← Combined Technical (NG)
Past Questions
The food chain in which micro-organisms breakdown dead producers is called:
A)
Consumer food chain
B)
Predator food chain
C)
Parasitic food chain
D)
Detritus food chain
Step-by-step reasoning:
1. **Definition of Detritus Food Chain (DFC):** A detritus food chain is a type of food chain that begins with dead organic matter (detritus), such as fallen leaves, dead animals, and decaying plant material. Micro-organisms (bacteria and fungi) and detritivores (like earthworms) break down this organic matter, recycling nutrients back into the ecosystem.
2. **Analyzing the Question:** The question specifically mentions the breakdown of 'dead producers' by 'micro-organisms'. This perfectly describes the starting point and process of a Detritus Food Chain.
3. **Evaluating Other Options:**
- **a. Consumer food chain:** This is a general term and not a specific ecological classification for decomposition.
- **b. Predator food chain (Grazing Food Chain):** This chain begins with living primary producers (green plants) and moves up to herbivores and then carnivores. It does not start with dead matter.
- **c. Parasitic food chain:** This chain starts with a host and moves to a parasite (and potentially a hyper-parasite). It is characterized by a smaller organism feeding on a larger one, not the breakdown of dead matter.
Therefore, the correct answer is the Detritus food chain.
In an ecotone, the species which become abundant are called:
A)
Edge species
B)
Keystone species
C)
Endemic species
D)
Foster species
Option A is correct: Edge species.
The study of individual organisms in relation to their environment is called:
A)
Synecology
B)
Autecology
C)
Habitat ecology
D)
Ecosystem ecology
The study of ecology is broadly divided into two main branches based on the level of biological organization being studied:
1. **Autecology (Option b):** Derived from the Greek word 'autos' (self), it is the study of a single species or an individual organism in relation to its environment. It focuses on the adaptations, behavior, and life history of a specific organism to survive in its habitat.
2. **Synecology (Option a):** Derived from the Greek word 'syn' (together), it is the study of groups of organisms (communities) and their interactions with each other and their shared environment. It deals with the ecology of populations and communities.
3. **Habitat ecology (Option c):** While 'habitat' refers to the physical place where an organism lives, it is not a formal academic term for the study of individual organisms; rather, it is a component of both autecology and synecology.
4. **Ecosystem ecology (Option d):** This is a broader study that examines the flow of energy and the cycling of matter between biotic (living) and abiotic (non-living) components of an entire ecosystem.
Therefore, the study of individual organisms in relation to their environment is specifically termed Autecology.
________ is the locus of points of different isoquants at which MRS of factors is constant.
A)
Iso-cost line
B)
PPC
C)
Expansion path
D)
Isoclines
Option D is correct: Isoclines.
Botanically pineapple fruit is:
A)
Sorosis
B)
Berry
C)
Balusta
D)
pome
Botanically, a pineapple is a multiple fruit (collective fruit). It develops from a spike of many individual flowers, where the ovaries of these flowers fuse together as they mature to form a single large fruit. This specific type of multiple fruit, derived from a spike or spadix, is called a 'Sorosis'.
Why other options are incorrect:
- b. Berry: A berry is a simple fleshy fruit produced from a single ovary (e.g., tomato, grape).
- c. Balusta: This is not a standard botanical term for fruit types (likely a distractor or misspelling of 'Balausta', which refers to fruits like pomegranate).
- d. Pome: A pome is an accessory fruit where the fleshy part is derived from the floral tube/receptacle rather than the ovary (e.g., apple, pear).
Which class of chemical insecticides 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)**, such as DDT, Heptachlor, and Endrin, are characterized by high stability, low water solubility, and high lipid solubility. This allows them to resist degradation by sunlight, water, and microbial action, leading to long-term persistence in soil and water, as well as bioaccumulation in the food chain.
2. **Organophosphates** (Option c) and **Carbamates** (Option a) are generally non-persistent. They are hydrolyzed relatively quickly in the environment and do not bioaccumulate significantly.
3. **Synthetic pyrethroids** (Option b) are designed to be more stable than natural pyrethrins but are still significantly more biodegradable and less persistent than chlorinated hydrocarbons.
Therefore, chlorinated hydrocarbons are the class most known for their high degree of environmental persistence.
Pheromones used against the fruit fly is:
A)
Methyle eugenol
B)
Carniform
C)
Methyl bromide
D)
Carbofuran
Step-by-step reasoning: 1. The question asks for a pheromone (or attractant) used specifically against fruit flies. 2. Methyl eugenol is a potent attractant used in 'Male Annihilation Technique' (MAT) to control fruit flies, particularly the Oriental fruit fly (Bactrocera dorsalis). While technically a kairomone (a chemical emitted by a plant that benefits the receiver), it is commonly categorized under pheromone-based trapping systems in agricultural entomology exams. 3. Analyzing other options: (b) 'Carniform' is not a recognized chemical attractant or pesticide. (c) Methyl bromide is a broad-spectrum fumigant used for soil and warehouse sterilization, not a pheromone. (d) Carbofuran is a carbamate insecticide (a toxic chemical), not a pheromone. Therefore, Methyl eugenol is the only correct choice for a lure used in fruit fly management.
