Which of the following best describes the algae known as diatoms?
a. Cells have intricate shells of silicon dioxide with two halves
b. Cells contain carotenoid pigments as well as chlorophyll A and B
c. Cells are encased in rigid walls composed of cellulose coated with silicon
d. Cells have flagella and a light-detecting eye spot
The correct answer and explanation is:
The correct answer is: a. Cells have intricate shells of silicon dioxide with two halves.
Explanation:
Diatoms are a type of algae known for their distinct and intricate silica (silicon dioxide) shells. These shells, also called frustules, are made of two interlocking halves, similar to a petri dish. The upper half fits into the lower half, and together they form a protective casing for the cell. The silica composition of the frustule gives diatoms their unique, often geometric appearance. This outer shell is an essential feature of diatoms and is used for protection, buoyancy, and regulation of the cell’s internal environment.
The silica structure of diatoms is incredibly diverse, with species exhibiting a wide range of patterns and shapes. The intricate and often highly ornate patterns can vary greatly between species, making them a subject of scientific study and artistic inspiration. This silica shell is highly resistant to decay, which is why diatomaceous earth, a substance made from fossilized diatom frustules, has been used in a variety of applications, including as a filtering material and abrasive.
Diatoms are also photosynthetic organisms, meaning they use sunlight to convert carbon dioxide and water into glucose and oxygen. The pigments they contain include chlorophyll a, along with other pigments like fucoxanthin, which helps them absorb light efficiently. However, the defining characteristic that sets them apart from other algae is their unique silica shell, not the presence of specific pigments or flagella.
Diatoms play a critical role in aquatic ecosystems, contributing to a significant portion of global oxygen production through photosynthesis and serving as a primary food source for many marine organisms.