Natality is the characteristic of population which means :

Options

A. the total number of individuals present per unit area at a given time.
B. the increase in number of individuals in a population under given environmental conditions.
C. loss of individuals due to death in a population under given environmental conditions
D. the movement of individuals into and out of population.

Answer

To solve the question regarding the meaning of natality in the context of population characteristics, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Term "Natality":**
- Natality refers to the birth rate within a population. It indicates how many individuals are born in a specific period of time.

2. **Analyze the Options Provided:**
- **Option A:** "The total number of individuals present per unit area at a given time."
- This describes population density, not natality.
- **Option B:** "The increase in the number of individuals in a population under a given environmental condition."
- This option aligns with the definition of natality, as it refers to the increase in population due to births.
- **Option C:** "The loss of individuals due to death in a population under given environmental conditions."
- This describes mortality, which is the opposite of natality.
- **Option D:** "The movement of individuals in and out of a population."
- This refers to migration, not natality.

3. **Identify the Correct Answer:**
- Based on the analysis, the correct definition of natality is captured in **Option B**, which states that it is the increase in the number of individuals in a population under given environmental conditions.

### Final Answer:
- **Natality is the characteristic of a population which means the increase in the number of individuals in a population under given environmental conditions.**

---