2020 JAMB BIOLOGY PAST QUESTIONS AND ANSWERS

Chromosomes are structures within the nucleus that carry genetic material in the form of DNA. They are the basis for inheritance, as they contain genes that pass traits from one generation to the next. Other organelles like ribosomes and the endoplasmic reticulum are not involved in inheritance.

Conifers produce seeds without a surrounding fruit, known as naked seeds, a characteristic feature of gymnosperms. In contrast, flowering plants (angiosperms) produce seeds enclosed within fruits.

Bryophytes lack a vascular system, which is present in pteridophytes. This makes bryophytes dependent on water for reproduction, as they do not have specialized tissues for water and nutrient transport.

Chloroplasts are common to both the sporophyte and gametophyte stages in ferns, allowing them to perform photosynthesis. Rhizoids, roots, and leaves differ between the two life stages, adapting to specific functions.

Euglena is a single-celled organism capable of movement, nutrition, growth, excretion, and photosynthesis. Other organisms like Amoeba perform some, but not all, of these functions, as they lack chloroplasts for photosynthesis.

Glycogen is stored in animals, with Rattus (rat) being an example. Plants, on the other hand, store starch as their energy reserve.

Arthropoda is the largest animal phylum, known for its immense diversity, including insects, arachnids, and crustaceans. Their exoskeleton and jointed appendages enable them to adapt to various environments.

Flame cells function as the excretory system in flatworms, helping them remove waste through a system of tubules. These specialized cells do not function in respiration or in worms outside of flatworms.

Spores of mucor (a type of mold) are dispersed by wind, allowing for widespread distribution and colonization of new environments. Water, insects, and explosive mechanisms are less common methods for mucor.

Part 3 in the jaw diagram represents the diastema, a gap found in herbivorous animals such as rabbits, allowing for the processing of vegetation. Other labeled parts correspond to different tooth types or bone sections.

Chromosomes are structures within the nucleus that carry genetic material in the form of DNA. They are the basis for inheritance, as they contain genes that pass traits from one generation to the next. Other organelles like ribosomes and the endoplasmic reticulum are not involved in inheritance.

Conifers produce seeds without a surrounding fruit, known as naked seeds, a characteristic feature of gymnosperms. In contrast, flowering plants (angiosperms) produce seeds enclosed within fruits.

Bryophytes lack a vascular system, which is present in pteridophytes. This makes bryophytes dependent on water for reproduction, as they do not have specialized tissues for water and nutrient transport.

Chloroplasts are common to both the sporophyte and gametophyte stages in ferns, allowing them to perform photosynthesis. Rhizoids, roots, and leaves differ between the two life stages, adapting to specific functions.

Euglena is a single-celled organism capable of movement, nutrition, growth, excretion, and photosynthesis. Other organisms like Amoeba perform some, but not all, of these functions, as they lack chloroplasts for photosynthesis.

Glycogen is stored in animals, with Rattus (rat) being an example. Plants, on the other hand, store starch as their energy reserve.

Arthropoda is the largest animal phylum, known for its immense diversity, including insects, arachnids, and crustaceans. Their exoskeleton and jointed appendages enable them to adapt to various environments.

Flame cells function as the excretory system in flatworms, helping them remove waste through a system of tubules. These specialized cells do not function in respiration or in worms outside of flatworms.

Spores of mucor (a type of mold) are dispersed by wind, allowing for widespread distribution and colonization of new environments. Water, insects, and explosive mechanisms are less common methods for mucor.

Part 3 in the jaw diagram represents the diastema, a gap found in herbivorous animals such as rabbits, allowing for the processing of vegetation. Other labeled parts correspond to different tooth types or bone sections.

Butterflies are important pollinators, transferring pollen from one flower to another, which aids in the reproduction of flowering plants and crops. This contributes to food production and ecological balance.

Phloem is responsible for the transport of manufactured food (like glucose) from leaves to other parts of the plant. The xylem, by contrast, mainly transports water and minerals from roots to leaves.

