What Darwin Never Saw
Lesson Introduction
In this lesson, students take on the role of birds who migrate back to their nesting sites each summer. The birds in this simulation game, like the finches in the video, What Darwin Never Saw, will find that different amounts, or even different kinds, of food are available every year.
Following the game, students discuss the fact that changing conditions have a far-reaching environmental impact (definition) because they can produce ever-changing food supplies. The students identify some important factors affecting these changes, and they see that members of a species (definition) do not survive unless they are capable of adaptation (definition). They realize that all animal and plant populations do not remain constant. Only the most "fit" individuals of a species survive and have baby birds of their own, so its population's numbers change with each passing generation. Finally, they explain how the process of natural selection (definition) brings about evolutionary change.
Grade Level
6 through 12
Objectives
The students will:
1. participate in a role playing activity.
2. name two factors affecting environmental conditions for wildlife populations.
3. explain how natural selection allows one species to survive and change.
Time Allotment
one 40-minute session
Materials
large area where students can migrate, either outdoors or indoors
flip chart or chalkboard
markers or chalk
student journals
pencils or pens
video/video player
Books to Read
The Beak of the Finch, by Jonathan Weiner, New York, NY: Vintage Books, 1994.
Charles Darwin's Natural Selection, by R.C. Stauffer, Cambridge, UK: Cambridge University Press, 1975.
Advanced Preparation and Teacher Notes
This activity is adapted from "Oh Deer!" which originally appeared in the Project Wild curriculum, developed by the Western Regional Environmental Education Council.
Procedure
Tap Prior Knowledge
1. Ask the students what caused changes in the finch population when Peter and Rosemary Grant were carrying out their study on Daphne Major, one of the Galapagos Islands.
Share with Neighbor/Revise Ideas
2. Encourage students to talk to each other about what they understood from the video, and accept all responses. Show the section of the What Darwin Never Saw video (from 37 20 to 41 03) which shows the bigger-beaked finches getting the seed. Share one of the biographies from our Career Connections with the students.
Engage Students in a Hands-on Activity
3. Have students count off by threes. All of the ones will be finches. They should gather together on one side of the open playing area. All twos will be large seeds. All threes will be small seeds. They should all gather at the other side, about 30 meters from the finches.
4. Introduce symbols to the students. The large seeds should hold their arms out to the sides to show that they are wide. The small seeds should bring their arms in, perhaps in a self-hugging motion, to show that they are small. The finches can either be big-beaked or small-beaked. Big-beaked will hold their arms out in front of them, placing them together like a large bird beak. Small-beaked will do a similar symbol, but just with their hands, held at the mouth.
5. Practice the four symbols with all of the students. Remind them that they may be any one of these during the game. It is important to know them all
6. Tell the finches to turn their backs and choose one type of finch to be (small or big-beaked finch), then make the appropriate symbol. Instruct the seeds, larger and small, to turn their backs and make their symbols.
7. Begin the first year migration by giving a signal to the finches to fly over to the nesting habitat. They fly while they maintain their chosen symbol.
8. When the finches arrive at the nesting site, they look for the seed that suits them. Small-beaked finches eat only small seeds. Large-beaked finches eat only large seeds. The student finches take the seed back with them and that seed becomes a finch - with the same kind of beak as the finch who ate it. Any student that does not find the right seed becomes a seed, either large or small. The choice is theirs. That completes one year of play.
9. Keep the track of finch population or designate a student to have that job. Record the number of finches on the flip chart or chalkboard at the beginning of the game and at the end of each round. The finch population should fluctuate each year. This happens naturally, with population peaking, declining, and rebuilding. During the course of the game you can manipulate the kinds of seeds available by telling students what particular seeds sizes to be.
Introduce the Scientific Principle/Concept
10. Discuss the implications of the recorded data with the students. Patterns of weather, or climate, can change the environment to make it difficult for some plants and animals to survive. In the case of the finches on Galapagos Islands, periods of dry weather make it difficult for them to find the smaller seeds. During times of drought, small seeds like pistachio nuts are quickly picked out and eaten by hungry birds. Only the larger seeds, from the Palo Santo, the cactus, and the Tribulus, for example, are available during dry weather. Peter and Rosemary Grant and their team of Finch Watchers have classified all the available seeds with a Struggle Index, a rating on how long it takes a finch to open and eat a particular seed. During the drought of 1977, they found that only the biggest males and females were able to crack open the large seeds. Before the drought, the beaks of the finches were 10.68 millimeters long and 9.42 deep. After the drought, the average was 11.07 millimeters long and 9.96 deep. These variations cannot be seen with the naked eye. Also, more males than females survived because they were typically larger in size with larger beaks.
11. After more than 50 millimeters of rain finally came on January 9, 1978, the island of Daphne Major began to spring back to life. The finches finally mated, with the largest males being the first choice of the few females that had survived. As a result, the next generation was larger, in body size and in beak size, than the previous generation. In this way, climate changes affect food supplies which determines the survival of certain finches.
12. Other things that can change the environment are the introduction of an animal or plant which is not from the area originally. This non-native, or exotic, species has no natural predators and can easily take over the environment. A disease which kills off the plants or animals which make up a diet for another species can also be a major change. Finally, the development done by humans can drastically alter the environment, forcing some species to adapt or not survive. Because the environment is always changing, the overall populations of animals and plants change from year to year, just like they did in the simulation game.
13. Clarify some important definitions for the students. Natural selection acts upon one generation. By itself, it is not evolution. It is a mechanism that brings about evolutionary change. Evolution takes place across many generations. The 13 species of finches in the Galapagos Islands probably descended from a single South American species, either the Blue-black grassquit or the St. Lucia black finch. While humans and larger mammals can find substitutions when our primary diet is not available, smaller animals like finches cannot. When their food supply is not available, they do not survive. In this way, natural selection acts on the entire population of a species so that only those who are most fit survive. The variation of organisms within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions, and a great diversity of species increases the likelihood that at least some living things will survive in the face of large changes in the environment.
14. There is a growing amount of scientific evidence from fossils to support the fact that species change to be better adapted to their environment. Over time, these changes can create very different species. Charles Darwin never saw evolution. He only hypothesized it. It took him many more years to come up with the theory. Now it is no longer called a theory. It is a fact.
Lesson Assessment
15. Have students write an entry in their journals. They should each name two factors affecting wildlife populations and explain how natural selection allows one species to survive and change.
Connect to Other Everyday Examples
16. Give students a chance to surf the World Wide Web to find out more about the finches on the Galapagos Islands:
