This set of Marine Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Phytoplankton – Set 2”.
1. Diatoms belong to the class _______________
a) Bacillariophyceae
b) Chrysophyceae
c) Chlorophyceae
d) Rhodophyceae
View Answer
Explanation: Diatoms are the most abundant phytoplanktons, belong to the division Bacillariophyceae of Chrysophyta. Diatoms are unicellular, some species however occur in chains or loose aggregates of cells.
2. Diatoms are larger than silicoflagellates and coccolithophores.
a) True
b) False
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Explanation: Diatoms are 15 µm to 1 mm in size, most are between 50 to 500 μm. Diatoms are much larger than members of the division Chrysophyceae i.e the silicoflagellates and coccolithophores.
3. Cell walls of diatoms are composed of __________________
a) collagen, starch
b) pectin, silica
c) calcium carbonate, pectin
d) silica, starch
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Explanation: Cell walls, also called frustules of diatoms are composed of pectin and silica. The frustule contains two halves namely the epitheca and the hypotheca (thicker than the former). Chloroplasts are scattered throughout the cytoplasm and in low-light intensities, they aggregate near the cell ends.
4. Only centric diatoms are capable of locomotion.
a) True
b) False
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Explanation: Depending upon the morphology, diatoms are classified into centric and pennate. Circular, triangular and modified square shapes are centric diatoms, incapable of locomotion. Most benthic forms are usually elongated and display bilateral symmetry, these are capable of locomotion.
5. Diatoms in the auxospore stage can undergo _____________________
a) metamorphosis
b) binary fission
c) fragmentation
d) sexual reproduction
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Explanation: After several rounds of diatom cell division, when cells reach a minimum of 25% of the original size the small diatoms shed their frustules; the naked cell is known as auxospore. The auxospore enlarges and forms new frustule, during the process several auxospores may fuse in a form of sexual reproduction.
6. Which is a characteristic feature of dinoflagellates?
a) Silica cell walls
b) Calcium carbonate shells
c) Cellulose plates
d) Membrane invaginations
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Explanation: Dinoflagellates are unicellular marine organisms with a large nucleus, two flagella and a broad ribbon-like flagellum called horn. In many forms, cell wall consists of irregular plates arranged over the cell surface.
7. In the dinoflagellate Gonyaulax, the maximal light output occurs after ____________________
a) pH drop in seawater
b) algal blooms
c) temperature drop
d) midnight
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Explanation: Gonyaulax catenella is species of dinoflagellate that produces biolumiscence like many other marine organisms. Its maximum light output occurs after midnight and the reproduction (sexual or cell division) also occurs in the dark.
8. Which is a producer of saxitoxin, the causative agent of paralytic shellfish poisoning?
a) Saxodomus
b) Alexandrium
c) Ptychodiscus
d) Pseudonitzschia
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Explanation: Paralytic shellfish poisoning afflicts people who consume toxic butter clams (Saxodomus) which retain the toxin after filter feeding on the dinoflagellate species called Alexandrium.
9. Match the following.
| i. Alexandrium | a) Ciguatera fish poisoning |
| ii. Pseudonitzschia | b) Paralytic shellfish poisoning |
| iii. Gambierdiscus | c) Domoic acid |
| iv. Ptychodiscus | d) Neurotoxin |
a) i-b ii-c iii-a iv-d
b) i-b ii-d iii-c iv-a
c) i-a ii-b iii-c iv-d
d) i-d ii-c iii-b iv-a
View Answer
Explanation: Many members of the Dinophyta cause tidal blooms, shellfish poisoning and other ill-effects. Alexandrium causes paralytic shellfish poisoning by producing saxitoxin, Pseudonitzschia produces domoic acid, Gambierdiscus produces ciguatera toxin and Ptychodiscus is the causative organism of neurotoxic shellfish poisoning.
10. Zooxanthellae are not symbiotically associated with ______________________
a) Corals
b) Sea anemones
c) Dinoflagellates
d) Flatworms
View Answer
Explanation: Zooxanthellae are a specialized group of dinoflagellates symbiotically associated with a wide range of marine animals. Examples of symbiosis of zooxanthallae with corals are common, the former being the provider of various colors found in corals.
Sanfoundry Global Education & Learning Series – Marine Biotechnology.
To practice all areas of Marine Biotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
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