Download F4 Biology Exercise 1

F4 Biology Exercise 3
Section A
1A
2D
3C
4B
5C
6C
7A
8D
Section B
1 (a) B – palisade mesophyll
C – spongy mesophyll
D – guard cell
E – xylem
F – phloem
5 x [½]
(b) The cell is rectangular in shape so it can be closely-packed [1]
There are many chloroplasts in each cell. [1]
Maximum amount of light can be absorbed [1]
for efficient photosynthesis.
(c) To allow rapid diffusion of carbon dioxide and oxygen [1]
(d) (i) In hot water, the air in the intercellular air spaces is warmed up and expands [1]
It can only escape from the leaf through stomata. [1]
(ii) Stomata are only found on the lower epidermis of this leaf. [1]
(e) A [1] and D [1] are absent in aquatic plants.
Reason : In aquatic leaves, cuticle is not present because there is no need to prevent water
evaporation from the leaf surfaces. [1]
Without cuticle, carbon dioxide / oxygen can diffuse all over the surface of the leaf. [1]
so guard cells are not necessary.
2
(a)
(b)
Sodium hydrogencarbonate solution releases carbon dioxide to the plant for photosynthesis. [1]
It will make the water temperature to become very high. [1]
The activities of enzymes in the plant will be affected / The enzymes in the plant will be denatured [1]
(c) Oxygen is collected. [1]
It relights a glowing splint. [1]
(d) In aquatic plant, the carbon dioxide evolved is in the form of bubbles and therefore they can be
counted. [1]
In terrestrial plant, the carbon dioxide evolved cannot be seen because it is colourless. [1]
(e) (i) The rate of gas production represents the rate of photosynthesis. [1]
1/distance2 represents the light intensity. [1]
(f) The rate of photosynthesis increases light intensity. [1]
But when the light intensity is increase further, the rate of photosynthesis remains constant. [1]