TEST OF PRACTICAL KNOWLEDGE QUESTION (a) ldentify specimens N, O, and P. Specimen N; Specimen O; Specimen P; %% (b) State the relationship between specimens...

Answer Details

(a) Identification of the specimens

• Specimen N: Water lettuce (a floating aquatic weed).
• Specimen O: Catfish (Clarias spp.).
• Specimen P: Tilapia (Tilapia spp.).

(b) Relationship between specimens O and P

It is a predator-prey relationship. The catfish (O) feeds on the fries and fingerlings of the tilapia (P), thereby helping to control the population of the tilapia in the pond.

(c) Five economic importance of specimen N (water lettuce) in an aquatic ecosystem

1. It serves as food for some herbivorous fish.
2. It provides a breeding ground and shelter that hides fish from predators.
3. It limits the penetration of light into the pond and hinders proper aeration.
4. It takes up nutrients that would otherwise be used by the planktons and competes with fish for dissolved oxygen through root respiration.
5. It hinders the free movement of aquatic organisms, interferes with fish harvesting and increases the cost of fish production.

(d) Three benefits of stocking specimens O and P together in the same pond

1. Population control: the catfish (O) preys on excess tilapia (P) fingerlings, preventing overcrowding and stunted growth so the survivors reach marketable size.
2. Fuller use of the pond and feed: tilapia feed mainly in the upper and middle water while catfish feed at the bottom, so all feeding levels and available food are used, giving a higher total yield.
3. Higher and more varied income: two marketable species are harvested from one pond, spreading risk and increasing the farmer's profit.