Cambridge IGCSE · Thinka 原創模擬試題

2025 Cambridge IGCSE Agriculture (0600) 模擬試題連答案詳解

Thinka Nov 2025 (V1) Cambridge International A Level-Style Mock — Agriculture (0600)

100 分105 分鐘2025

An original Thinka practice paper modelled on the structure and difficulty of the Nov 2025 (V1) Cambridge International A Level Agriculture (0600) paper. Not affiliated with or reproduced from Cambridge.

甲部

Answer all nine compulsory questions. Show all working and write answers in the spaces provided.

9 題目 · 70.02 分

題目 1 · Structured Short Answer

7.78 分

**(a)** Define the term *systemic pesticide* and explain how it controls sucking pests such as aphids. [3]

**(b)** Describe two advantages of using biological control methods rather than chemical pesticides on a crop. [2.78]

**(c)** Suggest why a farmer might choose an Integrated Pest Management (IPM) approach instead of relying solely on chemical control. [2]

查看答案詳解

解題

**(a)** A systemic pesticide is a chemical crop protection product that is absorbed into the plant's tissues (via leaves or roots) and transported throughout the plant's entire vascular system (primarily the phloem and xylem). When sucking insects, such as aphids, feed on the plant's sap, they ingest the pesticide and are poisoned. This method is highly effective because it targets only feeding pests and cannot be washed off by rainfall.

**(b)** Two key advantages of biological control over chemical methods are:
1. **Target Specificity:** Biological control agents (such as ladybirds or parasitic wasps) typically target only the specific pest species, sparing non-target organisms like bees, beneficial soil microbes, and local wildlife.
2. **No Chemical Residues:** Since no synthetic chemicals are applied, there are no toxic residues left on harvested crops, which makes the food safer for consumption and avoids environmental contamination.

**(c)** Relying solely on chemicals can lead to rapid development of pesticide resistance in insect populations, secondary pest outbreaks due to the destruction of natural predators, and high recurrent input costs. An IPM approach combines cultural, physical, biological, and target-specific chemical tactics to manage pests sustainably below an economic threshold, preserving the environment and reducing input costs.

評分準則

**(a)** Up to 3 marks:
- Definition: Pesticide is absorbed by the plant's leaves/roots/tissue [1]
- Translocation: Chemical is transported through the vascular system (xylem/phloem) to all parts of the plant [1]
- Action: Sucking pests ingest the toxic sap/chemical while feeding, leading to death [1]

**(b)** Up to 2.78 marks:
- Any two advantages described (1.39 marks each):
- High specificity / does not kill beneficial insects or non-target wildlife [1.39]
- No chemical residues on crops, making them safer for consumers [1.39]
- Pests do not easily develop resistance to predators/pathogens [1.39]
- Self-sustaining once established, lowering long-term labor and input costs [1.39]

**(c)** Up to 2 marks:
- Any two reasons suggested (1 mark each):
- Minimizes development of chemical resistance in pests [1]
- Reduces negative impacts on soil fertility, water systems, and local ecosystems [1]
- More economically sustainable/cost-effective in the long run [1]
- Decreases farm worker exposure to toxic chemicals [1]

題目 2 · Structured Short Answer

7.78 分

**(a)** Define *artificial insemination* (AI) and state two distinct advantages of using AI instead of natural service in cattle breeding. [3]

**(b)** Describe the biological role of the hormone progesterone in maintaining pregnancy in livestock. [2.78]

**(c)** Explain why it is vital for a newborn calf to receive colostrum within the first few hours of life. [2]

查看答案詳解

解題

**(a)** Artificial Insemination (AI) is the practice of collecting semen from a selected donor bull, processing/diluting it, and manually depositing it directly into the uterus of a cow in estrus by a technician. Two advantages include:
1. **Access to Superior Genetics:** Farmers can use semen from high-quality, proven bulls worldwide, improving production characteristics (like milk yield or daily weight gain) in the offspring without the expense of importing livestock.
2. **Prevention of Venereal Diseases:** It eliminates physical contact between animals, stopping the transmission of sexually transmitted infections like trichomoniasis and brucellosis.

