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Variations in the Clam Species Clamys sweetus 1 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 Selection” 3 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. 4 What is the role of natural selection in evolution? Comment on each statement. Which one do you agree with? Why? 5 Clamys Sweetus •Read the Introduction •Descent with modification: natural selection favors some variations resulting in them becoming more common in the next generation. 6 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. 7 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. 8 Clamys Sweetus •Follow Procedures 1-1 thru 16. •Record your results in Chart 2 (1-7) •Put your group’s results on the board. 9 Clamys Sweetus •Using the class data, complete the Analysis section (steps 4,5,6) •Read “Setting the Scene” •Answer step 7 10 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. 11 Clamys Sweetus •Step 6: Is there a difference in shell strength between the two varieties? Support your answer with data. 12 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? 13 Clamys Sweetus •Step 7b: How might this feeding preference affect the numbers of the two varieties in this and future populations of C.sweetus? 14 Wrap-Up • 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?” 15 Exit Ticket • Complete and return the exit ticket before you leave! 16 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. 17 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? 19 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 20 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. 21