JAMB UTME - Biology - 2009

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According to Charles Darwin's theory of evolution, the driving force behind evolutionary change is natural selection. Natural selection is the process by which certain traits become more or less common in a population over time, based on their ability to help individuals survive and reproduce in a given environment. Those individuals with advantageous traits are more likely to survive and pass on those traits to their offspring, while those with less advantageous traits are less likely to survive and reproduce. Over time, this can lead to significant changes in the characteristics of a population, ultimately resulting in evolution.

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Chewing the cud is an adaptation peculiar to ruminants. Ruminants, such as cows, sheep, and goats, have a four-chambered stomach that allows them to digest tough plant material. After the food is swallowed, it is initially stored in the rumen, the largest chamber of the stomach. The food is then regurgitated back into the mouth, where it is chewed again before being swallowed and passed into the other chambers of the stomach. This process of regurgitation and re-chewing of food is known as "chewing the cud" or "ruminating." It allows ruminants to break down tough plant material more effectively by increasing the surface area of the food and allowing more thorough digestion by the bacteria in the stomach. Chewing the cud is a unique adaptation that allows ruminants to extract as much nutrition as possible from their food and survive on a diet of tough plant material. It is not found in other types of animals such as omnivores, herbivores, or rodents.

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In plants, the structures that play roles similar to the arteries and veins of animals are the "xylem and phloem". Xylem and phloem are two types of specialized plant tissues that transport water, nutrients, and other substances throughout the plant. The xylem is responsible for transporting water and minerals from the roots to the leaves of the plant, while the phloem transports the products of photosynthesis, such as sugars, from the leaves to other parts of the plant. The xylem and phloem tissues are often arranged together in a structure called a vascular bundle, which can be thought of as similar to blood vessels in animals. Therefore, xylem and phloem are the structures that play roles similar to the arteries and veins of animals in plants.

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The axial skeleton is found in the skull, ribs, vertebral column, and breastbone. These are the central parts of the skeleton that form the body's longitudinal axis. The skull is the bony structure that forms the head and protects the brain. The ribs are curved bones that protect the chest and vital organs such as the heart and lungs. The vertebral column, also known as the spine, is a series of vertebrae that run from the base of the skull to the pelvis, providing support for the body and protecting the spinal cord. The breastbone, or sternum, is a long, flat bone in the center of the chest that forms part of the rib cage. Together, these bones provide support and protection for the body's vital organs, as well as giving structure to the body and allowing for movement. The axial skeleton also serves as an attachment point for muscles and helps to distribute weight and maintain balance.

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The ability to roll the tongue is a dominant genetic trait, while the inability to roll the tongue is a recessive trait. In this case, the woman is heterozygous for the tongue rolling gene (Tt), meaning she has one dominant and one recessive allele, while the man is homozygous recessive (tt). When these two individuals have children, each child receives one allele from each parent. Therefore, there are four possible combinations of alleles for each child: TT, Tt, tT, and tt. However, the tT combination is equivalent to Tt, so the only three possible combinations are TT, Tt, and tt. If a child inherits a dominant T allele from the mother, they will be a tongue roller, regardless of whether they inherit a dominant or recessive allele from the father. Therefore, there is a 50% chance that each child will inherit a T allele from the mother and be a tongue roller. The other 50% chance is that the child will inherit a recessive t allele from both parents and not be able to roll their tongue. Therefore, the probability of each of their children being a tongue roller is 50%, and the answer is 50%.

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One health condition that is known to have resulted from gene mutation is sickle-cell anemia. It is an inherited blood disorder that affects the red blood cells in the body. Sickle-cell anemia is caused by a mutation in the gene that codes for hemoglobin, a protein found in red blood cells that carries oxygen. The mutation causes the hemoglobin molecules to stick together and form long, rigid structures that distort the shape of the red blood cells. These distorted cells can block blood vessels, reducing the flow of oxygen to vital organs and causing pain, fatigue, and other complications. Sickle-cell anemia is an example of a genetic disorder that is caused by a mutation in a single gene. It is most common in people of African descent, but can also affect people of Hispanic, Middle Eastern, and Mediterranean ancestry. While there is currently no cure for sickle-cell anemia, treatment options are available to help manage the symptoms and complications of the disease.

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The diagram is a graph showing the growth of an organism at different temperatures. The x-axis represents temperature in degrees Celsius, and the y-axis represents growth rate. The highest point on the graph represents the optimum temperature for the growth of the organism. Based on the graph, the optimum temperature for the growth of the organism appears to be around 50oC. At this temperature, the growth rate of the organism is highest. At temperatures lower or higher than this optimum temperature, the growth rate of the organism decreases. Therefore, the answer to the question is 50oC.

