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2024 JAMB Biology past questions and answers
1. Question: The cilia in paramecium function for (A) locomotion (B) respiration (C) excretion (D) defence
Topic: Protist Biology / Cellular Structures and Functions
Correct Answer: (A) locomotion
Explanation: Cilia are short, hair-like projections covering the surface of Paramecium. They beat in a coordinated rhythm, propelling the organism through its aquatic environment. This movement is their primary function, along with creating water currents to bring food particles towards the oral groove.
Why other options are incorrect:
- (B) Respiration: Gas exchange (uptake of O2, release of CO2) occurs by diffusion across the entire cell membrane (pellicle). Cilia are not primarily involved.
- (C) Excretion: Removal of metabolic wastes (like ammonia) primarily occurs by diffusion across the cell membrane. Osmoregulation (water balance) is handled by contractile vacuoles.
- (D) Defence: Paramecium uses specialized structures called trichocysts for defence and anchorage, which are located beneath the pellicle and can be discharged. Cilia are not the primary defence mechanism.
2. Question: The Euglena may be classified as a plant due to its possession of (A) gullet (B) flagellum (C) chloroplast (D) pellicle
Topic: Protist Biology / Classification / Photosynthesis
Correct Answer: (C) chloroplast
Explanation: Chloroplasts are organelles containing chlorophyll, the pigment necessary for photosynthesis. The presence of chloroplasts allows Euglena to produce its own food using sunlight, a characteristic feature of plants (autotrophs). While Euglena also has animal-like features, the chloroplast is the key reason for its plant-like classification in older systems or its recognition as mixotrophic.
Why other options are incorrect:
- (A) Gullet: This structure is involved in ingesting food when light is unavailable, which is an animal-like characteristic (heterotrophy).
- (B) Flagellum: This whip-like structure is used for locomotion (movement), a feature found in many motile organisms, including some animal cells and other protists, not exclusive to plants.
- (D) Pellicle: This is a flexible proteinaceous layer beneath the cell membrane providing shape and protection, not a feature defining it as plant-like.
3. Question: Which of the following is the terminal portion of the alimentary canal of a mammal? (A) oesophagus (B) stomach (C) Rectum (D) colon
Topic: Digestive System (Mammals) / Anatomy
Correct Answer: (C) Rectum
Explanation: The alimentary canal (digestive tract) is the pathway food takes. The rectum is the final, terminal section of the large intestine, ending at the anus. It serves primarily to store faeces before defecation.
Why other options are incorrect:
- (A) Oesophagus: Connects the pharynx (throat) to the stomach. It’s near the beginning of the tract.
- (B) Stomach: A J-shaped organ between the oesophagus and small intestine where significant digestion begins.
- (D) Colon: The main part of the large intestine, located before the rectum, primarily responsible for water absorption and forming faeces.
4. Question: An organism that dwells on the remains of a dead plant is a/an (A) parasite (B) saprophyte (C) enigma (D) commensal
Topic: Ecology / Modes of Nutrition
Correct Answer: (B) saprophyte
Explanation: Saprophytes (or decomposers) are organisms, primarily fungi and bacteria, that obtain nutrients by breaking down dead organic matter (like dead plants or animals). They play a crucial role in nutrient cycling.
Why other options are incorrect:
- (A) Parasite: An organism that lives on or in another living organism (the host) and derives nutrients at the host’s expense.
- (C) Enigma: This means a puzzle or mystery; it’s not a biological term for a mode of nutrition.
- (D) Commensal: An organism that benefits from another organism (the host) without harming or benefiting the host.
5. Question: A Secchi disc is used in the determination of (A) rainfall (B) tides (C) waves (D) turbidity
Topic: Ecology / Aquatic Environments / Ecological Methods
Correct Answer: (D) turbidity
Explanation: A Secchi disc is a plain white or black-and-white circular disk lowered into water to measure its clarity or transparency. The depth at which the disk is no longer visible is the Secchi depth, which is an indicator of water turbidity (cloudiness caused by suspended particles).
Why other options are incorrect:
- (A) Rainfall: Measured using a rain gauge.
- (B) Tides: Measured using tide gauges or predicted based on astronomical data.
- (C) Waves: Wave height and frequency are measured using buoys or other oceanographic instruments.
6. Question: The blood vessel which carries digested food from the small intestine to the liver is the (A) renal artery (B) hepatic portal vein (C) hepatic artery (D) renal vein
Topic: Circulatory System / Digestive System Link
Correct Answer: (B) hepatic portal vein
Explanation: The hepatic portal system is a unique part of the circulatory system. The hepatic portal vein collects nutrient-rich, deoxygenated blood from the digestive organs (stomach, small intestine, large intestine, pancreas, spleen) and transports it directly to the liver for processing before it enters the general circulation.