**(b)** Progesterone is secreted by the corpus luteum (and later the placenta). Its primary functions include:
- Maintaining the vascularized lining of the uterus (endometrium) to allow implantation and support fetal development.
- Inhibiting the secretion of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), thereby preventing further heat cycles and ovulation during pregnancy.
- Relaxing the uterine muscles and preventing contractions that could result in a miscarriage or abortion.

**(c)** Colostrum is the first milk produced by the mother immediately after giving birth. It is critical because it contains a high concentration of immunoglobulins (antibodies) that provide immediate, passive immunity against local pathogens. The calf's intestinal lining is only permeable to these large proteins for the first 12 to 24 hours of life. It is also highly concentrated in nutrients and acts as a natural laxative to clear the first feces (meconium).

評分準則

**(a)** Up to 3 marks:
- Definition: Manual/artificial introduction of semen into the female's reproductive tract by a technician [1]
- Advantages (1 mark each, maximum 2):
- Allows access to genetically superior / proven sires [1]
- Reduces the transmission of sexually transmitted (venereal) diseases [1]
- Eliminates the danger/cost of keeping a bull on the farm [1]
- Semen can be stored frozen and transported globally [1]

**(b)** Up to 2.78 marks:
- Secreted by the corpus luteum / placenta [1]
- Inhibits LH/FSH secretion to prevent estrus / heat cycle / new ovulations [1]
- Prepares/maintains the endometrium (uterine lining) for embryo attachment [1]
- Quiets uterine muscles / prevents contractions / prevents abortion [1]
(Accept any three points described; allocate 0.93 marks per point, up to 2.78 marks maximum)

**(c)** Up to 2 marks:
- Any two reasons explained (1 mark each):
- Provides maternal antibodies for passive immunity against local diseases [1]
- High nutrient density (energy, proteins, vitamins) needed for newborn survival [1]
- Acts as a mild laxative to clear the meconium from the gut [1]

題目 3 · Structured Short Answer

7.78 分

**(a)** Explain the difference between a *maintenance ration* and a *production ration* for a dairy cow. [3]

**(b)** Outline how the nutritional requirements of a pregnant ewe change during the final six weeks of gestation and explain why these changes are necessary. [2.78]

**(c)** State two clinical signs of calcium deficiency (hypocalcemia) in livestock. [2]

查看答案詳解

解題

**(a)**
- **Maintenance Ration:** This is the minimum quantity of nutritionally balanced feed required daily by an animal just to maintain its vital life processes (such as respiration, circulation, and body temperature) and keep its body weight constant, without any weight loss, weight gain, or work.
- **Production Ration:** This is the additional feed supplied over and above the maintenance requirement. It is formulated specifically to support production outputs, such as milk secretion in dairy cows, fetal growth during late pregnancy, wool growth, or muscle accretion in growing beef cattle.

**(b)** In the final six weeks of gestation, more than 70% of fetal growth occurs, which increases the ewe’s demand for energy, proteins, calcium, and phosphorus. At the same time, the expanding uterus physically compresses the rumen, reducing the ewe's overall capacity to ingest bulky roughage. Therefore, a farmer must gradually increase the nutrient density of the diet by substituting low-quality roughage with high-protein, high-energy concentrates. This prevents metabolic diseases such as pregnancy toxemia (twin-lamb disease).

**(c)** Clinical signs of calcium deficiency (often called milk fever or parturient paresis in dairy cattle) include:
- Staggering gait, muscle tremors, or loss of muscular coordination.
- Inability to stand (becoming a "downer cow" lying on its chest).
- Cold ears and subnormal body temperature.

評分準則

**(a)** Up to 3 marks:
- Maintenance ration: Feed required to keep the animal alive / maintain vital processes / constant body weight [1]
- Production ration: Feed provided in addition to maintenance to support production [1]
- Distinction: Clearly shows production feed is given *above* the maintenance level [1]

**(b)** Up to 2.78 marks:
- Fetal growth: 70% of fetal development occurs in late gestation, requiring high energy/protein [1]
- Rumen compression: Growing uterus reduces abdominal space/rumen volume, limiting dry matter intake [1]
- Action: Switch to nutrient-dense concentrate feeds [0.78]
- Prevention: Prevents pregnancy toxemia / ketosis / twin-lamb disease [0.78]
(Maximum 2.78 marks)

