← Agri & Allied (CT)
Past Questions — 2024
Bud necrosis in groundnut is transmitted by-
A)
Aphids
B)
Thrips
C)
White fly
D)
Mealy bug
Bud necrosis of groundnut (also known as Peanut Bud Necrosis) is caused by the Groundnut Bud Necrosis Virus (GBNV), which belongs to the Tospovirus genus. This virus is specifically transmitted by thrips, most notably the species Thrips palmi. The thrips acquire the virus from infected plants and transmit it to healthy plants during feeding.
Why other options are incorrect:
- Aphids: While aphids transmit many plant viruses (like mosaic viruses), they are not the vectors for bud necrosis in groundnut.
- White fly: White flies are primary vectors for Geminiviruses (e.g., Yellow vein mosaic), not Tospoviruses.
- Mealy bug: Mealy bugs are not known as the primary vectors for the bud necrosis virus in groundnut.
Cleistogamy promotes which of the following?
A)
Cross pollination
B)
Selfpollination
C)
Male sterility
D)
Selfincompatibility
Cleistogamy refers to a condition in plants where flowers do not open (remain closed), ensuring that pollination occurs only between the anthers and the stigma of the same flower. Since the flower remains closed, pollen from other plants cannot enter, and the plant's own pollen cannot be carried away by pollinators. This mechanism effectively forces and promotes obligate self-pollination.
Why other options are incorrect:
- a. Cross pollination: This requires the flower to open (chasmogamy) to allow pollen transfer between different plants.
- c. Male sterility: This is a genetic condition where pollen is non-functional, which would prevent pollination rather than promote a specific type of it.
- d. Self-incompatibility: This is a biochemical mechanism that prevents self-fertilization even if pollen reaches the stigma; cleistogamy is a physical mechanism that ensures self-fertilization.
The process of accelerating the ability of flowering in plants by exposing them to cold temperature is known as-
A)
Vernalization
B)
Respiration
C)
Guttation
D)
Photoperiodism
Step-by-step reasoning:
1. **Analysis of the Question**: The question asks for the term describing the acceleration of flowering induced by exposure to cold temperatures.
2. **Evaluating Option (a) Vernalization**: Vernalization is the process in which some plants require a period of low temperature (cold treatment) to trigger the transition from vegetative growth to reproductive growth (flowering). This ensures that plants flower in the spring after a winter period. This matches the question perfectly.
3. **Evaluating Option (b) Respiration**: Respiration is the biochemical process by which cells break down glucose to produce energy (ATP). It is a metabolic process, not a flowering trigger.
4. **Evaluating Option (c) Guttation**: Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, usually occurring at night when soil moisture is high. It is related to water balance, not flowering.
5. **Evaluating Option (d) Photoperiodism**: Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. While it also affects flowering, it is triggered by light/dark cycles (day length), not by cold temperature.
Conclusion: The correct term for cold-induced flowering is Vernalization.
The term “ecdysis” refers to:
A)
The production of pheromones
B)
The excretion of waste products
C)
The process of moulting in insects
D)
The development of compound eyes
Step-by-step reasoning: 1. Definition: Ecdysis is the biological process by which an arthropod (including insects) sheds its old exoskeleton to make room for growth. 2. Mechanism: Because the insect's cuticle is rigid and does not expand, the insect must periodically cast off the old cuticle and secrete a new, larger one. This entire process is commonly known as 'moulting'. 3. Hormonal Control: This process is regulated by hormones, primarily ecdysone (the moulting hormone). 4. Analysis of other options: (a) Pheromone production is related to chemical communication, not structural growth. (b) Excretion of waste is handled by the Malpighian tubules. (d) The development of compound eyes is part of organogenesis/morphogenesis, not the process of shedding the skin.
Fruits like mango, peach, and cherry belong to which category based on their seed structure?
A)
Drupes
B)
Pome
C)
Berries
D)
Pepo
Step-by-step reasoning:
1. **Analysis of the fruits**: Mango, peach, and cherry all share a common structural characteristic: they have a fleshy outer part (mesocarp) surrounding a single, hard, stony inner layer (endocarp) that encloses the seed.