Why other options are incorrect:
- (A) Renal artery: Carries oxygenated blood from the aorta to the kidneys.
- (C) Hepatic artery: Carries oxygenated blood from the aorta to the liver, supplying its metabolic needs.
- (D) Renal vein: Carries deoxygenated, filtered blood from the kidneys back to the inferior vena cava.
7. Question: Nitrogen is utilized in (A) formation of ATP (B) formation of glucose (C) photosynthesis (D) formation of amino acids
Topic: Biochemistry / Macromolecules / Nutrient Cycling
Correct Answer: (D) formation of amino acids
Explanation: Amino acids are the building blocks of proteins. Every amino acid contains a central carbon atom, a hydrogen atom, a carboxyl group (-COOH), and an amino group (-NH2). The amino group contains nitrogen, making nitrogen an essential element for synthesizing amino acids and, consequently, proteins.
Why other options are incorrect:
- (A) Formation of ATP: ATP (Adenosine Triphosphate) contains nitrogen in its adenine base, but nitrogen’s primary role in metabolism isn’t defined by ATP formation. Nitrogen is more fundamentally required for the building blocks of proteins and nucleic acids.
- (B) Formation of glucose: Glucose (C6H12O6) is a carbohydrate and contains only carbon, hydrogen, and oxygen. Nitrogen is not utilized.
- (C) Photosynthesis: This process uses carbon dioxide, water, and light energy to produce glucose. Nitrogen is not directly utilized in the core reactions of photosynthesis, although plants need nitrogen from the soil to build the machinery (like chlorophyll and enzymes) for photosynthesis.
8. Question: Which of the following organs produces bile? (A) Gall bladder (B) pancreas (C) spleen (D) liver
Topic: Digestive System / Accessory Organs
Correct Answer: (D) liver
Explanation: The liver continuously produces bile, a fluid that aids in the digestion and absorption of fats in the small intestine by emulsifying them (breaking large fat globules into smaller ones).
Why other options are incorrect:
- (A) Gall bladder: This small organ stores and concentrates bile produced by the liver, releasing it into the small intestine when needed. It does not produce bile.
- (B) Pancreas: Produces digestive enzymes (like amylase, lipase, proteases) and hormones (like insulin and glucagon), but not bile.
- (C) Spleen: Part of the lymphatic and immune systems, involved in filtering blood and housing immune cells. It has no role in producing bile.
9. Question: Which part of the brain is concerned with reflexes controlling the rate of heartbeat and breathing? (A) medulla (B) cerebrum (C) cerebellum (D) pineal body
Topic: Nervous System / Brain Function
Correct Answer: (A) medulla
Explanation: The medulla oblongata, located in the brainstem, contains vital autonomic centers that regulate involuntary functions crucial for life, including the cardiovascular center (controlling heart rate and blood pressure) and the respiratory center (controlling the rate and depth of breathing).
Why other options are incorrect:
- (B) Cerebrum: The largest part of the brain, responsible for higher-level functions like thought, memory, voluntary movement, and sensory processing.
- (C) Cerebellum: Located at the back of the brain, primarily responsible for coordinating voluntary movements, posture, balance, and motor learning.
- (D) Pineal body (gland): Produces the hormone melatonin, which regulates sleep-wake cycles (circadian rhythms).
10. Question: Which of a following is cold-blooded? (A) cat (B) lizard (C) whale (D) bird
Topic: Animal Physiology / Thermoregulation
Correct Answer: (B) lizard
Explanation: “Cold-blooded” is a common term for poikilothermic or ectothermic animals. These animals cannot regulate their internal body temperature metabolically and rely on external environmental sources (like the sun) to maintain their body temperature. Lizards are reptiles, which are classic examples of ectotherms.
Why other options are incorrect:
- (A) Cat: A mammal, which is warm-blooded (homeothermic/endothermic), maintaining a constant internal body temperature through metabolic processes.
- (C) Whale: A marine mammal, also warm-blooded.
- (D) Bird: Birds are warm-blooded (homeothermic/endothermic).
11. Question: A character shown by an organism is due to the effects of (A) hormones only (B) genes only (C) genes and environment (D) environment only
Topic: Genetics / Basic Principles / Nature vs. Nurture
Correct Answer: (C) genes and environment
Explanation: An organism’s observable characteristics (phenotype) are the result of a complex interaction between its genetic makeup (genotype) and the environmental factors it is exposed to. Genes provide the blueprint or potential, while the environment influences how these genes are expressed. For example, a person might have genes for tallness, but poor nutrition (environment) could limit their actual height.
