12.3

1. 1. Listen to Track 108.

      Now answer the questions.

   1. What is this lecture mainly about?

      1. Recent research connecting whales to ray-finned fish
      2. Differences between mammals and other tetrapods
      3. Discussing the evolution of tetrapods
      4. The importance of DNA evidence in evolutionary research

   2. According to the professor, what are two evolutionary changes that occurred in the ancestors of tetrapods? Choose 2 answers.

      1. Their swimming ability improved dramatically.
      2. They developed lobe fins.
      3. They became more like ray-finned fish.
      4. Their air sacs developed into a more advanced lung.

   3. According to the professor, what was surprising about the discovery of a living coelacanth?

      1. Its DNA did not match that found in earlier fossils.
      2. Coelacanths were thought to have become extinct 66 million years ago.
      3. The fisherman who caught the coelacanth was testing out a new method of net fishing.
      4. Researchers had not previously thought to search fish markets for coelacanth specimens.

   4. What evidence suggests that modern, land-dwelling mammals are descended from lobe-finned fish?

      1. Lobe-finned fish are able to walk on land, even if only awkwardly.
      2. The coelacanth moves by “walking” on the ocean floor.
      3. Lobe fins include a bone extending from the body with smaller, finger-like bones attached.
      4. No lobe-finned fish use lungs to breathe air.

   5. What is the professor’s opinion about the studies investigating the DNA of lungfish, coelacanths, and tetrapods?

      1. She is disappointed that DNA research is relatively new.
      2. She is excited to discover what conclusions may arise from such studies.
      3. She hopes that future researchers will be more accurate in their reporting.
      4. She does not agree with the findings of most studies.

   6. What does DNA evidence indicate about the ancestral relationship among lungfish, coelacanths, and tetrapods?

      1. It is not clear which of the three are most closely related.
      2. Earlier beliefs about the relationships among the three were proven incorrect.
      3. Lungfish and tetrapods have the highest degree of similarity among the three.
      4. The DNA of tetrapods is too varied to study effectively.