Lesson Title: Assessing the quality of habitat for Monarch... Discipline Focus: life science, mathematics

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Lesson Title: Assessing the quality of habitat for Monarch Butterflies
Discipline Focus: life science, mathematics
Grade level: Middle – High school
Length of lesson: 45 minutes
Stage 1 – Desired Results
Content Standard(s):
Understanding (s)/goals
Students will understand:
1) the nature of an average
2) the purpose of calculating an
average (i.e. to estimate the real
value of some characteristic in a
population)
3) how the distribution on a population
in space affects your ability to
estimate it’s size
4) how different sampling methods
may affect your population estimate
5) What is accuracy?
Essential Question(s):
1) Why would you want to estimate a
population’s size?
2) Are most living things evenly spread across
space?
3) When you cannot count every individual in a
population, what measure do you use to
estimate it?
4) How can you estimate the accuracy of a
population estimate?
5) Is there one best way or does it depend?
Student objectives (outcomes):
Students will be able to:
1) calculate an average
2) assess the accuracy of that average (how close does it come to the real populations size?)
3) discuss how the distribution of organisms in space affects their ability to estimate the
populations size.
4) Identify which sampling method was the best for estimating the population size of two
differently arranged populations.
Stage 2 – Assessment Evidence
Performance Task(s):
Other Evidence:
After going through the exercise, students
1) Level of engagement and participation of
will be able to more accurately estimate the
students in activities and discussion.
size of a new unknown population.
2) Demonstration of correct concepts in follow-up
discussion.
Stage 3 – Learning Plan
Learning Activities:
Materials for each group:
8.5x11 blank sheet of paper (optional: field photo); 8.5x11 sheet of grid paper (~25 x 60 cells)
One population sheet: A=uniform (2823 dots), B= moderately clustered (949 dots), C=highly
clustered (684 dots)
Cutting tool (i.e. Exacto knife)
Optional: calculator; worksheet for extension activity
Background:
Scientists are very interested in monitoring the quality of different habitats for monarch
butterflies. Monarch butterflies rely exclusively on milkweed (Asclepias syriaca) to lay their eggs
and as food for their caterpillars. Therefore, the number of milkweed plants in a field is a good
indicator of the habitat quality for monarch butterflies.
There are two fields we wish to assess for habitat quality, but we have limited time and resources
so we cannot count every plant in the field. We have contracted with your students to find an
accurate estimate of the population size of milkweed in each habitat.
Procedure:
1) Hand out a field photo, a sheet of grid paper, and some kind of cutting tool.
2) Explain the background above, and that what they see before them is the field they are
going to survey. They know nothing about the population of plants in that field.
3) Explain that they will have 10 minutes to decide how they want to estimate the population
of milkweed plants in their field. You can assume that (after appropriate training) two
students will be able to sample one grid cell during an average field trip session.
4) Instruct students to cut out the areas on the grid paper that they intend to sample
5) Instructor will overlay their sampling design on their real population and hand them back
to the students.
6) Instruct students to estimate the size of the milkweed population (this will involve
calculating the average of the number found per grid cell and then multiplying that by the
total number of cells, but let’s let them figure that out?)
7) For each population, compare the results of student with the actual population to see how
accurate their estimate is.
a. Discussion point – in actual scientific studies you would never know what the real
populations size is so, how would you determine your accuracy?
(i.e. repeated measures, performance curves)
8) Compare the success of different sampling designs within each population.
9) Contrast how the distribution of the organism affected their ability to estimate the
population using various sampling methods.
Follow-up Discussion:
1) The Essential Questions above
Extension Exercise:
By plotting calculating and plotting the cumulative average, student can see how the accuracy of
the average increases with the number of plot/amount area sampled. This can also give an
indication of when you have collected enough plots to have an accurate average.
Plot
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
# of
Organisms
Plot
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
How many samples is enough?
# of
# of
Organisms
Plot
Organisms
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
# of
Organisms
Plot
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Calculate the average based on plots (or samples):
1 – 10
1 – 25
1 – 50
Density Estimate
1–5
1 – 100
Plot these numbers on the graph to the right.
After how many samples does the line begin to level?
0
2
0
4
0
60
# of Samples
80
100
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