Question:medium
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
Show Hint
Diatoms in a drowning case are silica-walled, chlorophyll-bearing algae — acid- and heat-resistant, which is why the diatom test works.
Updated On: Jun 22, 2026
- Contains silica & chlorophyll point
- Are microscopic unicellular bacteria
- Present only in bone marrow
- Are not resistant to acids & heat
Show Solution
The Correct Option is A
Solution and Explanation
Structure-and-forensics approach.
The picture - a symmetrical, finely ornamented, boat-shaped shell viewed under the microscope in a suspected drowning - is a diatom, and the question is testing what diatoms actually are.
Diatoms are unicellular eukaryotic algae that live in fresh and marine water. Two properties define them and explain their forensic use:
1. They are photosynthetic, so they contain chlorophyll.
2. Their rigid outer cell wall, the frustule, is built of hydrated silica (SiO$_2$).
Both of these match option $A$ ($silica$ and $chlorophyll$), which is therefore correct.
The silica shell is also the reason for the famous acid-digestion diatom test: tissue (classically bone marrow of a long bone, plus lung/liver/kidney) is dissolved in strong acid; the soft tissue is destroyed but the acid- and heat-resistant silica frustules survive and can be counted under the microscope. Recovery of diatoms matching those in the drowning water supports antemortem drowning.
This directly disproves the other choices:
• $B$ - they are algae (protists), not bacteria.
• $C$ - they are found in multiple organs, not only in bone marrow (marrow is just the favoured sampling site).
• $D$ - the silica wall makes them resistant to acid and heat, so saying they are not resistant is false.
Correct option: A - Contains silica & chlorophyll.
The picture - a symmetrical, finely ornamented, boat-shaped shell viewed under the microscope in a suspected drowning - is a diatom, and the question is testing what diatoms actually are.
Diatoms are unicellular eukaryotic algae that live in fresh and marine water. Two properties define them and explain their forensic use:
1. They are photosynthetic, so they contain chlorophyll.
2. Their rigid outer cell wall, the frustule, is built of hydrated silica (SiO$_2$).
Both of these match option $A$ ($silica$ and $chlorophyll$), which is therefore correct.
The silica shell is also the reason for the famous acid-digestion diatom test: tissue (classically bone marrow of a long bone, plus lung/liver/kidney) is dissolved in strong acid; the soft tissue is destroyed but the acid- and heat-resistant silica frustules survive and can be counted under the microscope. Recovery of diatoms matching those in the drowning water supports antemortem drowning.
This directly disproves the other choices:
• $B$ - they are algae (protists), not bacteria.
• $C$ - they are found in multiple organs, not only in bone marrow (marrow is just the favoured sampling site).
• $D$ - the silica wall makes them resistant to acid and heat, so saying they are not resistant is false.
Correct option: A - Contains silica & chlorophyll.
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