Why other options are incorrect:
- (A) Hormones only: Hormones influence many characters, but they are themselves often regulated by genes and environmental cues. They are mediators, not the sole cause.
- (B) Genes only: While genes are fundamental, the environment significantly modifies the expression of many genetic traits.
- (D) Environment only: The environment shapes expression, but the underlying potential and basic blueprint are determined by genes.
12. Question: A tapeworm has no alimentary canal because (A) it is autotrophic (B) it does not feed (C) it absorbs digested food (D) it has no enzymes
Topic: Animal Physiology / Parasitology / Adaptations
Correct Answer: (C) it absorbs digested food
Explanation: Tapeworms are endoparasites living in the intestines of their hosts. The host has already digested the food, breaking it down into simple, absorbable molecules. The tapeworm is highly adapted to this environment and simply absorbs these readily available nutrients directly through its body surface (tegument). Therefore, it has lost the need for its own digestive system (alimentary canal).
Why other options are incorrect:
- (A) It is autotrophic: Autotrophs (like plants) make their own food. Tapeworms are heterotrophs, obtaining food from others.
- (B) It does not feed: It feeds parasitically on the host’s digested food.
- (D) It has no enzymes: While it lacks digestive enzymes because it doesn’t need to break down complex food, the reason it has no alimentary canal is its mode of nutrient acquisition (absorption of pre-digested food). Option C is the primary reason.
13. Question: External ears of mammals consist of (A) pinna and tympanum (B) pinna only (C) pinna and auditory meatus (D) meatus only
Topic: Sense Organs / Anatomy of the Ear
Correct Answer: (C) pinna and auditory meatus
Explanation: The external ear in mammals typically comprises two main parts: the pinna (or auricle), which is the visible outer flap of cartilage and skin that collects sound waves, and the external auditory meatus (or ear canal), which is the tube that channels the sound waves from the pinna to the eardrum.
Why other options are incorrect:
- (A) Pinna and tympanum: The tympanum (eardrum) is part of the middle ear, marking the boundary between the external and middle ear.
- (B) Pinna only: This is incomplete; the ear canal is also part of the external ear structure.
- (D) Meatus only: This is also incomplete; the visible pinna is a key part of the external ear.
14. Question: Jointed skeleton is absent in (A) spider (B) snail (C) spider (D) millipede (Note: Options A and C are identical)
Topic: Animal Kingdom / Skeletal Systems
Correct Answer: (B) snail
Explanation: Spiders and millipedes are arthropods, characterized by a hard exoskeleton made of chitin and jointed appendages (legs), allowing for movement. Snails are molluscs; they typically have a hard, unjointed shell for protection (an exoskeleton, but not jointed in the arthropod sense) and move using a muscular foot, lacking an internal or jointed skeleton.
Why other options are incorrect:
- (A) Spider: An arachnid (arthropod) with a jointed exoskeleton and jointed legs.
- (C) Spider: Same as (A).
- (D) Millipede: A myriapod (arthropod) with a segmented body, a jointed exoskeleton, and many pairs of jointed legs.
15. Question: What is the genotype of a child from a man with normal haemoglobin (AA) and a woman who has sickle-cell haemoglobin (SS)? (A) AA (B) SS (C) AS (D) O
Topic: Genetics / Inheritance Patterns / Human Genetics
Correct Answer: (C) AS
Explanation: This is a monohybrid cross. The man (AA) can only produce gametes carrying the ‘A’ allele. The woman (SS) can only produce gametes carrying the ‘S’ allele. When these gametes combine during fertilization, all offspring will inherit one ‘A’ allele from the father and one ‘S’ allele from the mother, resulting in the genotype AS (sickle-cell trait).
Why other options are incorrect:
- (A) AA: Would require the mother to contribute an ‘A’ allele, which she cannot.
- (B) SS: Would require the father to contribute an ‘S’ allele, which he cannot.
- (D) O: This refers to the ABO blood group system, which is a different genetic trait and irrelevant to haemoglobin genotype inheritance.
