Developed by Chantier 7 project team members
Instructional goals: The purpose of this lesson is for students to understand that evolution a long process, and is the result of a species need to adapt to survive in the environment it lives in. The activity also introduces students to the work done by Charles Darwin on his voyage to the Galapagos islands, 1831-1836. The driving question guiding this lesson plan is: Why do plant and animal appearances change over a long period of time?
Grade level: Grade 7, 8
Duration: 75-150 minutes
Instructional Materials:
1. Picture of Darwin’s Finches (see Appendix A)
2. Worksheet from Eureka B Worksheet Encyclopedia 10
QEP POLs for secondary cycle 1 relevant to the concept of Evolution:
1. Describes the stages in the evolution of living organisms
2. Explains the natural selection process
Children’s preconceptions relevant to the concept of Evolution: Adaptations arise in response to an environmental challenge and that this environmental pressure is what drives evolution.
Assessment Items to explore or uncover students’ preconceptions around the concept of Evolution:
Question 1. Present day giraffes have long necks because:
A. They stretch them to reach the trees for food.
B. Their ancestors adapted to have long necks over time.
C. Giraffes with the longest necks are the strongest and most perfect.
D. Their neck length increases their body temperature.
E. Their neck length increases their speed.
(Retrieved from MOSART, Life Science Survey Test, Item form # 921, Q21)
Question 2. During the course of evolution, it is often the case that a structure, such as a functional eye, is lost in an animal’s body. This is because ...
A. It is no longer actively used.
B. Mutations accumulate that disrupt its function.
C, It interferes with other traits and functions.
D. The cost to maintain it is not justified by the benefits it brings
(Adapted from Biological Concepts Instrument, Q12)
Question 3. How can a catastrophic global event influence the course of evolution?
A. Unwanted versions of genes are removed.
B. New genes are generated.
C. Only some species may survive the event.
D. There are short term effects that disappear over time.
(Adapted from Biological Concepts Instrument, Q4)
Activity – Evolution and Natural Selection
Through this inquiry-based activity, titled Evolution and Natural Selection, students will understand that species adapt/evolve to survive in their specific habitats. In the following sections, we described the procedure of the activity and provide relevant discussion questions for teachers using this lesson plan.
Step 1: Eliciting Student Thinking/ Intuitive Models:
Began a discussion by telling the class that all dog breeds are descended from wolves and asking the class “If you had a bunch of wolves and wanted a Chihuahua, how would you create one?” In groups, students discussed the question. The teacher moves from group to group, eliciting answers from randomly selected students. Possible answers from students are:
- Chihuahuas can be bred from wolves by selectively breeding small wolves with short faces and wiry tan hair for many generations.
- Raising wolves in a warm environment so they will not need heavy fur and providing them with plenty of food so the wolves become less aggressive and develop smaller teeth. (Revealing the misconceptions that environment causes individuals and traits evolve from use or disuse).
Introduce the main activity by talking about Darwin’s voyage to the Galapagos Islands in 1831-1836: When Darwin arrived at the Galapagos, he found finches with small-sized beaks that fed mostly on insects living on Santa Maria Island; finches with large-sized beaks that fed mostly on hard seeds on Pinta Island; and finches with medium sized beaks that fed mostly on fruits on San Cristobal Island.
Next, have students look at the pictures of finches and ask: (1) What finch eats which food? and (2) Why do you think the beak sizes and shapes are specific to one island?. Looking at the photos and making the connection between food source, adaptation (beaks size), students come to realize that over time species adapt to survive.
Step 2: Collecting and Making Sense of Data:
Teacher asks students: What would happen if a volcanic eruption occurred and hard seeds became the only available food on Isabella Island (finches with large-sized beak are the only ones that can survive)?.
Then, teacher tells students that several finches moved to neighboring islands looking for new food. Students Teacher can also ask students what type of finches will survive on each island (the majority of finches on Pinta Island will have a large-sized beak, the majority of finches on San Cristobal Island will have a medium-sized beak, and the majority of finches on Santa Maria Island will have a small-sized beak).
Note: Teachers can create a table on a board and tally students’ response.
Teacher asks students to compare the distribution of finches on Pinta, San Cristobal and Santa Maria islands after the volcanic eruption, with what Darwin found (the finch populations are exactly the same). This question is leading students back to the concept that if there is huge disruption in an organism’s habitat, that the species who survive do so because they posses an adaptation that enhances survival. Of the finches that moved San Cristobal Island, only those with a medium-sized beak will survive because their beaks are best adapted to the food available on the island - fruit. Of the finches that moved to Santa Maria Island, only those with a small-sized beak will survive because their beak is suited to eating insects, the predominant food on the island. Finches that moved to Pinta Island would thrive if they had large-sized beaks, which are best suited to eating the hard seeds found on Pinta Island.
Step 3: Developing evidence-based explanations:
Teacher asks students to predict the relationships among the different types of finches. Students might suggest the following:
- The different finches were always different (incorrect).