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In insects, the structures that perform the same function as the kidney in humans is the "malphigian tubule". Malphigian tubules are a type of excretory organ in insects that are responsible for removing metabolic waste and excess water from the body. These tubules function by actively transporting waste products from the insect's blood into the tubules, where they are mixed with digestive enzymes and excreted as solid waste. This is similar to the function of kidneys in humans, which filter waste and excess water from the blood and excrete it as urine. Therefore, malphigian tubules are the structures in insects that perform the same function as the kidney in humans.

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The feature that makes locomotion in water easy for fish is their streamlined body shape. This means that their body is long and thin, with a pointed head and tapered tail, allowing them to move through the water with minimal resistance. This streamlined body shape helps reduce drag, which is the force that resists motion through a fluid, making it easier for fish to swim efficiently. In addition, some fish have a lateral line, which is a sensory system that detects changes in water pressure and helps fish navigate and locate prey. The scaly and slimy bodies of fish also provide protection and help reduce friction as they move through the water, but they are not as essential to fish locomotion as their streamlined body shape.

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The major cause of global warming is the burning of fossil fuels. Fossil fuels like coal, oil, and natural gas are burnt to produce energy for electricity, transportation, and other human activities. This process releases large amounts of greenhouse gases, particularly carbon dioxide, into the atmosphere. These gases trap heat from the sun, causing the Earth's temperature to rise, resulting in global warming. The other options mentioned, such as construction of dams, use of electricity, and exploration of space, do not have as significant an impact on global warming as burning of fossil fuels.

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In the diagram, the likely pollinating agent of the flower is an insect. The flower in the diagram is brightly colored and has a sweet scent. These are adaptations that attract insects such as bees, butterflies, and moths, which are important pollinators of many flowers. As insects feed on the nectar of the flower, they inadvertently pick up and transfer pollen from the anthers to the stigma, which fertilizes the flower and allows it to produce seeds. In contrast, wind and water pollination are more common in plants with small, inconspicuous flowers that do not produce nectar or have a scent. Man-made pollination techniques, such as hand-pollination or artificial insemination, may also be used in some cases, but are less likely to occur in natural ecosystems.

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The biomass that can be characterized by very low rainfall, cold nights, hot days, and fast blooming plants is the tropical desert. The tropical desert is a type of biome characterized by low precipitation (less than 250mm per year), high temperature, and dry soil. The vegetation in this region is sparse, and the plants are adapted to survive in the harsh environment by having shallow roots, small leaves, and thorns. The biomass in this region is dominated by cacti, succulents, and other drought-tolerant plants.

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In a cell, the genes are carried by chromatin threads. Chromatin is a complex of DNA and proteins that forms the chromosomes within the nucleus of a cell. The genes, which are sections of DNA that code for specific proteins, are organized within the chromatin threads. Therefore, the chromatin threads are responsible for carrying the genes that determine the traits and characteristics of an organism.

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Bladderwort is an example of a carnivorous plant. Bladderwort has tiny traps that it uses to capture and digest small aquatic organisms like protozoa, crustaceans, and even small fish. The plant has small bladders on its leaves that act as a vacuum trap. When an organism touches the trigger hairs on the bladders, they are sucked in and the trapdoor snaps shut. The bladder then uses digestive enzymes to break down the prey and absorb the nutrients.

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A phenotypic character with intermediate forms that can be graded from one extreme to the other is referred to as **continuous variation**. Continuous variation refers to the variation in a trait that can take on a range of values between two extremes. For example, height in humans is a trait that shows continuous variation, with individuals ranging from very short to very tall, and many intermediate heights in between. This is in contrast to discontinuous variation, which refers to traits that fall into distinct categories, such as blood type or the ability to roll one's tongue.

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The part of the alimentary system of a bird where food is ground into small particles is the gizzard. The gizzard is a muscular, thick-walled part of the bird's stomach that grinds food with the help of small stones and grit that the bird has swallowed. The muscles of the gizzard contract and relax rhythmically to mix and grind the food, breaking it down into small particles that can be further digested and absorbed. The gizzard is an important adaptation for birds that consume hard-shelled seeds or insects with tough exoskeletons.

