AY Honors/Coral Reefs/Answer Key

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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:

  1. Warm water
  2. Shallow water (so that there is enough sunlight),
  3. 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.

5. Define zooxanthellae.

Zooxanthellae are microscopic algae that live inside soft parts of corals. The different species of zooxanthellae give the corals their color (otherwise they would look white – the color of calcium carbonate). The calcium carbonate shell of the coral protects the delicate algae. The coral benefits by eating some of the sugar that the algae make using energy from the sun. This is a great example of symbiosis – both the coral and the algae benefit by living together.

6. Answer the following questions about how corals get their food:

a. Which type of feeding primarily occurs at night and why does this result in clear water?

b. Which type of feeding occurs primarily during daylight hours

c. Why are coral reefs found in clear water?

7. Identify five corals that can be found on a reef.

8. Identify ten fish that live in a coral reef.

9. Identify five species of non-coral invertebrates that might live on a reef.

10. Define "bleaching" as it pertains to corals, and explore the impact this has on the reef.

11. Identify at least one invasive species and how it affects reefs.

12. Why are reefs an important community? List at least three ways that you can help protect a reef.

13. Prepare an object lesson about an animal that lives in the reef. Present this lesson at a club worship or similar function. Be sure to include a Bible text in this presentation.

14. Do at least two of the following:

a. Visit an aquarium which exhibits reef species.

b. Make a collection of at least five species of dead coral you find washed up on a beach or fossil corals. Make sure you obey local laws about collecting.

c. Watch a presentation about reefs. Summarize what you learned about coral reefs.

d. Draw or paint a picture of a reef community with at least ten species.

e. As a group, make a short video about a reef conservation project. Explain why this specific habitat should be saved.

f. Create a 3D diorama of a coral community.

g. A similar project approved by your instructor.

References