Cambridge IGCSE · thinka 原创模拟试题

2023 Cambridge IGCSE Agriculture (0600) 模拟试题及答案详解

Thinka Nov 2023 (V2) Cambridge IGCSE-Style Mock — Agriculture (0600)

100 分105 分钟2023

An original Thinka practice paper modelled on the structure and difficulty of the Nov 2023 (V2) Cambridge IGCSE Agriculture (0600) paper. Not affiliated with or reproduced from Cambridge.

甲部

Answer all questions in the spaces provided.

9 题目 · 72 分

题目 1 · structured

8 分

A soil sample is analyzed and found to contain 40% sand, 40% silt, and 20% clay. (a) (i) State the texture class of this soil. (ii) Describe two characteristics of this soil type that make it highly suitable for growing arable crops. (b) (i) Explain how a high clay content can lead to soil compaction if heavy machinery is used. (ii) Suggest two management practices a farmer can implement to reduce soil compaction in a clay-dominant field.

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解题

(a) (i) The texture class is a loam. (ii) A loam soil has a balanced proportion of sand, silt, and clay, which gives it good water retention from the clay/silt components and adequate aeration/drainage from the sand component, making it easy to cultivate and highly fertile. (b) (i) Clay soils consist of very small, flat particles with high surface area. When wet, these particles easily slide past each other. Heavy machinery exerts high pressure, squeezing the particles closely together and reducing the pore spaces (air gaps), leading to a dense, compacted layer. (ii) Farmers can avoid using heavy machinery or cultivating when the soil is wet, add organic manure/compost to improve structure and stability, use low ground-pressure tyres, or practice minimal/zero-tillage.

评分标准

(a) (i) Loam [1] (ii) Two characteristics such as: balanced drainage/aeration [1], good moisture retention [1], nutrient-rich/fertile [1], easy to cultivate [1] (Max 2). (b) (i) Explanation of compaction: small flat clay particles slide/pack together [1], pressure from wheels/implements forces out air/water spaces [1]. (ii) Two practices: avoid wet-working [1], add organic matter [1], use wider/low-pressure tyres [1], minimal tillage [1] (Max 2).

题目 2 · structured

8 分

The phosphorus cycle is essential for plant growth. (a) (i) State the primary role of phosphorus in developing plants. (ii) Describe how soil pH affects the availability of phosphorus to crops. (b) A farmer has a choice between an inorganic NPK fertilizer (15-15-15) and well-rotted farmyard manure. (i) Calculate the mass of nitrogen in a 50 kg bag of NPK 15-15-15 fertilizer. Show your working. (ii) Explain three long-term advantages of using organic manure rather than inorganic NPK fertilizers on sandy soils.

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解题

(a) (i) Phosphorus is crucial for root development, energy transfer (ATP formation), and early maturity. (ii) Phosphorus availability is maximized at a near-neutral pH (6.0 to 7.0). In highly acidic soils, it binds with iron and aluminium; in highly alkaline soils, it precipitates with calcium, making it unavailable to plants. (b) (i) Nitrogen content = 15% of 50 kg = (15 / 100) * 50 = 7.5 kg. (ii) Organic manure improves the soil's structure by binding loose sand particles, which dramatically increases its water-holding capacity. It provides organic carbon that feeds beneficial soil organisms, and its slow-release nutrients are less prone to leaching during heavy rains compared to highly soluble synthetic NPK.

评分标准

(a) (i) Root growth / energy transfer (ATP) [1]. (ii) Maximum availability at pH 6-7 [1]; binds with iron/aluminium in acid soils OR with calcium in alkaline soils [1]. (b) (i) Working shown: 15% of 50 OR 0.15 * 50 [1]; correct answer: 7.5 kg [1]. (ii) Any three advantages explained: improves soil structure/aggregation [1], increases water retention [1], feeds soil microbes [1], reduces nutrient leaching [1] (Max 3).

题目 3 · structured

8 分

Hypogeal and epigeal are two types of seed germination. (a) (i) Define the term 'hypogeal germination'. (ii) State one crop that exhibits hypogeal germination and one that exhibits epigeal germination. (b) (i) Describe how a farmer can test the viability of a batch of seeds before sowing them in the field. (ii) Explain why planting seeds too deep in a heavy clay soil can result in a poor crop stand.

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解题

(a) (i) Hypogeal germination is a process where the cotyledons remain below the soil surface while the epicotyl elongates. (ii) Maize is a classic example of hypogeal germination, while the common bean (Phaseolus vulgaris) undergoes epigeal germination. (b) (i) A farmer can place a known number of seeds (e.g., 100) on a damp paper towel in a warm container, keep them moist, and count the sprouted seeds after several days to compute the percentage of viable seeds. (ii) Clay soils have very small pores that easily waterlog, limiting oxygen for respiration. Furthermore, a deep-planted seed must push through heavy, compacted clay; it may deplete all its stored starch reserves in the cotyledons/endosperm and die before its shoot reaches the surface.

评分标准

(a) (i) Cotyledons remain underground [1]. (ii) One hypogeal example (e.g., maize/wheat) [1]; one epigeal example (e.g., bean/sunflower) [1]. (b) (i) Viability test: place sample on moist medium [1], record germination count/percentage [1]. (ii) Reasons: lack of oxygen in clay pores [1], high resistance of clay particles/crusting [1], seed reserves exhausted before emergence [1].

题目 4 · structured

8 分

Pesticides are classified as either systemic or contact. (a) (i) Explain the difference in the mode of action between a systemic insecticide and a contact insecticide. (ii) State one disadvantage of using contact insecticides compared to systemic insecticides. (b) Integrated Pest Management (IPM) combines multiple control methods. (i) Describe two biological control methods that can be used to manage insect pests in a crop field. (ii) Outline three safety precautions a farmer must take when mixing and preparing concentrated liquid pesticides.

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解题

(a) (i) A systemic insecticide is absorbed by the plant and translocated through its vascular system, killing pests when they feed on the sap. A contact insecticide remains on the outer plant surfaces and kills pests directly when they come into physical contact with it. (ii) Contact insecticides are easily washed away by rain, require complete leaf coverage, and do not kill pests feeding inside stems or under leaves. (b) (i) Biological control includes introducing natural predators (like ladybird beetles to consume aphids) or using host-specific pathogens (such as Bacillus thuringiensis bacteria) that infect and kill pest larvae. (ii) When mixing concentrated pesticides, the farmer should wear full personal protective equipment (PPE) including chemical-resistant gloves and face shields, mix only in well-ventilated outdoor areas, and use specialized equipment to avoid splashes.

评分标准

(a) (i) Systemic: absorbed and translocated / kills on feeding [1]; Contact: stays on surface / kills on physical touch [1]. (ii) Disadvantage: washed off by rain / requires perfect coverage [1]. (b) (i) Two biological methods: release of predators/parasitoids [1], use of microbial pathogens/biopesticides [1], release of sterile males OR pheromones [1] (Max 2). (ii) Three safety steps: wear gloves/mask/goggles [1], mix in well-ventilated area [1], use dedicated utensils [1], avoid skin contact/splashes [1] (Max 3).

题目 5 · structured

8 分

Compare the stomach of a ruminant (e.g., sheep) with that of a non-ruminant (e.g., pig). (a) (i) Identify the four compartments of the ruminant stomach in the correct order of food passage. (ii) State which compartment is known as the 'true stomach' and explain why it is given this name. (b) (i) Explain the role of micro-organisms in the rumen of a sheep. (ii) Describe how the digestion of fats differs between ruminant and non-ruminant animals.

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解题

(a) (i) In order, the compartments are the rumen, reticulum, omasum, and abomasum. (ii) The abomasum is the 'true stomach' because, unlike the first three compartments which are specialized for microbial fermentation and water absorption, the abomasum secretes hydrochloric acid and gastric enzymes (like pepsin) to break down protein chemically, functioning exactly like a monogastric stomach. (b) (i) Rumen micro-organisms produce cellulase enzymes to break down tough plant cellulose into volatile fatty acids (VFAs) for energy, and they also synthesize essential amino acids and B-vitamins. (ii) In ruminants, microbes hydrogenate unsaturated dietary fats into saturated fatty acids before they reach the small intestine. In non-ruminants, fats travel unchanged to the duodenum, where they are emulsified by liver bile and digested by pancreatic lipase enzymes.

评分标准

(a) (i) Correct order: Rumen, reticulum, omasum, abomasum [2] (1 mark for any two correct, 2 marks for all four in order). (ii) Abomasum [1]; secretes hydrochloric acid / pepsin / enzymes for chemical protein digestion [1]. (b) (i) Rumen microbes role: produce cellulase to digest cellulose [1], synthesize microbial proteins / volatile fatty acids [1]. (ii) Fat digestion difference: ruminant microbes hydrogenate/saturate fats [1], non-ruminants emulsify fats using bile / digest with pancreatic lipase [1].

题目 6 · structured

8 分

The female reproductive tract of a cow plays a vital role in reproduction. (a) (i) State the function of the ovaries and the fallopian tubes (oviducts) in female mammals. (ii) Explain the changes that occur in the cervix of a cow during pregnancy. (b) (i) Describe three external physical signs that indicate a cow is approaching parturition (giving birth). (ii) Define the term 'colostrum' and state its primary benefit to a newborn calf.

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解题

(a) (i) Ovaries produce the female gametes (ova) and secrete sex hormones (oestrogen and progesterone). The fallopian tubes are where fertilization occurs and they transport the fertilized ovum to the uterus. (ii) Following successful fertilization, the cervix secretes a thick, gelatinous mucus plug (the cervical plug) that seals the cervical canal, preventing any ascending bacterial infection from entering the pregnant uterus and harming the fetus. (b) (i) Three signs include: a visibly swollen and reddened vulva; significant enlargement of the udder (springing) with colostrum leaking; and the relaxation of the pelvic ligaments, causing hollows to appear on either side of the tailhead. (ii) Colostrum is the initial antibody-rich milk produced immediately post-parturition, which provides essential passive immunity to the newborn calf to fight infections.

评分标准

(a) (i) Ovaries: egg/hormone production [1]; Fallopian tubes: fertilization site / egg transport [1]. (ii) Cervix changes: secretes thick mucus plug [1]; seals the uterus to prevent infection [1]. (b) (i) Three signs: swollen/red vulva [1], enlarged udder/milk let-down [1], relaxed pelvic ligaments/hollow tailhead [1], mucus discharge [1] (Max 3). (ii) Colostrum: first milk containing maternal antibodies for passive immunity [1].

题目 7 · structured

8 分

In cattle, the polled condition (lack of horns) is dominant (H) to the horned condition (h). (a) (i) Define the terms 'homozygous' and 'heterozygous'. (ii) A heterozygous polled bull (Hh) is crossed with a horned cow (hh). Determine the expected genotypic and phenotypic ratios of the offspring. Use a genetic diagram (Punnett square) to show your working. (b) (i) Explain why a recessive genetic disorder can suddenly appear in a herd even if both parents do not show the disorder. (ii) State one method a breeder can use to determine whether a polled bull is homozygous (HH) or heterozygous (Hh).

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解题

(a) (i) Homozygous means possessing two identical alleles for a specific gene (e.g., HH or hh). Heterozygous means possessing two different alleles for a specific gene (e.g., Hh). (ii) Crossing a heterozygous bull (Hh) with a horned cow (hh) yields: Gametes from bull: H, h. Gametes from cow: h. Punnett square results: Hh (polled) and hh (horned). The expected genotypic ratio is 1 Hh : 1 hh, and the expected phenotypic ratio is 1 polled : 1 horned. (b) (i) If a disorder is recessive, both parents can be carrier heterozygotes (carrying one normal dominant allele and one mutated recessive allele). They appear completely healthy. However, if both pass on their recessive allele to an offspring, the offspring will be homozygous recessive and exhibit the disorder. (ii) The breeder can perform a test cross by mating the polled bull with a homozygous recessive horned cow (hh). If any horned offspring are produced, the bull must be heterozygous (Hh); if all offspring are polled, the bull is likely homozygous (HH).