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To determine the percentage of water in the soil sample, we need to first calculate the mass of dry soil in the sample. This can be done by subtracting the mass of the empty crucible from the mass of the crucible and soil after heating: Mass of dry soil = Mass of crucible and soil before heating - Mass of crucible and soil after heating Mass of dry soil = 29g - 18g Mass of dry soil = 11g Next, we can calculate the mass of water in the soil sample by subtracting the mass of dry soil from the initial mass of the sample: Mass of water = Mass of crucible and soil before heating - Mass of dry soil Mass of water = 29g - 11g Mass of water = 18g Finally, we can calculate the percentage of water in the sample by dividing the mass of water by the initial mass of the sample and multiplying by 100: Percentage of water = (Mass of water / Mass of crucible and soil before heating) x 100% Percentage of water = (18g / 29g) x 100% Percentage of water = 62.07% Therefore, the percentage of water in the given soil sample is approximately 62.07%. None of the answer options provided match this value exactly, so the closest option would be 50%.

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The specialized pigment cells that are involved in colouration and colour change in animals are called chromatophores. Chromatophores are cells that contain pigments, such as melanin, xanthophylls, and carotenoids, that can change the color of the cell and therefore the color of the animal. Chromatophores are responsible for the coloration and patterns seen in many animals, such as chameleons, octopuses, and some fish. The chromatophores can contract and expand, causing the pigments to become more or less visible. This allows the animals to rapidly change color and blend in with their surroundings, communicate with other animals, and even display their emotions. While xanthophylls, melanin, and other pigments are involved in coloration, it is the specialized cells known as chromatophores that enable color change and control the appearance of the animal's skin or fur.

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The function of the correcting lens is to converge incoming rays. A lens is a curved piece of glass that can bend or refract light. When light passes through a convex (converging) lens, it is bent inward, causing the rays to converge at a point called the focal point. In the diagram, the correcting lens is a convex lens that is placed after the object and before the image. Its purpose is to converge the rays that have been diverged by the previous lens so that the final image is formed correctly. By bringing the diverging rays back together, the correcting lens helps to produce a clear and sharp image for the viewer.

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The most important ecological factor in a terrestrial environment is "soil". Soil is a critical component of terrestrial ecosystems because it provides a medium for plants to grow and obtain nutrients, which in turn supports the food chain for animals that depend on plants. Soil quality affects plant growth and determines the availability of nutrients and water for plants. It also plays an important role in regulating the carbon cycle and contributes to climate change. Soil is affected by many factors, including climate, topography, and the presence of microorganisms. Therefore, soil is the most important ecological factor in a terrestrial environment, as it supports the growth of plants and influences the functioning of entire ecosystems.

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The reproductive system of a male mammal is made up of the testes, prostate gland, sperm duct, and vas deferens. The testes are the primary reproductive organs responsible for producing sperm cells and the male sex hormone, testosterone. They are located outside the body within the scrotum to maintain a lower temperature that is optimal for sperm development. The prostate gland is a small gland located below the bladder, which produces a fluid that is a component of semen. This fluid helps to nourish and transport the sperm cells. The sperm ducts are muscular tubes that transport sperm cells from the testes to the prostate gland, where they are mixed with other fluids to form semen. The vas deferens is a duct that connects the sperm ducts to the urethra, which is the tube that carries semen and urine out of the body through the penis. Claspers are not part of the male mammal reproductive system, but rather a specialized structure found in some fish and reptiles to aid in mating. The oviduct is part of the female reproductive system and is responsible for carrying eggs from the ovaries to the uterus. Finally, the uterus is also part of the female reproductive system, responsible for carrying a fertilized egg and providing nutrients for fetal development.

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Plants that grow in an area that is neither too wet nor too dry are called mesophytes. Mesophytes are plants that prefer moderate levels of moisture and can tolerate average humidity levels. These plants are adapted to environments with consistent rainfall or access to water through other means, such as rivers or underground aquifers. Mesophytes can be found in a variety of habitats, including forests, grasslands, and wetlands. In contrast, xerophytes are plants that have adapted to dry environments, hydrophytes grow in water, and epiphytes grow on other plants. These plants have specialized adaptations to help them survive in their specific habitats. For example, xerophytes often have small leaves, thick cuticles, and deep root systems to conserve water. Epiphytes have adapted to growing on other plants by obtaining water and nutrients from the air and rain, while hydrophytes have adaptations such as air spaces in their tissues to help them float in water. Therefore, if the area is neither too wet nor too dry, and has moderate levels of moisture, the plants growing in it are most likely mesophytes.

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The correct sequence of blood flow from the heart to a tissue is: Heart → Artery → Arteriole → Tissue Blood is pumped from the heart into the arteries, which are muscular blood vessels that carry oxygenated blood away from the heart and into the arterioles, which are smaller blood vessels that regulate blood pressure and flow to the tissue. Finally, the arterioles lead to the capillaries, where the exchange of oxygen, nutrients, and waste products occurs between the blood and the tissue cells.

