1. Population Ecology Chapter 5

2. Population Sampling
Field biologist often must determine the population size of a species in an area, such as the number of fish in a lake or the number of fir trees in a forest. Such endeavors are not always easy, especially when the area to be studied is large

3. Consider the following scenarios:
A certain bird of prey will only nest in areas that have large hemlock fir trees. As part of a reintroduction project, an environmental agency needs to determine if the area around Mt St Helens has enough hemlock fir trees to support the birds. How would you determine this number?
A maintenance worker at your school is disgusted with the number of dandelions on the field. The principal says that there's really not that many and that it's not a big deal. How can you find out how many dandelions are growing on the field?

4. Random Sampling with Dandelions
Procedure:
In the field, using the meter sticks, mark an area 1 meter by 1 meter. Count the dandelions in the area, be sure to count even the ones that have not blossomed. Record the number of dandelions in a data table like the one below in your notebook.
Plot number
Number of dandelions
Total number of dandelions
Average

5. ANALYSIS
Answer the following questions in your notebook:
What is the population’s density of dandelions per m2?
If the total area you sampled is 20,000 m2, how many dandelions would you expect there to be overall?
Describe two factors that would result in errors with your estimate. What could be changed to improve the accuracy?
 Data gathered are often ESTIMATES, as biologist accept that they can never know an exact number for a population. Why would an exact number be so difficult to obtain?
In a forest that measures 5 miles by 5 miles, a sample was taken to count the number of silver maple trees in the forest. The number of trees counted in the grid is shown below. The grids where the survey was taken were chosen randomly. Determine how many silver maple trees are in this forest using the random sampling technique. Show your work!