2. **Definition of Drupe**: A drupe (or stone fruit) is a fleshy fruit with thin skin and a central stone containing the seed. The 'stone' is actually the hardened endocarp.
3. **Evaluating other options**:
- **Pome (b)**: These are accessory fruits where the fleshy part is derived from the receptacle (e.g., apple, pear). They have a core of cartilaginous tissue containing seeds, not a single stony pit.
- **Berries (c)**: These are fleshy fruits produced from a single ovary where the entire pericarp is fleshy and usually contain multiple seeds (e.g., tomato, grape).
- **Pepo (d)**: This is a specialized type of berry with a hard, thick rind, characteristic of the Cucurbitaceae family (e.g., watermelon, cucumber).
Conclusion: Since mango, peach, and cherry possess a stony endocarp, they are classified as drupes.
Amino acids are joined by which of the following?
A)
Phosphodiester bond
B)
Salt bridge
C)
Peptide bond
D)
Ester bond
Amino acids are the building blocks of proteins. They are linked together through a dehydration synthesis reaction where the carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH2) of another amino acid, releasing a molecule of water and forming a covalent C-N bond known as a peptide bond.
Analysis of other options:
- a. Phosphodiester bond: These bonds link nucleotides together to form the backbone of DNA and RNA.
- b. Salt bridge: This is a non-covalent interaction (electrostatic attraction) between oppositely charged side chains of amino acids, contributing to the tertiary structure of proteins, but not the primary linkage.
- d. Ester bond: These bonds typically link fatty acids to glycerol in lipids (triglycerides) or sugars in some carbohydrates.
The biggest honeybees which are distributed in India, in plains as well as hills are
A)
Apis cerana
B)
Apis mellifera
C)
Apis florae
D)
Apis dorsata
Step-by-step reasoning: 1. The question asks for the 'biggest' honeybee species distributed across India's plains and hills. 2. Analysis of the options:
- Apis cerana (Indian honeybee): Medium-sized, domesticated.
- Apis mellifera (European honeybee): Medium-sized, introduced to India for commercial purposes.
- Apis florae (Little honeybee): The smallest of the honeybees found in India.
- Apis dorsata (Rock bee/Giant honeybee): This is the largest species of honeybee found in Asia, including India. It is known for building large single combs in the open (on cliffs or high branches) and is widely distributed across various terrains, including plains and hilly regions. 3. Therefore, based on size and distribution, Apis dorsata is the correct answer.
How many ATP are consumed /utilized in glycolysis?
A)
1 ATP
B)
2ATP
C)
3 ATP
D)
4ATP
Glycolysis is the metabolic pathway that converts glucose into pyruvate. It consists of two main phases: the Energy Investment Phase (Preparatory Phase) and the Energy Payoff Phase.
1. Energy Investment Phase: In this initial stage, the cell actually 'spends' ATP to activate the glucose molecule.
- The first ATP is consumed by the enzyme Hexokinase to convert Glucose to Glucose-6-phosphate.
- The second ATP is consumed by the enzyme Phosphofructokinase-1 (PFK-1) to convert Fructose-6-phosphate to Fructose-1,6-bisphosphate.
2. Energy Payoff Phase: Later in the process, 4 ATP molecules are produced via substrate-level phosphorylation.
Since the question specifically asks how many ATP are 'consumed' or 'utilized', it refers to the investment phase. Therefore, 2 ATP molecules are utilized. (Note: The net gain of glycolysis is 2 ATP, because 4 are produced minus 2 consumed = 2 net ATP).
Which class of chemical insecticide is characterized by a relatively high degree of environmental persistence?
A)
Carbamates
B)
Synthetic pyrethroids
C)
Organophosphates
D)
Chlorinated hydrocarbons
Environmental persistence refers to the length of time a chemical remains active in the environment before breaking down.
1. **Chlorinated Hydrocarbons (Organochlorines):** This class (e.g., DDT, Endosulfan, Heptachlor) is characterized by high stability, low water solubility, and high lipid solubility. Because they do not degrade easily through hydrolysis or photolysis, they persist in the soil and water for years and undergo biomagnification in the food chain. This high persistence led to the banning of many of these chemicals globally.
