Question

Coral reefs are built by a small organism called a polyp. The polyp creates the structure of the coral reef by building a ____________ out of calcium carbonate

cup

pocket

shelf

plate

Answer 1

I think the answer is in here

http://oceanservice.noaa.gov/education/kits/corals/coral03_growth.html

Answer 2

Read this and you will find the answer


The skeletons of stony corals are secreted by the lower portion of the polyp. This process produces a cup, or calyx, in which the polyp sits. The walls surrounding the cup are called the theca, and the floor is called the basal plate. Periodically, a polyp will lift off its base and secrete a new basal plate above the old one, creating a small chamber in the skeleton. While the colony is alive, CaCO3 is deposited, adding partitions and elevating the coral.

branching coral

Coral species number in the thousands, and stony corals take on several characteristic forms. Click the image to see a series of eight major coral growth patterns.