These plants evolve resistance to the toxic metals while their ability to grow on uncontaminated soil decreases. Because grasses are wind pollinated, breeding between the resistant and nonresistant populations continues, but offspring of crosses between the two populations are intermediate and have low fitness. This is an example of:

Answer 1

This is an example of natural selection. Resistant grasses that can grow in toxic mine residues have evolved this ability through adaptations to the high concentrations of toxic metals.

Step-by-step explanation:

This is an example of natural selection. The grasses that are able to spread into the contaminated areas have evolved a resistance to the toxic metals, allowing them to survive and reproduce. However, their ability to grow on uncontaminated soil decreases because they have adapted specifically to the conditions of the contaminated soil.

When these resistant grasses breed with nonresistant populations, the offspring are intermediate and have low fitness. This means that they are not as well adapted to either the contaminated or uncontaminated soil, reducing their chances of survival and reproduction.