Biology JAMB Questions and Answers 2027

Correct Answer: C. 1 Pink : 1 White

Explanation/Tip: Incomplete dominance means heterozygotes (Rr) show an intermediate phenotype (pink). Crossing Rr (pink) with rr (white) yields 50% Rr (pink) and 50% rr (white), giving a 1:1 phenotypic ratio.

Correct Answer: B. Smooth Endoplasmic Reticulum

Explanation/Tip: The Smooth Endoplasmic Reticulum (SER) is specialized for lipid synthesis, carbohydrate metabolism, and detoxification. Cells active in lipid processing contain abundant SER.

Correct Answer: C. 2.8 g

Explanation/Tip: Total water uptake by a plant equals water lost through transpiration plus water retained for metabolic processes (Uptake = 2.4 g + 0.4 g = 2.8 g).

Correct Answer: B. Photolysis of water

Explanation/Tip: Water molecules are split by light energy into hydrogen ions, electrons, and oxygen gas. The electrons released replace those lost by reaction-center chlorophyll molecules.

Correct Answer: B. Proximal Convoluted Tubule and Glomerulus

Explanation/Tip: High protein (albumin) indicates ultrafiltration damage at the glomerulus. Glucose in urine suggests selective reabsorption failure in the proximal convoluted tubule.

Correct Answer: C. Pyramid of Energy

Explanation/Tip: Due to energy loss at each trophic level (where only about 10% is transferred upward), energy pyramids are always upright and can never be inverted.

Correct Answer: B. 25%

Explanation/Tip: Heterozygous group A carries alleles Ai and heterozygous group B carries alleles Bi. Crossing them gives genotypes AB, A, B, and ii (O). Thus, 1 out of 4 offspring (25%) will have blood group O.

Correct Answer: B. Migration of auxin to the shaded side, causing faster cell elongation

Explanation/Tip: Auxins accumulate on the shaded side of shoots, stimulating greater cell elongation there and causing the stem to bend toward the light source.

Correct Answer: B. High temperature, low humidity, windy conditions

Explanation/Tip: Low humidity increases the water vapor concentration gradient; high temperature increases kinetic energy; wind sweeps away saturated boundary layer air surrounding leaves.

Correct Answer: B. Predation and Parasitism

Explanation/Tip: Biological pest control introduces natural predators (such as ladybugs eating aphids) or parasites (such as parasitic wasps) to suppress pest populations.

Correct Answer: A. 2 ATP

Explanation/Tip: Glycolysis produces 4 ATP molecules but consumes 2 ATP in its initial activation steps, leaving a net yield of 2 ATP per glucose molecule.

Correct Answer: A. Artery

Explanation/Tip: Arteries carry blood under high pressure away from the heart and possess thick elastic muscular walls without valves along their length.

Correct Answer: B. Keratinized scaly skin

Explanation/Tip: Dry, keratinized epidermal scales prevent water loss through evaporation, adapting reptiles to terrestrial habitats.

Correct Answer: A. 22%

Explanation/Tip: According to Chargaff’s rule, % Cytosine = % Guanine = 28%. Therefore, C + G = 56%. The remaining bases (A + T) equal 100% – 56% = 44%. Since % Adenine = % Thymine, Thymine = 44% / 2 = 22%.

Correct Answer: B. Liver

Explanation/Tip: The liver breaks down excess amino acids into ammonia and urea through the process of deamination.

Correct Answer: B. Formation of a cell plate

Explanation/Tip: Due to rigid cellulose cell walls, plant cells divide by constructing a cell plate outward from Golgi vesicles, whereas animal cells form a cleavage furrow.

Correct Answer: B. Commensalism

Explanation/Tip: Commensalism is a symbiotic relationship where one organism benefits while the other is neither harmed nor helped.

Correct Answer: C. Uric acid

Explanation/Tip: Uric acid is non-toxic and insoluble in water, allowing birds, insects, and reptiles to excrete it as a semi-solid paste, conserving maximum water.

Correct Answer: B. RuBisCO

Explanation/Tip: Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) catalyzes the initial CO2 fixation step in the Calvin cycle of C3 plants.

