JAMB UTME - Biology - 2004

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The two cations involved in the action potential of nervous transmissions are sodium (Na+) and potassium (K+). During the resting state of a neuron, the concentration of sodium ions is higher outside the cell than inside, and the concentration of potassium ions is higher inside the cell than outside. When a stimulus is received by the neuron, it causes the opening of sodium channels, allowing sodium ions to flow into the cell, which results in a depolarization of the membrane potential. This depolarization triggers the opening of potassium channels, allowing potassium ions to flow out of the cell, which repolarizes the membrane potential back to the resting state. The movement of sodium and potassium ions across the neuron membrane generates the electrical signal, which is transmitted along the neuron axon as an action potential.

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A wide pith in the centre of the internal structure of plants is common to dicot stems and monocot stems. The pith is the central portion of the stem, surrounded by the vascular tissue, and consists of parenchyma cells that store food and water for the plant. Dicot stems and monocot stems are two types of plant stems. Dicot stems have a distinct pith in the center, surrounded by vascular tissue arranged in a ring. Monocot stems, on the other hand, have scattered vascular bundles throughout the stem, with no distinct pith in the center. Therefore, the presence of a wide pith in the center of the internal structure of plants indicates that the stem in question is a dicot stem or a monocot stem.

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The progressive loss of energy at each level in a food chain leads to a decrease in biomass at each successive level. Energy is transferred from one level to another in a food chain as organisms eat each other. However, not all of the energy that an organism ingests is available for growth or reproduction. Some of the energy is lost as heat or used for metabolic processes such as respiration. As a result, only a fraction of the energy that is consumed is passed on to the next level in the food chain. This means that as you move up the food chain, there is less and less energy available to support the growth and reproduction of organisms. This results in a decrease in the biomass, or total weight, of organisms at each successive level. For example, there may be many small plants at the base of the food chain, but only a few herbivores that feed on them, and even fewer carnivores that feed on the herbivores. Overall, the progressive loss of energy at each level in a food chain is an important principle in ecology that helps explain the structure and dynamics of ecosystems.

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Identical twins inherit their genes from the same egg and sperm. This happens when a single fertilized egg splits into two embryos, each with the same genetic material. As a result, identical twins have nearly identical DNA, which is why they look very similar and share many traits.

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The absence of special food and water-conducting systems restricts the body size in algae, liverworts, and mosses. These organisms are known as bryophytes and lack vascular tissue, which is responsible for transporting water and nutrients throughout the plant. Without these specialized tissues, bryophytes must rely on diffusion to transport materials, which is only effective over short distances. As a result, bryophytes are limited in their ability to grow large because they cannot efficiently transport water and nutrients to all parts of their body. The other options involve different groups of plants, which may have specialized tissues for water and nutrient transport, and thus do not describe this particular limitation.

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Nervous control differs from hormonal control in that the former produces short-term changes. Nervous control involves the transmission of electrical impulses through nerve cells, which then release chemical neurotransmitters to communicate with other cells. This allows for rapid and precise control over the body's functions. However, the effects of nervous control are short-lived and temporary. Hormonal control, on the other hand, involves the release of hormones by glands into the bloodstream, which then act on target cells throughout the body. This allows for slower but more long-lasting effects on the body's functions. Hormones also have specific target cells and pathways, whereas nervous impulses can be more diffuse and spread out. Therefore, based on the description, nervous control produces short-term changes, while hormonal control produces longer-lasting effects.

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The state in Nigeria that is most susceptible to desert encroachment is Katsina. Katsina is located in the northern region of Nigeria and falls within the Sahelian zone which is characterized by a semi-arid climate with low and erratic rainfall. This region is particularly vulnerable to desertification, which is the process of fertile land becoming desert due to a combination of natural and human factors such as deforestation, overgrazing, and climate change. The dry and dusty conditions in Katsina make it more prone to desertification and as such, the state is considered one of the most affected by desert encroachment in Nigeria.

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Yam is used in this set-up because it acts as a semi-permeable membrane. In this setup, yam is used as a model for understanding osmosis, which is the movement of water molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration. In this experiment, the yam serves as the semi-permeable membrane that separates the two salt solutions of different concentrations. The yam allows the movement of water molecules, but not the salt molecules, thus facilitating the movement of water from the region of lower salt concentration to the region of higher salt concentration. Therefore, yam is used in this set-up because of its semi-permeable nature, which enables the experiment to study the process of osmosis.

