Question:
The microscopic image of organism was analyzed in a drowning case. Which is correct about them
The microscopic image of organism was analyzed in a drowning case. Which is correct about them
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Diatoms in a drowning case are silica-walled, chlorophyll-bearing algae — acid- and heat-resistant, which is why the diatom test works.
Updated On: Aug 27, 2026
- Contains silica & chlorophyll point
- Are microscopic unicellular bacteria
- Present only in bone marrow
- Are not resistant to acids & heat
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The Correct Option is A
Solution and Explanation
Step 1: Identify the organism. The microscopic image in a drowning case showing an elongate, boat/spindle-shaped structure with an ornamented, symmetrically patterned shell (frustule) is a diatom. The diatom test is a classic forensic investigation used to support a diagnosis of antemortem drowning - diatoms inhaled/swallowed with water enter the circulation and are deposited in organs such as the bone marrow, lungs, liver and kidney.
Step 2: Recall the biology of diatoms. Diatoms are unicellular photosynthetic algae. Two key features: (i) they possess chlorophyll (hence they are photosynthetic, found in natural water bodies), and (ii) their cell wall (frustule) is made of silica (silicon dioxide). Because the wall is silica, diatoms are highly resistant to acids and heat - this is exactly why acid-digestion of tissues is used to recover them in the diatom test. Thus the true statement is option (A): they contain silica and chlorophyll.
Step 3: Why the other options are wrong.
• (B) Microscopic unicellular bacteria - false; diatoms are eukaryotic algae (protists), not bacteria.
• (C) Present only in bone marrow - false; in drowning, diatoms are found in many organs (lung, liver, kidney, brain, bone marrow). Bone marrow is a preferred site for the test (its remoteness reduces contamination) but they are not present "only" there, and in nature diatoms live in water, not in marrow.
• (D) Not resistant to acids & heat - false; the silica frustule makes diatoms resistant to strong acids and heat, which is the very basis of the acid-digestion recovery technique.
Final answer: Option A - Contains silica & chlorophyll.
Step 2: Recall the biology of diatoms. Diatoms are unicellular photosynthetic algae. Two key features: (i) they possess chlorophyll (hence they are photosynthetic, found in natural water bodies), and (ii) their cell wall (frustule) is made of silica (silicon dioxide). Because the wall is silica, diatoms are highly resistant to acids and heat - this is exactly why acid-digestion of tissues is used to recover them in the diatom test. Thus the true statement is option (A): they contain silica and chlorophyll.
Step 3: Why the other options are wrong.
• (B) Microscopic unicellular bacteria - false; diatoms are eukaryotic algae (protists), not bacteria.
• (C) Present only in bone marrow - false; in drowning, diatoms are found in many organs (lung, liver, kidney, brain, bone marrow). Bone marrow is a preferred site for the test (its remoteness reduces contamination) but they are not present "only" there, and in nature diatoms live in water, not in marrow.
• (D) Not resistant to acids & heat - false; the silica frustule makes diatoms resistant to strong acids and heat, which is the very basis of the acid-digestion recovery technique.
Final answer: Option A - Contains silica & chlorophyll.
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