JAMB UTME - Biology - 2012

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Color blindness is a genetic condition that is usually passed down from a parent to their child. It occurs when there is an issue with the genes that determine the colors that the eyes can see. Typically, the genes for color vision are located on the X chromosome. Since men have only one X chromosome, they are more likely to be color blind than women, who have two X chromosomes. In this scenario, a color-blind man has married a woman who is a carrier of the color blindness gene. This means that she has one normal X chromosome and one X chromosome with the color blindness gene. Each of their children has a 50% chance of inheriting the color blindness gene from their mother. If a child inherits the gene, whether they are male or female, they will have some form of color blindness. If the child does not inherit the gene, they will not have color blindness. Therefore, the probability of their offspring being color-blind is not 0% because the man is already color-blind, but it is also not 100% because the woman is only a carrier and has one normal X chromosome. The correct answer is 50%.

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The developing embryo is usually contained in the part labelled "II". This is because part II, also known as the uterus, is the organ that provides the necessary environment and nutrients for the embryo to develop and grow into a fetus. The uterus has a thick lining called the endometrium, which thickens and prepares for the implantation of the fertilized egg. Once the fertilized egg implants in the endometrium, it receives nourishment and support from the uterus as it develops into an embryo, which eventually becomes a fetus. Therefore, the uterus is the part of the female reproductive system that plays a crucial role in the development of the embryo.

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Countershading is an adaptive feature that enables animals to remain undetected. Countershading is a type of camouflage in which an animal's body is darker on the upper side and lighter on the lower side. This coloration helps to create an optical illusion that makes the animal harder to see in its natural environment. When viewed from above, the darker coloration blends in with the shadows on the ground, while the lighter coloration blends in with the brightness of the sky. When viewed from below, the lighter coloration blends in with the brightness of the water or the sky, while the darker coloration blends in with the shadows on the ground. This type of camouflage is especially useful for animals that live in open environments, such as the ocean or grasslands, where there is little cover to hide behind. By remaining undetected, animals can avoid predation and increase their chances of survival.

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Copper is required in minute quantities for the growth of plants. It is an essential micronutrient that plays a critical role in several plant processes such as photosynthesis, respiration, and the metabolism of carbohydrates and proteins. Despite being required in small amounts, copper deficiency can have a significant impact on plant growth and development. Without enough copper, plants can exhibit stunted growth, wilting, chlorosis (yellowing of leaves), and reduced fertility. In summary, while all of the nutrients listed are important for plant growth, copper is the one that is required in minute quantities for optimal growth and development.

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The polysaccharide among the options listed is cellulose. Carbohydrates are one of the main types of biomolecules in living organisms and they can be classified into three main groups: monosaccharides, disaccharides, and polysaccharides. Monosaccharides are simple sugars that cannot be further broken down into smaller sugars, while disaccharides are formed by two monosaccharides joined by a glycosidic bond. Polysaccharides are complex carbohydrates made up of many monosaccharide units linked together. They can be found in many biological structures, such as cell walls, energy storage molecules, and structural components. Glucose, sucrose, and maltose are all examples of simple sugars, and therefore not polysaccharides. Cellulose, on the other hand, is a polysaccharide that is an important structural component in the cell walls of plants and algae. It is composed of long chains of glucose molecules linked by β-glycosidic bonds, and it provides rigidity and strength to the cell wall.

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Plants that show secondary growth are usually found among the dicotyledons. Secondary growth refers to the increase in girth or thickness of a plant stem or root. It occurs due to the activity of lateral meristems, which produce new cells that differentiate into secondary tissues such as secondary xylem and phloem. These tissues provide mechanical support and conduct water and nutrients throughout the plant. Dicotyledons are a group of flowering plants that have two seed leaves (cotyledons) when they germinate. They typically have a taproot system and their stems show secondary growth, resulting in the formation of a woody stem. This is in contrast to monocotyledons, which have a fibrous root system and lack secondary growth in their stems. Therefore, based on these characteristics, it can be concluded that plants that show secondary growth are usually found among the dicotyledons.

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The diseases caused by water-borne pathogens mainly include typhoid and cholera. When water sources such as rivers, lakes or wells are contaminated with the bacteria or viruses that cause these diseases, they can spread to people who consume the contaminated water or use it for cooking, washing or bathing. Typhoid is caused by the bacterium Salmonella typhi, which is spread through contaminated food or water. Symptoms include fever, headache, stomach pain and diarrhea. Cholera is caused by the bacterium Vibrio cholerae, which is also spread through contaminated food or water. Symptoms include severe diarrhea and vomiting, which can quickly lead to dehydration and even death if left untreated. While other diseases such as tuberculosis and poliomyelitis can also be spread through water-borne pathogens, the most common and well-known ones are typhoid and cholera. It is important to ensure that drinking water is clean and safe to prevent the spread of these and other water-borne diseases.

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Secondary thickening in plants is primarily caused by the activity of the vascular cambium and the cork cambium. The vascular cambium is a layer of cells located between the xylem (the tissue responsible for transporting water and minerals from roots to the rest of the plant) and the phloem (the tissue responsible for transporting sugars and other organic compounds). The vascular cambium produces new cells that increase the diameter of the stem or root, leading to secondary growth and increased thickness. The cork cambium, on the other hand, produces cork cells that form a protective outer layer on the plant. This helps to prevent water loss and protect the plant from damage. Over time, as more cork cells are produced, the plant becomes thicker and more durable. In summary, both the vascular cambium and cork cambium are involved in secondary thickening in plants, with the vascular cambium increasing the diameter of the stem or root and the cork cambium producing a protective outer layer.

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The part in the mammalian male reproductive system that serves as a passage for both urine and semen is the urethra. The urethra is a tube-like structure that connects the urinary bladder to the outside of the body. In males, the urethra passes through the penis and serves as a passage for both urine and semen. During urination, urine travels from the bladder and out through the urethra to be expelled from the body. During ejaculation, semen (which contains sperm and other fluids) travels from the testes and out through the urethra to be expelled from the body. The urethra has a valve-like structure that prevents urine and semen from being expelled at the same time, ensuring that each fluid is expelled separately. Overall, the urethra is an important part of the male reproductive system as it serves as a common passage for both urine and semen to exit the body.

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Fungi are a distinct group of eukaryotic organisms mainly because they lack chlorophyll and therefore cannot perform photosynthesis like plants do. Instead, they obtain their nutrients by absorbing organic matter from their surroundings. Additionally, fungi are characterized by their ability to produce spores, which can be dispersed over long distances by wind or water to colonize new areas. Fungi can also produce fruiting bodies, such as mushrooms, which are used for reproduction. Fungi can reproduce both sexually and asexually, which allows them to adapt to changing environmental conditions and ensure the survival of their species.

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The short, thick beak in birds is an adaptation for crushing seeds. Seeds are a common food source for many birds, and having a strong beak that can crack open the hard outer shell allows them to access the nutritious interior. This type of beak is called a "crushing beak" or "seed crusher beak."

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Of the given options, it is likely that desert dwellers are the animals that can exist solely on the water they get from food and metabolic reactions. This is because desert environments are characterized by extreme aridity, with very little water available. As a result, many desert-dwelling animals have adaptations that allow them to obtain water from their food or through metabolic processes, rather than relying on external sources of water. For example, some desert animals may have very efficient kidneys that enable them to extract the maximum amount of water from their urine. Others may have specialized diets that allow them to obtain water from the food they eat, such as cacti that store water in their tissues. Some animals may also have adaptations that allow them to produce metabolic water, which is generated through the breakdown of food molecules. In contrast, forest arboreal dwellers, forest-ground dwellers, and rainforest dwellers generally have access to more water than desert dwellers, as these environments tend to be more humid and have greater amounts of precipitation. As a result, animals in these environments are less likely to have evolved specialized adaptations for obtaining water from their food or metabolic processes.

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Plant growth can be artificially stimulated by the addition of gibberellin. Gibberellin is a type of plant hormone that plays a role in promoting cell division and elongation, leading to an increase in plant height and overall growth. Gibberellin can also stimulate the production of flowers and fruits, and has been used commercially to increase yields in crops. By adding gibberellin to a plant, farmers and horticulturists can promote faster and more abundant growth, leading to improved crop production.

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The feature that links birds to reptiles in evolution is the possession of scales. Scales are bony or horny plates that cover the skin of reptiles and birds. Although birds have feathers, which are not found in reptiles, both birds and reptiles evolved from a common ancestor that had scales. Over time, some descendants of this common ancestor evolved feathers for various reasons, such as insulation, flight, or display, while others retained scales or evolved other adaptations. Thus, the possession of scales is a shared ancestral trait that helps to connect birds and reptiles in the tree of life.

