 |
SESSION 4: What Are the Processes for Evolution? |
|
|
Facilitator Notes for SESSION 4 |
|
Engage Part A
Note 1: Conduct a discussion after participants have read the Life's Grand Design
Web essay.
|
|
Explore Part C
Note 2: An important concept is that natural selection acts on the phenotype of
traits, but at the same time may reduce the frequency of certain genes in future
populations. Hidden variations that are not expressed in the phenotype cannot be selected
against. Deleterious genes for traits such as Tay-Sachs and Huntington's disease may
remain in the gene pool if they do not express themselves until after individuals have
reached reproductive maturity and begun having offspring. "Fitness" means
reproductive fitness; as long as an individual is able to reproduce, its genes will remain
in the gene pool of the population.
|
|
Explain Part A
Note 3: After participants have completed the simulation, ask them to work in teams
to discuss: the hypotheses they tested; how they tested them (what population they set up
for guppies and predators, and the environment they used); their results; and the
conclusion they reached based on their results. Have participants compare hypotheses and
make a group list of conclusions and their supporting evidence. Have each team present
their conclusions and evidence to the class.
|
|
Explain Part B
Note 4: The biological definition of species is a population that interbreeds and
produces fertile offspring. When organisms live in different geographical areas in the
wild, it may be difficult to determine whether they are the same species since you cannot
determine whether they would interbreed if they were in the same area. Reproductive
isolation that leads to speciation may be geographical, ecological, temporal, behavioral,
mechanical, gametic, or due to hybrid inviability or hybrid sterility. For more
information on reproductive isolation, have participants look at the suggested links.
|
|
Evaluate Part A
Note 5: Examples that can be used to explain the key statements about natural
selection include:
1. Finches in Grant's study
2. and 3. Sickle cell anemia genes in West Africa
4. Pekinese dogs evolved from wolves
5. Human eye
6. Bacteria that are antibiotic resistant are not as advanced as humans but are very
successful organisms.
|
|