2. **Organophosphates:** These are generally non-persistent. They degrade relatively quickly in the environment through hydrolysis and microbial action, meaning they do not accumulate in the food chain.
3. **Carbamates:** Similar to organophosphates, carbamates are designed to be short-lived in the environment and are degraded rapidly, reducing their long-term environmental impact.
4. **Synthetic Pyrethroids:** While more stable than natural pyrethrins, synthetic pyrethroids are still significantly more biodegradable and less persistent than chlorinated hydrocarbons, although they can be toxic to aquatic life.
The inflorescence of banana is-
A)
Umbel
B)
Catkin
C)
Spadix
D)
Raceme
The inflorescence of a banana plant (Musa spp.) is a Spadix. A spadix is a specialized type of spike where small, sessile flowers are arranged on a fleshy, thickened axis (the spadix), which is typically enclosed or subtended by a large, often colorful, modified leaf called a spathe. In bananas, the large purple heart-shaped structure is the spathe, which peels back to reveal the rows of flowers on the fleshy axis.
Why other options are incorrect:
- a. Umbel: An inflorescence where all flower stalks (pedicels) arise from a single point, forming an umbrella-like shape (e.g., Onion, Coriander).
- b. Catkin: A cylindrical, drooping spike usually consisting of unisexual flowers, common in wind-pollinated trees like Willow or Birch.
- d. Raceme: An unbranched inflorescence where flowers have short stalks (pedicels) attached to a central axis (e.g., Mustard). Unlike a spadix, the axis in a raceme is not fleshy.
Which amongst the following is a polyphagous pest?
A)
Brinjal Fruit Borer
B)
Bihar Hairy Caterpiller
C)
Cabbage butterfly
D)
Mustard sawfly
A polyphagous pest is an organism that feeds on a wide variety of plants from different families.
1. **Bihar Hairy Caterpillar (Spilosoma obliqua)**: This is a highly polyphagous pest. It feeds on a vast range of crops including vegetables, legumes, oilseeds, and ornamental plants (e.g., maize, cabbage, soybean, and various pulses). Because it attacks many unrelated plant species, it is classified as polyphagous.
2. **Brinjal Fruit Borer (Leucinodes orbonalis)**: This is primarily a monophagous or oligophagous pest, specifically targeting Solanaceous crops, with a strong preference for brinjal (eggplant).
3. **Cabbage Butterfly (Pieris rapae)**: This is an oligophagous pest, as it feeds almost exclusively on plants within the Brassicaceae (Cruciferae) family, such as cabbage, cauliflower, and broccoli.
4. **Mustard Sawfly (Athalia rosae)**: This is an oligophagous pest that specifically targets cruciferous crops, primarily mustard and rapeseed.
Therefore, the Bihar Hairy Caterpillar is the only polyphagous pest among the given options.
The inflorescence of jackfruit is called-
A)
Spadix
B)
Panicle
C)
Solitary
D)
Hypanthodium
The jackfruit (Artocarpus heterophyllus) possesses a specialized type of inflorescence known as a spadix. A spadix is a spike of small, densely packed flowers resting on a fleshy, thickened axis, which is typically enclosed by a large, modified leaf called a spathe. In jackfruit, the male and female flowers are located on separate spadices (monoecious).
Analysis of other options:
- b. Panicle: A branched inflorescence where the main axis has secondary branches (e.g., Mango).
- c. Solitary: A single flower arising from the axil or tip of a stem (e.g., Hibiscus).
- d. Hypanthodium: A specialized fleshy receptacle with a sunken cavity containing flowers, characteristic of the family Euphorbiaceae, specifically the genus Ficus (e.g., Fig).
A bacteria which have a large number of flagella all over the cell is categorized in-
A)
Atrichous
B)
Ampbhitrichous
C)
Lophotrichous
D)
Peritrichous
Bacteria are classified based on the arrangement and number of their flagella (the organelles used for motility).
