Fertilisation and development in hemichordates are respectively

Options

A. External and indirect
B. Internal and direct
C. External and direct
D. Internal and indirect

Answer

To answer the question regarding fertilization and development in hemichordates, we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Hemichordates**:
- Hemichordates are marine animals characterized by the presence of a true body cavity (coelom). Their body is divided into three main parts: the proboscis, collar, and trunk.

2. **Fertilization in Hemichordates**:
- Most hemichordates reproduce sexually through **external fertilization**. This means that fertilization occurs outside the female's body.
- In this process, the female releases eggs into the water, and the male simultaneously releases sperm in the same area. The fertilization of eggs occurs in the aquatic environment.

3. **Development in Hemichordates**:
- The development of hemichordates is classified as **indirect development**. This means that after fertilization, the embryo undergoes several larval stages before transforming into the adult form.
- During indirect development, the organism goes through a process called metamorphosis, where it changes from a larval stage to an adult stage.

4. **Conclusion**:
- Based on the understanding of fertilization and development in hemichordates, we conclude that the correct answer to the question is that fertilization is **external** and development is **indirect**.

### Final Answer:
Fertilization and development in hemichordates are respectively **external and indirect** (Option 1).

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