**(c)** Up to 2 marks:
- State any two clinical signs (1 mark each):
- Muscular weakness / trembling / staggering gait [1]
- Inability to stand / sternal recumbency [1]
- Cold extremities / subnormal body temperature [1]
- Dullness / loss of consciousness / coma [1]

題目 4 · Structured Short Answer

7.78 分

**(a)** Compare three structural differences between wind-pollinated and insect-pollinated flowers. [3]

**(b)** Explain the process and agricultural significance of double fertilization in flowering plants (angiosperms). [2.78]

**(c)** State two advantages of utilizing asexual reproduction (vegetative propagation) in crop production. [2]

查看答案詳解

解題

**(a)** Structural comparisons:
1. **Petals:** Insect-pollinated flowers have large, brightly colored petals to attract pollinators, whereas wind-pollinated flowers have small, green, or brown petals (or none) as attraction is unnecessary.
2. **Stigmas:** Wind-pollinated flowers have large, feathery stigmas protruding outside the flower to capture floating pollen grains from the air, while insect-pollinated flowers have small, sticky stigmas positioned inside the flower where insects will brush against them.
3. **Anthers/Filaments:** Wind-pollinated flowers have versatile anthers suspended on long, flexible filaments dangling outside the flower to release pollen easily into breeze currents. Insect-pollinated flowers have firm, short filaments holding anthers inside where visiting insects must rub past them.

**(b)** After a pollen grain lands on a receptive stigma, it germinates to form a pollen tube that grows down the style into the ovary's embryo sac. It delivers two haploid male gametes:
- **First Fertilization:** One male gamete fuses with the haploid egg cell to form a diploid zygote, which grows into the embryo.
- **Second Fertilization:** The second male gamete fuses with the two polar nuclei in the center of the embryo sac, forming a triploid nucleus that develops into the endosperm.
- **Significance:** It ensures that food storage tissue (endosperm) only develops if fertilization has occurred, saving resources. The endosperm provides nutrients for seed development and initial germination.

**(c)** Advantages of vegetative propagation:
- **Genetic Uniformity:** Since offspring are clones of the parent plant, they inherit identical characteristics (such as yield, height, disease resistance, and fruit quality), allowing for easier management and uniform mechanical harvesting.
- **Faster Maturity:** Vegetatively propagated crops (like sweet potato cuttings or cassava stems) skip the delicate, slow-growing seedling phase, resulting in faster establishment and earlier harvests.

評分準則

**(a)** Up to 3 marks:
- Compare three features (1 mark per correct comparison):
- Petals: large/brightly colored vs small/dull/absent [1]
- Stigma: small/sticky/inside vs large/feathery/protruding outside [1]
- Anthers/Filaments: stiff/fixed inside vs versatile/dangling on long filaments outside [1]
- Pollen: rough/sticky/produced in small quantities vs light/smooth/produced in huge quantities [1]

**(b)** Up to 2.78 marks:
- Gamete 1 + Egg cell = Diploid zygote / embryo [1]
- Gamete 2 + Polar nuclei = Triploid endosperm [1]
- Agricultural significance: Formation of nutritious seed reserves (endosperm) which supports germinating seedlings / ensures food tissue is only made when zygote is present [0.78]

**(c)** Up to 2 marks:
- State any two advantages (1 mark each):
- Retains desirable parental characteristics / genetic uniformity [1]
- Faster establishment / shorter time to harvest compared to growing from seed [1]
- High success rate / bypassing delicate seed germination stage [1]
- Only one parent plant required [1]

題目 5 · Structured Short Answer

7.78 分

**(a)** Explain how soil pH affects the availability of essential plant nutrients and crop growth. [3]

**(b)** Describe the practice of *green manuring* and explain how it improves soil fertility and structure. [2.78]

**(c)** State two distinct ways in which nitrogen can be lost from agricultural soil. [2]

查看答案詳解

解題

**(a)** Soil pH measures the acidity or alkalinity of the soil and directly controls nutrient solubility.
- In highly acidic soils (pH below 5.5), essential nutrients like phosphorus, calcium, and magnesium form insoluble chemical complexes with iron or aluminum, preventing plant roots from absorbing them.
- Conversely, in highly alkaline soils (pH above 8.0), micronutrients like iron, manganese, and boron become locked up.
- Additionally, extreme pH values suppress the activity of beneficial soil microorganisms, such as nitrifying bacteria and nitrogen-fixing *Rhizobium*, slowing the decomposition of organic matter and nutrient cycling.