1. **Peritrichous**: The prefix 'peri-' means 'around'. Peritrichous bacteria have flagella distributed all over the entire surface of the cell. An example is Escherichia coli.
2. **Atrichous**: The prefix 'a-' means 'without'. These bacteria lack flagella entirely and are non-motile.
3. **Amphitrichous**: The prefix 'amphi-' means 'both'. These bacteria have a single flagellum or a cluster of flagella at both opposite poles of the cell.
4. **Lophotrichous**: The prefix 'lopho-' means 'tuft'. These bacteria have a cluster (tuft) of flagella emerging from only one end (pole) of the cell.
Since the question specifies a large number of flagella 'all over the cell', the correct classification is Peritrichous.
Indian Institute of Vegetable Research is located in-
A)
Bihar
B)
Varanasi
C)
Maharashtra
D)
Karnataka
The Indian Institute of Vegetable Research (IIVR) is a premier research institute under the Indian Council of Agricultural Research (ICAR). It is located in Varanasi, Uttar Pradesh. Its primary mandate is to conduct basic and applied research on vegetable crops to improve productivity and quality.
Analysis of options:
- Bihar: No major national vegetable research institute is headquartered here.
- Varanasi: Correct. This is the location of IIVR.
- Maharashtra: While Maharashtra has various agricultural universities and research centers, the IIVR is not located here.
- Karnataka: Karnataka hosts other important institutes (like the Indian Institute of Horticultural Research - IIHR in Bengaluru), but not the IIVR.
In case of garlic, bulbils develop naturally from medication of which of the following?
A)
Roots
B)
Shoots
C)
Flower
D)
Fruit
In garlic (Allium sativum), bulbils are small, asexual propagules that develop as a result of the modification of the floral parts. Specifically, they are formed when the flower bud (inflorescence) fails to develop into a normal flower and instead transforms into small, fleshy bulbs called bulbils. This process is a form of vegetative reproduction.
- Option (a) Roots: Roots develop into tubers (like in sweet potato), not bulbils.
- Option (b) Shoots: While the main bulb is a modified shoot/stem, the specific 'bulbils' that appear in the flower head are modifications of the flower.
- Option (d) Fruit: Bulbils are vegetative structures and occur instead of, or in place of, the development of seeds/fruits.
Gemini viruses are often transmitted by____—_—in a persistent circulative manner.
A)
Leafhopper
B)
Tree hopper
C)
Plant hopper
D)
Whitefly
Gemini viruses (family Geminiviridae) are a group of plant viruses characterized by their twinned (geminate) icosahedral capsids. They are specifically transmitted by whiteflies (family Aleyrodidae) in a persistent, circulative, non-propagative manner. In this process, the virus is ingested by the whitefly from an infected plant, crosses the gut wall into the hemolymph, and eventually reaches the salivary glands to be inoculated into a healthy plant.
Comparison with other options:
- Leafhoppers (a) are primary vectors for viruses like the Rice Hoppers or various Phytoplasmas, but not Geminiviruses.
- Tree hoppers (b) and Plant hoppers (c) transmit various other plant pathogens (such as some members of the family Bunyaviridae or specific phytoplasmas), but they are not the vectors for the Geminiviridae family.
Any structural or functional modification in plants to survive and reproduce in a particular environment is known as-
A)
Tolerance
B)
Adaptation
C)
Resistant
D)
Modification
The question asks for the term describing structural or functional modifications that enable a plant to survive and reproduce in a specific environment.
1. **Adaptation (Option b):** This is the correct biological term. Adaptation refers to the evolutionary process whereby an organism becomes better suited to its habitat. These changes can be morphological (structural, e.g., succulent stems in cacti for water storage) or physiological (functional, e.g., CAM photosynthesis in desert plants) and are heritable traits that increase the fitness of the organism.
2. **Tolerance (Option a):** Tolerance refers to the ability of an organism to endure or withstand a particular stress (like salinity or drought) without necessarily having a permanent structural change or evolutionary modification. It is often a physiological response rather than a permanent evolutionary trait.
