Evolutionstechnik or Selection and Variation
in the Egyptian Origami Bird
Type of Activity:
Laboratory exercise simulating evolution
Students studying organic evolution, especially: Biology and AP Biology. This lesson is appropriate for SDAIE (Sheltered English) and GATE (gifted) high school students.
Student will demonstrate that:
Every model has its weakness, and this lab is no exception. Be aware of, and caution students against, these misconceptions:
- Mutations occur randomly.
- Selection is based on the immediate needs of the organism.
- Inherited characteristics (whether mutated or not) are contingent.
- Divergent evolution may occur when sub-populations face different environments.
- Convergent evolution may result in different populations independently solving a similar problem.
- One cause of speciation is isolation of sub-populations.
- Most mutations, at best, modestly effect phenotype and fitness.
- This lab does not model sexual reproduction.
- Other genetic loci are ignored. For example, a flightless Origami Bird might hide from its predators if it carried the appropriate coloration alleles.
Notes for teacher:
In order to examine the random nature of mutations and natural selection, students breed clutches of Egyptian Origami Birds (Avis papyrus) using random number generators (dice and coins) to mutate several genetic loci: anterior and posterior wing position, wing width, and wing length. The birds are then released. Only those birds which can fly the furthest survive to produce offspring. After several generations, students usually note a significant increase in flight distance and duration. In a second experiment, different groups of students study separate sub-populations of Egyptian Origami Birds which experience different selection pressures. Details of Origami Bird anatomy, breeding and selection, are in the student instructions and the accompanying graphic.
This lab presumes that the students have had some introduction to evolution. Students do not need a rigorous understanding of genetics to successfully complete and interpret this lab. The concept that progeny resemble parents is good enough. A few students may need assistance when they start to record their data. A sample data sheet is in the accompanying PICT graphic. A few readings, videos, and computer programs to prepare or to debrief students are described in the resource list below.
Gather materials listed in student instructions. Paper may be pre-printed with a 1cm grid to facilitate rapid cutting and breeding. A single 12-sided die can be used to replace the coin plus six-sided die protocol described here. It is recommended that you make a few Origami Birds before class so that students can see how they are put together.
Class Time: 2-4 hours are needed to breed birds.
Lesson: Student Instructions:
The Egyptian Origami Bird (Avis papyrus) lives in arid regions of North Africa. It feeds on prom dates (Palmus juniorseniorus) and drinks from Palm Springs. Only those birds which can successfully fly the long distances between the sparsely spaced oases will be able to live long enough to breed successfully. In this lab you will breed several generations of Origami Birds and observe the effect of various genotypes on the evolutionary success of these animals.
- Tape (clear or masking)
- Straws (non-bending are best)
- Six-sided die
- Copper, or other metal
- Binary random number generator (ie. a penny)
- 1. Prepare ancestral bird (see illustration):
- Cut two strips of paper, each 2 cm x 20 cm.
- Loop one strip of paper with a 1 cm overlap and tape. Repeat for the other strip.
- Tape each loop 3 cm from the edge of the straw.
- 2. Breed offspring: Each Origami Bird lays a clutch of the parent.
- A. The first egg has no mutations. It is a clone of the parent.
- In the interest of time you may substitute the parent when testing this chick.
- B. The other two chicks have mutations.
- For each chick, flip your coin and throw your die then record the results on the table.
- The coin flip determines where the mutation occurs: on the anterior or posterior end of the animal.
- Heads = anterior (front) mutation
- Tails = posterior (back) mutation
- The die throw determines how the mutations effect the wing.
- 1 =The wing position changes 1 cm distally (toward the end of the straw)
- 2 =The wing position changes 1 cm proximally (toward the middle of the straw)
- 3 =The circumference of the wing increases 2 cm.
- 4 =The circumference of the wing decreases 2 cm.
- 5 =The width of the wing increases 1 cm.
- 6 =The width of the wing decreases 1 cm.
- Lethal mutations: A mutations which results in a wing falling off of the straw, or in which the circumference of the wing is smaller than the circumference of the straw, etc. is lethal. Fortunately, Avis papyrus birds are known to "double clutch" when an egg is lost. If you should get a lethal mutation, disregard it and breed another chick.
- 3. Test the birds. Release the birds with a gentle, overhand pitch. It is important to release the birds as uniformly as possible. Test each bird at least twice.
- 4. The most successful bird is the one which can fly the farthest. Record the dimensions of the most successful bird on the table.
- 5. The most successful bird is the sole parent of the next generation. Continue to breed, test, and record data for _________ generations.
- Record the results of your coin flips and die throws.
- Record the dimensions of the most successful bird.
Discussion: Answer the questions.
- Did your selection process result in better flying birds?
- Describe two aspects of this lab which model evolution of biological organisms.
- Your bird has a different lineage than your neighboring groups'. Compare your bird with your neighbors'. What might happen to your bird and its offspring during a drought when oases are extremely far away from each other?
- What might happen to the offspring of your last bird if the selection conditions changed?
Breed birds for one of these scenarios:
- A flock of Origami Birds is blown off the mainland and onto a very small Mediterranean island. There are no predators here. Like the flightless fruit flies (Drosophila spp.) of Hawaii and the Dodo (Raphus cucullatus and Didus ineptus) before the arrival of humans on Mauritius and Reunion, these birds face little danger on the ground but experience significant risk when flying, since they can be blown off the island. The best survival strategy for these birds is to not fly at all. Continue the experiment for several generations selecting for birds which drop out of the sky the way bricks do.
- Another flock of Origami Birds is blown onto a different, somewhat larger, island. Silver Scissor Foxes (Vulpes cisoria ssp. argentatum) live on this island, so birds which cannot fly will be eaten. The best survival strategy for these birds is to fly in boomerang or loop-the-loop curves. Birds which fly straight might drift off the island and be swept away. Continue the experiment for several generations selecting for curved flight.
- Your Origami Bird remained on the mainland where a drought is occurring. Only those birds which can fly straight and far between oases will survive. Continue the experiment for several more generations while selecting for the characteristics which result in the most appropriate flight behavior.
- Compare your youngest bird with the youngest birds from neighboring groups with the same scenario.
- Compare your youngest bird with the youngest birds from neighboring groups with different scenarios.
- How might this lab help explain the observations Darwin made about finches in the Galapagos?
Evaluation, Extension and Reinforcement
A variety of student products, including lab reports and essays may be used to evaluate student learning.
- Dawkins, Richard. The Blind Watchmaker
- Horizon: The Blind Watchmaker. This is a 45 minute television show hosted by Dawkins which surveys the book. During the program, Dawkins demonstrates the use of evolutionary design techniques in German industry. He uses the German word "Evolutionstechnik," Thus the title of this activity.
- Scientific American Frontiers: Life's Big Question Program #501. The program includes a segment entitled "Will Robots Take Over?" about evolutionary design for artificial intelligence and robotics. It also shows a computer program modeling evolution which
is more complex than Dawkins' and which has non-teleological selection.
- Anything by Stephen Jay Gould. My students read the title article from The Panda's Thumb. However, they needed significant assistance with the advanced vocabulary and numerous cultural references.
This is an original lesson. I am not aware of any activity similar to it. This lesson was developed during the summer of 1994 as a result of two years of interaction with the National Science Foundation project, "Evolution and the Nature of Science." Since this lab is new, it may still have a few bugs in it. Ideas for improvement and enrichment activities are welcome.