21. Evolution

Kale, brussels sprouts, cabbage, broccoli, and kohlrabi are all vegetables that come from selecting for different traits in the wild mustard (Brassica oleracea). For example, to produce kale, humans selected plants with the large leaves. Over repeated generations of selection this led to the modern plant kale. This is an example of:

Which statement identifies the main difference between natural selection and artificial selection?

Bedbugs are a pest that has been a nuisance throughout human history. In the 1940s, the widespread introduction of the pesticide DDT allowed people to effectively kill bedbugs at home. However, a mutation in the gene that codes for sodium channels in these insects provided resistance to DDT in some bedbugs. DDT was banned in 1974, but most bedbugs today are still resistant to DDT. What could be an explanation for why most bedbugs still have resistance to DDT?

A proposed strategy for combatting the spread of antibiotic resistance is to allow doctors to prescribe only a certain subset of antibiotic drugs and regularly rotate which antibiotics are allowed to be prescribed over several years. Why could this approach limit the spread of antibiotic resistance?