16. Question: Fehling’s solution will readily change colour from blue to a reddish colour when it is (A) mixed with sugar solution in the cold (B) warmed by itself (C) mixed with a reducing sugar in the cold (D) warmed with a solution of reducing sugar
Topic: Biochemistry / Testing for Biomolecules
Correct Answer: (D) warmed with a solution of reducing sugar
Explanation: Fehling’s test is used to detect the presence of reducing sugars (like glucose, fructose, maltose, lactose). The test requires heat. In the presence of a reducing sugar and upon heating, the blue copper(II) ions (Cu2+) in Fehling’s solution are reduced to red/orange/brown copper(I) oxide (Cu2O), which precipitates out, causing the colour change.
Why other options are incorrect:
- (A) Mixed with sugar solution in the cold: Needs heat, and only works for reducing sugars (sucrose, a common sugar, is non-reducing).
- (B) Warmed by itself: No reaction occurs without a reducing agent (the sugar).
- (C) Mixed with a reducing sugar in the cold: The reaction requires heat to proceed at a noticeable rate.
17. Question: The axial skeleton of a mammal does not include the bones of the (A) skull (B) tail (C) limbs (D) back
Topic: Skeletal System / Divisions of the Skeleton
Correct Answer: (C) limbs
Explanation: The mammalian skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton forms the central axis of the body and includes the skull, vertebral column (including the tail/coccyx), ribs, and sternum. The appendicular skeleton consists of the bones of the limbs (arms and legs) and the girdles (pectoral/shoulder and pelvic/hip) that attach the limbs to the axial skeleton.
Why other options are incorrect:
- (A) Skull: Part of the axial skeleton.
- (B) Tail (coccyx): The terminal part of the vertebral column, part of the axial skeleton.
- (D) Back: Refers to the vertebral column, a core component of the axial skeleton.
18. Question: Which of the following elements is essential for the formation of haemoglobin? (A) sodium (B) Iron (C) calcium (D) potassium
Topic: Biochemistry / Blood Components / Minerals
Correct Answer: (B) Iron
Explanation: Haemoglobin is the protein in red blood cells responsible for transporting oxygen. Each haemoglobin molecule contains four heme groups, and at the center of each heme group is an atom of iron (Fe). This iron atom is what actually binds reversibly to oxygen.
Why other options are incorrect:
- (A) Sodium: Essential electrolyte, important for nerve impulse transmission and fluid balance.
- (C) Calcium: Essential for bone formation, muscle contraction, nerve function, and blood clotting.
- (D) Potassium: Essential electrolyte, important for nerve impulse transmission and muscle function.
19. Question: Which of the following is an example of discontinuous variation? (A) skin (B) colouration (C) left-handedness (D) height (D) weight (Note: Two options labelled D)
Topic: Genetics / Variation
Correct Answer: (C) left-handedness
Explanation: Variation refers to differences among individuals. Discontinuous variation (or qualitative variation) involves traits that fall into distinct, separate categories, with no intermediate forms. Handedness (left, right, or sometimes ambidextrous) is a classic example – individuals are typically categorized as one or the other. Blood groups (A, B, AB, O) are another example.
Why other options are incorrect:
- (A) Skin: Skin characteristics like colour show continuous variation.
- (B) Colouration: Assuming this refers to skin, hair, or eye colour, these traits typically show a wide range of intermediate shades (continuous variation), influenced by multiple genes.
- (D) Height: Shows continuous variation; individuals can be of many intermediate heights within a population range.
- (D) Weight: Also shows continuous variation, influenced by genetics and environment, with many possible intermediate values.
20. Question: Most cells in higher animals retain their power of division except (A) germ cells (B) nerve cells (C) erythrocytes (D) leucocytes
Topic: Cell Biology / Cell Cycle / Cell Differentiation
Correct Answer: (B) nerve cells
Explanation: Many cells in higher animals become highly specialized (differentiated) for specific functions. Highly differentiated cells, like mature neurons (nerve cells) and muscle cells, typically lose the ability to divide (enter a state called G0 phase). This makes recovery from nerve damage difficult.
Why other options are incorrect:
- (A) Germ cells: These are the cells (spermatogonia and oogonia) that divide by mitosis and meiosis to produce gametes (sperm and eggs). They actively divide.
- (C) Erythrocytes (Red Blood Cells): Mature mammalian erythrocytes lack a nucleus and organelles, so they cannot divide. However, they are continuously produced from dividing stem cells in the bone marrow. The question asks which cells lose the power, implying they once had it or their lineage does – nerve cells fit best as a differentiated cell type that stops dividing.
- (D) Leucocytes (White Blood Cells): Many types of leucocytes, especially lymphocytes, can divide rapidly when stimulated as part of an immune response.
