1. BIOLOGY WEEK 26

2. MUST DO Species are distinct natural entities, with a clear definition, that can be easily recognized by anyone. many bacteria reproduce mainly asexually Many plants and some animals form hybrids in nature, even if they largely mate within their own groups. Should groups that occasionally hybridize in selected areas be considered the same species or separate species? It is difficult to apply because the term species reflects our attempts to give discrete names to different parts of the tree of life — which is not discrete at all, but a continuous web of life, connected from its roots to its leaves.

3. DEEP SEA MYSTERY Johnson, et al. used molecular data to generate phylogenetic trees to test how closely related different specimens from the different fish groups were to one another. complete “An Exercise in Tree Interpretation” on page 9 Show me your answers when you are done.

4. DEEP SEA MYSTERY look at the Phylogenetic Tree on page 10 of the Student Research Notes. This tree is generated from DNA samples taken from individual species of fish including those that have been classified in the three groups. Select a color for each group of fish (Tapetails, Whalefish, and Bignose fish) to create their own color-coded key, and then use the Deep Sea Fish Specimen Key to color-code the Whalefish, Tapetails, and Bignose fish species depicted on the tree.

5. DEEP SEA MYSTERY review and discuss the process you went through to test the Three Clade and Single Clade Hypotheses. Summarize your findings in terms of how the different lines of evidence were used to test a hypothesis about the evolutionary relationships of deep sea fish. Answer the following questions on page 11. What kinds of evidence can scientists use to study relationships? How are these different lines of evidence useful If you were on the Johnson science team, what would you want to investigate about these fish next? What have you learned about how these fish are adapted to the environment where they live? What did you learn about how scientists investigate questions?

6. DEEP SEA MYSTERY read and discuss

7. SUMMATIVE LT: Write arguments to support claims in an analysis of substantive topics or texts, using valid reasoning and relevant and sufficient evidence. Create an argument for either the single clade hypothesis or the three clade hypothesis using evidence from class.