WBCS Prelims Biology Questions 2024
48. Which of the following animals is the natural reservoir of Nipah virus?
(A) Bats
(B) Turtles
(C) Migratory birds
(D) Horses
Answer & Explanation
Answer: (A) Bats
Explanation
Nipah virus is a zoonotic virus whose natural reservoir is fruit bats of the genus Pteropus (flying foxes). The virus can spread from bats to animals such as pigs and then to humans, or directly from bats to humans through contaminated food or close contact. Human-to-human transmission has also been reported during outbreaks.
Exam Facts
- Natural reservoir: Fruit bats (Pteropus spp.).
- Nipah virus is a zoonotic disease (transmitted from animals to humans).
- It mainly affects the brain (encephalitis) and respiratory system.
- First outbreak: Malaysia, 1998–99.
- Human-to-human transmission has also been reported.
- WHO has listed Nipah virus as a priority disease due to its epidemic potential.
49. Ginger is a stem because
(A) it grows horizontally in the soil.
(B) it stores food materials.
(C) absence of chlorophyll.
(D) it has nodes and inter-nodes.
Answer & Explanation
Answer: (D) it has nodes and inter-nodes.
Explanation
Ginger is an underground modified stem (rhizome). It is identified as a stem because it possesses nodes, internodes, scale leaves, and buds, which are characteristic features of stems. Merely growing underground or storing food does not distinguish a stem from a root.
Exam Facts
- Ginger (Zingiber officinale) is an underground modified stem (rhizome).
- Rhizome examples: Ginger, turmeric (Curcuma longa), and canna.
- Tuber (modified stem): Potato – has ‘eyes’, which are buds.
- Corm (modified stem): Colocasia (taro), gladiolus.
- Bulb (modified stem): Onion and garlic; food is mainly stored in fleshy scale leaves.
- Stem characters: Presence of nodes, internodes, buds, and leaves.
- Root characters: Root cap and root hairs are present; nodes and internodes are absent.
- Function of underground modified stems: Storage of food, perennation, and vegetative propagation.
66. Agar-agar is derived from a/an
(A) Bryophytes
(B) Algae
(C) Fungi
(D) Pteridophytes
Answer & Explanation
Answer: (B) Algae
Explanation
Agar-agar is obtained from red algae (Rhodophyceae), mainly from the genera Gelidium and Gracilaria. It is widely used as a solidifying agent in microbiological culture media, as well as in the food and pharmaceutical industries.
Exam Facts
- Source of agar: Red algae (Rhodophyceae).
- Major genera: Gelidium and Gracilaria.
- Primary use: Solidifying agent in microbiological culture media.
- Other uses: Food industry (jellies, desserts), pharmaceuticals, cosmetics, and biotechnology.
- Algal pigments: Red algae contain phycoerythrin, which gives them their red colour.
- Commercial products from algae: Agar, algin (brown algae), and carrageenan (red algae).
- Study of algae: Phycology.
- Algae are photosynthetic organisms and contribute significantly to global oxygen production and aquatic food chains.
74. How does a non-green (coloured) leaf synthesize food?
(A) The red and purple pigments directly absorb heat from the sunlight, thus replacing the need for photosynthesis.
(B) The leaf contains green chlorophyll but it remains hidden under other pigments.
(C) Coloured leaves steal glucose from neighbouring green plants through air using microscopic spores.
(D) None of the above.
Answer & Explanation
Answer: (B) The leaf contains green chlorophyll but it remains hidden under other pigments.
Explanation
Non-green leaves also contain chlorophyll, but it is masked by pigments like anthocyanin or carotenoids. Chlorophyll performs photosynthesis, allowing these leaves to prepare food like green leaves.
Exam Facts
- Chlorophyll is the main pigment responsible for photosynthesis.
- Anthocyanin gives red, purple, and blue colours to leaves, flowers, and fruits.
- Carotenoids produce yellow and orange colours and act as accessory pigments.
- Photosynthesis takes place in chloroplasts.
- Chlorophyll ‘a’ is the primary photosynthetic pigment.
- Examples of coloured-leaf plants: Croton and Coleus.
80. Why are antibiotics not prescribed to kill viral infections?
(A) Viruses take refuge in a cell organelle where antibiotics cannot reach.
(B) Viruses neither have cell walls nor their own metabolic machinery that can be targeted by antibiotics.