评分标准

(a) (i) Homozygous: two identical alleles [1]; Heterozygous: two different alleles [1]. (ii) Working/Punnett square showing Hh x hh [1]; correct Genotypes (1 Hh : 1 hh) [1] and Phenotypes (1 polled : 1 horned) [1] (Max 3 marks for this subpart). (b) (i) Explanation: parents are carriers/heterozygous [1]; offspring inherits recessive alleles from both parents [1]. (ii) Test cross / breeding with a horned cow [1].

题目 8 · structured

8 分

Water quality is crucial for livestock health and productivity. (a) (i) State two potential contaminants of natural surface water (e.g., ponds or streams) on a farm. (ii) Describe how a farmer can treat contaminated surface water to make it safe for livestock consumption. (b) (i) Explain how a lack of clean drinking water can lead to disease transmission in a sheep herd. (ii) Suggest two management practices to maintain hygiene around livestock drinking troughs.

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解题

(a) (i) Natural surface waters can be contaminated by agricultural runoff containing pesticides/fertilizers, and animal waste containing pathogenic bacteria (like E. coli) or parasite larvae. (ii) Farmers can set up a settlement tank to allow mud and silt to settle, filter the water through sand, and add chemical sanitizers like chlorine to kill harmful microbes. (b) (i) When clean water is unavailable, sheep are forced to drink from contaminated, stagnant muddy puddles. These pools often harbor high concentrations of parasitic worm larvae (e.g., liver fluke) and fecal bacteria, leading to rapid infection and disease spread. (ii) To keep troughs clean, farmers should scrub and flush them regularly to prevent algae build-up, fence them so livestock cannot step inside, and build a concrete apron around the trough base to prevent mud and dung accumulation.

评分标准

(a) (i) Two contaminants: animal faeces/pathogens [1], pesticide/fertilizer run-off [1], algae [1], silt/soil [1] (Max 2). (ii) Water treatment: filtration/sedimentation [1], chlorination/disinfection [1]. (b) (i) Transmission: sheep drink from dirty/stagnant mud pools [1], ingest parasite larvae or pathogenic bacteria [1]. (ii) Trough hygiene: clean/scrub regularly [1], concrete surrounding apron [1], fence off to prevent stepping inside [1], maintain float valves [1] (Max 2).

题目 9 · Structured

8 分

Answer all the questions in the spaces provided.

**1** Rainwater collected from farm buildings is a valuable source of water but often contains contaminants.

**(a) (i)** Suggest **two** reasons why untreated rainwater collected from a roof may be unsafe for young farm animals. [2]

**(ii)** Describe the process of **filtration** as a method of water treatment on a farm. [2]

**(b)** Gravity-fed water systems are commonly used to distribute water on farms.

**(i)** A rectangular water storage tank on a farm is \(5\text{ m}\) long, \(2\text{ m}\) wide and has a depth of \(1.5\text{ m}\).

Calculate the maximum volume of water, in **litres**, that this tank can store. Show your working. (\(1\text{ m}^3 = 1000\text{ litres}\))

........................................................................................................................................... litres [2]

**(ii)** Explain how a gravity-fed system supplies water to livestock troughs without the use of a mechanical pump. [2]

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解题

**(a)(i)**
* Bird droppings/animal faeces on the roof. (1)
* Dirt, dust, or organic debris washed off the roof. (1)
* Presence of pathogens/harmful micro-organisms. (1)
* (Max 2 marks)

**(a)(ii)**
* Water passes through a physical barrier / porous material (e.g., sand, gravel, cloth, or mesh). (1)
* This physical barrier traps and removes suspended particles/debris/dirt while letting clean water pass through. (1)

**(b)(i)**
* \(\text{Volume in m}^3 = 5 \times 2 \times 1.5 = 15\text{ m}^3\) (1)
* \(\text{Volume in litres} = 15 \times 1000 = 15,000\text{ litres}\) (1)

