back to index ofchapters1. Why would both diatoms and dinoflagellates be called phytoplankton?
Ans. Because they both contain chlorophyll.
2. Seaweed is a general term used to describe all plants that live inthe sea.
Which plants are the true seaweeds?
Ans. Brown algae is a complex marine plant that is commonly called seaweedor incorrectly just called kelp. This type of algae contains the pigmentchlorophyll and another pigment called carotene so it has a brown colour.
How would you classify seagrasses? Explain your answer.
Ans. Seagrasses are plants with roots, stems, leaves and flowers thathave adapted to living completely submerged in sea water. Because they haveflowers, they are classified as angiosperms but they are not related toeither seaweeds or true grasses.
3. What gives brown algae its colour? Why is this chemical importantto the algae?
Ans. Brown algae is a complex marine plant that is commonly called seaweedor incorrectly just called kelp. This type of algae contains the pigmentchlorophyll and another pigment called carotene so it has a brown colour.
4. Describe how seagrasses reproduce.
Ans. Seagrass plants reproduce like flowering land plants, needing theproduction of pollen which will attach itself to other flowers. The floweris then fertilised and seed is produced. The remarkable thing is that, inmany cases, the whole reproductive process occurs underwater, with the releasedpollen drifting in the current. Some seagrasses, however, produce flowerson long stems during low tide and reproduce in much the same way as landplants.
5. Why are seagrasses important to underwater sand banks?
Ans. Seagrasses are the homes for literally thousands of animals, fromthe herbivorous dugong to the smallest of zooplankton. A shortlist of theanimals that seagrass benefits would include fish such as flathead, snails,amphipods, jelly fish, baby prawns, bacteria, shellfish, mussels and babyfish. Without seagrasses, our inshore seas would be like underwater desertsand would not contain the basic food supplies for our billion dollar fishingindustry.
6. List some of the characteristics a plant needs to survive in sanddunes.
Ans. They are low-growing, have wide-spreading roots and leaves thatreduce water loss. Their leaves may be very small, have protective hairs,are coloured silver grey to reflect heat, store water and have a thick waxycoating on their surface. To survive, the roots spread to obtain as muchwater as possible.
7. What is blue-green algae and what causes it to bloom in estuaries?
Ans. Blue-green algae are an advanced form of bacteria which have chlorophyllin their cells. In estuaries that have become polluted with sewage and stormwaterrunoff, these algae grow very quickly and form an algal bloom. These bloomscan cover huge areas of water, often restricting light from penetratinginto the photic zone. This can reduce oxygen levels, killing fish and othermarine life. Blue-green algae can also be poisonous to humans and signsare erected during blooms to warn swimmers.
8. What is a holdfast and what does it look like?
Ans. The holdfast anchors or attaches the seaweed to rocks, corals oreven sand. It varies in shape and size according to where the seaweed grows.Seaweeds found in high wave zones have large sucker-like holdfasts whereascoralline algae have holdfasts to bore between coral polyps to get a hold.(See Figure 175.1)
9. Why are some algae called mortar of the reef?
Ans. Because they cement other living materials such as corals together.Some reefs may be entirely built from encrusting algae and coral polyps.
10. What does the term alternation of generation mean?
Ans. Green algae can reproduce by spores, or by eggs and sperm in a processcalled alternation of generations). The first sexual sporophyte generationproduces a second generation of plants called the gametophyte generation.
The gametophyte generation is either a male or a female and when thetime is right, they release either eggs or sperm which join up again togrow into a sporophyte generation.
Alternation of generations is a common adaptation used by plants to increasethe survival of the species.
11. What are mangroves?
Ans. Mangroves are a group of plants that are tolerant of salt waterand flooding by the tide every 12 hours.
12. Name eight ways marine plants can be conserved.
Ans.
1. Use garden fertiliser sparingly or plant native vegetation that needsno fertiliser.
2. Lobbying government for alternatives to ocean dumping of sewage
3. Support ways to keep stormwater drains clean.
4. When boating, drop anchors in sand rather than in seagrass beds.
5. Never drive power boats in shallow water.
6. Encourage the construction of mangrove walks so people can betterappreciate bird and plant life that lives in these areas.
7. When on the dunes, stick to the marked walking tracks and, if camping,make a common path to the beach for everyone to use.
8. Avoid camping on the primary dune and take all litter home.
1. What is algae used for commercially? How is the algae treated? Whatare the benefits of this product?
Suggestions:
Look on labels in the supermarket for ice cream and algin products. Useyour library encyclopedia.
2. Write to CSIRO Division of Fisheries in Hobart for a brochure on seagrassesand make up a poster.
Suggestions:
Check out their web pages .....
In 1997 their address was:
3. Make a dried algae collection. Research and try to name the more commonalgae that you have collected.
Ans. See the teachers guide to pressing Algae.
4. Obtain some edible seaweed from your teacher. Taste the differentalgae and try to describe its flavour. Find a simple Japanese recipe usingseaweed. Research why seaweed is such a vital part of the Japanese diet.
Suggestions:
Visit your supermarket. Ask an Asian cook to class to talk about Asianfood. Try cooking some. See also Chapter 22.
These are the answers you should have found in the Chapter.
1. producers
2. food
3. Diatoms
4. silica
5. Dinoflagellates
6. flagella
7. Zooxanthellae (zoo-zan-thellie)
8. sugars
9. stipe
10. bend
11. holdfast
12. pollen
13. flower
14. seed