Lesson Plan : Estimating Abundance: Quadrants

Teacher Name:
 S Gilligan
Grade:
 Grade 11-12
Subject:
 Science

Topic:
 Measuring Biotic Components of a System
Content:
 Methods of estimating the abundance of organisms in an ecosystem include using quadrants and the Lincoln Index (capture/mark/release). Abundance can be population size, population density, percentage frequency or percentage cover. There are limitations and possible sampling errors in the methods of measuring abundance. Vocabulary: System, biotic, abundance, estimate, sampling error, quadrant
Goals:
 Students should be able to use the quadrant method to estimate abundance in the field. Students should be able to evaluate the quadrant method, identifying limitations and possible sources of error.
Objectives:
 Given data on organisms living in an (imaginary) ecosystem, be able to estimate the population size of one species, based on at least three quadrat samples. Given class data on quadrant counts and the true population size, be able to analyses the sampling error of the quadrant method for estimating population size. At least two limitations of sampling should be identified and at least two specific suggestions for improvement in the sampling technique should be made.
Materials:
 A4 sheet of paper with a news clipping printed on it quadrant draw on Petri dish ruler TI-83 calculator (student-owned)
Introduction:
 Show students a glass jar filled with candies. Ask them to "guess" (estimate) the number of candies in the jar, by counting/measuring one feature to help them. The student with the closest guess will "win" the jar of candies. Pass the jar around. Each students may hold the jar only for about 10-15 seconds. Ask students to write down their estimates. The winner will be announced at the end of the lesson.
Development:
 Show the "prairie" on an OHP. Model the quadrant method, generate one or more counts, and ask students if they need any clarification. Students will: 1. Form small groups of 2-3. 2. Take one newspaper clipping per group and sample 5 areas on the paper. 3. Record each "A" or "a" as one Big Bluetem (each "R" or "r" is one Wild Rose). 4. Count each A/a individual found in the quadrants. 5. Calculate population estimates for the Big Bluestem and the Wild Rose populations. 6. Count all A/a individuals. 7. Compare the actual population size to the estimate obtained using the quadrants.
Practice:
 Students will repeat the quadrant procedure, trying to obtain the closest estimate to the actual population size. Students will calculate the percentage error as a measure of sampling error in the population estimate.
Checking For Understanding:
 Question students about the method of using quadrants as they carry out the task. Listen to the discussions that students have with each other as they carry out the task. Join each group and ask one student to demonstrate the calculate needed to estimate the whole population size from the quadrant samples. Answer questions that students have and help students who need support in calculating the population estimate.
Closure:
 Ask students to generate a list of key features that are important in using the quadrant method to estimate abundance of a species. Announce the winner of the candies-in-the-jar contest!
Evaluation:
 Student success in achieving the learning outcomes will be assessed by (1) the completion of a planning lab to measure the abundance of a weed/wildflower in the plot of land behind the school, and (2) IB Option A: Analyzing Ecosystems questions (paper 3)
Teacher Reflections:
 What worked? What didn't work" Why? Future modifications?

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