What are pests? Mention five (5) common insect pests of rice and explain the nature of damage, management strategies adopted for yellow stem borer infestation in rice.
The disease damping off seedlings during nursery stage is caused by the pathogen
A)
Physoderma maydis
B)
Fusarium spp
C)
Pythium spp
D)
Colletotrichum lindemuthianum
Damping-off is a common disease affecting seedlings in the nursery stage, characterized by the rotting of the stem at the soil line, leading to the collapse and death of the plant. It is primarily caused by soil-borne oomycetes and fungi. Pythium spp. is the most prominent pathogen associated with 'pre-emergence' and 'post-emergence' damping-off due to its ability to produce motile zoospores that swim through saturated soil to infect young roots and stems.
Analysis of other options:
- Physoderma maydis: Causes Physoderma stripe in maize, which is a foliar disease, not damping-off.
- Fusarium spp: While some Fusarium species can cause root rot and seedling blight, they are more typically associated with vascular wilts and crown rots in mature plants.
- Colletotrichum lindemuthianum: This is the causal agent of bean anthracnose, which typically affects leaves, pods, and stems of mature plants rather than causing nursery damping-off.
Which part of root absorb water and minerals?
A)
Root cap
B)
Epidermis
C)
Root hairs
D)
Endodermis
Step-by-step reasoning:
1. **Function of Root Hairs**: Root hairs are unicellular elongations of the epidermal cells (specifically trichoblasts). Their primary biological function is to increase the surface area of the root system, allowing for the maximum absorption of water and dissolved minerals from the soil via osmosis and active transport.
2. **Analysis of other options**:
- **Root cap (a)**: This is a protective layer of cells at the tip of the root that protects the apical meristem as the root pushes through the soil; it does not absorb water.
- **Epidermis (b)**: While root hairs are part of the epidermis, the general epidermal layer acts as a boundary. The specialized 'hairs' are the specific structures evolved for absorption. In a multiple-choice context, 'Root hairs' is the more precise and correct answer than the general 'Epidermis'.
- **Endodermis (d)**: This is the innermost layer of the root cortex. Its primary role is to regulate the flow of water and minerals into the vascular cylinder (stele) via the Casparian strip, rather than absorbing them from the soil.
Genetically most pure seed is:
A)
Breeder seed
B)
Foundation seeds
C)
Nucleus seed
D)
Certified seed
In seed science, seeds are categorized into a hierarchy based on their genetic purity and the stage of multiplication.
1. Nucleus Seed: This is the initial seed produced by the original plant breeder. It is the most genetically pure seed (100% pure) and serves as the source for all subsequent generations. It is produced in very small quantities.
2. Breeder Seed: Produced from nucleus seed. While it maintains very high genetic purity, it is the first step of multiplication and is used to produce foundation seeds.
3. Foundation Seed: Produced from breeder seed. These are the progeny of breeder seeds and are used to produce certified seeds.
4. Certified Seed: Produced from foundation seed. These are the seeds distributed to farmers for commercial crop production. They have the lowest genetic purity relative to the other three categories, although they still meet strict quality standards.
Therefore, the Nucleus seed is the most genetically pure as it is the direct output of the breeding process before any large-scale multiplication occurs.
What are the differences between Prokaryotic and Eukaryotic organisms? Explain Prokaryotic Bacterial Cell structure and functions with diagram indicating different types of structure.
Indian Institute of Horticultural Research (IIHR) is located at:
A)
N. Delhi
B)
Hyderabad
C)
Bengaluru (Bangalore)
D)
Kolkata
The Indian Institute of Horticultural Research (IIHR) is a premier research institute under the Indian Council of Agricultural Research (ICAR). It is located in Bengaluru, Karnataka. Its primary mandate is to conduct basic and applied research on various horticultural crops to improve productivity and quality.
Analysis of other options:
- N. Delhi: While many ICAR headquarters and institutes (like IARI) are in Delhi, IIHR is not one of them.
- Hyderabad: This city hosts other major institutes like the National Institute of Nutrition (NIN) and various agricultural research centers, but not IIHR.
- Kolkata: This city hosts institutes like the Central Inland Fisheries Research Institute (CIFRI), but not IIHR.
What is the source of Agar Agar?
