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).
Resistance to herbicides has arisen in the population through the process of __________.
a. natural selection
b. mutation
c. evolution
d. fertilization
A
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The SA node, also known as the __________ spontaneously generates the action potentials that set the pace for
cardiac contractions. Fill in the blank(s) with the appropriate word(s).
Which of the following hormones stimulates an increase in basal metabolic rate as a tropic hormone?
A) prolactin B) follicle-stimulating hormone C) thyroid-stimulating hormone D) adrenocorticotropic hormone
What ecological process causes a lake to change into a marsh over a long period of time?
A) Extinction B) Coevolution C) Eutrophication D) Competitive exclusion E) Succession
Through chemical digestion, nucleic acids are broken down into
A) fatty acids. B) monosaccharides. C) nucleotides. D) amino acids.