In which organisms external fertilization occurs:

Options

A. Echinodermata/Moss
B. Hemichordata / Fern
C. Reptila/ Gymnosperm
D. Amphibia / Algae

Answer

**Step-by-Step Solution:**

1. **Understand the Concept of Fertilization:**
- Fertilization is the process where male and female gametes fuse to form a zygote. It can occur either internally (inside the female body) or externally (outside the body in an external medium).

2. **Define External Fertilization:**
- External fertilization occurs when fertilization takes place in an external medium, typically water. This is common in aquatic environments.

3. **Identify Organisms that Exhibit External Fertilization:**
- External fertilization is primarily found in aquatic organisms. Examples include:
- **Aquatic Amphibians:** Many amphibians, such as frogs, lay their eggs in water where fertilization occurs outside the female's body.
- **Algae:** Many species of algae also reproduce through external fertilization, where gametes are released into the water.

4. **Differentiate from Other Groups:**
- It is important to note that other groups such as reptiles, gymnosperms, hemichordates, ferns, echinoderms, and mosses typically exhibit internal fertilization, where fertilization occurs inside the female body.

5. **Conclusion:**
- Based on the above points, the organisms that exhibit external fertilization are primarily amphibians (specifically aquatic ones) and algae.

**Final Answer:**
- The organisms in which external fertilization occurs are amphibians (aquatic) and algae.

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