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Agama lizards bask in the sun primarily to raise their body temperature and become more active. Like other reptiles, Agama lizards are cold-blooded and depend on external sources of heat to regulate their body temperature. By basking in the sun, they absorb heat and warm up their bodies, which allows them to become more active and better able to carry out essential activities such as foraging and hunting. While basking, Agama lizards may also change the color of their body, but this is a secondary function and not the primary reason for their behavior. The change in color is due to the movement of pigment cells in their skin, which respond to changes in temperature, light, and other environmental factors. Basking in the sun does not directly help Agama lizards fight to defend their territories or attract females for courtship. These are behaviors that are usually associated with male Agama lizards, who may engage in territorial displays and physical combat to establish dominance over their rivals and attract females. However, basking in the sun can indirectly support these behaviors by helping the lizards stay active and alert, which can give them an advantage in territorial disputes and courtship rituals.

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A plant structure that lacks a waterproof cuticle is the root. The cuticle is a waxy layer that covers the outer surface of leaves and stems in plants, which helps to prevent water loss. However, roots are usually buried in soil, and they do not need a cuticle to prevent water loss since soil provides moisture to the roots. In fact, roots often have tiny root hairs that increase their surface area for absorbing water from the soil. Therefore, roots do not have a waterproof cuticle like leaves and stems.

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Cockroach is most advanced in the evolutionary trend of animals among the given options. Evolutionary advancement in animals is a complex topic that involves several factors such as the development of complex organ systems, locomotion, sensory abilities, and other adaptations that allow animals to survive and thrive in their environments. Out of the given options, cockroaches are the most advanced in terms of evolutionary trend because they possess several characteristics that have allowed them to adapt and survive for over 300 million years. Cockroaches have a complex nervous system that allows them to sense their environment and respond to stimuli quickly. They have the ability to fly or run very quickly, which is a valuable adaptation for escaping predators. Furthermore, cockroaches have a hard exoskeleton that protects them from physical harm and desiccation. They also have the ability to live in a variety of environments, including human dwellings, which has contributed to their evolutionary success. In contrast, liver flukes, earthworms, and snails, while important organisms in their respective ecosystems, do not possess the same level of evolutionary advancement as cockroaches. Liver flukes are parasitic flatworms that have a simple body plan, while earthworms and snails have a more complex body plan, but lack some of the advanced adaptations of cockroaches. Therefore, based on these characteristics, it can be concluded that cockroach is most advanced in the evolutionary trend of animals among the given options.

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The lowest category of classification is species. In biology, organisms are classified based on their shared characteristics into a hierarchical system of groups, or taxa. The hierarchy of taxa, from the broadest to the most specific, is as follows: kingdom, phylum, class, order, family, genus, and species. Species is the most specific and lowest level of classification. It refers to a group of organisms that share common characteristics and can interbreed to produce fertile offspring. Each species is given a unique scientific name, consisting of two parts: the genus and species name. For example, Homo sapiens is the scientific name for humans, with "Homo" being the genus and "sapiens" being the species.

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The site of ultrafiltration in the kidney of mammals is Bowman's capsule. Bowman's capsule is the first part of the nephron, which is a microscopic structure responsible for filtering blood and producing urine. Blood enters the nephron through a tiny blood vessel called the afferent arteriole, which leads into the glomerulus, a network of capillaries surrounded by Bowman's capsule. As blood flows through the glomerulus, small molecules such as water, salts, and waste products are forced out of the blood vessels and into the capsule by a process called ultrafiltration. This filtered fluid, known as glomerular filtrate, then passes through the rest of the nephron, where additional filtering and processing takes place to produce urine.

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The presence of stilt roots, pneumatophores, sunken stomata, and salt glands are all adaptive features of plants found in mangrove swamps. Mangrove swamps are unique ecosystems found in tropical and subtropical regions where land meets the sea. These areas are characterized by fluctuating tidal levels, high salinity, and low oxygen levels, making them a challenging environment for most plants to survive in. Plants in mangrove swamps have evolved several adaptations to survive in these conditions. Stilt roots, for example, are long, thin roots that help anchor the plant in the soft, muddy substrate and allow it to remain stable during periods of high tidal currents. Pneumatophores, on the other hand, are specialized aerial roots that extend above the waterline and allow the plant to exchange gases with the atmosphere, ensuring that the root system remains oxygenated. Sunken stomata are another adaptation found in mangrove plants. Stomata are the small pores on the surface of leaves that allow for gas exchange. In mangroves, these stomata are located on the underside of the leaves, which helps to reduce water loss through transpiration in the high humidity environment of the mangrove swamp. Finally, mangrove plants also have salt glands, which are specialized structures located on the surface of the leaves that allow the plant to excrete excess salt. This is important because the high salt content of the water and soil in the mangrove swamp can be toxic to many plant species. Overall, these adaptations allow mangrove plants to survive and thrive in the challenging conditions of the mangrove swamp ecosystem.

