A Gardener Is Constantly Struggling with the Growth of Weeds

question 42

Multiple Choice

A gardener is constantly struggling with the growth of weeds in his perennial flower beds. At the start of the growing season one year, he sprays an herbicide to reduce the number of weeds. Although the herbicide kills many of the weeds, some develop resistance to the herbicide and continue to grow and spread among his flowering plants. After a few years, the gardener decides to stop all herbicide applications. One of the changes that he notices is that the weeds that have resistance to herbicides grow much more slowly and are easily outcompeted by other weeds when no pesticides are sprayed (i.e., the herbicide-susceptible weeds produce more seeds and quickly overtake some of the areas in the garden where the herbicide-resistant weeds had been growing) . Assuming the gardener continues to spray the herbicide for five years, do you think the weed population will evolve?

• A) Yes, there will be more individuals in the population with the herbicide-resistant allele.
• B) No, there will be no change in the genetic composition of the population.
• C) Yes, the population will have evolved because speciation will have occurred.
• D) No, evolution cannot occur over such a short time period.

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Definitions:

Regulatory Molecules

Substances such as hormones or neurotransmitters that control or regulate the activity of cells or organs in the body.

Energy Metabolism

The set of chemical reactions that occur within a living organism to convert energy from food into a form that cells can use.

Neuropeptide Y

A neurotransmitter found in the brain and autonomic nervous system, involved in regulating a variety of physiological processes such as appetite, stress response, and circadian rhythms.

Leptin

A hormone produced by adipose (fat) cells that helps to regulate energy balance by inhibiting hunger.