(C) Viruses mutate rapidly.
(D) None of the above.
Answer & Explanation
Answer: (B) Viruses neither have cell walls nor their own metabolic machinery that can be targeted by antibiotics.
Explanation
Antibiotics act by targeting bacterial structures such as cell walls, ribosomes, or metabolic pathways. Viruses lack these structures and depend entirely on the host cell for reproduction. Therefore, antibiotics are ineffective against viral infections.
Exam Facts
- Antibiotics are effective against bacteria, not viruses.
- Viral diseases include COVID-19, dengue, measles, chickenpox, polio, and influenza.
- Bacterial diseases include tuberculosis, typhoid, cholera, and tetanus.
- Antiviral drugs are used to treat viral infections, not antibiotics.
- Unnecessary use of antibiotics can lead to antimicrobial resistance (AMR).
- Alexander Fleming discovered penicillin in 1928, the first antibiotic.
82. Pneumatophores are modified roots and negatively geotropic. These are—
(A) Respiratory roots
(B) Photosynthetic roots
(C) Food storing roots
(D) Water storing roots
Answer & Explanation
Answer: (A) Respiratory roots
Explanation
Pneumatophores are specialized respiratory roots found in mangrove plants growing in waterlogged, oxygen-deficient soils. They grow upward (negative geotropism) above the soil surface and contain lenticels that help in gaseous exchange.
Exam Facts
- Pneumatophores are also called breathing roots or respiratory roots.
- They exhibit negative geotropism (grow upward against gravity).
- Commonly found in mangrove plants.
- Examples: Avicennia and Sonneratia.
- Lenticels present on pneumatophores facilitate the exchange of gases.
- Sundarbans in West Bengal is the largest mangrove forest in the world and a common habitat of plants with pneumatophores.
84. The most abundant enzyme in the living world is ________.
(A) Lipase
(B) DNase
(C) Zymase
(D) Rubisco
Answer & Explanation
Answer: (D) Rubisco
Explanation
Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the most abundant enzyme on Earth. It plays a key role in photosynthesis by fixing atmospheric carbon dioxide during the Calvin cycle to produce carbohydrates.
Exam Facts
- Rubisco is the most abundant enzyme in the living world.
- It is present in the chloroplasts of green plants.
- It catalyzes the first step of carbon fixation in the Calvin cycle.
- Calvin cycle is also known as the dark reaction or light-independent reaction of photosynthesis.
- Melvin Calvin received the 1961 Nobel Prize in Chemistry for discovering the Calvin cycle.
- Rubisco acts as both a carboxylase and an oxygenase enzyme.
111. Synapsis occurs during
(A) Leptotene
(B) Diplotene
(C) Zygotene
(D) Pachytene
Answer & Explanation
Answer: (C) Zygotene
Explanation
Synapsis is the pairing of homologous chromosomes during Zygotene, a stage of Prophase I of meiosis. This pairing forms bivalents, which are essential for the exchange of genetic material in the next stage.
Exam Facts
- Synapsis occurs during the Zygotene stage of Prophase I.
- Crossing over takes place during the Pachytene stage.
- Chiasmata become visible during the Diplotene stage.
- Leptotene is the stage where chromosomes first become visible.
- Meiosis produces four haploid daughter cells from one diploid cell.
- Crossing over increases genetic variation in offspring.
134. Which of the following carries oxygenated blood?
(A) Hepatic portal veins
(B) Pulmonary veins
(C) Renal veins
(D) Pulmonary artery
Answer & Explanation
Answer: (B) Pulmonary veins
Explanation
Pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. They are the only veins in the human body that normally carry oxygen-rich blood. In contrast, the pulmonary artery carries deoxygenated blood from the heart to the lungs.
Exam Facts
- Pulmonary veins carry oxygenated blood to the left atrium.
- Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
- Hepatic portal vein carries nutrient-rich blood from the digestive organs to the liver.
- Renal veins carry deoxygenated blood from the kidneys to the inferior vena cava.
- Exception: Pulmonary veins and the umbilical vein carry oxygenated blood, unlike most veins.
- Exception: Pulmonary artery and the umbilical arteries carry deoxygenated blood, unlike most arteries.
