The Following Questions Refer to the Description and Table 28

question 20

Multiple Choice

The following questions refer to the description and Table 28.1 below.
Diatoms are encased in Petri-plate-like cases (valves) made of translucent hydrated silica whose thickness can be varied. The material used to store excess calories can also be varied. At certain times, diatoms store excess calories in the form of the liquid polysaccharide, laminarin, and at other times, as oil. Below are data concerning the density (specific gravity) of various components of diatoms, and of their environment.
Table 28.1: Specific Gravities of Materials Relevant to Diatoms
$$\begin{array} { l l } \text { Material } & \text { Specific Gravity } ( \mathrm { kg } / / \mathrm { m }^{3} ) \\\text { Pure water } & 1000 \\\text { Seawater } & 1026 \\\text { Hydrated silica } & 2250 \\\text { Liquid laminarin } & 1500 \\\text { Diatom oil } & 910\end{array}$$
-Theoretically, which two of the following present the richest potential sources of silica?
1) marine sediments consisting of foram tests
2) marine sediments consisting of diatom cases (valves)
3) marine sediments consisting of radiolarian shells
4) marine sediments consisting of dinoflagellate plates

• A)1 and 2
• B)1 and 4
• C)2 and 3
• D)2 and 4
• E)3 and 4

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