A)
Bacteria
B)
Mycoplasma
C)
Fungi
D)
Algae
Agar-agar is a gelatinous substance derived from the cell walls of certain species of red algae (Rhodophyta), most notably from the genera Gelidium and Gracilaria. In microbiology, it is the most widely used solidifying agent for culture media because it remains solid at incubation temperatures (up to 100°C melting point and approx 40-45°C solidification point) and most bacteria cannot digest it, ensuring the medium remains solid during growth.
Why other options are incorrect:
- a. Bacteria: Bacteria are the organisms grown *on* agar, not the source of it.
- b. Mycoplasma: These are a specific type of bacteria lacking a cell wall; they do not produce agar.
- c. Fungi: Fungi have cell walls made of chitin, not the galactans (agarose and agaropectin) found in red algae.
Biological control is likely to be most effective when the predator or parasite has a:
A)
Long life cycle
B)
High reproductive rate
C)
Wide range of preferred hosts
D)
Short life cycle
In biological control, the goal is for the natural enemy (predator or parasite) to respond rapidly to an increase in the pest population to prevent an outbreak. A short life cycle is the most critical factor for this because it allows the biological control agent to multiply quickly, increasing its population density in synchronization with the pest's growth. This rapid numerical response ensures that the predator or parasite can suppress the pest population before it reaches the economic injury level.
Why other options are incorrect:
- a. Long life cycle: This would result in a slow population response, allowing the pest to multiply unchecked for longer periods.
- b. High reproductive rate: While generally helpful, a high reproductive rate is less effective if the life cycle is long (generation time is slow). The speed of the cycle (turnover) is more critical for immediate control.
- c. Wide range of preferred hosts: This is often a disadvantage (generalist). A specialist (narrow host range) is usually preferred in biological control to ensure the agent focuses specifically on the target pest and does not switch to non-target beneficial insects or crops.
What are plant parasitic Nematodes? Describe the symptoms of Root-knot Nematodes in the infected plants and management practices for controlling their population in soil.
Pests outbreaks tend to occur when:
A)
Crops are planted in monoculture
B)
Natural enemies are imported from abroad
C)
Farmers switch to new crops
D)
Mixed cropping
Step-by-step reasoning: 1. A pest outbreak occurs when a pest population increases rapidly to a level that causes significant economic damage. 2. Monoculture is the practice of growing a single crop species over a large area for consecutive seasons. This provides a continuous, abundant, and uniform food source for specialized pests, allowing their populations to grow exponentially without interruption. 3. Furthermore, monocultures often lack the biological diversity required to support a robust population of natural enemies (predators and parasitoids), which normally keep pest populations in check. 4. Analyzing other options: (b) Importing natural enemies usually helps control pests, not cause outbreaks. (c) Switching to new crops can sometimes introduce new pests, but it is not the primary systemic driver of widespread outbreaks compared to monoculture. (d) Mixed cropping increases biodiversity and disrupts the movement and feeding patterns of pests, acting as a deterrent to outbreaks.
Which is the most recent widely used fungicide for the control of Powdery mildew?
A)
Calaxin
B)
Sulphur dust
C)
Dithane M-45
D)
Apron SD-35
To determine the correct fungicide for Powdery mildew among the given options, we must analyze the chemical nature and target pathogens of each:
1. **Calaxin**: This is a systemic fungicide (often associated with the triazole or similar modern systemic classes depending on regional branding) specifically developed and widely used for the control of powdery mildew and other fungal diseases. Compared to the other options, it represents a more 'recent' systemic approach to disease management.
2. **Sulphur dust**: This is one of the oldest known fungicides used for powdery mildew. While still effective and widely used, it is not 'recent'.
3. **Dithane M-45**: This is a brand name for Mancozeb. It is a broad-spectrum protectant fungicide used for a wide variety of diseases (like blight and rust), but it is not specifically the 'most recent' targeted choice for powdery mildew compared to systemic options.
4. **Apron SD-35**: This is a seed treatment fungicide (containing Captan or similar agents) primarily used to control seed-borne and soil-borne diseases (damping-off), not for foliar powdery mildew.
Therefore, Calaxin is the most appropriate answer in the context of recent, targeted fungicide use for powdery mildew.
What are the principles of plant disease management? Elaborate different components of Integrated Disease Management (IDM) in plants with one example from each component.
Which crop is most susceptible to viral infection?
A)
Chillies
B)
Onion
C)
Tomato
D)
brinjal
In plant pathology, susceptibility to viral infections is often measured by the range of viruses a plant can host and the severity of the resulting disease. Among the options provided, Tomato (Solanum lycopersicum) is widely recognized as one of the most susceptible crops to a vast array of viral pathogens. It is frequently attacked by the Tomato Yellow Leaf Curl Virus (TYLCV), Tomato Mosaic Virus (ToMV), Cucumber Mosaic Virus (CMV), and various Potato viruses. While chillies and brinjal (both Solanaceous crops) are also susceptible to many of the same viruses, the tomato's broad susceptibility to both soil-borne and vector-borne (whitefly, aphid) viruses, combined with the high prevalence of devastating viral epidemics in tomato cultivation globally, makes it the most susceptible in this comparative list. Onions (Alliums) are generally less susceptible to the broad range of systemic viruses that plague the Solanaceae family.
