This was the least popular question in the paper and the performance of candidates was very poor on this question.
Most candidates could list similarities between specimen L and M namely, presence of simple leaves, entire leaf margins, presence of chlorophyll/green colour etc. But had difficulty in stating the observable differences between the two specimens.
The expected answers are:
Specimen L/Cocoa/Fig/Gmelina/
Cashew/ Avocado Pear |
Specimen M/Elephant grass/Any grass |
Woody/hard stem |
- Hollow/soft stem |
| Oval/broad leaves |
- Elongated/Narrow leaf blade |
| Net venation |
- Parallel venation |
| Leaf smooth |
- Leaf hairy |
| Leaf blade flat horizontally |
- Leaf blade standing vertically |
| Prominent pulvinus/petioles Present |
- No pulvinus/have sheaths |
| Roots not shown |
- Roots shown |
| A twig/branch |
- Whole plant |
| Internodes clearly seen |
- Internodes covered with sheaths |
| Bark present |
- Bark absent |
A good number of candidates could state the ecological zones of the specimens namely forest and savanna but could not state features of the specimens which adapt them to their ecological zones. Expected answers are:
Adaptation
L
- Broad/oval leaves trap adequate light in dim forest;
- Leaves lie flat exposing maximum leaf surface to dim forest light.
M
- Erect leaves avoid direct intense sunlight and hairs reduce rate of transpiration;
- Underground rhizome escape burning during bush fires/survives dry season/drought.
- Flexible stem to withstand winds.
Most candidates could not state how the density of specimen M could be measured with a quadrant but could state another instrument for measuring population density namely line transect.
Most candidates could not interpret the data in the table or state that it was dealing with inter-specific competition, they could not state the conclusion to be drawn from the data or the procedure to determine the mean dry weight of plants in one pot, expected answers include:
Deterrnination Density of Specimen M
- The area under study is demarcated;
- Use a quadrant of known size;
- The quadrant is randomly tossed;
- At least 10 times;
- The number of wild grasses within the quadrant is recorded for each throw;
- The average number of wild grasses in a quadrant is calculated by dividing the total number of grass by the number of throws;
- The density is determined by dividing the average number of times wild grass occurs within the quadrant/frequency of grass by the area of the quadrant.
Explanation of Data Plants crowded in pot R and S competed for water, light,rootspace; nutrients.
Conclusion
The competition reduced growth rate of the plants/mean dry weight decreased as number of plants per pot increase.
Determination of Mean dry Weight.
- Uproot the plants carefully to obtain all root parts;
- Wash off thoroughly the Soil particles adhering to the roots;
- Cut up individual plants into separate dishes to allow thorough drying;
- Heat the plants in an oven and weight periodically until a constant weight is achieved;
- Calculate total weight by adding weights of the individual plants;
- Divide the total by the number of plants to obtain the mean dry weight.
