Variations in the Clam Species Clamys sweetus


Variations in the

Clam Species Clamys



Learning Target

• I can describe how natural selection preserves favorable traits

• Create a new title/thread “Clamys sweetus”

• Update your table of contents 2

Entry Task

In your notebook, write 5 words or phrases that come to mind when you hear the term “Natural



Entry Task

• In groups of 4, take turns sharing your lists.

• Describe why you chose each word/phrase.

• Choose two words/phrases to share with the class.


What is the role of natural selection in evolution?

Comment on each statement.

Which one do you agree with?



Clamys Sweetus

• Read the Introduction

Descent with modification: natural selection favors some variations resulting in them becoming more common in the next generation.


Clamys Sweetus

• Without opening the bags, and without squeezing the clams, observe the two strains of clamys sweetus.

• Answer #1,2,3 in your packet.


Clamys Sweetus

• Read “Observations of Clamys sweetus” p. 2

• Using Chart 1, you will be comparing pairs of clams (1 strain R and 1 strain M) to determine if one clam has a stronger shell.


Clamys Sweetus

• Follow Procedures 1-1 thru 1-


• Record your results in Chart 2


• Put your group’s results on the board.


Clamys Sweetus

• Using the class data, complete the Analysis section (steps


• Read “Setting the Scene”

• Answer step 7


Clamys Sweetus

• Step 5: Why is it important to use class data and not just the data obtained by an individual team?

Class results are more reliable because there are more trials. A larger sample size leads to increased precision and more accurate data.


Clamys Sweetus

• Step 6: Is there a difference in shell strength between the two varieties? Support your answer with data.


Clamys Sweetus

• Step 7a: The arthropod is able to crack open only relatively weak clam shells. Which variety might the arthropod seek out as it hunts for food?


Clamys Sweetus

• Step 7b: How might this feeding preference affect the numbers of the two varieties in this and future populations of




• What trait was “selected for” in this activity?

• How does this activity relate to our learning target?

• How do you think this learning target fits in with our chapter goal of answering the question “What are the underlying biological mechanisms of evolution?”


Exit Ticket

• Complete and return the exit ticket before you leave!


Clamys Sweetus Day 2

• We are going to investigate the hypothesis that shell color and hardness are related.

• Follow 2-1 thru 2-3 to gather data

• Put your data on the board.


Clamys Sweetus Day 3

• A new color variation of Clamys Sweetus has appeared – Brown

• Formulate a hypothesis about the ability of brown clams to survive predation by the predatory arthropod.

• Design an experiment to test your hypothesis.

• This is very similar to the type of prompt you will see on the EOC!

• Complete #13 and #14 18

Clamys Sweetus Day 3

• Question:

Could the presence of a few brown clams eventually lead to a population that is mostly brown clams?


Clamys Sweetus Day 3

• Pocketmouse video

• Does fur color influence which pocket mouse survives and which does not?

• Could the pocket mouse information apply to

C. sweetus?

• What do you need to know to make this decision?

• Video


Clamys Sweetus Day 3

 Could the pocket mouse information apply to C. sweetus?

 If it does, what caused the brown color to appear in the clam population?

 Complete the rest of the packet.