VI. Wrapping it up (30 minutes)
Have students review and discuss the process they went through to test the Three Clade and Single Clade Hypotheses. Students should have an opportunity to review all of the data they collected then summarize their findings in terms of how the different lines of evidence were used to test a hypothesis about the evolutionary relationships of deep sea fish. They can take notes on page 11 of the Student Research Notes before sharing and discussing their findings. Students can also discuss and record questions and ideas for future investigations.
Discuss as a class:
What kinds of evidence can scientists use to study relationships? Different types of external and internal morphology and molecular data can be used to generate phylogenetic trees, hypotheses of evolutionary relationships.
How are these different lines of evidence useful? It is important that different and multiple lines of evidence are used to test hypotheses when possible. Morphological features were the first types of evidence used to test hypotheses and so have been around the longest; new techniques and strategies have expanded this area of analysis. Molecular data is much more recent, and therefore less of it is available. External morphological data is often the first information that researchers recognize.
If you were on the Johnson science team, what would you want to investigate about these fish next? Answers will vary. Students might be interested to know how such extreme differences evolve.
What have you learned about how these fish are adapted to the environment where they live? Answers will vary.
What did you learn about how scientists investigate questions? Answers will vary. It is helpful to highlight the problem solving and creativity needed for such investigations.
Have students read and discuss the Johnson et al. research using Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families and/ or Museum Collections Solve Whalefish Mystery. You may also wish to have your students explore an interactive fish phylogeny to learn about the evolution of the ray-finned fishes more broadly.
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