**(b)** Green manuring is the practice of planting a fast-growing cover crop (often leguminous species like clover or cowpeas) and plowing or tilling the crop directly back into the soil while it is still green and leafy.
- **Soil Fertility:** If leguminous, the plant fixes atmospheric nitrogen through root nodule bacteria, directly increasing soil nitrogen when incorporated. Decomposition also releases other trapped nutrients (potassium, phosphorus) back to the crop root zone.
- **Soil Structure:** The added organic matter decomposes to form humus, which binds sandy soil particles together (increasing water retention) and loosens clay soils (improving drainage and aeration).

**(c)** Nitrogen is lost from agricultural soils through:
1. **Leaching:** Soluble nitrate ions (\(\text{NO}_3^-\)) are easily washed downward through the porous soil profile by rain or irrigation water, out of reach of plant roots.
2. **Denitrification:** In waterlogged, anaerobic (oxygen-poor) soils, specialized denitrifying bacteria convert soil nitrates into nitrogen gas (\(\text{N}_2\)) or nitrous oxide (\(\text{N}_2\text{O}\)), which escapes into the atmosphere.

評分準則

**(a)** Up to 3 marks:
- Soil pH controls chemical solubility / nutrient availability [1]
- At acidic pH: phosphorus / calcium / magnesium is unavailable / aluminum toxicity occurs [1]
- At alkaline pH: iron / boron / copper is locked up [1]
- Soil pH affects beneficial microbial activity / nitrification is suppressed at low pH [1]
(Maximum 3 marks)

**(b)** Up to 2.78 marks:
- Description: Planting a crop and tilling/plowing it while green into the soil [1]
- Fertility benefit: Adds organic matter / nitrogen fixation (if legume) [1]
- Structure benefit: Improves soil aggregation / water retention / aeration [0.78]

**(c)** Up to 2 marks:
- State any two ways (1 mark each):
- Leaching / washing down of nitrates [1]
- Denitrification by anaerobic bacteria [1]
- Volatilization of ammonia gas [1]
- Soil erosion / surface runoff carrying topsoil [1]
- Crop removal / harvesting plants without replacing nutrients [1]

題目 6 · Structured Short Answer

7.78 分

In cattle, the allele for polled (hornless), **H**, is dominant to the allele for horned, **h**.

**(a)** Draw a complete genetic diagram to show the expected genotypes and phenotypes of the offspring from a cross between a heterozygous polled bull and a horned cow. [4]

**(b)** Calculate the percentage probability that an offspring from this cross will be horned. Show your working. [1.78]

**(c)** Define the term *heterozygous*. [2]

查看答案詳解

解題

**(a)** Genetic diagram:
- **Parental Phenotypes:** Polled Bull x Horned Cow
- **Parental Genotypes:** \(Hh\) (heterozygous polled) x \(hh\) (homozygous recessive horned)
- **Gametes:** Bull produces \(H\) and \(h\) gametes. Cow produces only \(h\) gametes.

**Punnett Square:**
| | H | h |
|---|---|---|
| **h** | Hh (Polled) | hh (Horned) |
| **h** | Hh (Polled) | hh (Horned) |

- **Offspring Genotypes:** \(Hh\) and \(hh\) (in a 1:1 ratio)
- **Offspring Phenotypes:** Polled and Horned (in a 1:1 ratio)

**(b)** Working:
From the genetic cross, the proportion of horned offspring (\(hh\)) is 2 out of 4, or \(1/2\).

\(\text{Percentage Probability} = \frac{2}{4} \times 100\% = 50\%\)

**(c)** **Heterozygous** refers to an organism that has inherited two different alleles of a particular gene (e.g., \(Hh\)) from its parents. One allele is dominant and dictates the physical appearance, while the other is recessive.

