Clipbirds: A Lesson in Natural Selection (Requires one 50 minute class period)
Concept or conceptual understanding:
Evolution results from selection acting on existing genetic variation in a population.
Inherited characteristics affect the likelihood of an organism’s survival and reproduction.
Reproductive isolation is necessary for speciation to occur.
Real world connections (Relevancy):
Organisms change over time.
AZ standards: (include grade level and text):
Concept 3: Populations of Organisms in an Ecosystem
PO 2. Explain how organisms obtain and use resources to develop and thrive in:
· niches
PO 3. Analyze the interactions of living organisms with their ecosystems:
· limiting factors
PO 5. Predict how environmental factors (e.g., floods, droughts, temperature changes)
affect survival rates in living organisms.
PO 6. Create a model of the interactions of living organisms within an ecosystem.
Grade 8
Strand 4: Life Science
Concept 4: Diversity, Adaptation, and Behavior
PO 3. Determine characteristics of organisms that could change over several generations.
PO 6. Describe the following factors that allow for the survival of living organisms:
· beak design
· seed dispersal
Incorporation of inquiry:
Students will perform the activity on their own. Students will also analyze their data and draw conclusions based on the results of this activity.
Behavior objectives:
1) Students will model natural selection using an imaginary scenario.
2) Students will identify traits that are advantageous under certain environmental conditions.
Prior knowledge necessary:
Students should be familiar with the basic principles of heredity.
Identify possible student preconceptions:
Environmental changes cause changes in traits that help organisms cope with the new environment.
Materials:
1 1/2 lb unpopped popcorn
1 1/4 lb lima beans
255 marbles
20 large bulldog binder clips No. 3 – 2 5/8 inches
20 medium-sized bulldog binder clips No. 2 – 2 1/4 inches
20 small-sized bulldog binder clips No. 1 – 1 1/4 inches
30 plastic cups
1 Food Values transparency*
1 Clipbird Populations transparency*
1 Clipland Scene transparency*
1 overhead transparency projector
* Transparencies available at http://www.ucmp.berkeley.edu/education/lessons/clipbirds/
Safety:
Only use the clips to pick up food, not to pinch other students.
Do not eat the popcorn or the lima beans.
Lesson Description:
This activity is designed to show beak size variation within a population and how natural selection acts on that variation. Over time, the proportion of small-, medium-, and large-beaked birds changes in relation to food availability. See http://www.ucmp.berkeley.edu/education/lessons/clipbirds/ for more details about how to carry out the activity.
Assessment:
Class discussion will demonstrate students’ understanding of how natural selection and speciation occur in real populations.