Cotton (Gossypium hirsutum) is a major textile crop cultivated globally.
Wild cotton plants produce a toxic chemical called gossypol in specialized pigment glands. Bollworms avoid feeding on wild cotton tissues containing high levels of gossypol because it disrupts their digestive systems.
Explain how wild cotton plants could have evolved to produce these high levels of toxic gossypol.
To make cotton seeds safe for use as protein-rich animal feed, plant breeders developed "glandless" cotton varieties with extremely low gossypol levels. These varieties were developed through artificial selection.
Describe how the process of artificial selection is carried out to produce these low-gossypol cotton varieties.
Scientists investigated different agricultural regions. They recorded the percentage of cotton fields planted with high-gossypol (glanded) varieties, and the local population density of bollworms.
The graph shows their results:
Suggest an explanation for the pattern of results shown in the graph.