163. Growth inhibiting hormone of plant is
(A) Auxin
(B) Gibberellin
(C) Cytokinin
(D) Abscisic acid
Answer & Explanation
Answer: (D) Abscisic acid
Explanation
Abscisic acid (ABA) is known as the growth-inhibiting or stress hormone of plants. It inhibits plant growth, induces seed and bud dormancy, and causes the closure of stomata during water stress to reduce water loss.
Exam Facts
- Abscisic acid (ABA) is called the stress hormone of plants.
- It inhibits plant growth and promotes seed and bud dormancy.
- ABA causes stomatal closure during drought conditions.
- Auxin promotes cell elongation and apical dominance.
- Gibberellin promotes stem elongation and seed germination.
- Cytokinin promotes cell division and delays leaf senescence.
172. Water available for plants within the soil is
(A) Hygroscopic water
(B) Capillary water
(C) Mineral water
(D) Chemically bound water
Answer & Explanation
Answer: (B) Capillary water
Explanation
Capillary water is held in the small pores between soil particles and is the main source of water absorbed by plant roots. Hygroscopic water and chemically bound water are held too tightly by soil particles to be available to plants.
Exam Facts
- Capillary water is the plant-available water in the soil.
- Hygroscopic water is tightly bound to soil particles and cannot be absorbed by plants.
- Gravitational water drains downward due to gravity and is generally unavailable after drainage.
- Chemically bound water is part of soil minerals and is unavailable to plants.
- Root hairs absorb water mainly through osmosis.
- Loamy soil is considered the best for plant growth because it retains adequate capillary water while allowing proper aeration.
195. Which of the following ape(s) is/are genetically closest to the modern humans (Homo sapiens)?
(A) Chimpanzee and Bonobo
(B) Gorilla
(C) Orangutan
(D) Gibbon
Answer & Explanation
Answer: (A) Chimpanzee and Bonobo
Explanation
Chimpanzees and bonobos are the closest living relatives of modern humans. Humans share about 98–99% of their DNA with these apes, indicating a common ancestor that lived millions of years ago.
Exam Facts
- Chimpanzee and Bonobo are the closest living relatives of Homo sapiens.
- Humans share approximately 98–99% DNA with chimpanzees and bonobos.
- Bonobo is also known as the pygmy chimpanzee.
- Scientific name of modern humans: Homo sapiens.
- Order: Primates; Family: Hominidae (Great Apes).
- Evolutionary sequence often asked in exams: Gibbon → Orangutan → Gorilla → Chimpanzee/Bonobo → Human (in increasing genetic closeness to humans).
WBCS Prelims Biology Questions 2023
30. Which of the following pairs comprises of the smallest and the largest endocrine glands of human respectively?
(A) Pituitary – Thyroid
(B) Thyroid – Pituitary
(C) Pineal body – Ovary
(D) Pineal body – Thyroid
Answer & Explanation
Answer: (D) Pineal body – Thyroid
Explanation
The pineal gland is the smallest endocrine gland in the human body, while the thyroid gland is the largest purely endocrine gland. The pineal gland secretes melatonin, whereas the thyroid gland secretes thyroxine (T₄) and triiodothyronine (T₃), which regulate metabolism.
Exam Facts
- Smallest endocrine gland: Pineal gland (Pineal body).
- Largest purely endocrine gland: Thyroid gland.
- Largest endocrine organ (not purely endocrine): Pancreas (mixed gland).
- Pineal gland secretes melatonin, which regulates the sleep–wake cycle.
- Thyroid gland secretes T₃ (Triiodothyronine) and T₄ (Thyroxine).
- Pituitary gland is known as the ‘Master gland’ because it controls the activity of many other endocrine glands.
101. Cause of myopia is
(A) Contraction of eyeball
(B) Expansion of eyeball
(C) Dryness of optic nerve
(D) All are true
Answer & Explanation
Answer: (B) Expansion of eyeball
Explanation
Myopia (short-sightedness) occurs when the eyeball becomes elongated (expanded) or the eye lens has excessive curvature. As a result, light rays are focused in front of the retina, making distant objects appear blurred. It is corrected using a concave (diverging) lens.
Exam Facts
- Myopia is also called short-sightedness.
- In myopia, the image is formed in front of the retina.
- It is corrected with a concave (diverging) lens.
- Hypermetropia (long-sightedness) is corrected with a convex lens.
- Presbyopia occurs due to age-related loss of elasticity of the eye lens.
- Astigmatism is caused by irregular curvature of the cornea or lens and is corrected using a cylindrical lens.
