All 40 questions from the Joint Admissions and Matriculation Board (JAMB) Biology 2025 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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A gene is best defined as
Genes determine the traits of an organism by encoding information necessary for the function and regulation of biological processes. Genes are inherited from one generation to the next, which is why they are considered the basic unit of heredity.
In human lungs, gas exchange takes place across a thin barrier between the alveoli and capillaries. Which statement about this exchange is correct?
The alveoli in the lungs are tiny sacs where the exchange of gases occurs. Oxygen from the inhaled air passes through the alveolar membrane into the blood in the capillaries, while carbon dioxide, a waste product of cellular metabolism, moves from the blood into the alveoli, where it is then exhaled.
In plants, sugar move from sources to sinks through
Phloem is the vascular tissue responsible for the transport of organic compounds, primarily sugars produced in the leaves during photosynthesis, to other parts of the plant such as roots, stems and flowers. This process is called translocation.
Plants such as Orchids that grow on other plants or objects for physical support without drawing nutrients from them are called
Epiphytes are plants that grow on other plants (usually trees) but do not take nutrients from their host.
According to the central dogma of molecular biology, genetic information flows from DNA to
The central dogma of molecular biology describes the flow of genetic information within a biological system. It states that DNA is transcribed into messenger RNA (mRNA) in the process of transcription, and the mRNA then serves as a template for protein synthesis during translation at the ribosome.
Crossing over between homologous chromosomes occurs during which stage of meiosis?
Crossing over is the process in which homologous chromosomes exchange genetic material during meiosis, specifically in Prophase 1. This genetic recombination increases genetic diversity among offspring.
Genes that are located close together on the same chromosome and tend to be inherited together are called
Linked genes are genes that are located near each other on the same chromosome.
In hydra, the form of asexual reproduction in which a new individual develops as an outgrowth of the parent is called
Hydra reproduces asexually through budding, where a small bud forms on the body of the parent organism. The bud eventually detaches and grows into a new, genetically identical organism.
The two strands of a DNA molecule are held together by which type of bond between complementary bases?
DNA is a double-helix structure, and the two strands of the helix are held together by hydrogen bonds between complementary nitrogenous bases. These bonds are crucial for maintaining the stability and structure of the DNA molecule.
A man with blood group AB marries a woman with blood group O. Which blood groups are possible among their children?
The man with blood group AB has the genotype AB while the woman with blood group O has the genotype OO. Their offspring can inherit either an A or a B allele from the father and the O allele from the mother. Thus, a child can either have blood group A (genotype AO) or blood group B (genotype BO).
Which part of a leaf contains the highest concentration of chloroplasts and is primarily responsible for photosynthesis?
The palisade mesophyll layer contains the highest concentration of chloroplasts and is primarily responsible for photosynthesis. This layer is located just beneath the upper epidermis and is rich in chloroplasts to maximize the absorption of light energy for photosynthesis.
Plants that produce seeds but not flowers are placed in the group
Gymnosperms are plants that produce seeds but do not produce flowers. They produce cones instead of flowers.
The role an organism plays in its environment including its habitat and interactions, is referred to as its
This refers to the ecological niche of the organism.
In primary ecological succession, the first organisms to colonize bare rock are usually
In primary succession, the first organisms to colonize bare rock are typically lichens. Lichens are a mutualistic combination of a fungus and an alga. They can survive in harsh conditions and help break down the rock into soil, facilitating the establishment of more complex plants later in the succession process.
In the human respiratory system, which structure closes over the opening of the trachea during swallowing to prevent food from entering the airway?
The epiglottis is a flap of tissue located at the base of the tongue that covers the trachea (windpipe) during swallowing. This prevents food and liquids from entering the airway and directs them towards the oesophagus.
In the nephron of the kidney, the structure where ultrafiltration of blood takes place is the
Bowman's capsule surrounds the glomerulus and is the site of ultrafiltration, where blood pressure forces small molecules such as water, salts, glucose and urea out of the blood. This is the first step in the formation of urine.
The main function of the large intestine is to
The large intestine (colon) is primarily responsible for absorbing water from the undigested food matter that enters it from the small intestine. This process forms solid waste (faeces), which is then eliminated from the body.
Which organ produces the hormone insulin that regulates blood glucose levels?
The pancreas produces insulin, a hormone that regulates blood glucose levels by facilitating the uptake of glucose into cells for energy production. The pancreas also produces glucagon, which works to raise blood sugar levels when they are too low.
Immunity gained after recovering from an infection such as measles is known as
Natural active immunity occurs when an individual's immune system produces antibodies in response to exposure to a pathogen, such as the measles virus. This type of immunity provides long-term protection by recognizing and combating the pathogen more effectively in the future.
In the human eye, which structure controls the amount of light entering by adjusting the size of the pupil?
The iris controls the size of the pupil by contracting or relaxing the muscles in response to the amount of light in the environment. In bright light, the iris constricts the pupil to reduce light entry, while in dim light, it dilates the pupil to allow more light in.