21. Question: A severe deficiency of thyroxine results in (A) diabetes mellitus (B) sexual underdevelopment (C) cretinism (D) gigantism
Topic: Endocrine System / Hormonal Disorders
Correct Answer: (C) cretinism
Explanation: Thyroxine is a hormone produced by the thyroid gland, essential for regulating metabolism and normal growth and development, especially of the brain. Severe deficiency of thyroxine during infancy and early childhood (congenital hypothyroidism) leads to cretinism, characterized by stunted physical growth and severe mental retardation.
Why other options are incorrect:
- (A) Diabetes mellitus: A disorder of glucose metabolism, typically related to insulin deficiency or resistance.
- (B) Sexual underdevelopment: Usually related to deficiencies in sex hormones (like testosterone or estrogen) produced by the gonads.
- (D) Gigantism: Caused by excessive production of growth hormone (GH) by the pituitary gland during childhood, leading to abnormally tall stature.
22. Question: The division thallophyta comprises (A) ferns and mosses (B) algae and fungi (C) mosses and liverworts (D) fungi and ferns
Topic: Plant Kingdom / Classification (Older Systems)
Correct Answer: (B) algae and fungi
Explanation: Thallophyta is an older, largely obsolete taxonomic division. It grouped together organisms with a simple body structure called a thallus, which lacks differentiation into true roots, stems, and leaves. This group traditionally included algae (mostly aquatic, photosynthetic), fungi (heterotrophic, absorptive), lichens (symbiosis of algae and fungi), and sometimes bacteria.
Why other options are incorrect:
- (A) Ferns and mosses: Ferns belong to Pteridophyta (vascular plants), and Mosses belong to Bryophyta (non-vascular plants).
- (C) Mosses and liverworts: Both belong to Bryophyta.
- (D) Fungi and ferns: Fungi were in Thallophyta, but Ferns are Pteridophytes.
23. Question: For an animal to have diastema, it must lack (A) incisors (B) molars (C) canines (D) premolars
Topic: Animal Anatomy / Dentition
Correct Answer: (C) canines
Explanation: A diastema is a space or gap between teeth, most commonly observed in mammals between the incisors and the premolars. This gap is typically present in herbivores (like rodents, rabbits, horses, cattle) where the canine teeth are absent or greatly reduced, reflecting their diet which doesn’t require tearing flesh.
Why other options are incorrect:
- (A) Incisors: Herbivores with diastema usually have prominent incisors for cutting vegetation.
- (B) Molars: Essential for grinding plant matter; present in animals with diastema.
- (D) Premolars: Usually present along with molars for grinding; located behind the diastema.
24. Question: Parenchyma cells serve as supporting tissue when they (A) contain crystals (B) become turgid (C) become flaccid (D) lose chloroplasts
Topic: Plant Anatomy & Physiology / Plant Tissues / Turgor Pressure
Correct Answer: (B) become turgid
Explanation: Parenchyma cells are relatively thin-walled living cells. When they absorb water by osmosis, the internal water pressure (turgor pressure) pushes the cell membrane against the cell wall, making the cell firm or turgid. This turgidity in many parenchyma cells collectively provides hydrostatic support (turgor support) to non-woody plant parts, like leaves and young stems, helping them maintain their shape and rigidity.
Why other options are incorrect:
- (A) Contain crystals: Crystals (like calcium oxalate) within parenchyma are usually for storage or defense, not primary support.
- (C) Become flaccid: When cells lose water, they become flaccid (limp), leading to wilting, the opposite of providing support.
- (D) Lose chloroplasts: Loss of chloroplasts affects photosynthesis, not the cell’s ability to provide turgor support.
25. Question: The mineral nutrient that easily gets leached out of the soil is (A) phosphorus (B) nitrate (C) calcium (D) magnesium
Topic: Ecology / Soil Science / Nutrient Cycling
Correct Answer: (B) nitrate
Explanation: Leaching is the process where water moving through the soil dissolves and carries away soluble nutrients. Nitrate (NO3-) is a negatively charged ion and is highly soluble in water. Soil particles (clay and humus) are typically negatively charged, so they repel nitrates, preventing them from binding tightly. This makes nitrates very susceptible to being washed (leached) out of the soil by rainfall or irrigation, potentially leading to nutrient loss and water pollution (eutrophication).
Why other options are incorrect:
- (A) Phosphorus: Often present as phosphate (PO4^3-), which binds relatively tightly to soil particles (especially in acidic or alkaline soils) and is less mobile/leachable.
- (C) Calcium (Ca2+): A positively charged ion (cation) that binds to negatively charged soil particles, making it less prone to leaching than nitrate.
- (D) Magnesium (Mg2+): Also a cation that binds to soil particles, reducing its leachability compared to nitrate.
