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There are many exciting methods to count populations. Each method has advantages and disadvantages. Some are accurate, some are fast, and some are fun. In this activity, you will be counting "red oak acorns." This may vary based on your species availability on or near your school grounds.

OBJECTIVE / OUTCOME

When you have completed this activity, you will be able to:

1. Count a population using 3 different methods.

2. Identify the pro and con points of population counting methods.

1. 1 lb. coffee can filled with your seeds/acorns.

2. Beaker, 50 ml.

3. Beaker, 400 ml.

4. Marking pen or crayon

Random Sampling (method #1)

1. Measure 50 ml. of your seeds/acorns. Carefully count and record this number.

2. Return the acorns to the can.

3. Pour the acorns from the can into the 400 ml. beaker, and measure this volume to the nearest 50 ml.

4. Determine the population factor. If the volume of acorns is 350 ml., then the population factor is seven. If the volume is 300 ml., then the population factor is six, and so on. Record this your population factor.

The population is equal to the count times the population factor.

____________ x ____________ = _______________ 

     (count)              (pop. factor)          (total population)

Lincoln Index (method #2)

The Lincoln Index is a method used to count populations based on proportions. In this procedure, specimens are collected, marked, and released back into the environment unharmed. Specimens are recollected, counted, and the marked specimens are identified and counted.

The total population is calculated using the following formula:

P:M  =  p:m     where     P  =  total population

        M  =  total sample in 1st collection

        p  =  total sample in 2nd collection

        m  =  # of marked individuals in 2nd collection

Example: A fisherman catches 35 trout in a pond. He marks and releases them. Later, he catches 20 trout, 10 of which have marks. Using the Lincoln Index, the trout population of the pond can be determined in the following manner.

P (total population) : M(35)  =  p(20) : m (10)

10P  =  35 x 20

P = 35 x 20

          10

P = 700

        10

P = 70

Calculate the population of your acorns in the following manner using the Lincoln Index:

Grab a small handful from your can and remove them. Using a marker, mark each kernel with a mark you can identify. Count them and return to the can. Record this number as M________. Put on the lid and shake the can. This helps the redistribution of the "organisms." Grab another handful of acorns, count them, and record this number as p________. Check the acorns in the second handful for marks. Count the number with marks and record them as m________. Using this information to calculate the population of acorns using the Lincoln Index.

P: M (______) = p (______) : m (______)

m (______) P = M (______) x p (______)

P = M (______) x p (______) / m (_______)

P = ____________________

Census Method

The census method is a simple count. Count and record the number of acorns in your can and record

1 .Which method of counting populations is most accurate?

2. Which method of counting populations is the fastest?

3. How accurate was the Lincoln Index compared to the other methods?

4. Why couldn't you use a census method on animals such as mice or squirrels?

5. Name some ways that you could mark animals without harming them. For example: birds, fish, and insects.

6. List some different organisms that would be best suited for each method of study.

7. Which technique would allow us to most accurately count our collected acorn population?

1. Depending on the number of acorns that your class has collected, you may want to use buckets, tubs, or milk jugs instead of 1 lb. coffee cans. The milk jugs allow for a controlled pour of your sample.

2. Acorns can easily be thrown, rolled, or lost. Monitor any "horseplay."

3. Contain your spilling acorns using a case beverage box or trays.

4. Playing background music during activities is a good idea. You can control:

A) Classroom noise level

B) Time your activity using timed length of songs selected.

C) Motivation and interest.

The "Chipmunks" songs can be fun as well as bluegrass pickin' and grinnin' tunes.

       The Forest Conservancy District Board for Baltimore County

9405 Old Harford Road

Baltimore, Maryland 21234

(410) 665-5820 

Email Robert Prenger ....... rprenger@dnr.state.md.us

 Melvin Noland ....... mlnoland@bcpl.net