AY Honors/Coral Reefs/Answer Key
1. What is a reef? Identify two types of "building blocks" of reefs.
Reefs form in sea water and are a build-up of the remains of the hard parts of animals – mostly calcium carbonate. Some reefs can be over 30 m thick. Some reefs are formed from layers of oysters (or other species of mollusk) growing on top of each other – called oyster reefs. Some reefs are composed of layers of coral skeletons growing on top of each other – called coral reefs.
2. Answer the following:
a. Is coral a plant or animal?
Corals are animals.
b. In what phylum is coral categorized?
Corals are in the phylum Cnidaria (the C is silent - nigh dare ia). Some forms of Cnidaria are mobile and swim around like jellyfish, other types are sessile which means they are anchored to the substrate and do not move around. These are the corals that build coral reefs.
c. What part of a coral reef is living?
Only the top layer of a reef is alive. As we will learn later, corals require sunlight to live so only those on top can survive.
d. Distinguish between soft and hard corals.
Hard corals are soft-bodied animals which secrete a hard calcium carbonate layer around them and have multiples of 8 tentacles used in feeding. These are the reef builders. Soft corals are soft bodied animals which secrete very little calcium carbonate so they are not hard, but can sway back and forth in the ocean currents. Soft corals have multiples 6 tentacles used in feeding.
3. Where are coral reefs found? Describe the conditions that are needed for healthy coral growth.
Coral reefs are found between 30 degrees north and south of the equator.
They require:
- Warm water
- Shallow water (so that there is enough sunlight),
- Saltwater
4. Describe and/or draw a diagram showing at least three different types of coral reefs.
- a. Fringing Reefs
- grow near the shoreline of continents and islands and are usually separated from the land by a shallow body of water called a lagoon.
- b. Barrier Reefs
- similar to fringing reefs but are further away from shore often grow along the edge of the continental shelf. If they grow to the surface, ships cannot get through to the mainland and thus are called "barriers". The resulting lagoons are deeper and larger than in fringing reefs.
- c. Atolls
- a fringe reef that grows around a small island but then the island erodes away or sinks which leaves a ring of reef surrounding a lagoon.
- d. Patch Reef
- an isolated patch of reef that grows up from the floor of the lagoon of a barrier reef. They seldom reach the surface of the water.