127. Which hormone is responsible for breaking the dormancy of a seed?
(A) Auxin
(B) Dormin
(C) Cytokinin
(D) Gibberellin
Answer & Explanation
Answer: (D) Gibberellin
Explanation
Gibberellins break seed dormancy and promote seed germination by stimulating the production of enzymes needed for the mobilization of stored food. They also promote stem elongation and flowering in some plants.
Exam Facts
- Gibberellin breaks seed dormancy and promotes germination.
- Abscisic acid (ABA) induces seed dormancy and inhibits plant growth.
- Auxin promotes cell elongation and apical dominance.
- Cytokinin promotes cell division and delays leaf senescence.
- Ethylene is a gaseous plant hormone that promotes fruit ripening.
- Remember: Gibberellin = Germination, ABA = Dormancy (frequently asked in competitive exams).
128. Which of the following reproduction is found in plants alone?
(A) Vegetative reproduction
(B) Asexual reproduction
(C) Sexual reproduction
(D) Parthenogenesis
Answer & Explanation
Answer: (A) Vegetative reproduction
Explanation
Vegetative reproduction is a type of asexual reproduction in which new plants arise from vegetative parts such as roots, stems, or leaves. It is characteristic of plants and does not occur naturally in animals.
Exam Facts
- Vegetative reproduction occurs through root, stem, or leaf.
- Examples: Potato (tuber), Ginger (rhizome), Onion (bulb), Bryophyllum (leaf).
- It is a form of asexual reproduction.
- Plants produced by vegetative reproduction are genetically identical (clones) to the parent plant.
- Parthenogenesis is the development of an individual from an unfertilized egg and is seen in organisms like honey bees, aphids, and some reptiles.
- Sexual reproduction occurs in both plants and animals.
161. One of the following terms includes the rest of the lot. Identify that single term:
Glucocorticoids, Adrenaline, Mineralocorticoids, Suprarenal gland.
(A) Mineralocorticoids
(B) Adrenaline
(C) Suprarenal gland
(D) Glucocorticoids
Answer & Explanation
Answer: (C) Suprarenal gland
Explanation
The suprarenal (adrenal) gland includes the rest because it secretes adrenaline, glucocorticoids, and mineralocorticoids. Thus, it is the broader term that encompasses the other three.
Exam Facts
- Suprarenal gland is another name for the adrenal gland.
- It is located above each kidney.
- Adrenal medulla secretes adrenaline (epinephrine).
- Adrenal cortex secretes glucocorticoids (e.g., cortisol).
- Adrenal cortex also secretes mineralocorticoids (e.g., aldosterone).
- Adrenaline is known as the “emergency” or “fight-or-flight” hormone.
174. In which substage of interphase is DNA doubled?
(A) G₁
(B) S
(C) G₂
(D) G₀
Answer & Explanation
Answer: (B) S
Explanation
DNA replication takes place during the S (Synthesis) phase of interphase. During this stage, the amount of DNA in the cell doubles, preparing the cell for division, while the chromosome number remains unchanged.
Exam Facts
- S phase is the stage of DNA replication.
- G₁ phase: Cell growth and synthesis of proteins and RNA.
- G₂ phase: Preparation for cell division.
- G₀ phase: Resting or inactive phase; the cell does not divide.
- Interphase consists of G₁, S, and G₂ phases.
- M phase is the phase of cell division (mitosis or meiosis).
196. Which of the following diseases is autosomal?
(A) Haemophilia
(B) Thalassemia
(C) Colourblindness
(D) All of the above
Answer & Explanation
Answer: (B) Thalassemia
Explanation
Thalassemia is an autosomal recessive genetic disorder, meaning the defective gene is located on an autosome (non-sex chromosome). In contrast, haemophilia and colour blindness are X-linked recessive disorders, occurring due to mutations on the X chromosome.
Exam Facts
- Thalassemia is an autosomal recessive disorder.
- Haemophilia is an X-linked recessive disorder affecting blood clotting.
- Colour blindness is also an X-linked recessive disorder.
- Sickle cell anaemia is another autosomal recessive genetic disease.
- Males are more commonly affected by X-linked recessive disorders because they have only one X chromosome.
- Carrier screening is important in the prevention of thalassemia in high-risk populations.
