The declining phase of a population occurs when

Options

A. Mortality `gt` Natality
B. Natality `gt` Mortality
C. Mortality = Natality
D. Natality = Mortality = 0

Answer

To determine when the declining phase of a population occurs, we need to analyze the relationship between two key factors: natality (birth rate) and mortality (death rate).

### Step-by-Step Solution:

1. **Understanding Natality and Mortality**:
- Natality refers to the number of births in a population during a specific time period.
- Mortality refers to the number of deaths in a population during the same time period.

2. **Identifying Population Growth Factors**:
- Population growth is influenced by four main factors:
- **Natality**: Increases population size.
- **Mortality**: Decreases population size.
- **Immigration**: Influx of individuals into a population, increasing size.
- **Emigration**: Outflux of individuals from a population, decreasing size.

3. **Analyzing the Declining Phase**:
- The declining phase of a population occurs when the number of deaths (mortality) exceeds the number of births (natality).
- Mathematically, this can be represented as:
- Mortality > Natality → Population declines.

4. **Considering Other Scenarios**:
- If natality is greater than mortality, the population will grow.
- If natality equals mortality, the population remains stable.
- If both natality and mortality are zero, the population will not change.

5. **Conclusion**:
- Therefore, the correct condition for a declining phase of a population is when mortality is greater than natality.

### Final Answer:
The declining phase of a population occurs when mortality is greater than natality.

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