評分準則

**(a)** Up to 4 marks:
- Correct parental genotypes shown: \(Hh\) and \(hh\) [1]
- Correct gametes shown: \(H\) and \(h\) from bull, and \(h\) from cow [1]
- Correct offspring genotypes in Punnett square: \(Hh\) and \(hh\) [1]
- Correct matching of offspring phenotypes: \(Hh\) is polled, \(hh\) is horned [1]

**(b)** Up to 1.78 marks:
- Correct working showing calculation: \(2/4\) or \(1/2\) of offspring are horned [1]
- Correct percentage probability: 50% [0.78]
(Accept 0.5 or 1:1 ratio for partial credit if working is clear)

**(c)** Up to 2 marks:
- Definition: Having two different alleles of a particular gene [2]
- (Award 1 mark if definition refers to 'different genes' or if they only give a valid genotype example like 'Hh' without defining it)

題目 7 · Structured Short Answer

7.78 分

**(a)** Explain how infectious diseases in livestock can be transmitted by both *direct* and *indirect* contact. Use farm examples to support your answer. [3]

**(b)** Distinguish between *active immunity* and *passive immunity* in livestock, and provide one example of how an animal acquires each type. [2.78]

**(c)** State two biosecurity measures a poultry farmer can implement to prevent a disease outbreak on their farm. [2]

查看答案詳解

解題

**(a)**
- **Direct Contact:** This occurs when a healthy animal physically touches an infected animal, and pathogens are directly transferred via body fluids, skin contact, or mating. For example, ringworm can be spread when animals rub against each other, and brucellosis can be transmitted through mating.
- **Indirect Contact:** This occurs when a healthy animal comes into contact with contaminated non-living objects (fomites). Pathogens are left behind by infected animals on shared feed troughs, water buckets, veterinary syringes, tractor wheels, or a farm worker's boots. For example, the highly contagious Foot-and-Mouth disease virus is frequently carried between barns on the mud of boots or vehicle tires.

**(b)**
- **Active Immunity:** The animal's own immune system actively produces antibodies in response to the presence of an antigen. This takes time to develop but is long-lasting. *Example:* Vaccination (e.g., against anthrax) or recovering from a natural infection.
- **Passive Immunity:** The animal receives pre-formed, ready-made antibodies from an external source. It provides immediate protection but is temporary because the animal's body does not produce memory cells. *Example:* A newborn calf consuming maternal antibodies through colostrum, or receiving an anti-tetanus serum injection.

**(c)** Effective biosecurity measures in a poultry unit include:
- Installing and maintaining disinfectant footbaths at the entrance of each poultry house.
- Restricting visitor and unauthorized vehicle access to the farm.
- Quarantining newly introduced birds in a separate facility for 14-30 days before letting them join the main flock.
- Fitting wild-bird-proof wire mesh on ventilation openings to prevent wild birds from introducing diseases like avian influenza.

評分準則

**(a)** Up to 3 marks:
- Direct contact: physical body-to-body contact/mating, plus valid example (e.g., ringworm/venereal disease) [1.5]
- Indirect contact: pathogents carried via non-living objects (fomites)/feeders/boots, plus valid example (e.g., foot-and-mouth on boots/shared troughs) [1.5]

**(b)** Up to 2.78 marks:
- Active immunity: defined as animal's immune system producing its own antibodies [1] + example (vaccine / recovery from disease) [0.39]
- Passive immunity: defined as receiving pre-formed/external antibodies [1] + example (colostrum / antiserum injection) [0.39]

**(c)** Up to 2 marks:
- State any two measures (1 mark each):
- Maintaining disinfectant footbaths [1]
- Quarantining new livestock [1]
- Restricting farm visitors / vehicle access [1]
- Installing wild-bird proof netting / fencing [1]
- regular disinfection of housing between batches [1]

題目 8 · Structured Short Answer

7.78 分

**(a)** List three essential safety practices a farm worker must follow when preparing and spraying liquid crop protection chemicals. [3]

**(b)** Explain how the improper storage and disposal of agricultural chemicals can lead to the pollution of local aquatic ecosystems. [2.78]

**(c)** State what is meant by a chemical’s *withholding period* (withdrawal period) and explain why it must be strictly observed. [2]

