Background and Information
By now you have learned that the Earth was very different in its beginning than it is today. The living things on the Earth have also changed and developed over time. Discovering how and why living things have changed over time is an entire field of science. In this final activity, we will simulate a scientific theory called natural selection. Natural selection explains how organisms can change over long periods of time. But first we need to introduce two terms:
Next semester, we will study genetics in more detail. However to understand this activity, you "I need to know a little bit about heredity and genes. Genes carry the message that controls the organism's characteristics. Organisms pass their genes to their offspring (children). Just like humans who come in different shapes and sizes, all living things have a variety of genes in their gene pool. A gene pool is a term that refers to all of the genes that are carried by a whole population of a certain species.
What are some of the different heights that are in the human gene pool?
Last year we studied plant adaptations in different biomes. These adaptations allow plants to survive better in a specific climate. For example, plants in the rainforest tend to have big leaves. The adaptation for big leaves allow the plant to live where there is not much light. Adaptations are passed onto the next generation in the genes. They increase an organism's chance of survival.
List two or three examples of adaptations in animals or plants:
There is not enough space and food for all so organisms must compete to survive. Today, you will simulate how a certain adaptation is "selected". Each participant in the simulation will receive a "beak"--either a pair of chopsticks or a fork. The "birds" will try to grab as many beans as possible in a one minute period and place them in their paper cup "nests". If the bird gets at least 10 beans, it "reproduces" and another bird joins the game with the same kind of beak.
The Jefferson Bean Grabber
The Jefferson Bean Grabber is a very large bird that lives in a small urban area in Southern California. It looks a lot like a high school student and it is only able to eat beans. Most Bean Grabbers have narrow bills but a few have shown up that have very wide bills (this is their gene pool for bill width). Every 6 months (I minute) the bean grabber must collect 10 beans or it will die. The Bean Grabber only reproduces once a year. At the beginning of each new year each surviving Bean Grabber will have one offspring. You can't reproduce if you don't survive. Since it passes its genes to the offspring, the offspring will have the same adaptation as the parent.
Record the population of each variation of Bean Grabber in the chart below.
Year Starting Population of Narrow Billed Bean Grabbers Starting Population of Wide Billed Bean Grabbers Ending Population of Narrow Billed Bean Grabbers Ending Population of wide Billed Bean Grabber 1 2 3 4 5 6 7 8 9 10
Compare the wide billed bean grabbers with the narrow billed bean grabbers in the graph below. Use a solid line to represent the narrow billed population and a dotted line to represent the wide billed population. Years will be your x-axis and population size will be your y-axis.
Graph Analysis: How are the two lines different? Why do you think they are different in this way?
Discussion and Conclusion: Answer the following question in two paragraphs.
- Why couldn't every bird survive?
- Which variation was most successful? How could you tell?
- How did the average genes in the population's "gene pool" change over time?
- What is natural selection? Does this simulation demonstrate the concept of natural selection? Why or why not?
- How was this activity like what happens in nature?
- How would conditions of competition and survival be different in nature?
- Were there other factors than bill size that also affected the survival of bean grabbers?
- How would natural selection help contribute to the large amount of biodiversity on the Earth?