Question

to investigate the effect of lizard predation on spider populations, a student in a biology class placed spiders in two enclosures, one with lizards and one without, and tracked the number of spiders in the enclosures for 30 days. the student concluded that the reduction in the spider population count in the enclosure with lizards by day 30 was entirely attributable to the presence of the lizards. which choice best describes data from the graph that weaken the students conclusion? choose 1 answer: a the spider population count was the same in both enclosures on day 1. b the spider population count also substantially declined by day 30 in the enclosure without lizards. c the largest decline in spider population count in the enclosure with lizards occurred from day 1 to day 10. d the spider population count on day was lower in the enclosure with lizards than in the enclosure without lizards.

Explanation:

The student's conclusion is that the reduction in the spider population in the enclosure with lizards is entirely due to the presence of lizards. If the spider population also declined in the enclosure without lizards (which has no lizards, so no lizard - related predation), it shows that there are other factors (not lizard predation) causing the decline. This weakens the student's conclusion that the decline in the lizard - enclosure is only because of lizards.

• Option A: If the population was the same on day 1, it just sets the starting point for a fair comparison but doesn't weaken the conclusion.
• Option C: The time - period of the largest decline in the lizard - enclosure doesn't address the cause (whether it's only lizards or not).
• Option D: A lower count on one day (assuming it's not day 30) doesn't necessarily weaken the conclusion about the cause of the decline by day 30.

Answer:

B. The spider population count also substantially declined by day 30 in the enclosure without lizards.