Population tagging is good for small groups, but it's tedious work for big groups.
- Independent variable: precision of tagging
- Dependent variable: size of population
- Controlled variables: plate, type of fish, size of ziploc bag
- Control Group: none
- Experimental Group: the whole experiment
How effective is population tagging?
- ziploc bag
- colored goldfish
- paper plate
- Obtain a bowl with your fish
- Do NOT count the number of fish in your pond yet!
- Have one member of your group remove a large handful of fish.
- Count the number of fish you just removed and write it in the table below.
- Replace these fish with "tagged" fish (in this case, colored "fish")
- Mix your pond well to redistribute the tagged fish among the other fish.
- One member at a time (and without looking), remove a handful of fish and record the number of total fish in the sample, the number of tagged fish, and figure out the percentage of tagged fish
- Return your handful to the bowl
- Continue with this until you have taken 20 samples
Observations and data
Analysis and COnclusion
Questions Specific to Lab
- What is the mean (average) of your percent tagged fish from your 20 sample? The average was 36%.
- Using the following formula, determine an estimated population for your pond. The estimated population was 83.
- Now, actually count the number of fish in your bowl. There were 100 fish.
- Find your percentage error by using the following formula. The percentage error was -17%.
- Does this method appear to be an effective way to assess population size? Why or why not? No, because it would take too long to really be accurate, especially if dealing with a big population. However, if the population was small, this method would work fine.
- What concerns should a biologist have about a species' habits before (s)he uses this method to approximate this size of a population? The biologist needs to look at the species' migrating habits, their habitat, and their reproduction rate.
- Evaluate your Hypothesis. The hypothesis was correct. Population tagging would be a great method for small populations that do not reproduce quickly, but a bad one for large populations that reproduce fast.
- Possible sources of error. The only error that could have been made, and that would improve the lab in accuracy, was human miscount. If there was a way the fish could be counted that would guarantee the count to be right every time, the lab could improve significantly. Scientists would know the population without any mistakes in calculation.
- Application. Population counting methods are important to statistics, scientists, and the average person. The discovery of an efficient and flawless method would change the population counting world. Although population tagging might not be a good method for, for example, counting fish, perhaps there is another method that would be better. Censuses seem to work well for counting human population, but if there was a way of finding animal populations through a census, this would probably be the best way to go as far as population counting goes.