Which waste product is generally excreted by diffusion across body surface in ionic form?

Options

A. Urea
B. Ammonia
C. Uric acid
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about a waste product that is excreted by diffusion across the body surface in ionic form. This implies that we are looking for a substance that is released from the body without the need for specialized excretory organs.

2. **Identifying Common Waste Products**: In biological systems, common waste products include urea, ammonia, carbon dioxide, and salts. Among these, we need to focus on which of these can be excreted in ionic form and through diffusion.

3. **Analyzing Ammonia**: Ammonia (NH3) is a highly toxic waste product that is produced from the breakdown of proteins. It is often converted to urea in mammals for safer excretion. However, ammonia can diffuse across cell membranes and is often excreted directly by aquatic organisms.

4. **Considering Salts**: Salts, such as sodium ions (Na+) and chloride ions (Cl-), can also be excreted through diffusion. Many aquatic organisms, such as fish, excrete excess salts directly through their skin and gills in ionic form.

5. **Conclusion**: The waste product that is generally excreted by diffusion across the body surface in ionic form is primarily **salts**. Aquatic organisms utilize this method to maintain osmotic balance and eliminate excess ions.

**Final Answer**: Salts (in ionic form) are generally excreted by diffusion across the body surface.

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