Question

Which of the following is not an example of using relative density to measure population density in a certain area?
A.Counting pugs’ marks of tiger to find population density of tigers 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 cc water to find out population density of phytoplanktons in a lake.

Answer 1

Hint: In ecology, before talking about population density, we must know what is population and population size and population density.
Population is a group of individuals, belonging to the same species, living in a particular area for a particular time.

Complete step by step answer:
-Population size is the actual number of individuals within a population and population density is the number of individuals per unit area, i.e., population size by total land area.
-But sometimes, actual or absolute density is not necessary and possible to calculate the population density. At this place, relative density helps equally to find the population density.
For instance, Tiger pug marks and the fecal pellets are the footprints of animals that help to know the density of their population. Similarly, the number of fishes inside the trap is good enough to measure the population density of fishes in lack.
-1 cc is cubic centimeters, which means unit volume of water. So counting the approximate number of phytoplankton in this particular amount of water can give the measurement of population density of the phytoplankton in the water body.

Hence option D is correct.

Note:
In the case of bacterial biomass measurement from bacterial culture can be very time consuming and difficult to do. As bacteria do have rapid growth in a short period of time. Which causes them to increase in a large number, which is difficult to count them in a unit area to measure the population density of them.