Population Dynamics: Wet Lab (Mark-Recapture Sampling)

Purpose of the lab: 

Estimate the numbers of pieces of pasta in a plastic bag by using the Mark-Recapture Sampling technique.

Materials needed for the lab:

• 1 bag of uncooked pasta

• Sharpie markers

Procedures: 

1) A small number (~30) pieces of pasta were "captured" and this number was recorded as (M).

2) A marker was used to indicate the captured population in a recognizable way.
Examples: by painting both ends of the pasta or using a simple letter (A).

3) This captured and marked population was then put back into the general population.

4) With eyes closed, a second random sample of pasta was captured (n) and the number of marked pasta was recorded (m).

5) The estimated size of the general population was then calculated. 

6) Two more trials were been done and more data was collected and recorded.

Calculations:

Estimated number of pieces of pasta (guessed before the lab) - 280 pieces of pasta

Trial One

M = 20    n = 1    m = 46

20/N = 1/46

N = 920     <- Outliner

Trial Two

M = 65    n = 8    m = 72

65/N = 8/72

N = 585

Trial Three

M = 64    n = 8    m = 69

64/N = 8/69

N = 552

Actual Population

558 pieces of pasta

Average population

(920+585+552) / 3 

= 685.6667 = 686

Average population without outliner

(585+552) / 2 

= 568.5 = 569

Percentage Error

| 686-558 | /558 x 100% 

= 23%

Percentage Error without outliner

| 569-558 | /558 x 100% 

= 2%

Photos taken in the lab:

 

 

Analysis:

1)   When comparing the estimated size of the pasta population versus the true size, 
and according to our calculations, we were within 2% (without the outliner).

2a)  The problems that could affect the accuracy of the estimate were: some of the previously marked pasta that may have been recounted and some samples of the pasta may have been lost which affected the count.

2b)  Some problems in outcome results from ecologists studying animal mark-recapture population sampling might be: hardware or software malfunction, tag out of range, lost tag, specimen died from starvation or being eaten.

3)   We can improve the sampling design by marking more pieces of pasta to improve the reliability of the outcome result.