Multi strand Science HOW IS THE GREAT BARRIER REEF MADE? 1. Copy Figure 9. 12 into your book. Include the underwater contours on your map.
How long is The Great Barrier Reef? Where is the reef widest? Where is it narrowest? 2. Why do you think it is called The Great Barrier Reef? Is it really a barrier? The reef got it's name by 'Great' because of it's size and 'Barrier' because it has been built up in front of the coast like some massive barrier. 3. Which factors have set its Northern and Southern extent? The Northern end doesn't extend any further because vast quantities of fresh water and sediment are dumped into the Gulf of Papua by the Fly River. The lower end won't stretch any further southward because large amounts of sand are being washed North along the coast and coral can't survive in sandy water.
4. What do you notice about the ocean depths to the East of the reef? How does this determine the Eastward extent of the reef? Describe what would happen if the ocean level fell 200 m. The reef is very deep towards the East of the reef but in the shallower bits there are lots of patch reefs which if the ocean was to fall 200 m the reefs would die because they would be exposed and they would have to re-adapt. 5.
What is the reef made from? How have changing sea levels affected the reef? The reef is made up of dead coral skeletons, (which make the shape) new coral, water plants and sea animals. When the sea levels where higher the reefs grew upwards, when the sea levels dropped the reef died, when the sea level rose again the new coral grew on top of the old coral. 6. What conditions favour the development of the reefs? What evidence in fig. 9. 12 suggests that this area would be favoured by coral polyps? Reef building corals live best in warm, salty and shallow waters of the tropics.
With our weather conditions the reef should continue to survive well for many years to come. WHAT IS CORAL? 1. Using the information in fig. 9. 13 sketch a coral polyp and on it mark the main parts of it's body.
2. What is the difference between the coral polyp in fig. 9. 13 and soft corals? Which corals build reefs? Which part of the coral polyp helps to build a reef? The difference between a hard corals and soft corals is that a hard coral has a hard shell where as soft coral move around in the water. (sway with the tide) When a hard coral dies a soft coral will attach itself and grow and when it matures form a hard shell. 3.
When do coral polyp feed? On what do they feed? How do they trap their pray? Coral polyp feed at night time on zooplankton and other tiny animals. The polyp catches them with it's waving tentacles. The polyp's tentacles have stinging cells on them which paralyze and collect the zooplankton and tiny animals. The polyp will then eat it's catch. 4. Study the different types of coral in fig.
9. 14 What do you notice about them? Make a sketch of each type. 5. What are zooxanthellae? Why are they so important to the coral polyp? Zooxanthellae are the microscopic plant cells that live in the body tissue of each coral polyp. The zooxanthellae absorbs energy from the sun and passes it to the coral polyp.
6. Fig. 9. 13 shows what happens to the living coral during the day time.
Describe what happens. In the day the food in the polyps sack is digested. The tentacles are withdrawn into the cup. zooxanthellae feed on the waste materials produced by the polyp.
They absorb energy from the sun and pass it to the polyp. 7. Describe how the reef builds up. When coral dies it's had skeleton is left and new coral grows on this. When that coral dies the skeleton will be left and new coral will grow etc. 8.
Use your dictionary to find the meaning of 'colony'. Corals live in colonies. What does this mean? Using the information from fig. 9. 13 describe how colonies are formed.
Colony- A group of similar organisms living close together. A colony of adult polyps let off planulae. The planulae attaches itself to something and new polyp and new colonies form. WHAT DOES THE REEF LOOK LIKE? 1.
Study fig. 9. 15. At which tide was this taken? How can you tell? What danger faces the coral at this time? This photo was taken at low tide as the reef is being exposed above the water. At low tide the reefs are at risk of drying out the coral and killing it.
2. Study figs 9. 12 and 9. 16 (a). Where are ribbon reefs located? What do you notice about their location in relation to the coast? Why are they called ribbon reefs? How where ribbon reefs formed? Why are the waters behind ribbon reefs sheltered? They are positioned in the shallower waters closer to the coast then the patch reefs. The ribbon reef is a long narrow winding section of reef that can over 20 km in length.
3. Study fig. 9. 16 (b). Where have fringing reefs formed? Why is the coral reef on the windward side usually narrower than the than the reef on the leeward side of most continental islands? Fringing reefs are formed in the shallow waters along the sides of continental islands. They are usually narrower on the windward side because they are exposed to the south easterly swell.
The leeward side is sheltered. 4. Study fig. 9. 16 (c). Where have patch reefs formed? Describe their shape.
How are the channels between the reefs formed? Why are the channels kept clear of coral? Patch reefs form in the shallow waters of the continental shelf. They are usually round or oval in shape and grow like a platform. The Channels which separate the patch reefs are formed by the changing tides. Currents generated by the rising and falling of tides keep the channels clear of coral. HOW ARE CAYS FORMED? 1. How are coral colonies broken down? Coral colonies are broken down by destructive waves, certain types of marine life like the crown of thorns starfish, sponges, molluscs, worms and fish also by people trampling on it.
2. Explain how each of the following contribute to the formation of a coral cay (fig. 9. 16): Coral rubble and sand are washed on top of the patch reef by waves.
This rubble then becomes stable as more of it is washed up. Birds come and deposit seed and phosphate other seeds are carried to the cay by the ocean currents. Grasses and creepers that are strong enough o withhold salt spray, strong sunlight and dry conditions grow, this helps to hold the sand together. Soil begins to develop and more and more fresh rain water is trapped beneath the sand, helping shrubs and forests to develop.
1. Copy fig. 9. 19 into your book. In each labelled box write down why each part of the environment is important to the reef.
2. What is a food chain? You may need to use you library to find the answer. The food chain Is he cycle of life that goes around in a circle, the bigger predator feeds on the smaller and the smaller feeds on the bigger when it dies. 3. Draw a series of arrows on your diagram to link the parts of one or more food chain that exist in this environment.
Write a brief summary of each food chain. 4. The great barrier reef has been called one of the biological wonders of the world. What does this mean? This means that it was created naturally (not man made) HOW HAVE PEOPLE USED THE REEF? 1. When did the first people settle along these coastal lands? The first people settled here 40 000 years ago.
2. Why has so much of the early aboriginal culture been lost? Because it was all covered when the sea levels rose. 3. It is said that the aborigines lived in harmony with the coastal environment. What does this mean? This means that they treated the environment as an important part of their life and respected it and lived there lives peacefully in co-existence with it. 4.
How did the aborigines use the reef and its sheltered waters? To gather shellfish, crabs fish and other sea life. 5. Why did early explorers see the coastal waters of the reef as both favourable and unfavourable for shipping? It was bad because a lot of ships where or nearly wrecked there but it was good too because it provided food, a safer passage for shipping and a source of guano and shells. THE CROWN OF THORNS STARFISH 1.
Brei fly describe how the crown of thorns starfish destroys coral reef. It spreads over the live coral, pushes its stomach e out through its mouth and then releases its digestive juices over the polyps. The polyps tissue breaks down and the crown of thorns sucks the 'polyp soup' back into its body. All that is left after this is the white coral skeleton, COMMERCIAL FISHING AND SHIPPING 1. How is commercial fishing on the reef controlled? By having restricted zones for fishing.