In the evolution of animals a heart to pump the blood is found for the first time in

Options

A. Annelids
B. Round worms
C. Arthropods
D. Flat worms

Answer

To answer the question "In the evolution of animals, a heart to pump the blood is found for the first time in," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Circulatory Systems**:
- Circulatory systems are essential for the transport of nutrients, gases, and waste products in animals. There are two main types: open and closed circulatory systems.

2. **Identifying the First Organisms with Circulatory Systems**:
- The first organisms to develop a circulatory system were the annelids (segmented worms), such as earthworms. They have a closed circulatory system, which includes a heart that pumps blood.

3. **Comparing Other Groups**:
- Roundworms (Nematodes) have a more primitive system and do not have a true heart.
- Arthropods (like insects) have an open circulatory system where the blood is not always contained within vessels, and while they do have a heart, it evolved after the annelids.
- Flatworms (Platyhelminthes) do not have a circulatory system at all.

4. **Conclusion**:
- Based on the information, the first organism in the evolutionary timeline to have a heart that pumps blood is the annelid, specifically the earthworm.

### Final Answer:
The heart to pump blood is found for the first time in **annelids (earthworms)**.

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