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A factory that makes cooking oil filters the oil through a bed of white powder called diatomaceous…
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A factory that makes cooking oil filters the oil through a bed of white powder called diatomaceous earth. What is this powder made of, and why does it last for millions of years? Why are diatoms called the chief producers of the oceans?
Need a reminder? The key ideaShow
Kingdom Protista holds the single-celled eukaryotes. Chrysophytes (diatoms) have walls of silica in two shells and form diatomaceous earth. Dinoflagellates have cellulose plates and two flagella; red ones such as Gonyaulax cause red tides. Euglenoids have a protein pellicle, no wall, and make food in light but eat in the dark. Slime moulds are saprophytes that form a plasmodium and spores.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The powder. It is made of the walls of dead diatoms, which pile up on the sea floor over very long times.
Step 2. Why it lasts. The walls hold silica, so they are practically indestructible.
Step 3. Its uses. The gritty powder is used for polishing and for filtering oils and syrups.
Step 4. Producers. Diatoms float in huge numbers and make food by photosynthesis, so they feed the food chains of the sea.
Answer: diatom walls of silica; silica does not decay; diatoms make most of the food in the oceans.
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