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The part of a domestic fowl responsible for preventing heat loss is the down feather. Down feathers are the soft, fluffy feathers found underneath the contour feathers, and they provide insulation to keep the bird warm by trapping heat close to the body.

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The theory that explains a farmer's assumption that the seed from a good harvest will produce a good yield is the theory of "heredity." This theory explains that traits and characteristics are passed down from one generation to another through genes. In this case, the farmer assumes that the good traits that led to a bountiful harvest will be passed down to the next generation of crops, resulting in a good yield.

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The association between bacteria residing in the caecum and the ruminant is mutualism. Ruminants, such as cows, sheep, and goats, have a complex digestive system that allows them to break down tough plant materials. They have a four-chambered stomach, with the largest chamber being the rumen, which is a large fermentation vat where bacteria and other microorganisms break down cellulose and other complex carbohydrates. The caecum is a pouch at the beginning of the large intestine, where undigested food is further broken down by bacteria. In ruminants, the caecum plays an important role in the digestion of cellulose and other plant materials. The bacteria in the caecum help to break down these materials into simpler compounds that can be absorbed by the ruminant's body. In return for providing a place for these bacteria to live and reproduce, ruminants benefit from the breakdown of plant material into nutrients that they can use for energy and growth. This mutualistic relationship between the bacteria and the ruminant is essential for the survival and health of both organisms.

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The content of the part labelled "III" is usually acidic. In the diagram, "III" refers to the stomach, which is a part of the digestive system. The stomach is a muscular sac that contains digestive enzymes and hydrochloric acid. The acid helps to break down food and kill any harmful bacteria that may be present. The pH level of the stomach acid is usually between 1.5 and 3.5, which is highly acidic. This acidic environment is necessary for the proper digestion of food and the absorption of nutrients. Therefore, the content of the stomach is usually acidic.

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A marine protozoan is likely to have no contractile vacuole mainly because the cytoplasm is isotonic to seawater. A contractile vacuole is an organelle found in some protozoa that is responsible for regulating the water content of the cell. It does this by pumping excess water out of the cell, which helps the organism maintain its shape and avoid bursting. However, marine protozoa live in an environment where the concentration of salt and other dissolved ions is similar to that of their cytoplasm. This means that they are already in a state of equilibrium with their surroundings and do not need to actively regulate their water content. As a result, marine protozoa are less likely to have a contractile vacuole than freshwater protozoa, which live in an environment that is hypotonic to their cytoplasm and constantly take up water by osmosis.

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Alternation of asexual modes of reproduction is found in ferns. Ferns exhibit alternation of generations, meaning they alternate between a haploid gametophyte generation and a diploid sporophyte generation. The gametophyte generation produces haploid gametes (eggs and sperm) through asexual reproduction, while the sporophyte generation produces spores through meiosis. The spores then grow into the gametophyte generation, and the cycle continues.

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In a bean seed, absorption of water at the beginning of germination is through the micropyle. The micropyle is a small opening in the seed coat that allows water to enter the seed. During the early stages of germination, the seed takes in water through this opening to initiate the metabolic processes that lead to growth. The water absorbed through the micropyle softens the seed coat, allowing the embryo inside to expand and break through the seed coat. The embryo then develops into the seedling, and the nutrients stored in the seed provide the initial energy for the plant to grow until it can photosynthesize on its own. While the hilum is the scar on the seed where it was attached to the parent plant, the testa is the outer seed coat, and the plumule is the embryonic shoot that emerges from the seed during germination. However, neither the hilum nor the testa nor the plumule are involved in the absorption of water at the beginning of germination in the bean seed.

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In fresh water marshes and swamps, the most important abiotic factor that organisms have to adapt to is the nature of substratum. The substratum is the bottom surface of the water body, which can be made up of mud, sand, rocks, or other materials. Organisms living in marshes and swamps have to adapt to the nature of the substratum because it affects their ability to find food, hide from predators, and anchor themselves in place. For example, plants growing in mud substratum have to develop specialized root systems to anchor themselves and obtain nutrients. Animals that live in sandy substratum have to be adapted for burrowing, while those that live among rocks have to be adapted for clinging and gripping. In contrast, factors such as high salinity, high temperature, and low pH are more common in marine and aquatic ecosystems, and may not be as important in freshwater marshes and swamps.

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The level of organization of an onion bulb is an organ. An organ is a group of different tissues that work together to perform a specific function. In the case of an onion bulb, it is an underground storage organ composed of layers of fleshy leaves that store nutrients and water for the growth of the plant. Therefore, an onion bulb is considered an organ because it is made up of different types of tissues (e.g., protective epidermal tissue, storage parenchyma tissue) that work together to carry out the specific function of storage.