Leaves Turn Color
Listen to part of a lecture in a botany class.
- What is the main purpose of the lecture?
- A. To explain how the red pigment in leaves breaks down
- B. To show that leaf color varies based on the tree species
- C. To introduce a theory about why leaves turn a particular color
- D. To explain how chlorophyll protects trees in autumn
- What does the professor imply when she explains why leaves are green?
- A. She wants to correct a common misconception about the topic.
- B. She thinks the students are probably already familiar with the material.
- C. She believes the process is too complicated to discuss in depth.
- D. She knows that students are often confused about the functions of chlorophyll
- What does the professor mean when she says that the classic theory is partially right?
- A. It describes what happens in the summer but not what happens in autumn
- B. It describes what happens in tree leaves but not what happens in leaves of other plants
- C. It explains how pigments are synthesized but not how they break down.
- D. It explains some cases of color change in tree leaves but not all cases.
- Why does the professor mention painting a car?
- A. To question why a large amount of anthocyanin is produced just before leaves fall
- B. To explain why most leaves turn red instead of other colors
- C. To remind students how cooler temperatures affect the color of leaves
- D. To show how anthocyanin absorbs sunlight to produce food for trees
- The professor mentions theories about why leaves turn red that involve predatory insects and fungi. What is her opinion about those theories?
- A. They are based on careful research.
- B. They do not completely explain the phenomenon.
- C. They have not received enough attention.
- D. They have been proved to be incorrect.
- According to the professor, why does anthocyanin appear on the upper side of some leaves?
- A. To help chlorophyll absorb the sunlight
- B. To maximize the leaves’ utilization of sunlight
- C. To accelerate the breakdown of chlorophyll
- D. To protect an important process from the sunlight
C B D A B D