3. **Resistant (Option c):** Resistance usually refers to the ability of a plant to avoid or fight off a specific pathogen, pest, or chemical stressor (e.g., disease resistance). It is a specific type of defense mechanism rather than a general environmental modification.
4. **Modification (Option d):** While 'modification' is used in the question stem, as a standalone term in biology, it is too general. A modification can be a temporary change or a mutation, whereas 'Adaptation' specifically links the modification to survival and reproduction in a particular environment.
Contribution of flag leaf in photosynthesis is-
A)
30-32%
B)
40-42%
C)
50-52%
D)
60-62%
In cereal crops (such as wheat, rice, and maize), the flag leaf is the uppermost leaf of the plant and plays a critical role in the grain-filling stage. Because it is positioned at the top of the canopy, it receives the maximum amount of solar radiation compared to lower leaves, which are often shaded. Research in plant physiology and agronomy indicates that the flag leaf contributes significantly to the total photoassimilates required for grain development. While the exact percentage can vary slightly by crop and variety, the generally accepted range for the contribution of the flag leaf to total photosynthesis during the grain-filling period is approximately 40% to 50%. Among the given options, 40-42% is the most accurate representation of this physiological contribution.
Crops which are grown to supplement the yield of main crop?
A)
Cash crops
B)
Cover crops
C)
Industrial crops
D)
Augment crops
In agronomy and cropping systems, 'Augment crops' (also known as augmentation crops) are those grown specifically to supplement or increase the total yield and productivity of the main crop per unit area. This is often achieved through intercropping or relay cropping, where the secondary crop utilizes resources (nutrients, light, space) that the main crop cannot, thereby 'augmenting' the overall output of the field.
Why other options are incorrect:
- a. Cash crops: These are crops grown primarily for sale in the market to earn profit (e.g., cotton, tobacco), regardless of whether they supplement another crop.
- b. Cover crops: These are grown primarily to protect the soil from erosion, suppress weeds, and improve soil health, rather than to supplement the yield of a main crop.
- c. Industrial crops: These are crops grown to provide raw materials for industries (e.g., rubber, oilseeds for processing), focusing on industrial utility rather than supplementing a main crop's yield.
Which gene is responsible for dwarfing characteristic in rice?
A)
Tift23-A
B)
Norin-10
C)
Dee-gee-woo-gen
D)
Opaque-2
The dwarfing characteristic in rice is primarily attributed to the 'sd1' gene, which was first identified and isolated from the Japanese variety 'Norin-10'. This gene reduces the plant height, preventing lodging and allowing the plant to respond more efficiently to nitrogen fertilizers, which was a cornerstone of the Green Revolution in rice.
Analysis of other options:
- Tift23-A: This is a variety of Bermudagrass (Cynodon dactylon), not a dwarfing gene for rice.
- Dee-gee-woo-gen: This is not a recognized gene for dwarfing in rice.
- Opaque-2: This is a well-known mutation in maize (corn) that affects the composition of the endosperm (specifically zein proteins), not a dwarfing gene for rice.
Gullies whose dimensions are enlarged with time called-
A)
U-shaped gully
B)
V-shaped gully
C)
Active gully
D)
Inactive gully
In soil conservation and geomorphology, gullies are classified based on their activity level and shape.
1. **Active Gullies (Correct):** These are gullies that are currently undergoing erosion. They are characterized by the continuous removal of soil from the bed and the sides, meaning their dimensions (depth, width, and length) are enlarged over time due to runoff.
2. **Inactive Gullies:** These are gullies where erosion has ceased. They are often stabilized by vegetation and their dimensions remain constant over time.
3. **V-shaped Gullies:** This refers to the cross-sectional shape of the gully, typically found in the early stages of gully development or in cohesive soils. While they may be active, the term 'V-shaped' describes the geometry, not the process of enlargement over time.
4. **U-shaped Gullies:** This refers to a broader cross-section, often resulting from the widening of a V-shaped gully or the erosion of non-cohesive soils. Like V-shaped gullies, this describes the shape rather than the activity status.