Magnesium deficiency leads to interveinal chlorosis, where leaf veins remain green but areas between veins turn yellow. Magnesium is essential for chlorophyll production, hence its deficiency affects photosynthesis.

The black precipitate in this reaction indicates fats and oils, as osmic acid stains lipids black. Proteins, amino acids, and starch would not yield this color change.

The lower jaw depicted resembles that of a rabbit, characterized by diastema (gap) and specific dental structures suited for herbivorous diets. Carnivores, like dogs and cats, have more specialized teeth for cutting and tearing.

Fats and oils are broken down into fatty acids and glycerol during digestion, which are absorbed and utilized for energy or stored as fat. Other products like glucose or fructose are derived from carbohydrates.

The right auricle contracts to push blood into the right ventricle through the tricuspid valve. This contraction is part of the heart’s pump cycle that moves blood to the lungs for oxygenation.

Oxygenated blood returns from the lungs to the left atrium (auricle) of the heart through the pulmonary veins. This blood then moves into the left ventricle and is pumped throughout the body.

Blood primarily transports oxygen from the lungs to body tissues and removes carbon dioxide from tissues back to the lungs. It also carries nutrients, hormones, and waste products for elimination.

The contractile vacuole in protozoa, such as Amoeba, helps regulate water balance by expelling excess water from the cell, preventing it from bursting. It is not used for movement or digestion.

Geotropism is the response of plants to gravity. Roots display positive geotropism by growing downwards, while shoots show negative geotropism by growing upwards. Other tropisms, such as phototropism, respond to light rather than gravity.

Geotropism is the response of plants to gravity. Roots display positive geotropism by growing downwards, while shoots show negative geotropism by growing upwards. Other tropisms, such as phototropism, respond to light rather than gravity.

The correct order from the top down is Atlas, Axis, Cervical, Thoracic, Lumbar, Sacral. This sequence represents the arrangement of vertebrae from the neck to the lower back.

During conjugation in Paramecium, the micronucleus divides twice while the macronucleus disintegrates. This genetic exchange process enhances genetic diversity in Paramecium.

The bright colors of the peacock’s feathers are for courtship, as they are used to attract mates during mating displays. This is an example of sexual selection. Other options do not relate to the purpose of these vibrant colors.

Petals attract pollinators with their color and scent, increasing the chances of pollination. While they may also serve as landing platforms, their primary role is to draw pollination agents to the flower.

The autonomic nervous system is composed of the sympathetic and parasympathetic systems, which regulate involuntary actions such as heart rate and digestion. Other nervous system components like cranial nerves are not part of this division.

In hypogeal germination, the cotyledons remain below the soil surface, as the epicotyl elongates. This is seen in plants like peas. Epigeal germination, in contrast, raises the cotyledons above ground.

Temperature and rainfall are primary abiotic factors influencing ecosystems, affecting the availability of water, growth rates, and reproduction. Other factors like turbidity or wind direction are more specific to certain habitats.

Wave action is the dominant physical factor in intertidal zones, impacting organisms’ attachment, feeding, and survival. Organisms here must adapt to withstand strong water currents and fluctuating tides.

Tertiary consumers experience the highest accumulation of non-biodegradable substances due to biomagnification. These substances become more concentrated at higher trophic levels as each consumer accumulates them from its prey.

Commensals are two species that live together, where one benefits and the other is neither harmed nor helped. Unlike parasites or symbionts, commensal relationships are neutral for one of the species involved.

Carbon monoxide binds with hemoglobin more strongly than oxygen, reducing oxygen transport in the blood and leading to tissue hypoxia. This can result in organ damage or even death if exposure is prolonged.

Tongue rolling is an example of discontinuous variation, a genetic trait that individuals either possess or do not possess, with no intermediate form. Continuous variations, like height or skin color, show a range of expressions.

Agglutination occurs when contrasting antigens react with contrasting antibodies, leading to clumping. This reaction happens if blood types are not matched correctly during transfusion.

A microscope is used to observe small organisms and structures but is not used to measure abiotic factors, unlike instruments like thermometers or hygrometers that measure temperature and humidity, respectively.