2024 Cambridge IGCSE Agriculture (0600) Practice Paper with Answers

(a) (i) Maintenance ration is the quantity of feed required to keep an animal in a healthy state, maintaining its body weight and vital functions without gaining or losing weight, or producing any output.
(ii) Production ration is the extra feed required in addition to the maintenance ration to support milk, meat, wool, egg production, growth, or physical work.

(b) Age, body size/mass, level of production/yield, environmental temperature/climate, activity level/exercise.

(c) A lack of calcium leads to soft-shelled or thin-shelled eggs, which break easily. The hen may cease egg production altogether due to depleted calcium reserves. It also leads to weak, brittle bones (osteoporosis) as the hen mobilises calcium from her own skeleton to produce eggshells.

(a) (i) 1 mark for: Feed needed to maintain life/vital functions and constant body weight.
(ii) 1 mark for: Additional feed required for growth/reproduction/production of milk, meat, or eggs.

(b) Max 3 marks, 1 mark for each valid factor:
- Age of the animal
- Body weight / size
- Level of production/yield
- Environmental temperature / climate / weather
- Activity level / amount of exercise / work
- Health status

(c) Max 3 marks:
- Thin-shelled / soft-shelled eggs [1]
- Reduced egg laying / cessation of production [1]
- Brittle bones / osteoporosis / leg weakness / rickets [1]
- Poor muscle contraction / nerve function issues [1]

(a) Systemic pesticides are absorbed into the plant's vascular system and translocated throughout the plant. Sucking pests feed directly on the sap containing the toxin, ensuring ingestion. Contact pesticides rely on direct physical contact, which is difficult as sucking pests often hide on the undersides of leaves or inside curled foliage.

(b) The farmer could use crop rotation or timely weeding (cultural methods) to disrupt pest life cycles and remove alternative hosts. Simultaneously, they can introduce natural predators like ladybirds (biological method) to feed on any remaining pests, ensuring long-term control with minimal chemical inputs.

(c) Avoid spraying on windy days to prevent chemical drift; use low-drift nozzles; maintain an unsprayed buffer strip/zone along the water boundary.

(a) Max 2 marks:
- Systemic pesticides are absorbed by the plant and move through the sap [1]
- Sucking pests ingest the chemical directly while feeding on plant juices [1]
- Contact pesticides fail because sucking pests are often hidden / sheltered under leaves [1]

(b) Max 4 marks:
- Cultural method identified (e.g. weeding, crop rotation, trap cropping) [1]
- Explanation of how this cultural method reduces pest population/disrupts life cycle [1]
- Biological method identified (e.g. introducing predators, parasites, pheromone traps) [1]
- Explanation of how this biological control kills/reduces remaining pests [1]

(c) Max 2 marks, 1 mark for each valid precaution:
- Do not spray on windy days / avoid spray drift [1]
- Maintain an unsprayed buffer zone near the water [1]
- Use low-drift nozzles [1]
- Do not wash spraying equipment in or near the water body [1]

(a) Soil texture is the relative proportion of sand, silt, and clay particles (it is a permanent characteristic). Soil structure is the way these individual soil particles are clumped or arranged together into aggregates or crumbs (and can be altered by management).

(b) 1. Adding organic matter (manure, compost) to bind clay particles into larger, stable crumb aggregates, which increases pore space. 2. Adding lime (calcium carbonate/calcium hydroxide) to promote flocculation, causing fine clay particles to group together into larger aggregates.

(c) Sandy soils have larger pore spaces and drain water much faster than clay soils, holding less water. Water has a high specific heat capacity, meaning it takes a lot of energy to heat up; because sandy soil holds less water, it requires less heat energy to increase in temperature.

(a) Max 2 marks:
- Texture refers to the proportion of sand, silt, and clay / size of soil particles [1]
- Structure refers to how these particles are arranged / aggregated into crumbs [1]

(b) Max 4 marks (2 marks for each method, including description of how it works):
- Method 1: Add organic matter / manure / compost [1]; binds particles together to form stable crumb structures, increasing macro-pores [1]
- Method 2: Add lime / calcium compounds [1]; causes flocculation of clay particles into aggregates, improving aeration and drainage [1]
- Method 3: Minimise tillage / avoid heavy machinery when wet [1]; prevents compaction and breakdown of existing structure [1]

(c) Max 2 marks:
- Sandy soils drain faster / hold less water than clay soils [1]
- Water has a high specific heat capacity / requires more heat to warm up, so drier soils warm up quicker [1]

(a) Heterozygous means having two different alleles for a particular gene (e.g., Bb).

