A petri dish looks like a shallow, clear, circular container, often with a lid.
Petri dishes are essential tools in biology, particularly in microbiology, for culturing cells and observing small organisms. Here's a more detailed description:
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Shape: Typically cylindrical and shallow. The width is significantly larger than its depth.
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Material:
- Plastic: Usually made of clear plastics like polystyrene or polycarbonate. These are often disposable.
- Glass: Borosilicate glass dishes are also available. These are reusable after sterilization.
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Appearance: Transparent, allowing easy observation of the contents.
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Lid: Most petri dishes come with a slightly larger, loose-fitting lid. This lid serves several purposes:
- It prevents airborne contaminants from entering and affecting the culture.
- It reduces evaporation, maintaining a suitable moisture level for the microorganisms.
- It isn't airtight, allowing for gas exchange (e.g., oxygen and carbon dioxide).
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Size: Common sizes range from about 50 mm to 150 mm in diameter, although other sizes are available depending on the application.
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Sterility: Petri dishes used for culturing microorganisms must be sterile to prevent unwanted contamination. Pre-sterilized disposable plastic dishes are widely available.
Here's a summary table:
| Feature | Description |
|---|---|
| Shape | Shallow, circular |
| Material | Clear plastic (polystyrene, polycarbonate) or glass |
| Transparency | Transparent |
| Lid | Loose-fitting, allows gas exchange |
| Purpose | Culturing microorganisms and other cells |
| Sterility | Essential for microbiological applications |
In essence, a petri dish is a simple yet crucial piece of laboratory equipment designed to provide a controlled environment for observing and studying microscopic life.
