Summative Practice 4 – Question 1 & 2 (Form 5 Biology Textbook Exercise and Answer)

Question 1:
(a) Are xylem vessels living or dead structures? Give a reason for your answer.

(b) What is the main function of the xylem vessel? State three structural adaptations of the xylem vessels and their functions.

(c) How are the adaptations in the roots of plants similar to the adaptations of the small intestines in humans for nutrient absorption? Explain.

(d) Systemic pesticides could be absorbed and carried throughout the whole plant. Does spraying pesticides systematically onto leaves kill insects such as aphids that primarily feed on the shoots of plants? Explain.

Xylem tissues are dead cells at maturity as they are hollow and do not have cytoplasm.

To transport water and mineral salts that are absorbed by the roots, to the stems and leaves.

• The tissue is hollow to allow water transport.
• The walls have lignin to provide support and prevent them from collapsing.
• Arranged longitudinally from end to end to allow water flow.

The high number of root hairs increases the surface area for water absorbtion. This is similar to the high number of vili in small intestine that increases the surface area for nutrient absorbtion from digested food.

Systemic pesticides seep into plants. When insect pests consume and digest the plant, the chemicals in the pesticide kills it.

Question 2:
Photosynthesis product such as sucrose is transported by the phloem through translocation from the leaves to other parts of the plants such as the seeds, fruit, roots and tubers.
(a) Describe the pathway of sucrose molecules as it is transported from the leaves to other part of the plant such as the fruit.
(b) Plan an experiment using aphid to prove that the translocation of sucrose and amino acids occur in the phloem.

Sucrose is transported through companion cells from the leaves to the sieve tubes. This reduces the water potential in the sieve tube. Water diffuse into the sieve tube by osmosis and increases the hydrostatic pressure in the sieve tube. The phloem sap is transported from the sieve tubes to other parts such as fruits and tubers.

1. Expose a balsam plant under sunlight for one hour.

2. Introduce an aphid to the young stem of the plant.

3. Observe the aphid with a magnifying glass.

4. Using a knife, separate the body of the aphid from the stylet once the stylets is embedded into the phloem.

5. Place a microscope slide at the edge of the stylet to collect the secreted liquid.

6. Observe the liquid under a light microscope.

Leave a Comment