ZERO-IN

Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that the planet we live on is constantly changing. To survive and reproduce, all living organisms must adjust to these changes. If organisms are not able to adapt to changing environmental factors — including competition for resources, predation, infectious diseases, and climate – they may not survive.

BRANCH OUT

Remind students that paleoanthropologists study how human beings have adapted and evolved over many years. By analyzing archeological records, such as tools and traces of campfires, they have been able to observe how certain groups or individuals changed their ways in order to be better suited to their environment and habitat. They have also observed the differences in the physical structure of what humans and prehumans were hundreds of thousands of years ago with that of modern humans. Some of these differences include increases in brain capacity, the switch to walking upright, and dietary clues through wear patterns on the fossil teeth.

GET FOCUSED

• How does genetic variation affect the type of traits or the adaptations in the individuals of a species? Genetic variation is responsible for all the different traits that an individual possesses.

• What is the relationship between genetic variation and natural selection? If members of a species did not have different traits no natural selection could exist because all the members of that species would be equally adapted to each environmental pressure. However, there is genetic variation in populations and some individuals are more adapted to their surroundings than others. The ones that survive are more likely to pass on their genes.

• How can an environmental change affect a population? Environmental pressures can affect the population because some members are more adapted to the new environment than others.

Note: This question is located in students’ SDRs at the beginning and end of the Investigation.

Note: This is a succinct response to the Focus Question and is placed here for your reference at this time. A fully developed response to the Focus Question can be found on the PostLab page.

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

• environmental pressure
• natural selection

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

• Direct students to complete the Recall section in their SDRs. Student answers will vary.

What is natural selection?

What is environmental pressure?

• Explain to students that in this Investigation, they will investigate how environmental pressure affects the frequency of a recessive allele and a dominant allele. In the model, increased bone density in a penguin species is the recessive allele, and decreased bone density is the dominant allele.
• Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
• After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

Tell students that they should review the Investigation in preparation for the Lab.