After reading the paragraph below, answer the questions that follow.
Crop plants can have higher densities of stomata on the underside of their leaves than on the
surfaces of their leaves. Some scientists hypothesize that that the evolution of this adaptation
enhanced the ability of these plants to regulate the rate of CO2 uptake for each surface.
5) Suppose you wanted to test this hypothesis using sunflower plants. Which of the following
would be the best procedure regarding the groups you use in your experiment?
A) Choose two equal-size groups of sunflower plants. One would be the experimental group and
one would be the control group.
B) Choose equal-size groups of sunflower plants and zinnia plants. The sunflower plants would
be the experimental group and the zinnia plants would be the control group.
C) Choose two groups of sunflower plants. The experimental group would have twice as many
plants as the control group.
D) Choose two groups of sunflower plants. The experimental group would have half as many
plants as the control group.
6) You designed and performed an experiment that measured CO2 gas exchange levels at the
upper side of a sunflower leaf (fewer stomata) and the bottom side of a sunflower leaf (greater
stomata). After collecting and analyzing your data, you conclude that there was not a significant
difference in CO2 gas exchange between the two sides of the leaf. Which of the following
possibly explains this finding?
A) The difference in the density of stomata on the two leaf surfaces is not likely due to an
adaptation related to gas exchange regulation.
B) The difference in the density of stomata on the two leaf surfaces is likely due to specific
mechanisms that sunflowers use to disperse their seeds.
C) The difference in the density of stomata on the two leaf surfaces is likely due to mycorrhizal
associations with other plants.
D) The difference in the density of stomata on the two leaf surfaces is likely due to different
pollination needs for each surface.