Question 2
The diagrams below are illustrations of types of leaves from two different plants. Study them and answer questions 2(a) to 2(f).
(a)(i) Identify diagrams Y and Z. [2 marks]
(b)(i) What is the main biological importance of Y? [1 mark]
(ii) State two features of biological importance in Z. [2 marks]
(c)(i) Identify the parts labelled I to VI. [3 marks]
(ii) State one function each of the parts labelled II, IV, V and VI. [4 marks]
(d)(i) Name the mineral element that is deficient in the soil where plant Z is found. [1 mark]
(ii) Name two feeding habits of plant Z.
[2 marks]
(e) Explain how gaseous exchange takes place in the leaf of plant Y. [4 marks]
(f) In the table below, state three leaf modifications in plants other than that shown in plant Z and give one example of each of the modifications.
|
Leaf modification |
One example |
(i) |
|
|
(ii) |
|
|
(iii) |
|
|
Observation
In this question, many candidates were unable to answer the questions correctly. Hence, they lost a lot of marks.
The few questions where they scored averagely were in (a) and (b).
The expected answers are:
(a) Identification of Plants
Y - Hibiscus plant
Z - Venus flytrap
(b)(i) Biological importance of Y
- Has leaves for photosynthesis;
-Has flowers for pollination.
(ii) Features of biological importance of Z
- It has (green) leaf that carries out photosynthesis;- It has modified leaves for trapping insects;
- Has flowers for pollination.
(c)(i) Labelled parts
I - Leaf margin/apex;
II - Lamina/leaf blade;
III - Vein;
IV - Vein/leaf margin;
V - Petiole/leaf stalk ;
VI - Axillary bud;
(ii) Functions of labelled parts
- II/leaf blade/lamina: for absorption of sunlight/for photosynthesis/gaseous exchange/transpiration.
- IV/ vein/leaf margin: for transportation/translocation of food/conduction of water/nutrient/ leaf margin gives shape to the leaf.
- V/Petiole: holds leaves in position/attach leaf to stem.
- VI/Axillary bud: develops into branch.
(d) (i) Mineral element deficient in the soil of Z
Nitrogen
(ii) Feeding habits of Z
- Insectivorous/carnivorous
- Photosynthetic /Photosynthesis/Autotrophic
(e) Gaseous exchange in the leaves of plant Y
- when the stomata open;
- oxygen diffuses into the intercellular air spaces;
- carbon dioxide diffuses out during respiration;
- carbon dioxide diffuses in during photosynthesis;
- oxygen diffuses out during photosynthesis.
(f) Modifications of the leaf
Leaf Modification |
Example |
Succulent/fleshy leaves |
Kalanchoe/Bryophyllum/Life plant/Everlasting leaf, Onion leaf; Aloe |
Tendrils of petiole/leaf tips modified into tendrils |
Yam; Melons; Pumpkin/Gloriosa uperb. |
Leaves reduced to spines |
Cactus/Euphorbia/Opuntia |
Leaf with lateral buds |
Bryophyllum |
Leaves modified into pitchers |
Pitcher plant/Nepenthes |
Leaf covered with sticky glands |
Sundew/Drosera |
Scale leaves |
Onion, Ginger, Imperata, Canna lily |
Reduced into small size |
Casuarina/Whistling pine |
1 mark for leaf modification, 1 mark for corresponding example