Mark and Recapture

Essential Question
How do scientists keep track of populations in different species?

Objectives

 * Estimate populations of different species using the mark and recapture technique
 * Distinguish between population counting techniques and marking to different species and environments

Introduction & Student Background
What species are common, or rare, in your local area? How would you be able to count plants or trees, in comparison to animals? This method of estimating populations of species, called mark and recapture, addresses that issue. (Above questions can be used to introduce topic to students)

In this activity, students will use Starburst (or a similar object/candy) to model individuals of a population. They will count the number of individuals captured from a candy jar and then 'mark' each organism/candy. The individuals captured will then be returned, the jar of candy will be mixed, and students will then capture a second set of individuals. Using a ratio, they will determine the total number of populations in the environment.

Materials

 * Bag of Starburst/similar candy/object
 * Sharpies (3+ colors)
 * Half sheet chart/paper (print out)
 * Simple calculator
 * Pencils
 * Tub/Jar for Starburst

PREP

 * 1) Put the starburst in the jar or tub. Pack it in loosely enough so you can stir the mixture later.
 * 2) Lay out the half sheet chart, pencil and calculator in one area/table setting size each.

ACTIVITY

 * 1) Have students initially guess how many Starbursts are in the jar and write down their prediction. Ask them how they came to this conclusion.
 * 2) Explain about the various complications of tracking a highly moveable population or a very large population.
 * 3) Have students grab up to a handful of starburst m. Record the amount of starburst and use a sharpie to distinctly mark each every one of them.
 * 4) Put the marked starburst  back into the jar/container.
 * 5) Have the students mix the Starbursts around with with a stick.
 * 6) After thoroughly mixing the Starbursts, have students draw out another group of Starbursts. Count how many of the Starbursts were in the original group (how many are marked) out of the total.
 * 7) Set the ratio: total marked/total population to marked in second group/total in second group. Solve for the total population.

How it fits to Standard

 * Carry out investigations by using instruments, observing, recording, and drawing evidence-based conclusions

Follow Up
Ask students about which animals they would use this method in and how they would mark them (leg band, colored fur, etc). How would this affect the animals lifestyle, if at all.