Workbook Answers 7.5

A

1.     B

2.     C

3.     C

4.     D

5.     C

B

(a)

Tube	Does respiration take place? (ü / û)	Does photosynthesis take place? (ü / û)	Colour of the indicator	The level of carbon dioxide (unchanged / increase / decrease)
A	ü	ü	red	unchanged
B	ü	ü	purple	decrease
C	û	û	red	unchanged
D	ü	û	yellow	increase
E	ü	û	yellow	increase
F	ü	û	yellow	increase
G	û	û	red	unchanged
H	ü	û	yellow	increase

(b)    In the dark, the plant does not undergo photosynthesis. However, both the plant and snail carry out respiration which gives out carbon dioxide. Therefore, the level of carbon dioxide increases and the indicator changes from red to yellow.

(c)    Under bright light, there is a net intake of carbon dioxide in plants. In the dark, there is a net release of carbon dioxide in plants.