(b) (i)
- Parents: Heterozygous Black Bull (Bb) x Red Cow (bb)
- Gametes from Bull: B and b; Gametes from Cow: b
- Punnett Square / Offspring Genotypes:
- B x b -> Bb
- b x b -> bb
- Genotypes: 50% Bb, 50% bb
- Phenotypes: 50% Black, 50% Red
(ii) 50% (or 1:1 ratio / 0.5 probability).

(c) A farmer may want to eliminate the red coat to maintain breed purity standards, to meet specific market/premium demands for uniform black cattle, or because uniform coat colors make herd management and marketing simpler.

(a) 1 mark for: Having two different alleles for a gene / genotype with one dominant and one recessive allele.

(b) (i) Max 4 marks:
- Correct parental genotypes: Bb x bb [1]
- Correct gametes: (B and b) and (b and b) [1]
- Correct offspring genotypes: Bb and bb [1]
- Correct offspring phenotypes matched to genotypes: Bb = black, bb = red [1]
(ii) 1 mark for: 50% / 1 in 2 / 1:1 / 0.5 [1]

(c) Max 2 marks, 1 mark for each valid suggestion:
- Breed standards / purebred criteria [1]
- Higher market price / customer preference for uniform black coats [1]
- Ease of grading / uniform herd appearance [1]

(a) Water in the soil has a higher water potential than the cell sap inside the root hair cell. Water moves down this water potential gradient into the root hair cell by osmosis, passing through the selectively permeable cell membrane.

(b) Xylem vessels are made of dead cells with lignified walls, forming hollow tubes; they transport water and mineral salts in a one-way flow upwards from roots to leaves. Phloem tubes are made of living cells (sieve tubes and companion cells) with perforated sieve plates; they transport manufactured food/sucrose in a two-way flow (translocation) from leaves to sinks.

(c) High humidity reduces the water vapor concentration gradient between the air spaces inside the leaf and the external atmosphere. This decreases the rate of diffusion of water vapor out through the stomata, thereby slowing down the rate of transpiration.

(a) Max 3 marks:
- Concentration of water / water potential is higher in soil than in the root cell [1]
- Water moves by osmosis [1]
- Across a selectively/partially permeable membrane [1]

(b) Max 3 marks, contrasting points must match:
- Structure: Xylem contains dead cells / lignified walls / hollow tubes vs Phloem contains living cells / sieve plates / companion cells [1]
- Direction of flow: Xylem flow is upwards only vs Phloem flow is two-way (up and down) [1]
- Transport material: Xylem transports water and minerals vs Phloem transports sucrose / amino acids / manufactured food [1]

(c) Max 2 marks:
- Decreases the concentration gradient of water vapor between leaf interior and atmosphere [1]
- Reduces rate of diffusion out of stomata / decreases transpiration rate [1]

(a) Selective herbicides kill only specific target weeds (e.g., broadleaf weeds) while leaving the main crop unharmed. Non-selective herbicides kill all green vegetation they come into contact with, including both weeds and crops.

(b) Weeds can contaminate the harvested grain with weed seeds, lowering crop purity; weed residues can stain or discolor the maize grain during harvesting; weed presence can result in smaller, poorly formed maize cobs due to competition for resources, leading to a lower grade.

(c) Mulch forms a physical barrier that blocks sunlight from reaching the soil surface, preventing weed seeds from germinating and photosynthesising. Another benefit of mulching is that it reduces evaporation, thereby conserving soil moisture (or regulates soil temperature, or prevents soil erosion).

(a) Max 2 marks:
- Selective: kills only target plants / does not harm the crop [1]
- Non-selective: kills all plants / any green plant tissue it contacts [1]

(b) Max 3 marks, 1 mark for each valid description:
- Contaminating harvested grain with weed seeds / reduces purity [1]
- Discoloring or staining maize grains [1]
- Causing small/stunted/poorly developed cobs (reducing quality grade) [1]
- Imparting off-flavours or odors to the grain [1]

(c) Max 3 marks:
- Mulch blocks sunlight [1]
- Prevents weed seeds from germinating / photosynthesising [1]
- Other benefit (1 mark): conserves soil moisture / reduces evaporation / prevents erosion / regulates soil temperature [1]

(a) A pathogen is the actual microorganism (such as a bacterium, virus, or protozoan) that causes the disease. A vector is an organism (such as a tick or tsetse fly) that does not cause the disease itself but transmits the pathogen from one host to another.