WBCS Prelims Biology Questions 2022
29. Phytophthora palmivora is a
(A) Bio-pesticide
(B) Bio-insecticide
(C) Mycoherbicide
(D) First bio-herbicide
Answer & Explanation
Answer: (D) First bio-herbicide
Explanation
Phytophthora palmivora was developed as DeVine, the world’s first commercially registered bio-herbicide. It is used to control milkweed vine in citrus plantations and is therefore recognized as the first bio-herbicide.
Exam Facts
- DeVine is the first commercially registered bio-herbicide.
- It is based on Phytophthora palmivora.
- It is used to control milkweed vine in citrus orchards.
- A mycoherbicide is a herbicide derived from fungi or fungus-like organisms.
- Phytophthora belongs to the group Oomycetes (water moulds).
- Another well-known mycoherbicide is Collego, developed from Colletotrichum gloeosporioides.
41. ‘ELISA’ test is employed to diagnose
(A) Polio Virus
(B) AIDS antibodies
(C) Tuberculosis
(D) Cancer
Answer & Explanation
Answer: (B) AIDS antibodies
Explanation
ELISA (Enzyme-Linked Immunosorbent Assay) is commonly used to detect antibodies against HIV, the virus that causes AIDS. It is a screening test, and positive results are usually confirmed by more specific tests.
Exam Facts
- ELISA stands for Enzyme-Linked Immunosorbent Assay.
- It is widely used for screening HIV (AIDS) infection.
- ELISA detects antigens or antibodies in blood samples.
- HIV stands for Human Immunodeficiency Virus.
- AIDS stands for Acquired Immunodeficiency Syndrome.
- ELISA is also used to diagnose several other infectious and autoimmune diseases.
63. Which of the following is an aquatic fern?
(A) Adiantum
(B) Dryopteris
(C) Salvinia
(D) Equisetum
Answer & Explanation
Answer: (C) Salvinia
Explanation
Salvinia is a free-floating aquatic fern commonly found in ponds, lakes, and other freshwater bodies. The other options are terrestrial plants, while Equisetum is a horsetail and not a true fern.
Exam Facts
- Salvinia is a floating aquatic fern.
- Azolla is another important aquatic fern, often used as green manure in paddy fields.
- Adiantum is commonly known as the Maidenhair fern.
- Dryopteris is a terrestrial fern (wood fern).
- Equisetum is commonly called horsetail and belongs to the Pteridophytes.
- Pteridophytes are the first vascular plants and reproduce by spores.
81. Which one of the following animals is known as a ‘living fossil’?
(A) Peripatus
(B) Amoeba
(C) Prawn
(D) Apple snail
Answer & Explanation
Answer: (A) Peripatus
Explanation
Peripatus is called a living fossil because it has retained many primitive characteristics over millions of years. It is also regarded as a connecting link between Annelida (segmented worms) and Arthropoda (joint-legged animals).
Exam Facts
- Peripatus is known as a living fossil.
- It is a connecting link between Annelida and Arthropoda.
- Limulus (King crab) and Sphenodon (Tuatara) are other famous examples of living fossils.
- Living fossils are organisms that have remained largely unchanged for millions of years.
- Amoeba is a unicellular protozoan.
- Prawn is a crustacean, while Apple snail is a mollusc.
84. The vitamin which helps in clotting of blood is
(A) A
(B) D
(C) B
(D) K
Answer & Explanation
Answer: (D) K
Explanation
Vitamin K is essential for the synthesis of prothrombin and other clotting factors in the liver. A deficiency of Vitamin K can lead to excessive bleeding due to impaired blood clotting.
Exam Facts
- Vitamin K is essential for blood clotting.
- It helps in the synthesis of prothrombin (Factor II).
- Deficiency of Vitamin K causes delayed blood clotting and bleeding.
- Vitamin A is important for vision and healthy skin.
- Vitamin D helps in the absorption of calcium and phosphorus for healthy bones.
- Vitamin B-complex is mainly involved in energy metabolism and nervous system functions.
86. What is the chromosome number in human ovum?
(A) 36
(B) 46
(C) 48
(D) None of the above
Answer & Explanation
Answer: (D) None of the above (Human ovum contains 23 chromosomes.)
Explanation
A human ovum is a haploid (n) cell formed by meiosis and therefore contains 23 chromosomes. After fertilization, the ovum (23) fuses with the sperm (23) to form a diploid zygote (46 chromosomes).
