A novel fungicide is introduced and widely applied to cereal crops. After five years, resistant genotypes of the fungal pathogen are detected at a frequency of about 1%; resistance is widely distributed across the pathogen’s range. Within two years, these have become so common that the fungicide becomes worthless.
Explain how this pattern can be explained by the basic features of natural selection. Include in your answer:
- A brief description of what natural selection is.
- The conditions that must be met in order for natural selection to occur.
- How natural selection explains the scenario above.