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Investigation 2 – PreLab









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.


This Investigation is designed to help you to answer the following Focus Questions:

  • How does genetic variation affect the type of traits or the adaptations in the individuals of a species? 
  • What is the relationship between genetic variation and natural selection? 
  • How can an environmental change affect a population? 

Note: These questions are located in your SDR at the beginning and end of the Investigation.



As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • Organisms that are adapted to their environments tend to survive and pass on their genes to their offspring.
  • Organisms that are not as well adapted to their environment tend not to survive and do not pass on their genes.
  • This process is called natural selection.
  • In order for any species to survive, it needs to reproduce.
  • The alleles of the surviving generation will determine what the new generation looks like.



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


  • Complete the Recall section in your SDR.

What is natural selection?

What is environmental pressure?

  • In this Investigation, you 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. Remember to follow along with your SDR and make any notes that you think might be helpful.
  • After the video, divide into lab groups to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You 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.


You should review the Investigation and video in preparation for the Lab.