(b) Tick-borne diseases can be controlled by regular dipping or spraying of cattle with acaricides to kill ticks; practicing rotational grazing or pasture spelling to break the tick life cycle; and breeding tick-resistant cattle breeds (such as Bos indicus crosses).

(c) Weight loss or poor body condition; pale gums/eyes indicating anemia; a swollen, watery area under the jaw known as 'bottle jaw' (edema); a rough, dull fleece coat; persistent diarrhea (scours).

(a) Max 2 marks:
- Pathogen: the disease-causing organism / microbe (e.g., bacteria, protozoa) [1]
- Vector: the carrier organism that transmits the pathogen (e.g., tick) [1]

(b) Max 3 marks, 1 mark for each valid control measure:
- Apply acaricides / dip cattle / spray cattle [1]
- Rotational grazing / pasture spelling (breaks life cycle) [1]
- Breed tick-resistant cattle [1]
- Clear brush/tall grass where ticks live [1]

(c) Max 3 marks, 1 mark for each valid clinical sign:
- Weight loss / poor growth rate / emargination [1]
- Pale mucous membranes / anemia [1]
- Bottle jaw / swelling under jaw [1]
- Rough / dull / dry wool [1]
- Diarrhea / scours / dirty hindquarters [1]
- Lethargy / weakness [1]

(a) Artificial selection is the process by which humans identify desirable traits in plants or animals, and systematically breed those individuals together to produce offspring with those desired characteristics.

(b) First, cross a parent plant known for drought resistance with a parent plant known for high sweetness. Grow the resulting offspring under dry conditions and test their fruits for sugar content. Select the individual plants that survive best and produce the sweetest fruit. Cross these selected plants with each other, and repeat this selection and crossing process over several generations until a stable variety that breeds true for both traits is established.

(c) 1. Reduced genetic diversity/narrow gene pool, making the entire crop vulnerable to a single new disease. 2. Loss of other beneficial traits (such as pest resistance or shelf life) that were not selected for.

(a) Max 2 marks:
- Humans select parents with desirable traits [1]
- Breed them to pass these genes/traits to the next generation [1]

(b) Max 4 marks:
- Step 1: Identify and cross a drought-resistant parent with a sweet-fruiting parent [1]
- Step 2: Grow offspring under drought conditions / select survivors with high sweetness [1]
- Step 3: Breed the selected sweet, drought-resistant offspring together [1]
- Step 4: Repeat the process over several generations until the traits breed true [1]

(c) Max 2 marks, 1 mark for each valid disadvantage:
- Loss of genetic variation / smaller gene pool [1]
- Increased vulnerability to diseases / pests [1]
- Inbreeding depression [1]
- Loss of non-selected beneficial traits [1]

(a)
**A** - Protein (necessary for tissue growth and repair)
**B** - Bone and teeth formation / milk production / muscle function
**C** - Cereal grains (e.g., maize, barley, oats) / molasses
**D** - Good eyesight / maintaining healthy mucous membranes and skin / disease resistance

(b)
(i) A production ration is the extra feed provided to an animal above its maintenance requirements to enable it to produce milk, meat, wool, work, or support foetal growth.
(ii) Situations include growth (in young animals), pregnancy (gestation), egg production, wool production, or heavy draft work.

(c) In the final trimester, the foetus grows at a very rapid rate, demanding a high amount of protein for muscle and skeletal tissue development. Additionally, the mother needs protein to prepare for lactation (colostrum and milk synthesis).

