WAEC SSCE - Agricultural Science - 2020 (Practical)

(a)(i) Toxic substance in specimen G (fresh cassava tuber)

The toxic substance is hydrocyanic acid (prussic acid / hydrogen cyanide), derived from a cyanogenic glycoside.

(a)(ii) Four ways of removing the toxic substance

• Grating the tubers and squeezing out the juice under pressure.
• Soaking (steeping) the tubers in water for some days to ferment.
• Boiling or cooking the tubers thoroughly.
• Sun-drying or frying the grated mash.

(b) Two uses each of specimens I and J

Specimen I (onion bulbs):

• Used for flavouring food and eaten as a vegetable.
• Used medicinally and as a source of vitamins A and C.

Specimen J (pepper fruits):

• Used as a spice or condiment to flavour food.
• Used medicinally and as an insect repellant in stored produce.

(c) Four pests of specimen I (onion)

• Thrips.
• Onion maggot (onion fly).
• Nematodes (eelworm).
• Rodents.

(d) Two groups of crops to which specimens I and J belong (based on use)

• Vegetable crops.
• Spice (condiment) crops.

(a) Two uses each of specimens A and B

Specimen A (hoe):

• Making ridges, heaps, mounds and seedbeds.
• Weeding and loosening or tilling the topsoil.

Specimen B (pick axe):

• Breaking up hard, compact or stony ground.
• Digging holes and pits and uprooting tree stumps, roots and stones.

(b) Four crops that require specimen D (budding knife) during propagation

• Citrus (orange).
• Mango.
• Cocoa.
• Rubber (cashew and avocado are also budded).

(c) Three other tools that serve the same purpose as specimen E (Burdizzo)

Specimen E is a bloodless castrating instrument, so other tools used to castrate livestock are:

• Elastrator (rubber-ring applicator).
• Emasculator.
• Castrating knife or scalpel.

(d) Four ways of maintaining specimen A (hoe) on the farm

• Wash off soil and dry the hoe after every use.
• Sharpen the blunt cutting edge regularly.
• Oil or grease the metal blade to prevent rusting.
• Store in a cool, dry tool shed and tighten or replace a loose or termite-damaged handle.

(a) Three reasons for stocking specimen K (tilapia) and specimen L (catfish) together in a pond

• They have different feeding habits and occupy different feeding zones. Tilapia is a herbivorous surface feeder while catfish is a carnivorous bottom feeder, so the food and space in the pond are fully utilised.
• The catfish preys on and controls the population of tilapia, which breeds rapidly and would otherwise overpopulate and become stunted in the pond.
• Stocking the two together increases total fish yield and maximises the farmer's income per unit area of pond.

(b) Four fishing gears used for harvesting specimens K and L

• Hook and line.
• Fish trap/basket.
• Cast net (or seine net, drag net, scoop net).
• Fishing spear/harpoon.

(c) Four products that could be made from specimen M (milk)

• Cheese.
• Yoghurt.
• Butter.
• Ice cream (skimmed/condensed milk, casein, ghee and whey are also obtained).

(d) Four reasons for adding specimen N (lime) to the pond

• It neutralises acidity and corrects the pH of the pond water and mud.
• It reduces turbidity, causing suspended particles to settle so that the water becomes clearer.
• It supplies calcium for the bone development of the fish and destroys leeches and other parasites on the fish.
• It increases the availability of nutrients such as phosphorus and encourages the growth of plankton (natural fish food).