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Sex-linked genes are located on the X-chromosome or Y-chromosome. In humans, females have two X chromosomes while males have one X and one Y chromosome. Since sex chromosomes determine the sex of an individual, genes located on the X or Y chromosome are called sex-linked genes. Genes on the X chromosome are considered X-linked, while genes on the Y chromosome are Y-linked. Because males only have one X chromosome, they express any X-linked gene, whether it is dominant or recessive, whereas females must inherit two copies of a recessive X-linked gene to express the trait. Therefore, sex-linked genes play an important role in the inheritance of many genetic disorders and traits.

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Plants can survive hot and dry conditions by storing water in their large cells. These cells, called parenchyma cells, act like water reservoirs, holding onto water for the plant to use during periods of drought. Additionally, plants can also reduce their water loss by having fewer leaves, having leaves with a waxy coating, and having numerous stomata, which are tiny openings on the surface of leaves that can close to prevent water loss. Some plants, like evergreen trees, are adapted to survive in hot and dry conditions by having thick, waxy leaves that are able to retain water and stay green all year round.

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The best evidence of the relationship between living organisms and their extinct relatives can be obtained from paleontology. Paleontology is the study of fossils, which are the remains or traces of ancient organisms that are preserved in rock. By studying fossils, scientists can learn about the anatomy, behavior, and evolution of extinct species and compare them to living organisms. Comparative anatomy and physiology are also useful for understanding relationships between organisms, but they only provide information about living species. Comparative anatomy involves comparing the physical structures of different organisms, while comparative physiology looks at the functions of those structures. Embryology focuses on the development of organisms from the fertilized egg stage to birth or hatching. While embryology can provide insight into evolutionary relationships, it also has limitations, as organisms with very different adult forms can have very similar embryos. In contrast, paleontology provides a unique window into the evolutionary history of life on Earth by allowing us to observe extinct species and compare them with living ones. Through paleontology, scientists can construct detailed evolutionary trees that show how different groups of organisms are related to each other and how they have changed over time.

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The larval stage of a mosquito is called a wriggler. When a mosquito lays its eggs in water, they hatch into wrigglers, which are aquatic larvae. Wrigglers live in the water and breathe through a snorkel-like structure called a siphon. They feed on small organisms in the water and grow rapidly, molting several times as they increase in size. After several days or weeks, depending on the species and environmental conditions, the wrigglers pupate and transform into adult mosquitoes. During the pupal stage, the mosquito undergoes a dramatic metamorphosis, developing wings and other structures that are not present in the larval stage. Finally, the adult mosquito emerges from the pupa and flies away in search of a blood meal. In contrast, grubs are the larvae of beetles, maggots are the larvae of flies, and caterpillars are the larvae of butterflies and moths. While these larvae share some similarities with mosquito wrigglers, they have different body shapes and behaviors, and they do not go through the same developmental stages.

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The tiny blood vessels that are well supplied in the surface of an alveolus in a mammal are called capillaries. These vessels are extremely small, and they allow for the exchange of oxygen and carbon dioxide between the blood and the air in the lungs. This exchange is essential for breathing, as oxygen is needed to support the body's vital functions, and carbon dioxide is a waste product that needs to be removed. Capillaries are the smallest type of blood vessels in the body and are responsible for delivering oxygen and nutrients to the tissues while also removing waste products.

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A plant-like feature in Euglena is the presence of a pigment spot, also called an eyespot or stigma. This is a small, colored organelle located near the base of the flagellum (a long, whip-like structure that helps Euglena move). The pigment spot contains a light-sensitive pigment that helps Euglena detect and move towards light, which is important for photosynthesis. While Euglena is a unicellular organism, it has features of both plants and animals. The pellicle is a proteinaceous layer that covers and supports the cell membrane, the gullet is a feeding structure found in some protozoa, and the large spot is not a known feature of Euglena.

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Water is necessary for all living cells because it serves as a medium for all metabolic reactions in the cell. In other words, many chemical reactions occur in water inside the cell, which enables various cellular processes to occur. Water is also essential for the transport of nutrients, waste products, and other substances within the cell and between cells. Additionally, water helps regulate the temperature of the cell and maintain its shape.

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The eggs of birds contain relatively larger quantities of yolk than those of amphibians and reptiles because embryonic development is longer in birds. Yolk is a food source for the developing embryo inside the egg, providing nutrients and energy for growth and development. Birds have a longer incubation period than amphibians and reptiles, which means that the developing embryo requires more nutrients to sustain its growth for a longer period of time. The yolk provides these nutrients in the form of proteins, fats, and vitamins, which are essential for the development of the chick. This is why the eggs of birds have a larger yolk compared to those of amphibians and reptiles, which have a shorter incubation period and require less nutrients for embryonic development.