(a) [4 marks]
1 mark for each correct answer:
- **A**: Protein
- **B**: Bone/teeth development / milk production / muscle contraction
- **C**: Cereal grain / named cereal (e.g., maize, wheat, barley) / molasses
- **D**: Vision / eyesight / healthy skin / healthy mucous membranes / disease resistance

(b)(i) [1 mark]
- Feed given in addition to maintenance ration to support production/output (meat, milk, growth, work) [1]

(b)(ii) [1 mark]
- Growth / young animals [1]
- Pregnancy / gestation / foetal development [1]
- Egg production [1]
- Wool production [1]
- Work / draft power [1]
(Accept any one correct point)

(c) [2 marks]
- Rapid foetal growth occurs in the final stages of pregnancy [1]
- Protein is required for development of foetal tissues/muscles/organs [1]
- Protein is needed to prepare for colostrum/milk production [1]
(Max 2 marks)

(a)
**A** - Protein (necessary for tissue growth and repair)
**B** - Bone and teeth formation / milk production / muscle function
**C** - Cereal grains (e.g., maize, barley, oats) / molasses
**D** - Good eyesight / maintaining healthy mucous membranes and skin / disease resistance

(b)
(i) A production ration is the extra feed provided to an animal above its maintenance requirements to enable it to produce milk, meat, wool, work, or support foetal growth.
(ii) Situations include growth (in young animals), pregnancy (gestation), egg production, wool production, or heavy draft work.

(c) In the final trimester, the foetus grows at a very rapid rate, demanding a high amount of protein for muscle and skeletal tissue development. Additionally, the mother needs protein to prepare for lactation (colostrum and milk synthesis).

(a) [4 marks]
1 mark for each correct answer:
- **A**: Protein
- **B**: Bone/teeth development / milk production / muscle contraction
- **C**: Cereal grain / named cereal (e.g., maize, wheat, barley) / molasses
- **D**: Vision / eyesight / healthy skin / healthy mucous membranes / disease resistance

(b)(i) [1 mark]
- Feed given in addition to maintenance ration to support production/output (meat, milk, growth, work) [1]

(b)(ii) [1 mark]
- Growth / young animals [1]
- Pregnancy / gestation / foetal development [1]
- Egg production [1]
- Wool production [1]
- Work / draft power [1]
(Accept any one correct point)

(c) [2 marks]
- Rapid foetal growth occurs in the final stages of pregnancy [1]
- Protein is required for development of foetal tissues/muscles/organs [1]
- Protein is needed to prepare for colostrum/milk production [1]
(Max 2 marks)

(a) A maintenance ration is the minimum daily feed required to keep an animal alive and healthy, maintaining its constant body weight without any loss or gain, and without producing any milk, meat, wool, or eggs. A production ration is the extra feed supplied above the maintenance level to provide the nutrients needed for productive functions, such as producing milk, growing muscle, developing a foetus, or producing wool.

(b) During peak lactation, the animal has extremely high energy and protein requirements to synthesize milk. It also needs significantly higher levels of calcium, phosphorus, and water to sustain high milk yields and prevent metabolic disorders like milk fever. In contrast, during the dry period, milk production stops, causing a major drop in overall daily energy requirements. However, the ration must still provide adequate nutrients (especially high-quality protein and minerals) to support rapid foetal development in the final stages of pregnancy and prepare the animal for the next lactation cycle, while avoiding overfeeding which leads to obesity and calving difficulties.

(c) Rotational grazing improves pasture utilization because paddocks are grazed sequentially, allowing rested areas time to recover and regrow. It reduces selective overgrazing of highly palatable species, ensuring more uniform pasture defoliation. High stocking densities for short periods also minimize food wastage from trampling and fouling. It improves livestock health by breaking the life cycles of internal parasites; moving stock to clean paddocks before worm eggs can hatch and develop into infective larvae reduces pasture contamination. Animals also feed on fresher, highly nutritious forage, which boosts their immunity against diseases.

(a) [Max 4 marks]
- Maintenance ration definition: daily feed needed to keep animal alive / in healthy condition [1]
- without change in body mass / without production [1]
- Production ration definition: feed required in excess of maintenance requirements [1]
- for producing milk / meat / eggs / wool / reproduction / work [1]

(b) [Max 5 marks]
- Peak lactation requires high energy and protein for milk synthesis [1]
- High mineral demand (especially calcium/phosphorus) to prevent milk fever [1]
- Extremely high water demand during peak lactation [1]
- Dry period energy requirements drop significantly as milking stops [1]
- Nutrients must still support rapid foetal growth in late pregnancy [1]
- Overfeeding in the dry period must be avoided to prevent obesity/calving issues [1]