Correct Answer: C. Abscisic acid

Explanation/Tip: Abscisic acid (ABA) functions as a stress hormone, inducing stomatal closure to minimize water loss during drought and maintaining seed dormancy.

Correct Answer: B. Pulmonary vein into the left atrium

Explanation/Tip: Pulmonary veins are unique because they carry oxygenated blood from the lungs back to the left atrium of the heart.

Correct Answer: B. Small, isolated populations

Explanation/Tip: Genetic drift involves random fluctuations in allele frequencies, which have a significantly greater impact in small populations where chance events easily alter allele percentages.

Correct Answer: B. Anaphase I

Explanation/Tip: Homologous chromosome pairs separate during Anaphase I, whereas individual sister chromatids separate during Anaphase II.

Correct Answer: C. Denitrifying bacteria (e.g., Pseudomonas)

Explanation/Tip: Denitrifying bacteria thrive in anaerobic (waterlogged) soil conditions, converting nitrates back into gaseous atmospheric nitrogen.

Correct Answer: C. Bile salts from the liver

Explanation/Tip: Bile salts break large fat droplets into smaller droplets (emulsification) to increase the surface area available for lipase action.

Correct Answer: B. Convex lens

Explanation/Tip: In hypermetropia, light rays focus behind the retina. A converging (convex) lens converges light rays so they focus properly on the retina.

Correct Answer: B. Canine

Explanation/Tip: Canines are long, pointed teeth positioned beside incisors, designed for piercing and tearing flesh in carnivores.

Correct Answer: B. Tropical Rain Forest

Explanation/Tip: Tropical rain forests feature continuous broadleaf multi-layered canopies, high rainfall, and rich epiphytic vegetation.

Correct Answer: B. To prevent the trachea from collapsing under negative pressure during breathing

Explanation/Tip: C-shaped cartilaginous rings hold the airway open continuously against suction forces created during inhalation.

Correct Answer: B. Haemophilia

Explanation/Tip: Haemophilia and red-green color blindness are sex-linked (X-linked) recessive disorders. Sickle-cell anaemia and albinism are autosomal recessive traits.

Correct Answer: C. 6 moles

Explanation/Tip: Photosynthesis equation: 6 CO2 + 6 H2O -> C6H12O6 + 6 O2. The balanced reaction shows a 1:1 molar ratio between consumed carbon dioxide and produced oxygen gas.

Correct Answer: C. Arthropoda

Explanation/Tip: Arthropods (insects, crustaceans, arachnids, myriapods) are defined by chitinous exoskeletons and jointed appendages.

Correct Answer: C. Luteinizing Hormone (LH)

Explanation/Tip: A rapid surge in Luteinizing Hormone (LH) around day 14 of the menstrual cycle induces rupture of the Graafian follicle and release of the mature ovum.

Correct Answer: B. Phloem sieve tube

Explanation/Tip: Translocation of manufactured food materials takes place via phloem sieve tubes, whereas xylem transports water and dissolved mineral salts.

Correct Answer: B. Crossing over in Prophase I and independent assortment

Explanation/Tip: Genetic recombination during crossing over in meiotic Prophase I along with random alignment and independent assortment of chromosomes creates unique genetic combinations in gametes.

Correct Answer: B. Lowering the activation energy required for the reaction

Explanation/Tip: Enzymes speed up metabolic reactions by lowering the activation energy barrier needed to convert substrates into products without being consumed themselves.

Correct Answer: B. Sleeping sickness (Trypanosomiasis)

Explanation/Tip: Sleeping sickness is caused by the protozoan Trypanosoma, transmitted by the tsetse fly vector (Glossina).

Correct Answer: B. Guard cells

Explanation/Tip: A pair of bean-shaped guard cells control stomatal openings through changes in turgor pressure.

Correct Answer: B. Homologous structures

Explanation/Tip: Homologous structures reflect anatomical similarities due to shared evolutionary origin (divergent evolution). Analogous structures have different origins but similar functions.

Correct Answer: C. Rickets

Explanation/Tip: Vitamin D promotes calcium absorption in intestines. Deficiency leads to soft, weak bones known as rickets in children and osteomalacia in adults.