**(b)(ii)**
* The header tank/reservoir is placed at a higher level than the animal troughs. (1)
* The force of gravity pulls the water down through the pipelines to create natural pressure, ensuring flow without a pump. (1)

评分标准

**(a)(i)**
Award 1 mark for each valid reason, up to a maximum of 2 marks:
* bird droppings / animal waste on roof
* dust / soil / organic matter / leaves
* pathogens / bacteria / viruses / parasites
* toxic chemical residues from the roofing material (e.g., paint, asbestos, rust)

**(a)(ii)**
Award up to 2 marks:
* water passed through a physical media / filter bed / sand / gravel / mesh (1 mark)
* to remove suspended solids / insoluble dirt / particles / debris (1 mark)

**(b)(i)**
Award up to 2 marks:
* \(5 \times 2 \times 1.5 = 15\text{ m}^3\) (1 mark for correct volume calculation in \(\text{m}^3\))
* \(15 \times 1000 = 15,000\text{ litres}\) (1 mark for correct conversion to litres)
* Note: Award 2 marks for correct final answer without working.

**(b)(ii)**
Award up to 2 marks:
* water storage tank is positioned on high ground / elevated on a stand (above the level of the troughs) (1 mark)
* gravity pulls water downwards through pipes / potential energy is converted to kinetic energy / pressure is created by the height difference (1 mark)

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Answer any two questions of your choice.

2 题目 · 30 分

题目 1 · structured_essay

15 分

(a) Describe the methods a farmer can use to collect and store clean rainwater on a farm. [4]

(b) Compare the advantages and disadvantages of using overhead sprinkler irrigation versus drip irrigation for a vegetable crop. [5]

(c) Explain how a farmer can ensure that water supplied to housed livestock remains clean and free from contamination. [6]

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解题

(a) Rainwater collection and storage methods:

Install gutters and downpipes on large roofs of farm buildings (e.g., barns, machinery sheds) to collect runoff.
Use a first-flush diverter to redirect initial debris-laden runoff away from the main tank.
Channel water into durable, sealed storage tanks (such as concrete, UV-stabilized plastic, or galvanized metal).
Cover storage tanks securely with tight-fitting lids to prevent evaporation, mosquito breeding, and dirt contamination.
Construct small farm dams or earth reservoirs on sloped pasture with silt traps at the inlet to capture clean surface runoff.

(b) Comparison of overhead sprinkler and drip irrigation:

Drip Irrigation: Highly efficient as water is delivered directly to the root zone, reducing evaporation losses. It minimizes weed growth by keeping inter-row soils dry and is ideal for sloped land. However, it has high installation costs and emitters can clog easily, requiring filtration.
Overhead Sprinkler: Can cover larger areas rapidly with lower initial pipe layouts compared to extensive drip tubing. However, it suffers from high evaporation losses in hot/windy climates, can cause soil capping/erosion, and wet foliage can promote fungal diseases.

(c) Ensuring clean water for housed livestock:

Install automatic nipple drinkers or water bowls instead of open troughs to prevent animals from stepping in or defecating in the water.
Perform daily cleaning and scrubbing of drinkers to eliminate algae, slime, and feed residues.
Maintain covered, elevated header tanks to keep water cool, shaded, and protected from birds, pests, or dust.
Ensure pipework and storage vessels are made from non-toxic materials (e.g., food-grade plastic) and check regularly for leaks or blocks.
Conduct regular chemical and microbiological testing of the source water (well, borehole) to detect pathogens like E. coli.
Apply water treatment methods such as filtration or low-dose chlorination if contamination is suspected.

评分标准

(a) Collection & storage [Max 4 marks]:

1 mark for roof guttering / catchment systems.
1 mark for first-flush diverters to exclude dirt.
1 mark for storing in covered/sealed tanks (concrete/plastic).
1 mark for farm dams/reservoirs with silt traps.