查看答案詳解

解題

**(a)** Safety practices during chemical preparation and spraying include:
1. **Personal Protective Equipment (PPE):** Wear a respirator mask, protective goggles, rubber gloves, chemical-resistant overalls, and rubber boots to prevent skin absorption and inhalation of mist.
2. **Safe Mixing:** Mix chemicals in a well-ventilated outdoor area using dedicated, clearly marked measuring tools. Never use bare hands or blow through clogged nozzles.
3. **Weather Awareness:** Avoid spraying on windy days to prevent spray drift onto non-target areas and the operator, and do not spray before heavy rain to prevent the chemical from washing off and causing soil and water runoff.

**(b)** Improper chemical management leads to aquatic pollution through:
- **Storage leaks:** Keeping chemicals in damaged containers or in buildings without a concrete floor allows spills to penetrate the ground and leach into subterranean water aquifers.
- **Disposal and runoff:** Washing sprayers or dumping residual chemical mixtures in or near waterways results in direct introduction of toxins. Discarding un-rinsed containers near streams allows rain to carry concentrated chemical residues into local waters. This poisons aquatic life, disrupts food webs, and can cause eutrophication if fertilizer-based chemicals are washed into ponds.

**(c)** The withholding period is the mandatory minimum time that must elapse between the last application of a chemical and the harvesting of the crop (or slaughter/milking of livestock). It must be strictly observed to allow the chemical's active ingredients to naturally degrade to safe, non-toxic levels. This prevents consumers from ingesting harmful chemical residues, which can cause acute poisoning or chronic health problems.

評分準則

**(a)** Up to 3 marks:
- State three safety practices (1 mark each):
- Wear appropriate PPE (mask/gloves/boots/goggles) [1]
- Avoid spraying in windy conditions to prevent spray drift [1]
- Do not spray when heavy rain is imminent to avoid runoff [1]
- Mix chemicals outdoors or in a well-ventilated area [1]
- Do not eat, drink, or smoke while handling chemicals [1]
- Wash skin and change clothes immediately after spraying [1]

**(b)** Up to 2.78 marks:
- Poor storage: leaks seep into soil and leach into groundwater [1]
- Poor disposal: washing sprayers near surface streams causes direct runoff [1]
- Empty containers: leaving un-rinsed bottles near waterways releases high concentrations during rain [0.78]
- Consequence: leads to poisoning of non-target fish / bioaccumulation [0.78]
(Maximum 2.78 marks)

**(c)** Up to 2 marks:
- Definition: Minimum duration between chemical application and harvest/slaughter/consumption [1]
- Reason: To ensure chemical residues break down to safe levels / prevent toxicity to consumers [1]

題目 9 · Structured Short Answer

7.78 分

A farmer notices that crops grown in a field with an acidic soil pH of 4.5 show poor growth and leaf discoloration.

(a) (i) Identify two primary macronutrients required by crops for healthy growth. [2]
(ii) State one distinct deficiency symptom for each of the nutrients identified in (a)(i). [2]

(b) Explain how the application of agricultural lime improves the fertility of this acidic soil. [2]

(c) Describe how growing a leguminous cover crop can biologically improve the nitrogen content of this soil. [1.78]

查看答案詳解

解題

(a) (i) Nitrogen (N) and Phosphorus (P). (ii) Nitrogen deficiency causes yellowing of older leaves (chlorosis) or stunted vegetative growth; Phosphorus deficiency causes a purple or dark bronze tint on the leaves and poor root development. (b) Agricultural lime (calcium carbonate) neutralizes soil acidity, which raises the pH closer to neutral. This pH increase makes essential plant nutrients (such as phosphorus) more soluble and available to crops, while also stimulating beneficial soil microbial activity. (c) Leguminous crops form a symbiotic relationship with Rhizobium bacteria in their root nodules. These bacteria fix inert atmospheric nitrogen into a plant-available form (nitrates/ammonium), which enriches the soil when the legume plants die and decompose.

