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

question 170

Multiple Choice

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

---

Definitions:

Cellular Membrane

The cellular membrane, or plasma membrane, is the biological membrane that separates the interior of all cells from the outside environment, controlling the movement of substances in and out of cells.

Exocytosis

The active transport of materials out of the cell by fusion of cytoplasmic vesicles with the plasma membrane. Compare with endocytosis.

Plasma Membrane

The semipermeable membrane surrounding the cytoplasm of a cell, responsible for controlling the passage of substances in and out of the cell.

Vesicle

(vesicle) Any small sac, especially a small, spherical, membrane-enclosed compartment, within the cytoplasm.