Agriculture 0600 | Paper 2 Mock 01 | Component: Practical Coursework

Labelled answer diagram:

(a) The genotype of the yellow-grained parent plant is pp. [1] Yellow grain colour is the recessive trait, so the plant must carry two copies of the recessive allele to express it. There is no dominant P allele present to mask the yellow phenotype.

(b) The phenotype of all F1 offspring is purple-grained. [1] Since one parent is homozygous dominant (PP) and the other is homozygous recessive (pp), every F1 individual inherits one P allele and one p allele, making them all Pp. The dominant P allele produces the purple colour.

(c) The genotype of all F1 plants is Pp (heterozygous). [1]

(d)(i) The gametes produced by an F1 plant (Pp) are P and p. [1] During meiosis, the two alleles separate into different gametes, so each gamete carries only one allele.

(d)(ii) Punnett square for the F1 cross (Pp x Pp):

The gametes P and p are shown across the top (from one parent) and down the side (from the other parent). [1] The four offspring genotypes are correctly placed: PP, Pp, Pp, and pp. [1]

(d)(iii) The expected phenotypic ratio in the F2 generation is 3 purple : 1 yellow (3:1). [1] Three of the four genotypes (PP, Pp, Pp) express the dominant purple phenotype; only pp expresses the recessive yellow phenotype.

(e) A farmer might carry out a test cross on a purple-grained plant because:

1. A purple-grained plant could be either homozygous (PP) or heterozygous (Pp), since the dominant allele masks the recessive one in both cases. The phenotype alone does not reveal the genotype. [1]
2. The farmer needs to determine the genotype to predict offspring from future crosses and to select reliable breeding stock that will breed true for purple grain. [1]

(f) How a test cross is carried out and interpreted:

1. Cross the purple-grained plant with a homozygous recessive (yellow-grained, pp) plant. [1] The recessive parent can only contribute p alleles, so the offspring's phenotype depends entirely on what allele the purple parent donates.
2. If all offspring are purple, the parent is likely homozygous (PP), because every offspring receives P from the tested parent and p from the yellow parent, giving Pp (purple) every time. [1]
3. If approximately half the offspring are purple and half are yellow (a 1:1 ratio), the parent is heterozygous (Pp), because half the gametes carry P (giving Pp, purple offspring) and half carry p (giving pp, yellow offspring). [1]

(a) The hand hoe method (cutlass and hoe) took the longest time at 80 hours per hectare [1].

(b) One hand tool other than a cutlass and hoe that could be used for land preparation: machete (or rake, spade, shovel, pickaxe, mattock) [1].

(c) Two advantages of using a tractor-drawn plough compared to a hand hoe:

1. A tractor covers a much larger area in far less time (4 hours vs 80 hours per hectare), making it dramatically faster [1].
2. A tractor produces a more uniform and deeper tillage, giving better soil preparation across the entire field [1].

Another acceptable advantage: requires less human physical effort and labour.

(d)(i) For a small-scale farmer with a 2-hectare plot and limited money, the animal-drawn plough would be most suitable [1]. It offers a good balance between cost and speed: it is much faster than the hand hoe (20 hours vs 80 hours per hectare) while costing significantly less than the tractor method ($200 vs $450 per hectare) [1].

(d)(ii) Two ways the farmer could reduce the cost of using animal-drawn equipment:

1. Share the animals and equipment with neighbouring farmers, splitting the costs [1].
2. Use own animals instead of hiring, eliminating rental fees [1].

Other acceptable methods: maintain the implements regularly to avoid costly repairs, and join a cooperative to share costs.

(e) The plot prepared with a tractor-drawn plough gave the highest maize yield because the tractor ploughs deeper and more thoroughly than the other methods [1]. This deeper tillage improves soil aeration, water infiltration, and root penetration, allowing the maize plants to access more nutrients and water from a greater volume of soil [1].

(a) The crop most likely to be wind-pollinated is Plant C (maize). [1]

Reason: maize has green flowers with no petals, produces no scent, has light smooth abundant pollen grains, and a long feathery stigma (silk). [1] All of these are classic adaptations for wind pollination: no need to attract insects, light pollen carried by air currents, and a large feathery stigma to catch airborne pollen.

