Two species of barnacles, stellate and rock barnacles, occupy the rocky intertidal zone of the Scottish coast and illustrate factors that can determine species distribution in a community.Larvae of both species settle throughout the intertidal zone, but adult barnacles occupy specific zones.The smaller stellate barnacle lives only in higher zones, where the environment dries out between high tides.The larger, faster-reproducing rock barnacle lives only at lower zones.Differences in the distribution of larval and adult barnacles suggest that stellate barnacles are primarily restricted by _______ and rock barnacles are restricted by _______.
A) water availability; cold temperatures
B) predation; competition
C) competition; predation
D) competition; water availability
E) parasitism; cold temperatures

Question

Quizplus · Accepted Answer

The distribution of the stellate barnacle suggests that it is primarily restricted by water availability since it lives only in higher zones where the environment dries out between high tides. The distribution of the rock barnacle suggests that it is primarily restricted by competition since it lives only in lower zones where there is likely less competition for resources.

Two Species of Barnacles, Stellate and Rock Barnacles, Occupy the Rocky