Diatoms and Silica
டயட்டம்கள் மற்றும் சிலிக்கா
Diatoms are the primary producers of the ocean, yet they are essentially living glass. Their cell walls are impregnated with silica, making them indestructible by biological decay. If you think they are just 'algae,' you are losing marks.
The idea
Diatoms belong to the group Chrysophytes. Their cell walls form two thin overlapping shells that fit together like a soap box. These walls are embedded with silica, making them indestructible. Over billions of years, these deposits accumulate to form 'diatomaceous earth'.
Why it matters
The silica-embedded wall provides structural protection and durability, allowing them to survive and accumulate in aquatic environments.
NEET lens
NEET focuses on the 'soap box' analogy and the chemical composition of the cell wall. Remember: they are photosynthetic and chief producers. Do not confuse them with Dinoflagellates; focus on the silica deposition.
Clinical significance
Diatomaceous earth is highly abrasive and absorbent, used in filtration systems for antibiotics and sugar refining. In forensic medicine, the presence of diatoms in bone marrow is the gold standard for diagnosing death by drowning.
Introduction
Diatoms build their cell walls from silicon dioxide — the same material as glass. Each cell is enclosed in a two-part silica case called a frustule, one half fitting over the other like a Petri dish. Under a microscope, the geometric precision — hexagons, radial symmetry, intricate lattices — is extraordinary. When diatoms die, their frustules sink and accumulate over millions of years into diatomite, mined and used as a filtration medium, insecticide, and abrasive.
Core concept
Diatoms: unicellular, photosynthetic algae in Kingdom Protista (Chrysophytes). Key NEET features:Cell wall (frustule) made of silica (SiO2) — two overlapping halvesBoth freshwater and marine; chief producers in aquatic ecosystemsPigments: chlorophyll a, chlorophyll c, fucoxanthin (golden/brown colour)Food reserve: chrysolaminarinAccumulated dead walls = diatomite or kieselguhrUses of diatomite: filtration (swimming pools, beverages), mild abrasive (toothpaste), insecticide (damages insect cuticle).
Go deeper
Diatoms account for approximately 20–25% of all oxygen produced on Earth annually and fix the same proportion of global carbon. Diatomite was used by Alfred Nobel as an absorbent for nitroglycerin in dynamite — a historical fact that occasionally surfaces in NEET context questions.
From Class 10
In Class 10, you did not study diatoms formally. In Class 11, they emerge as one of the most important groups on Earth — photosynthetically dominant in the oceans, with cell walls made not of cellulose or chitin but of silica.