(b) Irrigation comparison [Max 5 marks]:

Max 4 marks if only one system is discussed.
1 mark for drip advantage (high water efficiency / targets roots).
1 mark for drip disadvantage (clogging / filtration required / setup cost).
1 mark for sprinkler advantage (covers large area / low foliage management).
1 mark for sprinkler disadvantage (high evaporation / promotes fungal disease / soil capping).

(c) Clean water for livestock [Max 6 marks]:

1 mark for using automatic nipple/bowl drinkers instead of open troughs.
1 mark for daily/regular scrubbing and cleaning of drinking devices.
1 mark for fully enclosed, shaded header tanks (prevents algae/pests).
1 mark for locating drinkers at an appropriate height to avoid litter/manure contamination.
1 mark for routine water quality testing (microbial/pathogen check).
1 mark for water treatment (chlorination/filtration).

题目 2 · structured_essay

15 分

(a) Describe what is meant by a 'maintenance ration' and a 'production ration' for livestock. [4]

(b) Outline the structural differences between the stomach of a ruminant animal and a non-ruminant animal. [5]

(c) Explain how the microbial population in the rumen helps a ruminant digest cellulose and synthesize essential nutrients. [6]

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解题

(a) Maintenance vs Production ration:

Maintenance ration: The minimum amount of feed required daily by an animal simply to keep it alive, maintain its body temperature, and support basic life processes (e.g., respiration, circulation) without any loss or gain in body weight.
Production ration: The extra feed supplied to the animal in addition to its maintenance requirements. This ration is used specifically to support productive outputs, including milk secretion, meat/muscle growth, egg production, wool growth, work, or gestation.

(b) Structural differences of the stomach:

A ruminant stomach is complex and divided into four distinct chambers (rumen, reticulum, omasum, and abomasum), whereas a non-ruminant stomach is a simple, single-chambered organ (monogastric).
The ruminant has a very large rumen (fermentation vat) lined with papillae, which is absent in non-ruminants.
The reticulum has a characteristic honeycomb-patterned lining to catch foreign objects, absent in non-ruminants.
The omasum has many muscular folds resembling pages of a book to absorb water, absent in non-ruminants.
Only the abomasum in ruminants matches the single stomach of a non-ruminant in secreting hydrochloric acid and digestive enzymes.

(c) Role of rumen microbes:

Rumen microbes (bacteria, fungi, and protozoa) produce cellulase, an enzyme that mammals cannot synthesize, allowing the breakdown of cellulose and hemicellulose in plant cell walls.
Microbes ferment these broken-down plant sugars, producing Volatile Fatty Acids (VFAs) like acetate, propionate, and butyrate, which are absorbed directly through the rumen wall as the ruminant's primary energy source.
They can utilize non-protein nitrogen (NPN) sources like urea to build high-quality microbial proteins. These microbes eventually pass to the lower digestive tract where they are digested, providing essential amino acids to the host animal.
The microflora synthesize essential B-group vitamins and Vitamin K, ensuring the host is self-sufficient even on low-quality forage.

评分标准

(a) Rations [Max 4 marks]:

1 mark for defining maintenance ration (feed for survival/no weight change).
1 mark for explaining maintenance functions (body temp, respiration).
1 mark for defining production ration (feed above maintenance).
1 mark for listing productive functions (milk, eggs, muscle growth, gestation).

(b) Stomach structures [Max 5 marks]:

1 mark for identifying four-chambered vs single-chambered.
1 mark for description/function of rumen (absent in non-ruminants).
1 mark for reticulum honeycomb structure (absent in non-ruminants).
1 mark for omasum folds/water absorption (absent in non-ruminants).
1 mark for abomasum as the true stomach secreting acid/enzymes, analogous to non-ruminant stomach.

(c) Microbial actions [Max 6 marks]:

1 mark for production of cellulase enzyme to digest cell walls.
1 mark for fermentation of sugars into Volatile Fatty Acids (VFAs).
1 mark for VFA absorption as main energy.
1 mark for synthesis of microbial protein from non-protein nitrogen (NPN).
1 mark for host digestion of microbial bodies in the lower tract to absorb essential amino acids.
1 mark for synthesis of Vitamin K and B-complex vitamins.

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