(b) When pollen from Plant B (tomato) lands on the stigma of a different flower on the same plant, this is self-pollination. [1] Self-pollination is the transfer of pollen from an anther to a stigma of the same plant, whether within the same flower or between different flowers on the same individual.

(c) How a farmer carries out controlled cross-pollination to produce hybrid maize seed (4 marks):

1. Select the female parent plant and remove the tassels (male flowers) before they shed pollen. This process is called detasseling and prevents self-pollination. [1]
2. Cover the silk (female flower) with a paper or cellophane bag to prevent unwanted pollen from other plants reaching it. [1]
3. Collect fresh pollen from the tassels of the selected male parent plant. [1]
4. Carefully dust the collected pollen onto the exposed silk of the female parent, then re-cover with the bag to exclude any further uncontrolled pollination. [1]

This ensures the resulting seed carries genetic material from both chosen parents, producing F1 hybrid seed with predictable traits.

(d) Two advantages of using hybrid seed:

1. Higher yields due to hybrid vigour (heterosis): the F1 generation outperforms both parents in growth rate and productivity. [1]
2. More uniform crop: hybrid plants mature at the same time and are similar in height and quality, making harvesting and marketing easier. [1]

Other acceptable answers: improved disease resistance; better quality produce.

Labelled answer diagram:

(a) Parts of the pig digestive tract [3]

1. P - Oesophagus (gullet): the muscular tube that conveys swallowed food from the mouth to the stomach by peristalsis. [1]
2. Q - Stomach: the sac-like organ where hydrochloric acid and pepsin begin chemical digestion of proteins. [1]
3. R - Small intestine: the long, coiled tube where most chemical digestion and nutrient absorption occur, aided by enzymes from the pancreas and bile from the liver. [1]

(b) Main site of protein digestion in the pig [1]

The stomach (where pepsin begins breaking polypeptide chains) and especially the small intestine (where pancreatic trypsin and chymotrypsin complete digestion to amino acids). [1]

(c) Two concentrate feeds used in pig rations [2]

Any two of:

1. Maize (corn) - a high-energy cereal grain that forms the base of most pig rations. [1]
2. Soybean meal (or groundnut cake) - a protein-rich supplement to balance the cereal energy. [1]
3. Wheat, barley, or sorghum - alternative cereal grains.
4. Fish meal - a high-quality animal protein source.
5. Palm kernel cake - a by-product protein source.

(d) Why pigs need more concentrate feed than cattle [2]

1. Pigs are monogastric animals with a simple stomach and cannot digest large amounts of fibre or cellulose, because they lack the rumen microorganisms that produce cellulase. [1]
2. They therefore depend on energy-dense, protein-rich concentrate feeds (grains, oilseed meals) to meet their nutritional requirements for rapid growth and fattening. [1]

(e) Two signs of protein deficiency in pigs [2]

Any two of:

1. Slow growth rate / poor weight gain - protein is essential for building muscle tissue, so deficiency directly limits growth. [1]
2. Loss of body condition - the animal becomes thin or emaciated as the body breaks down its own muscle to supply amino acids. [1]
3. Poor hair or coat condition / rough, dull coat.
4. Reduced reproductive performance / smaller litter size.
5. Oedema (fluid swelling of tissues), particularly in severe cases.

(f) Importance of clean water for pigs in a fattening unit [1]

Water is essential for digestion, metabolic processes, and temperature regulation. [1] A lack of clean water reduces feed intake and slows growth, directly undermining the fattening objective.

(a) Two mineral particles commonly found in sandstone:

1. Quartz (silica / silicon dioxide) [1].
2. Feldspar [1].

Mica is also acceptable. Sandstone is a sedimentary rock composed primarily of sand-sized mineral grains cemented together.

(b) The soil on this hillside is shallow compared to soil on the flat land at the bottom of the hill because:

1. Soil on the hillside is continuously removed by erosion; surface runoff from rain carries soil particles downhill [1].
2. The eroded soil accumulates and is deposited at the bottom of the hill, building up a deeper soil layer there [1].
3. On a slope, there is insufficient time for deep soil to develop because material is constantly being removed faster than it can form from the underlying rock [1].

(c) The type of weathering that occurs when minerals in the rock react with acidic rainwater is chemical weathering [1]. Carbonic acid (formed when carbon dioxide dissolves in rainwater) and other acids dissolve susceptible minerals, gradually breaking down the rock structure.

