These seven original questions follow the four lessons in the chapter. Answer in full sentences first, then open the model answer.
Questions
Question 1. State the difference between a tropic response and a nastic response.
Answer
In a tropic response, the direction of the movement depends on the direction of the stimulus. In a nastic response, the movement does not depend on the direction of the stimulus.
Question 2. A root grows downward in a dark cupboard. Name the response and say whether it is positive or negative.
Answer
The response is geotropism (gravitropism). The root grows toward gravity, so it is positive.
Question 3. A tendril coils around a bamboo stick. Is this tropic or nastic? Give a reason.
Answer
It is tropic (thigmotropism). The coiling starts on the side that touches the stick, so the direction of growth depends on the direction of the touch stimulus.
Question 4. Explain why a shoot bends toward a window.
Answer
Light comes from one side, so auxin moves to the shaded side of the shoot. The higher concentration of auxin makes the shaded cells elongate more, so the shaded side grows longer and the shoot bends toward the light.
Question 5. The tip of an oat coleoptile is removed and the coleoptile stops growing. Explain what this shows.
Answer
It shows that the tip is needed for growth, because the tip makes auxin that moves down and makes the cells below elongate. Without the tip, there is no source of auxin.
Question 6. An agar block containing auxin is placed on the right side of a decapitated coleoptile in the dark. Predict the result and explain.
Answer
The coleoptile bends to the left, away from the block. The right side receives more auxin, so those cells elongate more and the right side becomes the longer side of the curve.
Question 7. A seedling is placed on a slowly rotating disc, so light reaches it evenly from every side. Predict how the shoot grows and explain.
Answer
The shoot grows straight upward. Light reaches all sides equally, so auxin stays evenly distributed and the cells on every side elongate by the same amount. There is no shaded side, so there is no bending.
If you got these wrong
Questions 1 to 3 point to distinguishing tropic and nastic responses. Question 4 uses explaining growth responses to stimuli.
Questions 5 and 6 need interpreting plant-hormone investigations. Question 7 comes from predicting responses using supplied evidence.
Log each slip in the mistake log and paper-error review, then build a timed set with the timed original practice session builder. For a teacher to go through your answers, see online one-to-one Biology tuition.