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 regarding the first appearance of a heart in the evolution of animals, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the first appearance of a heart in the evolution of animals. A heart is an organ that pumps blood, and its evolution is significant in the development of circulatory systems in animals.

2. **Reviewing the Options**:
- **Option 1: Annelids**: This group includes segmented worms like earthworms. They have a more complex circulatory system.
- **Option 2: Roundworms**: These organisms have a simpler body structure and rely on diffusion for circulation.
- **Option 3: Arthropods**: This group includes insects and crustaceans, which have an open circulatory system but do not have a true heart like that of annelids.
- **Option 4: Flatworms**: These organisms also use diffusion for nutrient and gas exchange and do not possess a heart.

3. **Analyzing the Circulatory Systems**:
- **Sponges**: They lack a circulatory system and do not have a heart.
- **Flatworms and Roundworms**: Both rely on diffusion for circulation and lack a true heart.
- **Annelids**: They possess a muscular structure that functions as a heart, which is responsible for pumping blood throughout their body. This is the first instance of a heart-like organ in the evolution of animals.

4. **Conclusion**: Based on the analysis, the correct answer is **Option 1: Annelids**, as they are the first group of animals to have a heart-like organ that pumps blood.

### Final Answer:
The heart to pump blood is found for the first time in **Annelids**.

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