(d) Two ways the farmer could improve the depth and fertility of this shallow soil over time:

1. Add organic matter such as compost or manure to increase the humus content, which improves nutrient supply and water-holding capacity [1].
2. Build terraces or contour ridges to slow erosion and allow soil to accumulate on the slope rather than being washed away [1].

Other acceptable methods: plant cover crops or grass to reduce erosion and add organic matter through root decay, and apply mulch to protect the surface and encourage earthworm activity.

Labelled answer diagram:

(a) Meaning of soil texture [1]

Soil texture refers to the relative proportion of different-sized mineral particles - sand, silt, and clay - in a soil sample. [1] It determines many of the soil's physical properties including drainage, water-holding capacity, and workability.

(b)(i) Soil type of sample P [1]

Clay (clay soil). [1] The ribbon test produces a long, smooth ribbon from clay soil because the tiny, flat particles stick together when moist and can be moulded without breaking.

(b)(ii) Soil type of sample Q [1]

Sandy (sandy soil). [1] Sandy soil produces a ribbon that breaks apart quickly and feels gritty because the large, rounded particles do not bind together well.

(c) Why sample Q drains faster than sample P [2]

1. Sandy soil (Q) has larger particles with bigger pore spaces (macropores) between them. [1]
2. Water moves through these large pore spaces quickly under gravity, draining freely. In contrast, clay soil (P) has tiny particles with narrow pore spaces that hold water tightly by capillary forces, so drainage is very slow. [1]

(d) Which sample is more suitable for rice, and why [2]

Sample P (clay soil) is more suitable. [1] Rice (paddy rice) is grown in flooded fields and requires the soil to retain standing water. Clay soil holds water well because its small particles and narrow pores resist drainage, maintaining the waterlogged conditions that rice needs for healthy growth. [1]

(e) One way to improve water-holding ability of sample Q [1]

Add organic matter (compost, manure, or humus) to the sandy soil. [1] Organic matter acts like a sponge, absorbing and retaining moisture in the large pore spaces between sand grains. Adding clay to the sandy soil is also acceptable.

Labelled answer diagram:

(a) Two signs of insect attack in stored grain:

1. Small round holes (exit holes) visible on the surface of individual grains, where adult insects have emerged after completing their development inside the kernel. [1]
2. Fine powdery dust (frass) found at the bottom of bags or containers, produced as insects feed on and bore through the grain. [1]

Other acceptable signs: presence of live or dead insects; webbing on the grain surface (from grain moths); unpleasant musty smell; grain feels warm to the touch due to insect metabolic activity.

(b) Two common insects that attack stored grain:

1. Maize weevil (Sitophilus zeamais), one of the most destructive pests of stored maize in tropical regions. [1]
2. Larger grain borer (Prostephanus truncatus), which bores into grain and can cause very heavy losses. [1]

Other acceptable answers: rice weevil (Sitophilus oryzae), flour beetle (Tribolium spp.), grain moth (Sitotroga cerealella).

(c) Why grain must be dried to low moisture before storage:

1. High moisture encourages mould (fungal) growth and creates warm, humid conditions inside the grain bulk that favour rapid insect breeding and egg development. [1]
2. Grain dried to below about 13% moisture content is too dry for insect eggs to develop successfully and the rate of grain deterioration (through fungal decay, heating and germination) is greatly reduced. [1]

(d) Two physical methods to protect stored grain from insect attack:

1. Use hermetic (airtight) storage bags or containers: sealing the grain removes oxygen and builds up carbon dioxide from the respiration of any insects present, suffocating them without chemicals. [1]
2. Sun drying and heat treatment: exposing grain to direct sunlight on a clean surface raises the temperature enough to kill insect eggs and larvae within the grain. [1]

Other acceptable methods: sieving and winnowing to physically remove insects; mixing grain with inert dust (ash, sand) to block air spaces and abrade insect cuticles; raising storage containers off the ground.

(e)

Advantage of fumigants: they can kill all life stages of insects (eggs, larvae, pupae and adults), including those hidden deep inside the grain kernels, and can treat large quantities of grain quickly. [1]

Disadvantage of fumigants: they are highly toxic to humans and animals and require careful handling with specialised equipment and training; improper use can cause serious poisoning. [1]

Other disadvantages: they leave no residual protection so grain can be re-infested after treatment; they may leave chemical residues on the grain.

