Diatomaceous earth filter media is the fossil-like skeleton of microscopic plants called ________.

Diatomaceous earth filter media is derived from the fossilized remains of diatoms, which are a type of microscopic algae. Diatoms are characterized by their unique silica cell walls, giving them a distinct skeletal structure that becomes the filter media once they accumulate and fossilize. This material is highly effective in filtration processes, particularly due to its porous nature, which allows for the capture of fine particles and impurities from liquids, such as water.

In this context, diatoms are significant because they contribute to the ecological balance in aquatic environments and are essential in various industrial applications, including water treatment. This specific relationship between diatoms and the production of diatomaceous earth is what makes the correct answer relevant for understanding filtration processes and the material used within them.