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Organisms living in an estuarine habitat are adapted to withstand wide fluctuations in salinity. An estuary is a partially enclosed body of water where freshwater from rivers and streams meets and mixes with saltwater from the ocean. As a result, the salinity (salt content) of the water in an estuary can vary widely, ranging from almost fresh to fully marine. Organisms that live in estuaries have to be adapted to these changing conditions in order to survive. For example, some estuarine organisms have mechanisms to regulate the amount of salt in their bodies, such as by excreting excess salt or retaining more water. Others may be able to tolerate a range of salinities, but still need time to adjust to rapid changes in salinity. In addition to salinity, estuarine organisms may also need to cope with other environmental stresses, such as wide fluctuations in temperature, changing levels of dissolved oxygen, and variable nutrient availability. However, their ability to withstand changes in salinity is a key adaptation that allows them to live in this unique and challenging habitat.

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The use and disuse of body parts and the inheritance of acquired traits were used to explain Lamarck's theory of evolution. Lamarck's theory of evolution was proposed before Darwin's theory and it proposed that acquired characteristics can be passed down from one generation to another. For example, if a giraffe stretches its neck to reach higher leaves, then its neck will become longer and this acquired trait can be passed down to its offspring. This theory also proposed that the disuse of body parts could lead to the loss of those characteristics in the offspring. However, Lamarck's theory was later disproven by scientific evidence and replaced by Darwin's theory of evolution, which proposed that evolution occurs through natural selection and the survival of the fittest. Darwin's theory explained that random genetic mutations occur, and the individuals with favorable mutations are more likely to survive and pass on their genes to their offspring, while those with unfavorable mutations are less likely to survive and reproduce. In summary, the use and disuse of body parts and the inheritance of acquired traits were used to explain Lamarck's theory of evolution, which was later disproven and replaced by Darwin's theory of evolution based on natural selection.

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Out of the four options, only the whale possesses mammary glands. Mammary glands are a defining characteristic of mammals and are responsible for producing milk to nourish their offspring. While all four animals are vertebrates, not all vertebrates are mammals. Mammals are a group of animals characterized by the presence of hair or fur, the ability to regulate their body temperature internally, and the presence of mammary glands. Dogs, cats, whales, and sharks are all different types of vertebrates, but only whales are mammals and possess mammary glands. Dogs, cats, and sharks are all examples of non-mammalian vertebrates. While they may produce some form of nourishment for their young, it is not produced by mammary glands. Catfish, on the other hand, are a type of fish and do not produce milk or any other form of nourishment for their young beyond their initial supply of yolk sac nutrients.

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An indigenous method of renewing and maintaining soil fertility is by crop rotation and shifting cultivation. This method involves growing different crops on the same land in a rotating pattern, rather than planting the same crop year after year. This helps to maintain soil fertility because different crops have different nutrient requirements. Growing different crops also helps to reduce soil erosion, as some crops have roots that hold the soil in place, while others have leaves that protect the soil from the sun and wind. Additionally, shifting cultivation involves moving from one plot of land to another, allowing the previously farmed land to lie fallow and recover its fertility. This method is often used in traditional agricultural systems and can be an effective way to maintain soil fertility and productivity for future generations.

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The most likely first colonizers of a bare rock are lichens. Lichens are a symbiotic relationship between a fungus and an alga or a cyanobacterium. They are well adapted to grow on bare rocks and can tolerate extreme temperatures, high radiation, and minimal nutrients. Lichens are capable of breaking down the rock surface through a process called chemical weathering. The acids produced by the lichen can dissolve minerals in the rock and create small crevices where organic matter can accumulate. These crevices provide a habitat for other organisms like mosses and ferns. Over time, as mosses and ferns establish themselves on the rock surface, they can trap more organic matter and create soil. This soil provides a better environment for larger plants like shrubs and trees to grow. In summary, lichens are the most likely first colonizers of a bare rock due to their ability to tolerate extreme conditions and break down the rock surface. As they create small crevices, other organisms like mosses and ferns can establish themselves, leading to the development of soil and the growth of larger plants.

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The water cycle, also known as the hydrological cycle, is maintained by the processes of evaporation, condensation, and precipitation. Water from oceans, lakes, rivers, and other bodies of water evaporates due to the sun's heat. This water vapor then rises into the atmosphere, where it cools and condenses to form clouds. As these clouds become heavier, the condensed water droplets fall back to the earth as precipitation in the form of rain, snow, sleet, or hail. Some of this precipitation infiltrates the ground to replenish groundwater supplies, while the rest flows over the land into rivers, lakes, and oceans, completing the cycle. Therefore, the water cycle is maintained mainly by the processes of evaporation and condensation of water in the environment, which constantly move water between the earth's surface and the atmosphere.

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