26. Question: Hydra removes undigested food by (A) passing it through the mouth (B) passing it through the anus (C) passing it through the body surface (D) passing it through its contractile vacuole
Topic: Animal Physiology / Digestive Systems (Invertebrates)
Correct Answer: (A) passing it through the mouth
Explanation: Hydra has a simple, sac-like digestive system called a gastrovascular cavity, which has only one opening that serves as both the mouth (for ingestion) and the anus (for egestion of undigested waste). Food enters through this opening, is digested within the cavity, and undigestible materials are expelled back out through the same opening.
Why other options are incorrect:
- (B) Passing it through the anus: Hydra does not have a separate anus.
- (C) Passing it through the body surface: Diffusion across the body surface is mainly for gas exchange and excretion of soluble metabolic wastes, not undigested solids.
- (D) Passing it through its contractile vacuole: Contractile vacuoles are primarily involved in osmoregulation (expelling excess water), not removing undigested food.
27. Question: A feature which adapts birds to flight is the possession of (A) scales (B) legs (C) light bones (D) pointed beaks
Topic: Animal Anatomy & Physiology / Adaptations for Flight
Correct Answer: (C) light bones
Explanation: Flight requires minimizing weight. Birds have evolved several adaptations for this, including lightweight bones. Their bones are often pneumatic (hollow and reinforced with internal struts or trusses), reducing skeletal weight significantly without sacrificing strength. Other adaptations include feathers, powerful flight muscles attached to a keeled sternum, and an efficient respiratory system.
Why other options are incorrect:
- (A) Scales: Birds have scales on their legs, a remnant of their reptilian ancestry, but scales do not aid flight. Feathers are the key epidermal structures for flight.
- (B) Legs: Adapted for perching, walking, or swimming, depending on the bird, but not directly for flight itself (though used for takeoff/landing).
- (D) Pointed beaks: Beaks are adapted for various feeding strategies, not directly for the mechanics of flight.
28. Question: The gill rakers of fishes take part in (A) feeding (B) cellular respiration (C) swimming (D) diffusion
Topic: Animal Anatomy & Physiology / Respiration & Feeding (Fish)
Correct Answer: (A) feeding
Explanation: Gill rakers are bony or cartilaginous projections located along the inner edge of the gill arches in fish. They function primarily as a sieve, straining food particles (like plankton or small invertebrates) from the water that passes over the gills. In filter-feeding fish, they are often long and numerous, while in predatory fish, they may be short and stubby or reduced.
Why other options are incorrect:
- (B) Cellular respiration: This occurs within the mitochondria of cells throughout the body. Gas exchange (external respiration) occurs across the gill filaments, not the rakers.
- (C) Swimming: Primarily achieved using fins and body musculature.
- (D) Diffusion: Gas exchange (O2 and CO2) between water and blood occurs by diffusion across the thin surfaces of the gill filaments (lamellae), not the gill rakers.
29. Question: Epigeal germination can be found in (A) sorghum (B) maize (C) millet (D) groundnut
Topic: Plant Physiology / Germination
Correct Answer: (D) groundnut
Explanation: Germination is the process by which a seed sprouts. In epigeal germination, the hypocotyl (the part of the embryonic axis below the cotyledons) elongates, pulling the cotyledons (seed leaves) and the epicotyl (embryonic shoot) up above the soil surface. Examples include beans, castor oil, sunflower, and groundnut (peanut). In hypogeal germination, the cotyledons remain below ground, and only the epicotyl emerges.
Why other options are incorrect:
- (A) Sorghum: A grass, typically exhibits hypogeal germination.
- (B) Maize (Corn): A grass, exhibits hypogeal germination.
- (C) Millet: A grass, typically exhibits hypogeal germination.
30. Question: The greatest contribution to genetic studies was made by (A) Robert Hooke (B) Gregor Mendel (C) Charles Darwin (D) Thomas Morgan
Topic: History of Biology / Genetics
Correct Answer: (B) Gregor Mendel
Explanation: Gregor Mendel, through his meticulous experiments with pea plants in the mid-19th century, established the fundamental principles of heredity, including the concepts of dominant and recessive alleles, segregation, and independent assortment. His work laid the foundation for the entire field of genetics, earning him the title “Father of Genetics.”
Why other options are incorrect:
- (A) Robert Hooke: Coined the term “cell” after observing cork under a microscope; pioneer of microscopy.
- (C) Charles Darwin: Developed the theory of evolution by natural selection; made immense contributions to biology, but Mendel specifically founded genetics.
