What are the four factors demographers look at to determine population size

Sampling

- counting the number of organisms in a small area and multiplying to estimate the number in a larger area

Mark & Recapture

- capture an organism & release it to remix with population. Then recapture some more in that area to determine population size. Formula is as follows: R (marked recaptures) / C (total in second sample) = M (marked initially) / N (total pop. size)

Indirect Observation -

estimating the population size by tracks, nest or other animal signs in an ecosystem.