評分準則

(a) (i) Award 1 mark for each correct macronutrient listed (such as Nitrogen, Phosphorus, or Potassium) up to a maximum of 2 marks.
(a) (ii) Award 1 mark for each matching deficiency symptom up to a maximum of 2 marks.
- Nitrogen: chlorosis, stunted growth, or pale green/yellow leaves.
- Phosphorus: purple/bronze leaf margins, poor root development, or stunted growth.
- Potassium: leaf margin necrosis, scorching, or weak stems.
(b) Award up to 2 marks:
- 1 mark for stating that lime neutralizes acidity / raises soil pH.
- 1 mark for explaining that this increases the availability of essential plant nutrients (e.g., phosphorus) or enhances soil microbial/decomposer activity.
(c) Award up to 1.78 marks:
- 1.00 mark for explaining that Rhizobium bacteria in root nodules fix atmospheric nitrogen.
- 0.78 marks for explaining that this nitrogen is released and enriches the soil when the organic matter is decomposed or plowed back.

乙部

Answer any two extended response questions out of five options.

2 題目 · 30 分

題目 1 · Extended Response Essay

15 分

(a) Describe how insect pests can damage crops and reduce their yield. [4]

(b) Compare the use of chemical pest control with biological pest control, highlighting the advantages and disadvantages of each. [6]

(c) Explain what is meant by Integrated Pest Management (IPM) and explain why this approach is sustainable for a small-scale crop producer. [5]

查看答案詳解

解題

(a) How insect pests damage crops:
1. Chewing and biting: Pests such as caterpillars and locusts feed on leaves, stems, and roots. This reduces the total photosynthetic surface area, leading to lower crop vigor, stunted growth, and reduced yield. Damage to roots also hinders nutrient and water uptake.
2. Piercing and sucking: Pests like aphids and whiteflies insert mouthparts into the phloem to suck plant sap. This deprives the plant of manufactured food, causing wilting, leaf curling, and loss of productivity.
3. Disease vectors: Sucking insects can transmit viral, bacterial, or fungal pathogens from diseased plants to healthy ones during feeding.
4. Boring and tunneling: Insects such as stem borers tunnel into stems or fruit, weakening the physical structure of the crop or spoiling the harvestable produce, making it unmarketable.

(b) Chemical vs. Biological Pest Control:
- Chemical Control:
- Advantages: Acts very quickly; highly effective during sudden severe outbreaks; easily applied across large fields using sprayers.
- Disadvantages: Expensive to buy chemicals and equipment; risk of environmental pollution and water contamination; kills beneficial non-target organisms like pollinators; pests can develop chemical resistance; leaves toxic residues on food crops.
- Biological Control:
- Advantages: Environmentally safe and non-polluting; targets only the specific pest species; long-term self-sustaining control once natural predators are established; no danger of toxic residues.
- Disadvantages: Takes a long time to show results; rarely eradicates the pest completely; predators may migrate away; risk of the introduced biological agent becoming a pest itself if not carefully researched.

(c) Integrated Pest Management (IPM) & Sustainability:
- IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Chemical pesticides are used only as a last resort, applied in a way that minimizes hazards to human health and the environment.
- Why sustainable for smallholders:
1. Cost savings: Reduces reliance on costly chemical sprays, lowering overall farm inputs.
2. Safety: Minimizes health hazards to the farming family and livestock who live close to the fields.
3. Environmental balance: Protects local beneficial organisms (like bees and soil microbes) and keeps local drinking water clean.
4. Prevention of secondary pest outbreaks: Maintains ecological balance so minor pests do not become major problems due to the elimination of natural predators.

評分準則

Part (a): [Max 4 marks]
- 1 mark for explaining chewing/biting damage (e.g., eating leaves/roots, reducing photosynthesis).
- 1 mark for explaining piercing/sucking damage (e.g., sap depletion, causing wilting).
- 1 mark for explaining transmission of plant pathogens/diseases.
- 1 mark for explaining boring damage (e.g., physical damage to stems/fruits, lowering market value).

Part (b): [Max 6 marks]
- Up to 3 marks for chemical control (at least 1 advantage and 1 disadvantage clearly explained).
- Up to 3 marks for biological control (at least 1 advantage and 1 disadvantage clearly explained).

