What is the closed circulatory system? Name two groups of animals having this types of circulation.

Explanation

### Step-by-Step Solution:

1. **Definition of Closed Circulatory System**:
- A closed circulatory system is a type of circulatory system in which the blood is contained within a network of blood vessels. The heart pumps the blood through these vessels, allowing it to reach various organs and tissues in the body.

2. **Comparison with Open Circulatory System**:
- In contrast to a closed circulatory system, an open circulatory system allows blood to flow freely within the body cavity, where it directly bathes the organs. In this system, blood is not confined to blood vessels.

...