Which of the followinf is not an example of using relative density to measure population density in a certain area ?

Options

A. Counting pugmarks of tigers to find population density to tigers in a forest.
B. Counting the number of fishes caught in a trap to find population density of fishes in a lake
C. Measuring biomass of bacterial culture to find out population density of bacteria in a petri dish.
D. Measuring biomass of phytoplanktons in 1 c c water to find out population density of phytoplanktons in a lake.

Explanation

To determine which of the following is not an example of using relative density to measure population density in a certain area, we can analyze each option provided.

1. **Counting of tigers to find population density of tigers in a forest.**
- This method involves direct counting of a specific species (tigers) in a defined area (the forest). It is a valid example of using relative density.

2. **Counting the number of fishes caught in a trap to find the population density of fish in a lake.**
- This method also involves counting a specific species (fish) in a defined area (the lake) based on the number caught in a trap. This is another valid example of using relative density.

3. **Measure of biomass of the sea.**
- This option refers to measuring the biomass, which is a total mass of organisms in a given area, rather than counting individual organisms. Biomass measurement does not provide a direct count of population density and can be challenging to quantify accurately, especially in vast areas like the sea. Therefore, this is not a valid example of using relative density.

4. **Measurement of biomass of phytoplankton in water to find out the population density.**
- Similar to the previous option, this involves measuring biomass. However, phytoplankton can be quantified in terms of density in a water sample, making this a valid example of using relative density.

Based on this analysis, the option that is not an example of using relative density to measure population density is:

**C. Measure of biomass of the sea.**

### Step-by-Step Solution:
1. **Identify the options provided.**
- A: Counting of tigers in a forest.
- B: Counting fish caught in a trap in a lake.
- C: Measure of biomass of the sea.
- D: Measurement of biomass of phytoplankton in water.

2. **Evaluate each option for its relevance to relative density.**
- A: Valid example (direct count of tigers).
- B: Valid example (count of fish caught).
- C: Not a valid example (measuring biomass, not direct count).
- D: Valid example (biomass can be quantified).

3. **Determine which option does not fit the criteria.**
- C is the only option that does not provide a direct count of individuals.