Open type of circulatroy system is seen in all of the following except

Options

A. Hemichordata
B. Arthropoda
C. Mollusca
D. Annelida

Answer

To solve the question "Open type of circulatory system is seen in all of the following except," we will follow these steps:

### Step 1: Understand the Types of Circulatory Systems
- There are two main types of circulatory systems: open and closed.
- **Open circulatory system**: Blood is not confined to blood vessels and is pumped into the body cavity, bathing the organs directly.
- **Closed circulatory system**: Blood is contained within blood vessels, allowing for more efficient transport of nutrients and gases.

**Hint**: Remember the definitions of open and closed circulatory systems, as they are crucial for identifying the organisms.

### Step 2: Identify Organisms with Open Circulatory Systems
- Common examples of organisms with an open circulatory system include:
- **Arthropoda**: This group includes insects, arachnids, and crustaceans.
- **Mollusca**: This group includes snails, clams, and squids.
- **Hemicorata**: This group also has an open circulatory system.

**Hint**: Think of common animals in these groups to help recall their circulatory systems.

### Step 3: Identify Organisms with Closed Circulatory Systems
- An example of an organism with a closed circulatory system is:
- **Annelida**: This group includes earthworms and leeches, which have blood contained within vessels.

**Hint**: Focus on the characteristics of annelids to remember that they have a closed circulatory system.

### Step 4: Analyze the Options Given
- The options provided are:
1. Hemicorata (open)
2. Arthropoda (open)
3. Mollusca (open)
4. Annelida (closed)

**Hint**: Compare each option to the definitions of open and closed circulatory systems.

### Step 5: Determine the Correct Answer
- Since hemicorata, arthropoda, and mollusca all have open circulatory systems, the only group that does not is **Annelida**.

**Final Answer**: The correct answer is **Annelida**, as it does not have an open type of circulatory system.