Exam Facts
- Human ovum: 23 chromosomes (n).
- Human sperm: 23 chromosomes (n).
- Human somatic (body) cells: 46 chromosomes (2n).
- Zygote: 46 chromosomes (2n) after fertilization.
- Meiosis produces haploid gametes.
- Mitosis maintains the chromosome number in body cells.
87. ‘Seahorse’ is a
(A) Mammal
(B) Plant
(C) Fish
(D) None of the above
Answer & Explanation
Answer: (C) Fish
Explanation
The seahorse is a marine fish belonging to the genus Hippocampus. It breathes through gills, has fins, and belongs to the family Syngnathidae. Unlike most fishes, the male seahorse carries and incubates the eggs in a brood pouch.
Exam Facts
- Seahorse is a marine fish.
- Scientific genus: Hippocampus.
- Family: Syngnathidae.
- Male seahorse carries the fertilized eggs in a brood pouch.
- Seahorses breathe through gills and swim using fins.
- The male gives birth to the young, a unique feature among fishes.
113. The ‘powerhouse’ of the cell is
(A) Nucleus
(B) Lysosome
(C) Mitochondria
(D) DNA
Answer & Explanation
Answer: (C) Mitochondria
Explanation
Mitochondria are called the powerhouse of the cell because they produce ATP (Adenosine Triphosphate) through cellular respiration. ATP serves as the primary source of energy for various cellular activities.
Exam Facts
- Mitochondria are known as the powerhouse of the cell.
- They produce ATP, the energy currency of the cell.
- Mitochondria contain their own DNA and ribosomes.
- They are double membrane-bound organelles.
- Nucleus is the control centre of the cell.
- Lysosomes are called the ‘suicidal bags’ of the cell due to their digestive enzymes.
138. Which metal is present in haemoglobin?
(A) Iron
(B) Zinc
(C) Magnesium
(D) Copper
Answer & Explanation
Answer: (A) Iron
Explanation
Haemoglobin contains iron (Fe) in its haem group. Iron binds with oxygen in the lungs and transports it to different parts of the body through the blood.
Exam Facts
- Iron (Fe) is the metal present in haemoglobin.
- Haemoglobin is found in red blood cells (RBCs).
- The main function of haemoglobin is transport of oxygen.
- Iron deficiency can cause anaemia.
- Magnesium (Mg) is the central metal ion in chlorophyll.
- Copper (Cu) is present in the respiratory pigment haemocyanin of some molluscs and arthropods.
141. Which part of the human eye has the maximum refractive index?
(A) Aqueous humour
(B) Vitreous humour
(C) Lens
(D) Cornea
Answer & Explanation
Answer: (C) Lens
Explanation
The crystalline lens has the highest refractive index among the transparent parts of the human eye. It helps focus light precisely on the retina by changing its curvature during accommodation.
Exam Facts
- Lens has the maximum refractive index in the human eye.
- Cornea provides the maximum refraction (bending of light) in the eye.
- Lens is responsible for accommodation (adjusting focus for near and distant objects).
- Aqueous humour is present between the cornea and lens.
- Vitreous humour is present between the lens and retina.
- Retina is the light-sensitive layer where the image is formed.
149. ‘Ornithology’ is the science of
(A) Birds
(B) Reptiles
(C) Amphibians
(D) Mammals
Answer & Explanation
Answer: (A) Birds
Explanation
Ornithology is the branch of zoology that deals with the study of birds. It includes their classification, behaviour, anatomy, ecology, and evolution.
Exam Facts
- Ornithology – Study of birds.
- Herpetology – Study of reptiles and amphibians.
- Ichthyology – Study of fishes.
- Entomology – Study of insects.
- Mammalogy – Study of mammals.
- Ophiology – Study of snakes.
153. Which one of the following animals is not ‘warm-blooded’?
(A) Hen
(B) Tiger
(C) Bat
(D) Toad
Answer & Explanation
Answer: (D) Toad
Explanation
Toad is an amphibian and is cold-blooded (ectothermic), meaning its body temperature varies with the surrounding environment. Birds and mammals, such as hen, tiger, and bat, are warm-blooded (endothermic) and maintain a nearly constant body temperature.
Exam Facts
- Birds and mammals are warm-blooded (endothermic) animals.
- Amphibians, reptiles, and fishes are cold-blooded (ectothermic).