Which of the following fungicide is not systemic in nature?
A)
Vitavax
B)
Benlate
C)
Thiram
D)
Topsin
Fungicides are classified based on their mode of action and movement within the plant into contact (non-systemic) and systemic fungicides.
1. **Thiram (Option c):** This is a dithiocarbamate fungicide. It acts as a protectant and is non-systemic (contact fungicide). It remains on the surface of the plant tissue and does not penetrate or move through the vascular system of the plant. Therefore, it is not systemic in nature.
2. **Vitavax (Option a):** This is a trade name for Carboxin. Carboxin is a systemic fungicide used primarily for seed treatment to control smuts and bunts.
3. **Benlate (Option b):** This is a trade name for Benomyl. Benomyl is a well-known systemic fungicide belonging to the benzimidazole group.
4. **Topsin (Option d):** This is also a trade name for Thiophanate-methyl (or sometimes Benomyl depending on the region/formulation), both of which are systemic fungicides.
Since Vitavax, Benlate, and Topsin are all systemic, and Thiram is a contact fungicide, the correct answer is Thiram.
Multiple effects of a single gene is known as:
A)
Pleiotropy
B)
Heteroploidy
C)
Polyploidy
D)
Monoploidy
Step-by-step reasoning: 1. The question asks for the term describing a scenario where a single gene influences multiple, seemingly unrelated phenotypic traits. 2. Pleiotropy (from Greek 'pleion' meaning more and 'tropos' meaning way) is the genetic phenomenon where one gene affects multiple traits. A classic example is Sickle Cell Anemia, where a single mutation in the hemoglobin gene leads to various effects including anemia, organ damage, and resistance to malaria. 3. Analysis of other options: (b) Heteroploidy refers to having a chromosome number that is not an exact multiple of the haploid set. (c) Polyploidy is the condition of possessing more than two complete sets of chromosomes (e.g., triploid, tetraploid). (d) Monoploidy refers to having a single set of chromosomes. Since options b, c, and d relate to chromosomal number (ploidy) rather than gene expression effects, they are incorrect.
Explain the diagnostic symptoms of Fusarium wilt of Tomato, Late blight of Potato, Rhizome rot of Ginger and what are the practices adopted for effective management of soil borne disease incidence.
The major storage fungi that affects the food grain is:
A)
Rhizobium
B)
Cercospora
C)
Mucor
D)
Aspergillus
Step-by-step reasoning:
1. Storage fungi are microorganisms that infect grains after harvest, typically during storage in warehouses or silos. They are characterized by their ability to grow at lower moisture contents than field fungi.
2. Aspergillus is a genus of fungi well-known for causing storage rots in food grains (such as maize, wheat, and rice). Some species, like Aspergillus flavus, are particularly dangerous because they produce aflatoxins, which are carcinogenic and toxic to humans and livestock.
3. Evaluating other options:
- Rhizobium (a): This is a genus of nitrogen-fixing bacteria that forms symbiotic relationships with legumes; it is not a fungus and does not cause grain rot.
- Cercospora (b): This is a genus of fungi that primarily causes leaf spot diseases in the field (foliar pathogens), not storage rot.
- Mucor (c): While Mucor can be found on decaying organic matter and some fruits/vegetables (as a zygomycete), it is not considered a 'major' storage fungus for food grains compared to the prevalence and economic impact of Aspergillus and Penicillium.
4. Therefore, Aspergillus is the most accurate answer among the given choices.
Stomata open and close due to:
A)
Circadian rhythm
B)
Pressure of gases inside the leaves
C)
Genetic clock
D)
Turgor pressure of guard cells
The opening and closing of stomata is primarily governed by the turgidity of the guard cells. When guard cells take up water (due to an influx of potassium ions K+ and subsequent osmotic movement of water), they become turgid. Because the inner walls of guard cells are thicker and less elastic than the outer walls, the cells bow outward, pulling the stomatal pore open. Conversely, when guard cells lose water, they become flaccid, and the pore closes.
Why other options are incorrect:
- a. Circadian rhythm: While the biological clock can influence the timing of stomatal movement, it is a regulatory signal, not the physical mechanism that causes the opening/closing.
- b. Pressure of gases: Gas exchange occurs through the stomata, but the pressure of gases inside the leaf does not mechanically drive the opening or closing of the pore.
- c. Genetic clock: Similar to circadian rhythms, genetics provide the blueprint for how the plant responds to stimuli, but the immediate physical cause is hydraulic (turgor pressure).