- The finches are now a different species but they had a common ancestry. If students suggest this explanation, ask what might have happened that caused one species to change into many different species? They are different from each other because of an event that separated the populations - the isolation result of living on different islands with different food supplies.
After this discussion, ask students what might have brought about the beak-size changes (the volcanic eruption that changed the availability of the food on Isabella Island caused this example of evolutionary change). Discussion can focus on the following:
Ø Pressing for explanations: For example: Why do you think that beak-size changed? Can you share with me more about what you are thinking?
Ø Orienting students to each other's’ thinking. This could help teachers to find similarities and differences among students’ responses. For example: Do you agree or disagree with what Students A said? And why?
Note: Teachers can write down students’ responses on a board. Teachers can use different colours of chalks and markers for same ideas. If similar ideas are brought forward, teachers can use the same colours.
Step 4: Extension and discussion of antibiotic resistance:
A very serious application of evolution is happening to antibiotic resistant bacteria. The purpose of this extension activity is to heighten student awareness about an increasingly serious health problem our society is facing now and into the future that is evolution in action. A driving question guiding this discussion is: What does natural selection predict about the evolution of antibiotic resistance in E. coli?
Students will be invited to discuss this driving question in groups. They will also be invited to write their answers on the board. Specifically, questions for groups are as follow:
- How many of you have used antibiotics in the past year?
- Antibiotics have been around since 1933. How did people fight infections prior to the discovery of antibiotics?
- Do you think people always need antibiotics when they are sick? Have an earache? Have mononucleosis?
- When dealing with some mononucleosis is bacterial, antibiotics would work. Other times it is viral, so antibiotics do not work. But invariably, antibiotics are prescribed just in case. What do you think is the problem here?
- Would antibiotics cure a cold (The answer is so because colds are caused by a virus. But people still want antibiotics)? What do you think is the problem here?
- Why would some bacteria become resistant to antibiotics? (If a small number of bacteria survive in the presence of antibiotics, they reproduce and pass this advantageous trait to their offspring.)
- The average generation time for bacteria is 20-30 minutes. How would this be a factor in bacteria developing resistance to antibiotics?
Note: Antibiotic resistance in E. coli. E. coli are rod-shaped bacteria that live in the human digestive tract. Most strains are harmless, but some cause infections that doctors may treat with penicillin or other antibiotics. Some E. coli have an enzyme that can break down penicillin and other antibiotics. Some E. coli are now resistant to antibiotics.
Note: Use of free multimedia software that examines evolution and natural selection: http://learn.genetics.utah.edu/content/selection/recipe/http://learn.gen...
Step 5: Evaluation:
The goal of this lesson is to engage students by providing them with a research topic of their choosing that focuses on evolution and adaptation. In order to evaluate students’ learning outcome, teachers can invite students to write a report on natural selection, using any organism of interest. Students should include an explanation of how natural selections works to demonstrate their understanding of evolution and natural selection. Possible examples might include:
- Skeletal Adaptations: Giraffes, lizards, and other species adapted to their environments through genetic changes to their skeletons. Members of the population who didn't develop and present these skeletal changes died out. For example, giraffes developed long necks to reach food sources higher up in trees, so members of the giraffe population who didn't develop a long neck died out. At the same time, certain lizards in one region developed longer leg bones to help it climb up during periods of flood and to escape predators in the ground; shorter legged lizards of the same population died out until only the lizards with the long legs survived.
- Coloration: Many species have been studied who've adapted to their environment through adaptations in coloring. Once the optimal coloration is present, natural selection occurs when members of the species without the adaptive coloring died out more quickly and therefore didn't reproduce as abundantly. Some example include the deer mouse, the peppered moth, and the peacock.
- Bacteria: Some colonies of bacteria can produce several generations in one day, letting researchers see a fast forward version of evolution and natural selection. Some bacteria have adapted to new food sources that were previously unusable. Bacteria have adapted to the presence of antibiotics and exhibited traits that let them survive and reproduce offspring that are also resistant to the antibiotic.
- Physiological: Different species go through changes over time that help them adapt to different environments, including humans. One of the physiological changes that different groups of human beings have made involves the ability to digest cow's milk. In regions where cattle are not raised, the human population is often lactose intolerant, lacking the enzyme to break down the milk. However, in regions where cattle are grown domestically and their milk is used as a chief part of the food supply, those humans as a whole produce the enzyme needed to digest milk.
This lesson plan is inspired by the following articles:
Kalinowski, S. T., Leonard, M. J., Andrews, T. M., & Litt, A. R. (2013). Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students. CBE Life Sciences Education, 12(3), 483–493. http://doi.org/10.1187/cbe-12-06-0070
Kampourakis, K. (2006). The finches' beaks: Introducing evolutionary concepts. Science Scope, 29(6), 14–17.
Natural Selection Examples: http://www.softschools.com/examples/science/natural_selection_examples/26/">Natural Selection Examples