A species-area relation is used by ecologists to -

Options

A. Determine the population density of a species in a certain habitat
B. Examine how hunian populations are growing
C. Estimate the number of species extinctions resulting from habitat destruction
D. None

Answer

### Step-by-Step Solution:

1. **Understanding the Species-Area Relationship**: The species-area relationship is a fundamental ecological principle that describes how the number of species (species richness) increases with the area of habitat available. This relationship is often represented mathematically and graphically.

2. **Identifying the Key Ecologist**: The concept of the species-area relationship was notably articulated by the ecologist Alexander von Humboldt. He provided a mathematical model that relates species richness (S) to the area (A) of a habitat.

3. **Mathematical Representation**: The species-area relationship can be expressed with the formula:
\[ S = C \cdot A^Z \]
When transformed into logarithmic form, it becomes:
\[ \log S = \log C + Z \log A \]
Here, S is the number of species, A is the area, C is a constant, and Z is the slope of the line when plotted on a log-log graph.

4. **Interpreting the Graph**: The graph of the species-area relationship typically shows that as the area increases, the number of species also increases, indicating a positive correlation between area and species richness.

5. **Evaluating Statements**:
- **First Statement**: "Determine the population density of species in a certain habitat." This is incorrect as the species-area relationship focuses on species richness, not population density.
- **Second Statement**: "Examine how human population affects species." This is also incorrect since the species-area relationship does not directly address human population dynamics.
- **Third Statement**: "Estimate the number of species extinction resulting from habitat destruction." This statement is correct. As habitat area decreases due to destruction, species richness is expected to decline, leading to potential extinctions.

6. **Conclusion**: The correct use of the species-area relationship by ecologists is to estimate the number of species extinction resulting from habitat destruction, confirming that loss of area leads to loss of species richness.