Part (c): [Max 5 marks]
- 1 mark for a clear definition of IPM (using multiple compatible methods to keep pest populations below economic injury levels).
- Up to 4 marks for explaining why it is sustainable for small-scale producers (e.g., cost-effectiveness, environmental protection, health benefits, prevention of resistance/pest resurgence).

題目 2 · Extended Response Essay

15 分

(a) Distinguish between a 'maintenance ration' and a 'production ration' for a farm animal. [4]

(b) State the main nutritional requirements of a high-yielding lactating dairy cow and explain why its nutritional needs change during peak lactation. [5]

(c) Describe the symptoms and effects of protein and calcium deficiencies in young growing livestock. [6]

查看答案詳解

解題

(a) Maintenance vs. Production Ration:
- Maintenance Ration: This is the minimum amount of feed required daily to keep an animal alive, healthy, and at a constant body weight, assuming it is performing no work and producing nothing (such as milk, meat, eggs, or wool). It supplies energy for basic metabolic processes (respiration, circulation, digestion) and maintaining body temperature, along with essential vitamins and minerals.
- Production Ration: This is the extra feed provided to the animal in addition to its maintenance ration to support productive activities. These activities include rapid growth, pregnancy/gestation, work, or the production of milk, eggs, or wool. It is richer in specific nutrients needed for the particular product (e.g., high protein for growth/milk, calcium for milk/eggshells).

(b) Lactating Dairy Cow Requirements and Peak Lactation Changes:
- Nutritional Requirements: High concentration of energy (carbohydrates), high quality crude protein, clean water in large quantities, minerals (especially Calcium and Phosphorus), and vitamins.
- Changes during Peak Lactation: At peak lactation (usually 4 to 8 weeks after calving), milk production reaches its maximum. The demand for energy, protein, and calcium to synthesize milk exceeds the animal's voluntary dry matter intake capacity, leading to a 'negative energy balance.' The cow will mobilize body fat and bone calcium reserves. To prevent metabolic conditions like ketosis (due to excessive fat mobilization) and milk fever (due to rapid calcium depletion), the nutrient density of the ration must be significantly increased, containing highly digestible concentrates and bypass proteins.

(c) Protein and Calcium Deficiencies in Young Growing Livestock:
- Protein Deficiency:
- Symptoms/Effects: Severe stunting and slow growth rate; muscle wasting or failure to develop muscle tissue; poor immune function leading to frequent infectious diseases; coarse, dull hair coat or poor wool quality; general weakness and lethargy.
- Calcium Deficiency:
- Symptoms/Effects: Poor bone mineralization resulting in rickets in young growing animals; malformed, soft, or easily fractured bones; swollen, painful joints and lameness; muscle tremors, weakness, or inability to stand; delayed teeth development which further hinders feeding.

評分準則

Part (a): [Max 4 marks]
- 1 mark for defining maintenance ration (keeping animal alive, constant weight, basic metabolism).
- 1 mark for identifying maintenance components (energy, basic cellular nutrients).
- 1 mark for defining production ration (extra food given above maintenance for yield/work).
- 1 mark for giving examples of production requirements (e.g., milk, meat, wool, work).

Part (b): [Max 5 marks]
- 1 mark for identifying key nutrients needed for lactation (energy/carbohydrates, protein, calcium, phosphorus, water).
- 2 marks for explaining peak lactation demand and negative energy balance (milk yield peaks before dry matter intake peaks, body reserves mobilized).
- 2 marks for explaining the risks/management of this phase (risk of ketosis/milk fever, need for high-density concentrate feeds).

Part (c): [Max 6 marks]
- Up to 3 marks for protein deficiency symptoms and effects in young stock (1 mark for each distinct, valid point, e.g., stunted growth, muscle wasting, poor coat, weak immunity).
- Up to 3 marks for calcium deficiency symptoms and effects in young stock (1 mark for each distinct, valid point, e.g., rickets/soft bones, joint swelling/lameness, bone fractures, muscle tremors).

想知道自己有幾分把握？

Thinka 是 DSE 學生用的 AI 練習應用程式，有無限量練習題、即時自動批改和詳細解題步驟。逾 100,000 名學生用它確認自己真的識，而不只是「以為識」。

免費開始練習查看計劃

想練更多類似題型？在 Thinka 無限量操練，即時知道答案。

免費開始練習