Question

command of quantitative evidence: foundations
spider population count
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 30 was lower in the enclosure with lizards than in the enclosure without lizards.

Explanation:

The student claims the spider - population reduction in the lizard - enclosure is due to lizards. But if the spider population also declined substantially in the no - lizard enclosure by day 30, it suggests other factors are at play, weakening the claim that lizards are the sole cause.

Answer:

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