The study of soils in relation to crop growth is known as-
A)
Soil Ecology
B)
Pedology
C)
Edhaphology
D)
Agrogeology
Soil science is broadly divided into two main branches: Pedology and Edaphology.
1. **Edaphology (Option c):** This is the study of soil in relation to the growth of plants. It focuses on the soil as a medium for plant growth, examining how soil properties (chemical, physical, and biological) influence crop yield and plant health. This is the correct answer.
2. **Pedology (Option b):** This is the study of soil in its natural environment. It focuses on soil formation (pedogenesis), morphology, classification, and distribution across the landscape, regardless of its use for plant growth.
3. **Soil Ecology (Option a):** This is a broader interdisciplinary field that studies the interactions between soil organisms and their environment, including the cycling of nutrients and energy.
4. **Agrogeology (Option d):** This refers to the application of geological principles to agriculture, such as studying the mineral sources of nutrients in the soil, but it is not the standard term for the study of soil in relation to crop growth.
Which term describes the portion of solar energy that is reflected back into space by the Earth?
A)
Solar irradiance
B)
Earth’s emissivity
C)
Albedo
D)
Radioactive forcing
Step-by-step reasoning:
1. Definition: Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation received by a body (such as the Earth, a cloud, or a leaf). It is expressed as a dimensionless fraction or percentage.
2. Application: Fresh snow has a high albedo (reflects most light), while dark oceans or forests have a low albedo (absorb most light). The Earth's average albedo is approximately 0.30, meaning 30% of incoming solar energy is reflected back into space.
3. Analysis of other options:
- (a) Solar irradiance: This refers to the power per unit area received from the Sun in the form of electromagnetic radiation (e.g., the solar constant).
- (b) Earth’s emissivity: This refers to the effectiveness of the Earth's surface in emitting energy as thermal infrared radiation, not reflecting incoming solar light.
- (d) Radioactive forcing (Radiative forcing): This is the difference between the incoming solar radiation absorbed by the Earth and the energy radiated back to space, which drives climate change.
Khaira disease of rice is due to-
A)
Calcium deficiency
B)
Zine deficiency
C)
Boron deficiency
D)
Phosphorus deficiency
Khaira disease of rice is a physiological disorder caused by the deficiency of Zinc (Zn). It was first reported in the early 1960s in the Indo-Gangetic plains. The symptoms include the appearance of rusty brown spots or streaks on the leaves, which may eventually lead to the stunting of the plant and failure to produce panicles. This deficiency is common in calcareous soils, sandy soils, and soils with high organic matter where zinc becomes unavailable to the plant.
Analysis of other options:
- Calcium deficiency (a): Typically leads to tip burn or failure of root growth, not Khaira disease.
- Boron deficiency (c): Usually results in the death of the growing point (apical meristem) and poor grain filling.
- Phosphorus deficiency (d): Typically manifests as purpling of the leaves and stunted growth.
The nutrient concentration range in which added nutrient will not increase yield but can increase nutrient concentration is referred as-
A)
Deficient range
B)
Critical range
C)
Toxic range
D)
Luxury consumption
In soil fertility and plant nutrition, the relationship between nutrient availability and crop yield is typically represented by a response curve.
1. **Deficient Range**: At very low nutrient levels, the plant shows deficiency symptoms and yield is significantly reduced.
2. **Critical Range**: This is the narrow range where a small increase in nutrient availability leads to a significant increase in yield. It is the boundary between deficiency and sufficiency.
3. **Sufficiency Range**: In this range, the plant has enough nutrients to achieve maximum yield. Adding more nutrients does not further increase the yield.
4. **Luxury Consumption**: When nutrients are added beyond the sufficiency range, the plant continues to absorb the nutrient and increase its internal concentration, but this does not result in any further increase in biomass or yield. This phenomenon is known as 'luxury consumption'.
5. **Toxic Range**: If nutrient concentrations become excessively high, they can become toxic to the plant, leading to a decrease in yield and potential plant death.
Since the question describes a scenario where added nutrients increase the concentration within the plant but NOT the yield, it specifically refers to luxury consumption.