- (D) Thomas Hunt Morgan: Provided key evidence for the chromosome theory of inheritance through his work with fruit flies (Drosophila) in the early 20th century, building upon Mendel’s work.
31. Question: Neurons that receive stimuli from the body or internal organs are called (A) motor neurons (B) sensory neurons (C) efferent neurons (D) relay neurons
Topic: Nervous System / Neuron Types and Function
Correct Answer: (B) sensory neurons
Explanation: Sensory neurons (also called afferent neurons) are responsible for detecting stimuli (like touch, light, sound, temperature, internal changes) from sensory receptors located in the body (skin, eyes, ears, internal organs) and transmitting this information as nerve impulses towards the central nervous system (CNS – brain and spinal cord).
Why other options are incorrect:
- (A) Motor neurons: Transmit signals from the CNS to effector organs (muscles or glands), causing a response.
- (C) Efferent neurons: Another term for motor neurons (carrying signals away from the CNS).
- (D) Relay neurons (Interneurons): Found within the CNS, they connect sensory neurons to motor neurons or other interneurons, processing information.
32. Question: Which of the following stores carbohydrate as glycogen? (A) spirogyra (B) Mangifera (C) Rattus (D) Chlamydomonas
Topic: Biochemistry / Carbohydrate Storage
Correct Answer: (C) Rattus
Explanation: Glycogen is the primary storage form of glucose (a carbohydrate) in animals and fungi. It is a large, branched polysaccharide stored mainly in the liver and muscles. Rattus is the genus name for rats, which are animals (mammals) and therefore store carbohydrates as glycogen.
Why other options are incorrect:
- (A) Spirogyra: A type of filamentous green algae (plant-like protist). Plants and algae typically store carbohydrates primarily as starch.
- (B) Mangifera: The genus name for mango, which is a plant. Plants store carbohydrates as starch.
- (D) Chlamydomonas: A type of single-celled green algae. Stores carbohydrates as starch.
33. Question: The sex-linked defect in which very slight cut produces severe bleeding is known as (A) anaemia (B) anorexia (C) haemophilia (D) haemolysis
Topic: Genetics / Human Genetics / Sex-linked Traits / Blood Disorders
Correct Answer: (C) haemophilia
Explanation: Haemophilia is a genetic disorder, typically sex-linked (specifically X-linked recessive), that impairs the body’s ability to control blood clotting. Individuals with haemophilia lack sufficient levels of certain clotting factors, leading to prolonged bleeding even from minor injuries.
Why other options are incorrect:
- (A) Anaemia: A condition characterized by a deficiency of red blood cells or haemoglobin, resulting in reduced oxygen transport.
- (B) Anorexia: An eating disorder characterized by an abnormally low body weight, intense fear of gaining weight, and a distorted perception of weight.
- (D) Haemolysis: The rupture or destruction of red blood cells, which can lead to anaemia but is not the primary defect causing prolonged bleeding from cuts.
34. Question: A band of connective tissue linking two bones in a joint is known as (A) tendon (B) cartilage (C) synovial membrane (D) ligament
Topic: Skeletal System / Connective Tissues / Joints
Correct Answer: (D) ligament
Explanation: Ligaments are strong, fibrous bands of connective tissue that connect bones to other bones across a joint. They provide stability to the joint, limiting excessive or unwanted movement.
Why other options are incorrect:
- (A) Tendon: Strong, fibrous connective tissue that connects muscle to bone, transmitting the force of muscle contraction to move the skeleton.
- (B) Cartilage: A flexible connective tissue found covering the ends of bones in joints (articular cartilage), providing cushioning and reducing friction. Also forms structures like the nose and ears.
- (C) Synovial membrane: Lines the inner surface of the joint capsule in synovial joints, secreting synovial fluid for lubrication.
35. Question: The speed of the wind can be measured with an instrument called (A) anemometer (B) hydrometer (C) wind vane (D) barometer
Topic: Ecology / Meteorological Instruments
Correct Answer: (A) anemometer
Explanation: An anemometer is a device specifically designed to measure wind speed. Common types include cup anemometers (rotating cups) and hot-wire anemometers.
Why other options are incorrect:
- (B) Hydrometer: Measures the specific gravity (relative density) of liquids.
- (C) Wind vane: Measures wind direction, often shaped like an arrow that points into the wind.
- (D) Barometer: Measures atmospheric pressure.
