Although total number is generally the most appropriate measure of population density, it is in some cases either meaningless or difficult to determine as in the case of

Although total number is generally the most appropriate measure of population density, it is in some cases either meaningless or difficult to determine. What is the alternative method?

The most appropriate measure of population density is generally

In some cases, population density is measured in terms of biomass rather than in terms of number because

In some cases, population density is measured in terms of biomass rather than in terms of number because