- Toad belongs to Class Amphibia.
- Bat is the only true flying mammal.
- Hen belongs to Class Aves.
- Tiger belongs to Class Mammalia.
159. The first transgenic crop was
(A) Tobacco
(B) Cotton
(C) Pea
(D) Rice
Answer & Explanation
Answer: (A) Tobacco
Explanation
Tobacco was the first transgenic crop developed using genetic engineering. A foreign gene was introduced into the tobacco plant to demonstrate that desirable traits could be transferred into plants through recombinant DNA technology.
Exam Facts
- Tobacco was the first transgenic crop.
- The first commercial transgenic crop was the Flavr Savr tomato (1994).
- Bt cotton is the first GM crop commercially cultivated in India.
- Bt cotton contains the Cry gene from the bacterium Bacillus thuringiensis (Bt).
- Golden Rice is a genetically modified crop enriched with Vitamin A (β-carotene).
- Genetic engineering involves the transfer of desirable genes using recombinant DNA (rDNA) technology.
190. Fermentation ability of Yeast is due to
(A) Amylase
(B) Zymase
(C) Invertase
(D) Galactase
Answer & Explanation
Answer: (B) Zymase
Explanation
Zymase is an enzyme complex present in yeast that converts sugars into ethyl alcohol and carbon dioxide during fermentation. This process is widely used in the baking and brewing industries.
Exam Facts
- Zymase is the enzyme complex responsible for alcoholic fermentation in yeast.
- Yeast is a unicellular fungus (Saccharomyces cerevisiae).
- Fermentation produces ethyl alcohol and carbon dioxide (CO₂).
- CO₂ released during fermentation helps bread dough rise.
- Invertase converts sucrose into glucose and fructose.
- Yeast reproduces mainly by budding.
WBCS Prelims Biology Questions 2020
122. Plants receive nutrients from
(A) Atmosphere
(B) Chlorophyll
(C) Soil
(D) Light
Answer & Explanation
Answer: (C) Soil
Explanation
Plants absorb mineral nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium from the soil through their roots. While carbon dioxide comes from the atmosphere and light provides energy for photosynthesis, mineral nutrients are obtained mainly from the soil.
Exam Facts
- Plants absorb water and minerals from the soil through their roots.
- Root hairs increase the surface area for absorption.
- Nitrogen (N), Phosphorus (P), and Potassium (K) are the primary macronutrients (NPK).
- Chlorophyll helps in photosynthesis; it is not a source of nutrients.
- Sunlight provides energy for photosynthesis but is not a nutrient.
- Carbon dioxide is taken from the atmosphere for photosynthesis, while mineral nutrients come from the soil.
155. Which can bind O₂ molecules?
(A) Red blood cells
(B) White blood cells
(C) Vitamin B₁₂
(D) Vitamin E
Answer & Explanation
Answer: (A) Red blood cells
Explanation
Red blood cells (RBCs) contain haemoglobin, which binds with oxygen in the lungs and transports it to different tissues of the body. White blood cells are involved in immunity, while Vitamins B₁₂ and E do not transport oxygen.
Exam Facts
- Haemoglobin in RBCs binds and transports oxygen.
- Red blood cells (RBCs) are also called erythrocytes.
- White blood cells (WBCs) provide defence against infections.
- Vitamin B₁₂ is essential for RBC formation and nervous system function.
- Vitamin E acts as an antioxidant.
- RBCs are produced in the red bone marrow and have an average lifespan of about 120 days.
189. Excess fluoride in drinking water causes
(A) Lung disease
(B) Intestinal infection
(C) Fluorosis
(D) Rickets
Answer & Explanation
Answer: (C) Fluorosis
Explanation
Excess intake of fluoride through drinking water causes fluorosis, which affects the teeth and bones. Long-term exposure can lead to dental fluorosis (discoloured teeth) and skeletal fluorosis (joint pain and bone deformities).
Exam Facts
- Excess fluoride in drinking water causes fluorosis.
- Dental fluorosis causes mottling and discoloration of teeth.
- Skeletal fluorosis affects bones and joints.
- Rickets is caused by Vitamin D deficiency, not fluoride.
- Deficiency of fluoride may increase the risk of dental caries (tooth decay).
- Fluorosis is a common public health problem in some parts of Rajasthan, Andhra Pradesh, Telangana, Gujarat, and Karnataka.
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