(f) Two reasons rodents are a serious problem in grain stores:

1. Rodents eat and contaminate large quantities of grain with their droppings and urine, making it unfit for human consumption and causing significant economic losses. [1]
2. They damage storage containers and building structures by gnawing through sacks, wood and even thin metal, creating entry points for further infestation. [1]

Other acceptable answers: rodents carry and spread diseases (e.g. leptospirosis, salmonellosis); they reproduce rapidly so a small infestation can grow quickly into a large one.

(a) The process by which mineral salts enter root hair cells from the soil solution is active transport. [1] This requires energy from cellular respiration because minerals are moved against their concentration gradient (from a lower concentration in the soil solution to a higher concentration inside the cell).

(b) Two mineral elements that the yellowing plants are most likely lacking:

1. Nitrogen - essential for making amino acids, proteins, and chlorophyll. Deficiency causes general yellowing (chlorosis) of older leaves first, as nitrogen is mobile and redistributed to younger growth. [1]
2. Magnesium - a central atom in the chlorophyll molecule. Deficiency causes yellowing between the leaf veins (interveinal chlorosis). [1]

Other acceptable answers: iron or sulphur, both of which are involved in chlorophyll synthesis or function.

(c) How water moves from the soil into the root hair cell:

1. The soil solution has a higher water concentration (higher water potential) than the cell sap inside the root hair cell's vacuole, which contains dissolved sugars and salts. [1]
2. Water moves by osmosis - the net movement of water molecules from a region of higher water potential to a region of lower water potential. [1]
3. This movement occurs through the partially permeable cell membrane, which allows water molecules to pass but restricts larger solute molecules. [1]

(d) One reason plants on one side of the field may have received fewer minerals: the soil on that side may be more sandy, causing nutrients to leach away more quickly with drainage water. [1] Other acceptable reasons: uneven distribution of fertiliser during application; the previous crop on that side removed more nutrients; or drainage patterns differ across the field.

(e) To correct the yellowing, the farmer should:

1. Apply a nitrogenous fertiliser or top-dress with a compound fertiliser containing nitrogen and magnesium to replace the deficient elements. [1]
2. Apply as a foliar spray for faster uptake through the leaves, or apply to the soil around the affected plants and water in. [1]

Foliar application is faster-acting because nutrients are absorbed directly through the leaf epidermis, bypassing the slower root uptake pathway.

(a) Why the soil sample was shaken with water [1]

Shaking separates the different-sized particles from each other by breaking up soil aggregates (clumps). [1] This allows each particle type to settle individually according to its size and weight when the cylinder is left undisturbed.

(b) Particle that settled first, and why [2]

Sand settled at the bottom of the cylinder first. [1] Sand particles are the largest and heaviest of the three mineral fractions, so they sink through the water most rapidly under gravity. Silt settles next (medium-sized), and clay particles, being the smallest and lightest, remain suspended longest and settle last at the top. [1]

(c) Textural class of the soil (45% sand, 30% silt, 25% clay) [1]

Loam (loamy soil). [1] A loam contains a relatively balanced proportion of sand, silt, and clay, without any single fraction dominating to the point where it controls all the soil's properties.

(d) Why loam is good for growing vegetables [3]

Any three of:

1. Loam has good drainage so roots do not become waterlogged, preventing root rot - an important factor for most vegetable crops. [1]
2. It retains enough moisture between waterings for steady plant uptake, reducing the need for constant irrigation. [1]
3. It is easy to cultivate and has good tilth - it breaks into a fine, crumbly structure ideal for sowing small vegetable seeds and transplanting seedlings. [1]
4. It holds nutrients reasonably well (moderate cation exchange capacity) so applied fertiliser stays in the root zone.
5. It allows good root penetration, enabling vegetables to develop strong, deep root systems.

(e) Two ways organic matter improves this soil [2]

Any two of:

1. Increases water-holding capacity by acting as a sponge that absorbs and retains moisture. [1]
2. Improves soil structure and aggregation, creating a more stable crumb structure with better aeration. [1]
3. Adds nutrients as the humus decomposes, releasing nitrogen, phosphorus, and other elements slowly.
4. Increases microbial activity, which further breaks down organic residues and cycles nutrients.
5. Improves aeration by creating more pore spaces.