formation of organs is

Options

A. Organogenesis
B. Neurogenesis
C. Mesogenesis
D. Notogenesis

Answer

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks about the term used for the formation of organs during the development of an organism.

2. **Gestation Period Overview**: The gestation period in humans lasts approximately nine months and is divided into three trimesters:
- **First Trimester**: From the 1st to the 3rd month.
- **Second Trimester**: From the 4th to the 6th month.
- **Third Trimester**: From the 7th to the 9th month.

3. **Focus on Organ Formation**: The formation of organs occurs primarily during the first trimester of pregnancy. This is when the major organs begin to develop.

4. **Defining Organogenesis**: The specific term for the process of organ formation is called **organogenesis**. This process is crucial as it lays the foundation for the development of the body’s systems.

5. **Clarifying Other Terms**:
- **Neurogenesis** refers to the formation of neurons.
- **Mesogenesis** pertains to the formation of the mesoderm layer.
- **Notogenesis** is related to the formation of the notochord.

6. **Conclusion**: Therefore, the correct answer to the question "formation of organs is called as what?" is **organogenesis**.