Question

exercise 2
evolution by natural selection
directions: choose the best answer for each of the following items.
question 1 is based on the following passage:
in a scientific study, a change in the independent variable results in
a change in the dependent variable. for example, a change in tree
trunk color resulted in a change in wing - color frequencies in
england’s peppered moth population.

1. when studying natural selection, which of the following

observations would provide the clearest proof that selection is
happening?
a. a change in the dependent variable
b. no change in the dependent variable
c. a change in the independent variable
d. no change in the independent variable
question 2 is based on the following passage:
the fish population in a freshwater lake has been monitored by
local ecologists for 26 years. the population includes both dark-
and light - colored fish. over this period, the ratio of dark to light
fish has remained about 3 to 2.

Explanation:

To determine the answer, we analyze the relationship between independent and dependent variables in natural selection studies. The passage states that a change in the independent variable causes a change in the dependent variable. For natural selection (a process of selection), we need to see the effect (change in dependent variable) as the independent variable (e.g., environmental factor) changes. Option A says a change in the dependent variable, which aligns with the idea that selection (driven by independent variable changes) causes a change in the dependent variable (e.g., trait frequencies in a population). Option B (no change in dependent) would mean no selection effect. Option C (change in independent) is the cause, not the proof of selection happening. Option D (no change in independent) can't show selection as there's no driving factor change. So A is correct.

Answer:

A. a change in the dependent variable