JAMB Biology 2006
Questions & Answers

Students might incorrectly pick the absorption of nutrients, thinking all digestive processes happen in the same place. By reasoning through the digestive tract, we know that nutrient absorption primarily occurs in the small intestine, whereas the large intestine is responsible for absorbing water from indigestible food residues, ultimately forming solid feces for excretion. Common mistake: Confusing the primary functions of the small and large intestines regarding nutrients and water.

An examinee might select 50%, 75%, or 100% by misreading the genotypic ratios. Mapping out a Punnett square for a cross between two heterozygous tall plants (Tt) yields 1/4 or 25% TT, 2/4 or 50% Tt, and 1/4 or 25% tt, meaning the chance of producing a homozygous recessive offspring is 25%. Common mistake: Confusing the probability of the heterozygous genotype with the homozygous recessive genotype.

One might mistakenly pick high species diversity, dependence on other species, or slow growth rate by assuming pioneer species share traits of mature ecosystems. Pioneer species like lichens and mosses must be able to tolerate extreme conditions such as bare rock, allowing them to initiate succession by improving soil for other species. Common mistake: Assuming pioneer species require stable, diverse environments rather than harsh ones.

A student might incorrectly choose the nucleus, ribosome, or plasmid, assuming bacteria share eukaryotic cell structures. Because bacteria lack a membrane-bound nucleus, their genetic material is instead located in the nucleoid, which is a specific region within the cytoplasm. Common mistake: Assuming bacterial cells contain a true membrane-bound nucleus like eukaryotic cells.

An individual might choose increased soil fertility, reduced soil erosion, or increased biodiversity, misinterpreting the ecological damage caused by excessive grazing. Overgrazing removes grass cover, which exposes the soil to erosion and diminishes the habitat for other species, as frequently observed in Nigerian savannas. Common mistake: Believing that heavy grazing by livestock improves ecosystem health and soil stability.

A student might choose prolactin, progesterone, or adrenaline due to confusion over various reproductive and stress hormones. The hormone responsible for triggering rhythmic uterine contractions during labor and delivery is oxytocin, which is secreted by the posterior pituitary. Common mistake: Confusing oxytocin with prolactin or progesterone when considering childbirth processes.

One might select options where both organisms benefit or are harmed by confusing parasitism with mutualism or competition. In a parasitic relationship, one organism benefits, such as a tapeworm gaining nutrients, while the other organism is harmed, such as the host suffering from nutrient loss. Common mistake: Confusing parasitism with mutualism where both parties benefit.

A test-taker could mistakenly choose skeletal, cardiac, or striated muscle by confusing voluntary and involuntary muscle types. Smooth muscle is both involuntary and non-striated, making it the tissue that lines blood vessel walls to control their diameter and regulate blood flow. Common mistake: Confusing smooth muscle with striated or cardiac muscle locations.

A candidate might pick transpiration, respiration, or translocation by mixing up plant physiological processes. Magnesium is a core component of chlorophyll, making it essential for photosynthesis, and its deficiency leads directly to chlorosis or yellowing leaves. Common mistake: Associating magnesium deficiency with general water transport instead of chlorophyll formation.

A student might mistakenly select budding, fragmentation, or binary fission by confusing different modes of asexual reproduction. Parthenogenesis, which is observed in aphids, involves unfertilized eggs developing directly into offspring, typically occurring in favorable conditions. Common mistake: Confusing parthenogenesis with cellular splitting methods like binary fission.

One might mistakenly choose increased nutrient availability, reduced toxicity, or decreased primary producer population by misunderstanding toxin pathways. Biomagnification concentrates toxins like mercury in top predators, which ultimately harms species such as fish-eating birds at the top of the food chain. Common mistake: Assuming toxins dilute as they move up the trophic levels.

A student could select petals, stamens, or carpels by confusing the reproductive parts with protective structures. Sepals, which form the calyx, enclose and protect the developing flower bud before it blooms, as seen clearly in hibiscus plants. Common mistake: Confusing the protective function of sepals with the attraction role of petals.

An examinee might pick rapid population growth, high death rate, or low birth rate by misunderstanding population dynamics. At carrying capacity, resource limitations balance birth rates and death rates, which stabilizes the overall population size. Common mistake: Assuming a population at carrying capacity continues to experience exponential growth.

A student might mistakenly select the cornea, lens, or retina by confusing structural parts of the eye. The iris adjusts the size of the pupil in order to regulate the amount of light entering the eye, thereby protecting the delicate retina. Common mistake: Confusing the light-focusing role of the lens or cornea with the light-regulating role of the iris.

A candidate could choose photosynthesis-related or multicellular options by misidentifying fungal characteristics. Fungal spores are resistant structures that can withstand extreme conditions, allowing them to aid in both dispersal and reproduction across sexual and asexual cycles. Common mistake: Assuming fungal spores are always delicate or strictly tied to sexual reproduction.

One might select stabilizing, directional, or artificial selection by confusing the different patterns of evolutionary forces. Disruptive selection favors extreme phenotypes like very large and very small sizes over average ones, which can potentially lead to speciation. Common mistake: Confusing disruptive selection with directional selection that favors a single extreme trait.

A student might pick large broad leaves, weak stems, or high transpiration rates by overlooking physical adaptations to wind. Thick, rigid stems, such as those found in grasses, help plants resist wind-induced breakage in open environments. Common mistake: Assuming broad leaves are beneficial in windy environments.

An examinee might mistakenly choose the crop, cloaca, or proventriculus by confusing various sections of the avian digestive tract. The gizzard is a muscular stomach that uses ingested grit to grind food before digestion in birds like chickens. Common mistake: Confusing the food-storage function of the crop with the grinding function of the gizzard.

A student might select increased genetic diversity or reduced risk of disorders by misunderstanding genetic principles. Inbreeding increases homozygosity within a population, which raises the likelihood of expressing recessive, and often deleterious, traits. Common mistake: Assuming inbreeding purges harmful genetic variations rather than exposing them.

1) Distractor check: A student might mistakenly choose Option B, thinking metabolic waste removal is the primary vascular task, or Option A, confusing transport with systemic gas delivery. 2) Reasoning to the answer: Fluid balance is preserved as lymph is collected from interstitial spaces and routed back to the bloodstream, which is precisely how the system handles excess tissue fluid. 3) Common mistake: Confusing the lymphatic clearance of interstitial liquid with cardiovascular transport of respiratory gases.