Use the following description and table to answer the question.
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. The following are data concerning the density (specific gravity) of various components of diatoms, and of their environment.
Specific Gravities of Materials Relevant to Diatoms

Water's density and, consequently, its buoyancy decrease at warmer temperatures. Based on this consideration, and using data from the table above, at which time of year should one expect diatoms to be storing excess calories mostly as oil?
A) mid-winter
B) early spring
C) late summer
D) late fall

Question

Use the following description and table to answer the question.
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. The following are data concerning the density (specific gravity) of various components of diatoms, and of their environment.
Specific Gravities of Materials Relevant to Diatoms

Water's density and, consequently, its buoyancy decrease at warmer temperatures. Based on this consideration, and using data from the table above, at which time of year should one expect diatoms to be storing excess calories mostly as oil?
A) mid-winter 
B) early spring 
C) late summer 
D) late fall

Quizplus · Accepted Answer

Since the buoyancy of water decreases at warmer temperatures, we can infer that the buoyancy of the diatoms' environment will also decrease in the summer months when the water is warmer. Looking at the table, we can see that the specific gravity of oil is lower than that of water, so storing excess calories as oil would be beneficial for buoyancy during this time. Therefore, we should expect diatoms to be storing excess calories mostly as oil in late summer.

Use the Following Description and Table to Answer the Question