Ecologists studying urban meadows counted insect visits to flowers during daytime and nighttime periods under three levels of artificial nighttime lighting. They proposed that moderate lighting mainly changes when visits occur without reducing overall visitation, whereas brighter lighting suppresses overall visitation rather than merely redistributing it across the day. The graph shows the average numbers of daytime and nighttime visits per plot over a 24-hour period.
Which choice most effectively uses data from the graph to support the ecologists’ proposal?
For graph-based evidence questions, convert every part of the claim into a required comparison. When categories are stacked, calculate totals or net changes rather than relying on the direction of a single segment, and reject choices that cite accurate data but draw an unsupported conclusion.
Hints
Translate the proposal into comparisons
Identify what the proposal predicts about the total number of visits at moderate lighting and at brighter lighting.
Find each net change
For each lighted condition, combine the change in daytime visits with the change in nighttime visits relative to 0 lux.
Evaluate the conclusions
Several choices cite accurate values, so check whether each choice interprets those values correctly and addresses both lighting levels.
Step-by-step Explanation
Identify both parts of the proposal
The evidence must show that moderate lighting changes the distribution of visits without substantially changing their total, whereas brighter lighting lowers the total.
Compare each condition with the control
From 0 to 5 lux, daytime visits change by 13 and nighttime visits change by −11, giving a net change of 2. From 0 to 20 lux, daytime visits change by 6 and nighttime visits change by −24, giving a net change of −18.
Select the evidence with the correct net comparisons
The choice that accurately expresses both net changes is: Relative to 0 lux, the 5-lux condition had 13 more daytime visits and 11 fewer nighttime visits, a net increase of 2; the 20-lux condition had 6 more daytime visits and 24 fewer nighttime visits, a net decrease of 18.