36. Question: The organism that has a hydrostatic skeleton is (A) tilapia (B) Hydra (C) earthworm (D) Lizard
Topic: Animal Kingdom / Skeletal Systems
Correct Answer: (C) earthworm
Explanation: A hydrostatic skeleton consists of a fluid-filled cavity (coelom or gastrovascular cavity) surrounded by muscles. The pressure of the fluid provides support, and coordinated muscle contractions acting against this incompressible fluid allow for movement. Earthworms have a well-developed hydrostatic skeleton based on their segmented coelom, allowing them to burrow effectively. Hydra also has a hydrostatic skeleton, but the earthworm is a more complex and classic example provided in the options.
Why other options are incorrect:
- (A) Tilapia: A bony fish with an internal bony skeleton (endoskeleton).
- (B) Hydra: Has a simple hydrostatic skeleton based on its gastrovascular cavity, but the earthworm’s coelomic system is a more elaborate example often contrasted with endo/exoskeletons. Among the choices, the earthworm is the best fit for a prominent hydrostatic skeleton.
- (D) Lizard: A reptile with an internal bony skeleton (endoskeleton).
37. Question: Fertilization in humans usually takes place in the (A) lower part of the uterus (B) upper part of the uterus (C) lower part of the oviduct (D) upper part of the oviduct
Topic: Human Reproduction / Fertilization
Correct Answer: (D) upper part of the oviduct
Explanation: Fertilization, the fusion of sperm and egg to form a zygote, typically occurs in the ampulla, which is the widest, upper part of the oviduct (Fallopian tube), near the ovary. The egg is viable for about 12-24 hours after ovulation, and sperm must travel up through the uterus into the oviducts to meet it there.
Why other options are incorrect:
- (A) Lower part of the uterus: Implantation of the blastocyst occurs in the uterus, but fertilization does not.
- (B) Upper part of the uterus: Same as (A).
- (C) Lower part of the oviduct: Fertilization is possible here but less common than in the upper part (ampulla) where the egg is usually encountered first by sperm.
38. Question: In mammalian males, the excretory and reproductive systems share the (A) ureter (B) testes (C) vas deferens (D) urethra
Topic: Excretory & Reproductive Systems (Mammals) / Anatomy
Correct Answer: (D) urethra
Explanation: In males, the urethra serves a dual function (urogenital function). It is the tube that carries urine from the bladder out of the body (excretory function), and it also serves as the passageway for semen (containing sperm) during ejaculation (reproductive function).
Why other options are incorrect:
- (A) Ureter: Tube carrying urine from the kidney to the bladder; purely excretory function.
- (B) Testes: Produce sperm and male hormones (testosterone); purely reproductive function.
- (C) Vas deferens (Ductus deferens): Tube carrying sperm from the epididymis towards the urethra; purely reproductive function.
39. Question: The dominant phase in the life cycle of a bryophyte is the (A) gametangium (B) sporophyte (C) gametophyte (D) prothallus
Topic: Plant Kingdom / Life Cycles / Bryophytes
Correct Answer: (C) gametophyte
Explanation: Bryophytes (mosses, liverworts, hornworts) exhibit an alternation of generations where the haploid gametophyte generation is the dominant, conspicuous, and independent phase. The familiar green moss plant, for example, is the gametophyte. The diploid sporophyte generation is typically smaller, dependent on the gametophyte for nutrition, and relatively short-lived.
Why other options are incorrect:
- (A) Gametangium: A structure on the gametophyte that produces gametes (archegonium for eggs, antheridium for sperm); not a life cycle phase itself.
- (B) Sporophyte: The diploid generation that produces spores; it is not dominant in bryophytes.
- (D) Prothallus: The term for the typically small, independent gametophyte generation in ferns and other pteridophytes, not bryophytes.
40. Question: In the mammalian kidney, the Bowman’s capsule is located in the (A) ureter (B) pelvis (C) cortex (D) medulla
Topic: Excretory System / Kidney Anatomy / Nephron Structure
Correct Answer: (C) cortex
Explanation: The kidney is divided into an outer region called the cortex and an inner region called the medulla. The nephron is the functional unit of the kidney. The Bowman’s capsule (or glomerular capsule), which surrounds the glomerulus and is the site of initial blood filtration, along with the proximal convoluted tubule and distal convoluted tubule, are located primarily within the renal cortex.
Why other options are incorrect:
- (A) Ureter: The tube that carries urine from the kidney to the bladder; outside the main kidney structure where filtration occurs.
- (B) Pelvis: The renal pelvis is the funnel-shaped cavity within the kidney that collects urine from the collecting ducts before it flows into the ureter.
- (D) Medulla: The inner part of the kidney, containing primarily the Loops of Henle and the collecting ducts.
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