(c) [Max 6 marks]
Pasture utilization (Max 3 marks):
- Resting periods allow pasture species to regrow and recover [1]
- Confining stock prevents selective grazing, promoting uniform forage utilization [1]
- Short, high-density grazing sessions reduce forage waste from trampling/fouling [1]
- Increases the carrying capacity of the land [1]
Livestock health (Max 3 marks):
- Moving animals breaks the life cycle of gastrointestinal parasites [1]
- Animals are moved to clean paddocks before parasite larvae become infective [1]
- Higher nutritional value of fresh pasture boosts stock immunity [1]
- Reduced risk of pasture-borne hoof diseases (e.g. foot rot) by avoiding muddy, over-grazed areas [1]

(a) Three main causes of soil erosion are:
1. Wind action: strong winds blowing over dry, loose, and unprotected soils (especially sandy soils) carry away fine particles.
2. Water action / rainfall: heavy storm rain on bare slopes creates surface runoff that washes away loose topsoil.
3. Deforestation / removal of vegetation cover: clearing trees and crops exposes the soil directly to rain splash impact and wind, while removing roots that bind soil particles together.

(b) Conserving soil on a sloping field can be achieved through:
- Mechanical methods:
1. Terracing: constructing level steps or platforms along the slope to reduce the speed and volume of water runoff.
2. Contour bunds: building earth or stone ridges along the contours of the slope to trap sediment and water.
3. Cut-off drains: digging channels at the top or sides of the slope to intercept and safely divert excess runoff away from the cultivated field.
- Biological methods:
1. Cover cropping: planting fast-growing, low-lying crops (such as sweet potato or legumes) to shield the soil surface from water droplets and wind.
2. Mulching: covering bare soil with organic material (e.g., straw, crop residues) to absorb rainfall energy, prevent soil crusting, and slow down runoff.
3. Strip cropping: growing alternating strips of row crops and close-growing cover crops across the slope to catch moving soil particles.

(c) Soil erosion reduces fertility and crop yields because:
- It removes the topsoil, which is the layer containing the highest concentration of organic matter and plant-available nutrients.
- The loss of organic matter reduces the soil's cation exchange capacity (CEC), meaning the soil is less able to retain mineral nutrients.
- It damages soil structure, leading to surface crusting and compaction, which hinders root penetration and respiration.
- Water infiltration rates are lowered, which reduces the water-holding capacity of the soil, causing crops to suffer from drought stress.
- The infertile, acidic, or rocky subsoil is exposed, providing a poor environment for seed germination and plant growth, resulting in stunted crops and severely reduced yields.

(a) [Max 3 marks - 1 mark for each described cause]
- Heavy rainfall/water runoff washing away loose soil on slopes [1]
- Strong winds lifting and carrying away dry, unprotected soil particles [1]
- Deforestation/vegetation clearing exposing the soil surface [1]
- Overgrazing by livestock which removes ground cover and weakens soil binding [1]
- Incorrect tillage practices, such as ploughing up and down slopes [1]

(b) [Max 6 marks - Max 3 marks for mechanical, Max 3 marks for biological]
Mechanical methods (Max 3 marks):
- Terracing: leveling slopes into steps to slow runoff [1]
- Contour bunds/ridges: soil/stone barriers across slopes to trap water and soil [1]
- Cut-off drains: channels to divert run-on water safely away from crops [1]
Biological methods (Max 3 marks):
- Cover cropping: growing dense plants to protect soil from rain splash [1]
- Mulching: applying plant residues to cover bare soil and reduce runoff velocity [1]
- Strip cropping: alternating strips of different crops along contours to capture sediment [1]
- Windbreaks/shelterbelts: planting rows of trees/shrubs to reduce wind speed [1]
- Contour grass strips: maintaining strips of permanent grass along contours [1]

(c) [Max 6 marks - 1 mark for each explained point]
- Topsoil removal depletes the most fertile, nutrient-dense layer of the soil [1]
- Loss of organic matter lowers the soil's nutrient-holding capacity / CEC [1]
- Essential macro-nutrients (N, P, K) are washed away or blown off [1]
- Loss of soil structure leads to compaction / poor aeration [1]
- Water infiltration decreases, reducing the water-holding capacity of the root zone [1]
- Exposure of subsoil, which is often acidic / stony / nutrient-deficient [1]
- Stunted crop growth and lower crop yields due to nutrient deficiency and moisture stress [1]