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Continuous cropping is a farm practice that can result in the loss of soil fertility. This is because the same crop is planted on the same land over and over again without allowing the soil to rest and recover its nutrients. As a result, the soil becomes depleted of its essential nutrients, which reduces crop yields and can lead to soil erosion. To prevent soil degradation, farmers can adopt practices such as crop rotation, intercropping, and the use of fertilizers to replenish the soil's nutrients.

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The group of enzymes that catalyze the breakdown of fats and oils into simpler absorbable compounds are called lipases. These enzymes break down the fats and oils by breaking the chemical bonds between the fatty acids and glycerol molecules that make up the fat or oil. This process is known as hydrolysis because water is used to break the bonds. Lipases are a type of hydrolase enzyme, which means they use water to break down complex molecules into simpler ones. Amylases and peptidases, on the other hand, are enzymes that break down carbohydrates and proteins, respectively.

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In a Mendelian cross of red and white varieties of the four O'clock plants, the F1 generation expresses incomplete dominance by having flowers that are pink. Incomplete dominance occurs when neither of the two alleles (versions of the gene) is completely dominant over the other, resulting in a phenotype (observable trait) that is intermediate between the two. In the case of the four O'clock plants, the gene for flower color has two alleles: one for red and one for white. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation inherits one allele from each parent and expresses an intermediate phenotype of pink flowers. This is because the red pigment and the absence of pigment in the white flowers mix together to create a pink color. The F2 generation resulting from the cross of F1 plants can have a ratio of 1:2:1 for red:pink:white flowers, indicating the incomplete dominance inheritance pattern.

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Respiration is primarily the responsibility of the respiratory system, which includes organs such as the lungs, trachea, bronchi, and diaphragm in humans. This system facilitates the exchange of gases, allowing oxygen from the air to enter the body and carbon dioxide to be expelled.

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The association between termites and the cellulose-digesting protozoans in their guts is an example of mutualism. Mutualism is a type of symbiotic relationship where both organisms benefit from each other. In the case of termites and the cellulose-digesting protozoans in their guts, termites provide a warm, moist environment and a source of food (cellulose) for the protozoans, while the protozoans break down the cellulose into simpler molecules that can be absorbed and digested by the termites. This relationship is essential for both organisms to survive as termites cannot digest cellulose on their own, and protozoans cannot survive outside the termite gut. Therefore, this association is an example of mutualism.

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Pollination is the process by which pollen grains from the male reproductive part of a flower, called the anther, are transferred to the female reproductive part of a flower, called the stigma. So, the correct option would be "II to III" since pollen grains are transferred from the anther (located in the stamen of the flower) to the stigma (located in the pistil of the flower).

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Paternity disputes can most accurately be resolved through the use of DNA analysis. DNA is a genetic material found in every cell of the body, and each person's DNA is unique except for identical twins. The DNA of a child is inherited from both the mother and the father, with half of the child's DNA coming from each parent. DNA analysis involves comparing the DNA of the child to that of the alleged father to determine if they share genetic markers. The analysis can be done using a variety of samples, such as blood, hair, skin, or saliva. DNA analysis is extremely accurate and can provide conclusive evidence of whether or not an individual is the biological father of a child. Finger printing, blood group typing, and tongue-rolling are not accurate methods for determining paternity. Therefore, based on the description, DNA analysis is the most accurate method for resolving paternity disputes.

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The function of the long-winged reproductives of the termite colony is to disperse the population. These winged termites are also called alates, and they are responsible for starting new colonies in different locations. During a swarm, they fly out of their colony and mate with each other, then the female alates shed their wings and burrow into the ground to start a new colony. This process helps to increase the range of the termite population and ensure their survival.

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Epigeal germination of a seed is characterized by more rapid elongation of the epicotyl than the hypocotyl. This means that the part of the plant above the cotyledons (the epicotyl) will grow faster and emerge from the soil, while the part below the cotyledons (the hypocotyl) will also grow but at a slower rate. In other words, the shoot will grow faster than the root during epigeal germination. This type of germination is commonly seen in dicotyledonous plants such as beans, peas, and sunflowers.

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A caterpillar and an aphid living in different parts of the same plant occupy different ecological niches. An ecological niche refers to the specific role and position of an organism within its environment, including its interactions with other organisms and its use of resources. While the caterpillar and aphid may share some similarities in their lifestyles and feeding habits, they occupy different parts of the plant and have different feeding behaviors, which allows them to coexist without directly competing for resources. Therefore, they occupy different ecological niches within the same habitat. The other options, such as occupying the same ecological niche or being in the same microhabitats, are not accurate descriptions for these organisms since they have different roles and locations within the same plant.

