Summary
Students will learn that when two genetically-distinct members of a species are placed in the same environment, one of the members will survive, and the other will become extinct. The organism that survives likely has better survivability in that environment. This process is called natural selection. In a sense, through competition, nature selects the most adaptive individuals of a species to survive and procreate.
Implementation
Teacher: Ask the students to pick two gene sets. Tell them that the gene sets should be different, but both must be able to survive. Select "Jungle" from the scenario menu. Create an organism with the first gene set and add it to the world. Ask students what will happen if we advance several hundred turns (students should have learned from the second lesson that the population will increase exponentially until the carrying capacity has been met.) Advance the simulation several hundered turns to ensure that the first gene set can survive. Reset the word by choosing "jungle" from the scenario menu. Repeat the same process for the second gene set to ensure that the second set can survive.
Note: Almost any gene set is viable, unless it contains an extremely low number for one of the individual genes.
To Students: It is clear that both of these organisms can survive. Now what will happen if we put them in the world together? Will there be more of one than the other? Will they be the same? If you think there will be more of one than the other, which one will be the most numerous?
Teacher: Reset the simulation by selecting "jungle" from the scenario menu. Add 20 organisms of each gene type to the world. Make sure that you assign them different letters so you can tell them apart. Start advancing the simulation and watch what happens. Continue advancing the simulation until one of the organisms becomes
extinct.
Note: After enough turns, one of the organisms will always become extinct. If advancing by 100 turns is moving too slowly, start advancing by 1k or 20k turns.
To Students: What did you observe? Do you think one gene set will become extinct every time? Why do you think one gene set became extinct and not the other?
Teacher: This is a good place to allow students to explore the program. Allow them to pair different gene sets together. Let them test hypothesis about what does and doesn't lead to extinction. After several bouts of experimentation, students should learn that:
(1) One gene set always becomes extinct.
(2) When two gene sets compete, usually the same one will become extinct no matter how many times they are matched up. This demonstrates that
natural selection favors genes that enable an organism to survive. Natural selection is the process by which one gene set (trait) becomes more numerous in the population because the gene set is better-adapted for survival.
(3) Students can somewhat predict which organisms will survive. The organism that survive are best adapted to survive in the jungle. Usually they must reproduce a lot, consume a lot, and move a little bit less. The organisms do not need to move around as much because the jungle environment contains a lot of food.
(4) The reason one organism becomes extinct is that there is limited food in the environment and only a limited number of organisms can survive. If one organism is better and getting food, it will be less likely to starve than its neighbor.
(5) Extinction can take a long time. Even though one organism is better at surviving than the other, both are viable. Therefore, it will take a long time before the slight (or great) advantage of one organism results in the demise of the other.
Links
en.wikipedia.org/wiki/Natural_selection