1. Do Now:
Open notebook to lab section. Write the title of the lab, “Studying Population Size Lab”.
Write the date.
Answer this question…
A plane crashes into the Colorado landscape disturbing a population of aspen trees. The plane leaked fuel and its engine caught on fire. How would you know if the plane crash affected the aspen population after one year and beyond.

2. Period 8 Responses
Measure population size after the crash hoping to compare with previous population size
Observe the growing patterns in crash site after and compare to unaffected areas
Observe the physical features of trees after the crash and compare them to unaffected areas: height after development, leaf color and size, etc
To support a claim, data must be collected and compared with
Existing information. Ecologists will look for similarities and differences.

3. Getting Data: Ecologists Use Population Size
Complete Count
Incomplete Count
Counts EVERY member of a population
Uses direct or indirect ways to estimate population size
“Estimate” – not actual
Direct means using the individual organisms
Indirect means using items related to the life of the organisms in the population
Click on the You Count link. Watch video. What type of count is it about? Method?
You Count

4. Studying Population Size: Two Part Lab
Chapter 36 Estimating Population Size
Studying Population Size: Two Part Lab
Write name and partner’s name on the lab.
Pencil is recommended.
Read and follow directions step by step.
Listen for teacher clarifications during the lab.
Let’s begin…

5. Quadrat Method: Answer questions under the data tables
Why was the paper-slip method used to select the grid segment?
How does the total # sunflowers obtained from sampling compare with actual #?
What would make you not feel confident with your quadrat method count? Think about factors which could cause the estimate to be off.

6. Do Now
Last class, you used the quadrat method of sampling. What dispersion pattern would give you the best estimate of population size? Explain.

7. Part 1 Quadrant Method Lab

8. Quadrat Method (Random Sampling)
Quadrats are small plots, of uniform shape and size, placed in randomly selected sites. They do not have to be square shaped.
By counting the number of individuals within each sampling plot, we can see how the density of individuals changes from one part of the habitat to another. Why would you do this? Performing the Quadrat Method
The density can then be used to estimate the population size using the data from the quadrat method:
Population size can then be estimated using the formula:
N = (A/a) * n
where:
N = the estimated total population size
A = the total study area
a = the area of the quadrat
n = the number of organisms per quadrat

9. Sampling Technique
Quadrat Method Video link
*Organisms in a few small areas are counted for determining density – infer about biodiversity of an area Biodiversity is the amount of variety of organisms within a given area…. *Used on organisms that are usually sessile animals or plants

10. Review for Lab Test
List the three different dispersion patterns and describe each, give example.
State the purpose of the Quadrat Method lab and understand the procedure
Be able to calculate population size and density
Understand conditions that would give the best estimates for the quadrat method
Define biodiversity
Anything else?

11. Part 2: Mark and Recapture Lab
Another method to estimate population size

12. Mark and Recapture Overview
Chapter 36 Estimating Population Size
Mark and Recapture Overview
Used for organisms which are mobile
Involves marking a sample of individuals from a given population and placing them back into the population AND then obtain subsequent samples in which the number of marked individuals are counted.
Uses the number of marked individuals from a subsequent sample to estimate population size.
Video on the Method

13. Mark & Recapture Assumptions
Nothing happens to upset the proportions of marked to unmarked individuals. The population is a “closed” system.
Chance of capturing a marked or unmarked individual is equal.
Individuals do not lose their marks or tags.
There is a sufficient or appropriate amount of time between sampling.
If the four assumptions are made, then one can feel comfortable with the estimate population size using the Mark and Recapture Technique

14. DO NOW: For each assumption, can you describe one or two specific ways during the lab when each assumption did not hold true
“Closed” system
Equal chance for capture
Remained marked
Time between sampling is appropriated.

15. DO NOW AGAIN: For each assumption, can you describe one or two specific ways when each assumption would not hold true for a real bird population
“Closed” system
Equal chance for capture
Remained marked
Time between sampling is appropriated.

16. Actual population size = 32
Increasing the number of Trial Notes: “What do the two estimated population sizes tell us about data collecting?”
Looking at the data… Which number pair reflects the data you obtained? Did your estimated population value increase, decrease or stay the same?
31, , , 25
First number represents estimated population size after 10 trials; second number is after 20 trials.
Actual population size = 32
Question: Is there a difference between the 10 trials and the 20 trials estimates? How do they compare to the actual?
To answer this, you need the actual count. For this example, the actual count is 32 birds in the population. Now answer, the question by comparing the trial values to the actual value.
*The values were 31 and 31. It appears that the number of trials does not make a difference.
*The values were 28 and 31. It appears that the number of trials brings the estimated population number closer to the actual number.
* The values were 29 and 25. It appears that the number of trials moves the estimated population number further away from the actual number.
In theory, the greater the number of trials, the closer one gets to the actual value because the total number of individuals (birds) in the sample gets larger. By making the sample size get larger, one minimizes the outside influences.

17. Part 1 Mark and Recapture Technique Conclusion:
Estimating population size must take into account the behavior of the organisms, where the organisms live, the way in which the organisms live, mathematical principles, and scientific methods.

18. Where are population counts happening today. For your own interest
Where are population counts happening today? For your own interest! African elephants are threatened by habitat loss and by poaching to support the ivory trade. Conservation groups estimate that as many as 100 elephants are killed each day, so it is critically important to determine how many elephants remain and where they are. Scientists involved in the Great Elephant Census project (founded and managed by philanthropist Paul G. Allen) are conducting aerial surveys across millions of square kilometers to obtain accurate elephant census data. This video describes the strip transect sampling method they are using and how elephants are counted.
Click on this link: HHMI Great Elephant Census

19. Preparing for the Mark and Recapture Lab Test: Can you…
State the reason for doing the lab
Describe how the lab simulated the mark and recapture technique
Calculate and explain the purpose of the percent error
If given sample data for a given population, determine the estimated population size using the Lincoln-Petersen formula
Apply knowledge about the M & R to new situations
Recall the three types of dispersion pattern
Solve estimating population size problems: Using both Quadrat and Mark & Recapture Technique
Lab Test on Thursday, 10/12
Be sure to have a pen and/or pencil; calculator provided

20. Sample Problems
#1 Dr. Squarius wants to find out how many Canada Geese occupy the area around Lake Escherichia. So he and his Research Assistant (RA), Ms. Eri, set out shore nets to trap the birds. They managed to trap and fit 50 geese with neck bands. After 1 week, the RA returns to the site with a pair of binoculars and counts 130 geese, of which 30 geese had neck tags. From this data, approximately how many geese are estimated to be at the Lake?
#2 Over the period of a month, you trap and tag 8 Red foxes, with uniquely colored tags, in the 'Watchmacallit Forest' in New Jersey. You set up motion sensitive remote cameras up at various locations in the forest. 1 months later, you collect all the the cameras and review the pictures. You record the results and note that The cameras took pictures of 3 tagged foxes and 5 Red foxes you without tags. What would be the total population of Red foxes in the area, using the Petersen Lincoln estimation?