The diagrams given below represent the relationship between a mouse and a physiological process that occurs in green plants. Bell jar A contains a mouse with a green plant; bell jar B contains a mouse with a burning candle and no plant. Study the diagrams and answer the questions that follow: The diagrams given below represent the relationship between a mouse and a physiological process that occurs in green plants. Bell jar A contains a mouse with a green plant; bell jar B contains a mouse with a burning candle and no plant. Study the diagrams and answer the questions that follow:
Why did the mouse die in bell jar B?
Topic: Why the mouse died in jar B
Answer
Because there was NO GREEN PLANT in jar B to replenish the oxygen, and the BURNING CANDLE consumed the oxygen already present. With the oxygen exhausted, the mouse could not respire and died of suffocation.
Give BOTH halves of the reason — the ABSENCE of a source (the plant) and the PRESENCE of a competitor for oxygen (the candle). Either alone is incomplete.
THE LOGIC OF THE EXPERIMENT: jar A and jar B differ in ONE respect only — the presence of a green plant. Since the mouse lived in A and died in B, the plant must be what kept it alive. That is a properly controlled comparison.
The candle serves two purposes: it uses up oxygen faster, so the result is quick and unmistakable, and it shows visibly when the oxygen is gone by going out.