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One of the adaptations of reptiles to water loss is the presence of keratinous scales. These scales are made of a tough and water-resistant protein called keratin, which helps to prevent water loss through the skin. Reptiles are ectothermic, which means they rely on external heat sources to regulate their body temperature. This adaptation helps to protect them from dehydration in dry environments, by minimizing water loss from their skin. Additionally, the scales also provide protection against predators and physical damage, making them an important adaptation for reptiles.

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The spots and stripes of the leopard and tiger are examples of disruptive coloration. Disruptive coloration is a type of camouflage that helps animals blend in with their surroundings by breaking up their outline and making it harder for predators or prey to spot them. In the case of the leopard and tiger, their spots and stripes help them blend in with the dappled light and shadows of the forest. This makes it easier for them to sneak up on their prey or avoid detection by other animals. Disruptive coloration is also found in many other animals, such as zebras, cheetahs, and certain types of birds and insects.

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The soil type that will be most difficult to plough in a wet season is clayey soil. Clay soil is composed of very fine mineral particles that pack tightly together. When clay soil becomes wet, the spaces between the particles fill with water, causing the soil to become heavy and sticky. This makes it difficult for farm equipment to move through the soil, and it can also cause the soil to clump and clog machinery. In contrast, sandy soil has larger particles with more space between them, so it drains water more quickly and does not become as compacted when wet. Loamy soil is a mixture of sand, silt, and clay, and it tends to be more workable than clayey soil. Silty soil is similar to clayey soil, but it has a higher proportion of silt particles and is typically more fertile. However, all these soils can become difficult to plough in wet seasons, but clayey soils are generally the most challenging.

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The anaerobic fermentation of a glucose molecule yields 2 ATP molecules and either lactic acid or alcohol, depending on the type of fermentation. During anaerobic fermentation, glucose is converted into pyruvic acid, which is then broken down into either lactic acid or alcohol. This process releases a small amount of energy in the form of 2 ATP molecules, which is not as efficient as the aerobic respiration of glucose, which yields 38 ATP molecules. The byproducts of fermentation, lactic acid or alcohol, can be useful in certain industrial processes, such as the production of yogurt or alcoholic beverages.

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If a nursing mother is not producing enough milk, her hormonal system is probably deficient in prolactin. Prolactin is a hormone produced by the pituitary gland that stimulates milk production in the mammary glands of the breast. When a baby suckles at the breast, nerve impulses are sent to the hypothalamus, which then signals the pituitary gland to release prolactin. Prolactin then stimulates the milk-producing cells in the breast to make and secrete milk. If there is a deficiency in prolactin, there will be a reduction in milk production, which may lead to inadequate milk supply for the baby. Testosterone is a male sex hormone and has no role in milk production. Thyroxin is a hormone produced by the thyroid gland that regulates metabolism, but has no direct role in milk production. Insulin is a hormone produced by the pancreas that regulates blood sugar levels and also has no role in milk production. Therefore, based on the description, if a nursing mother is not producing enough milk, her hormonal system is probably deficient in prolactin.

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The type of reproduction that is common to both Hydra and yeast is budding. Budding is a form of asexual reproduction in which a new individual develops as an outgrowth or bud from the parent organism. In Hydra, budding involves the growth of a new individual from the body of the parent organism, which then separates to become a new, independent organism. In yeast, budding involves the growth of a small protrusion from the parent cell, which then develops into a new, independent cell. Both Hydra and yeast are capable of other forms of reproduction as well. For example, Hydra can also reproduce sexually through the fusion of gametes, while yeast can reproduce through a form of cell division called binary fission. However, the common type of reproduction that is shared between Hydra and yeast is budding.

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Rodents gnaw on food with their chisel-like front teeth. These teeth, called incisors, are specialized for gnawing and chewing. Rodents use them to bite and scrape hard surfaces like wood, bark, and seeds to obtain food or to create tunnels and nests. Their incisors are continuously growing, and gnawing helps wear them down to a manageable length. The other options, molar teeth, strong jaws, and flat-ridged teeth, are also important for grinding and chewing food, but they are not specifically used for gnawing.

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The rods in the retina of the eyes are examples of cells. Cells are the basic unit of life and are the smallest structures that can carry out all of the functions necessary for an organism to survive. The rods are one of two types of specialized photoreceptor cells in the retina that are responsible for detecting light and allowing us to see. Rods are particularly important for vision in low light conditions and for detecting motion. The other type of photoreceptor cell in the retina is called cones, which are responsible for color vision and visual acuity. The rods and cones work together to help us see the world around us.