Which unicellular organism reproduces by binary fission?
Amoeba is a unicellular organism that reproduces by binary fission, a form of asexual reproduction. During binary fission, the cell duplicates its genetic material and then divides into two genetically identical daughter cells.
In placental mammals, the placenta functions to
The placenta is an organ that connects the developing foetus to the mother's uterine wall. It facilitates the exchange of nutrients, oxygen and waste products between the mother and foetus, supporting foetal development throughout pregnancy.
The theory of natural selection was proposed by
The theory of natural selection was independently proposed by both Charles Darwin and Alfred Russel Wallace. It posits that organisms with traits that provide a survival advantage in their environment are more likely to reproduce, passing those beneficial traits on to the next generation.
Binomial nomenclature assigns each species a scientific name consisting of
Binomial nomenclature is the system of naming species by two terms: the genus name and the species name. This system, developed by Carl Linnaeus, is used worldwide to ensure consistency and clarity in identifying organisms.
An animal that is warm-blooded, has hair or fur and produces milk to feed its young is a/an
Mammals are characterized by being warm-blooded (homoiothermic), having hair or fur, and producing milk for their offspring through mammary glands. These features distinguish mammals from other animal classes.
The fossil record shows that
The fossil record provides evidence that life on earth has changed over time. Fossils show a progression of species from simple to more complex forms, supporting the theory of evolution and the idea that life has evolved over millions of years.
A mutation that changes one nucleotide base in a DNA sequence is called a
A point mutation occurs when a single nucleotide base in the DNA sequence is replaced, deleted or inserted. This can result in changes to the protein encoded by the gene.
Which of the following is an example of a hinge joint in the human body?
A hinge joint allows movement in one plane, similar to the way a door hinge works, permitting flexion and extension. The knee joint is a classic example of a hinge joint, allowing for bending and straightening.
Which kingdom comprises Prokaryotic organisms?
The Monera kingdom comprises prokaryotic organisms, which are single-celled organisms that lack a well-defined nucleus and other membrane-bound organelles. This includes bacteria and archaea.
Mycorrhiza is a symbiotic association between
Mycorrhiza refers to the mutualistic relationship between plant roots and fungi. The fungus provides the plant with enhanced access to water and nutrients while the plant supplies the fungus with carbohydrates produced via photosynthesis.
Which of the following is the primary function of the lymphatic system?
The lymphatic system plays a critical role in the immune system by defending the body against infections. It is a network of vessels, nodes and organs that help in the transport of lymph, a clear fluid containing white blood cells, which are essential for immune responses.
What is the role of NADH and FADH2 in cellular respiration?
In cellular respiration, NADH and FADH2 are key molecules that function as electron carriers. Their primary role is to shuttle electrons to the electron transport chain in the mitochondria.
During photosynthesis, the Calvin cycle is responsible for
The Calvin cycle, also known as the light-independent reactions, is a key part of photosynthesis where carbon dioxide is converted into glucose. This cycle occurs in the stroma of chloroplasts and involves three main stages: carbon fixation, reduction and regeneration of RuBP.
Which of the following is an example of a mutualistic relationship?
A mutualistic relationship is a type of symbiosis in which both organisms benefit from the interaction. The interaction between a bee and a flower is a classic example of mutualism: bees collect nectar from flowers for nourishment while they simultaneously help the flower in pollination.
A student places a piece of celery in a solution of salt and water. After several hours, the celery becomes limp. What process best explains the result?
The salt solution has a higher solute concentration compared to the inside of the celery cells. Water from the cells will move out into the surrounding salt solution, trying to balance the concentration of solutes on both sides of the membrane.
The process in which a cell engulfs and ingests particles such as bacteria is called
The process by which a cell engulfs and ingests particles, such as bacteria or dead cells, is called phagocytosis. It is a key part of the immune response; white blood cells such as macrophages and neutrophils perform phagocytosis to defend the body against pathogens.
In a food chain, energy is transferred from one organism to another. Which of the following represents the correct flow of energy?
In an ecological food chain, energy flows from the sun to producers (usually plants) and then up to consumers (herbivores and carnivores).
Which of the following best describes the role of the mitochondrion in the cell?
The mitochondrion is known as the "powerhouse" of the cell because it is responsible for producing ATP, which is the main source of energy for cellular processes.
Which of the following is an example of a biotic factor that influences the growth of a population?
A biotic factor relates to a living component of an ecosystem that affects the organisms in the environment. Predation is an example of a biotic factor as it involves one organism (the predator) hunting and killing another (the prey), which can affect the population size and structure of both species.
Which of the following describes the function of the plasma membrane in a cell?
The plasma membrane serves as a selective barrier that controls the movement of substances into and out of the cell. It is composed of a phospholipid bi-layer with embedded proteins that allow the cell to maintain homeostasis by regulating the passage of ions, nutrients and waste products.
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