Determining Population Sizes

4 Ways of Determining Population Size Direct Observation Indirect Observation Random Sampling Mark-and-recapture study

Direct Observation Definition to count each and every organism of a population in an area. Pros Exact population count Cons May take a long time Example Counting all of the crabs that live in a tide pool

Indirect Observation Definition to observe signs of an organism rather than the organism itself. Pros Not as time consuming Cons Evidence of an organism does not tell you exactly how many there are; may be inaccurate Example Counting the number of nesting sites in an area

Random Sampling Definition Finding a method of randomly choosing individuals and then multiplying the number of individuals by the area Pros Fast data collection Cons Inaccuracy Example Count the number of penguins in a small area, then multiply to find the number ion the entire colony.

Mark-and-recapture Study Definition to catch, mark, release and recapture an organism. Then use mathematical formulas to estimate the total population. Pros Accurate Cons Expensive, time consuming Example Counting hawks with bands of their legs

Sea turtle mark-and-recapture lab