JAMB UTME - Biology - 1997

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The substance responsible for optical dominance in plants is auxin. Auxin is a plant hormone that plays a crucial role in the growth and development of plants, including the regulation of plant cell elongation, apical dominance, and phototropism. Apical dominance refers to the phenomenon whereby the terminal bud of a plant inhibits the growth of lateral buds, resulting in the vertical growth of the plant. Auxin is produced in the apical meristem of the plant and is transported downward through the stem.

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If both parents have the sickling trait, they each carry one copy of the sickle cell gene (HbS) and one copy of the normal hemoglobin gene (HbA). When they have children, each parent randomly passes on one of their two copies of the hemoglobin gene to their offspring. There are four possible combinations of genes that their children can inherit from the parents: HbA/HbA (normal), HbA/HbS (sickle trait), HbS/HbA (sickle trait), and HbS/HbS (sickle cell anemia). The probability of having a normal child is therefore 1/4, as only one out of the four possible gene combinations will result in a normal child (HbA/HbA).

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To survive in the environment of its predator, a prey should develop camouflage, well developed limbs and effective vision. Camouflage helps the prey to blend into its surroundings and remain undetected by the predator, while well developed limbs help it to escape quickly and effectively. Effective vision enables the prey to detect the presence of the predator from a distance and take necessary actions to escape. Showy colours, big body, well developed muscles, and acute sense of smell may not be effective in helping the prey to survive the environment of its predator, as they may attract the attention of the predator, making the prey an easy target.

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The most effective way of controlling guinea worm is by providing portable drinking water. Guinea worm is a waterborne parasitic disease that is transmitted through contaminated drinking water. The larvae of the guinea worm enter the human body when infected water is consumed, and eventually grow into mature worms that can be up to 3 feet long. Providing clean, safe drinking water to affected communities can break the cycle of transmission and prevent new cases of the disease. Other interventions such as treating infected individuals and raising awareness through public enlightenment campaigns can also be helpful, but providing clean water is the most effective way to control the spread of guinea worm.

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The term "sex-linked" refers to genes that are located on the sex chromosomes (X and Y). In humans, females have two X chromosomes (XX) while males have one X and one Y chromosome (XY). Therefore, any gene located on the X chromosome will be present in two copies in females and only one copy in males. Out of the options given, albinism is not sex-linked. It is caused by a mutation in a gene on chromosome 11 and is inherited in an autosomal recessive manner. This means that both parents must carry a copy of the mutated gene for their child to inherit the condition. On the other hand, baldness, haemophilia, and colour blindness are all sex-linked conditions. Male-pattern baldness is caused by a gene on the X chromosome, while haemophilia and colour blindness are caused by genes located on the X chromosome. As a result, these conditions are more common in males than in females and can be inherited differently depending on the sex of the parent carrying the mutated gene.

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The group of insects that undergoes complete metamorphosis is the one that includes houseflies, beetles, and butterflies. Complete metamorphosis is a process that involves four distinct stages: egg, larva, pupa, and adult. Insects that undergo complete metamorphosis have a larval stage that looks very different from the adult stage, and they go through a pupal stage during which they transform into the adult form. Houseflies, beetles, and butterflies all undergo complete metamorphosis. Housefly larvae are known as maggots, while beetle larvae are called grubs. Butterfly larvae are commonly known as caterpillars. These larvae look very different from their adult counterparts and go through a pupal stage before emerging as adults.

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Trace elements are required by plants mainly for the formation of pigments and enzymes. These elements, such as iron, zinc, copper, and manganese, are essential micronutrients that are required in small amounts for the growth and development of plants. They play a crucial role in various biological processes, including photosynthesis, respiration, and the synthesis of proteins and other important molecules. Without these trace elements, plants may develop deficiencies that can lead to stunted growth, reduced yields, and even death.

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Water loss is regulated in plants and animals by both the leathery cuticle and the feathers/skin. The leathery cuticle is a waxy layer covering the surface of leaves that helps reduce water loss in plants by limiting evaporation. Feathers and skin in animals serve a similar purpose, helping to reduce water loss by creating a barrier between the animal and the environment. Additionally, animals regulate water loss through various physiological mechanisms such as sweating and panting, while plants regulate water loss through stomata, tiny pores on the leaves that can open and close to control water loss.

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In ferns, the sporophyte is diploid and independent of the gametophyte. This means that the sporophyte, which is the dominant phase in the fern life cycle, is a separate and distinct organism from the gametophyte. It develops from a fertilized egg (zygote) produced by the fusion of haploid gametes. The sporophyte is responsible for producing spores through a process called meiosis, which are then released into the environment and can grow into new gametophytes. The gametophyte is a small, independent, and short-lived phase that produces gametes through mitosis, which then fertilize to form the diploid zygote. The fern life cycle is an example of alternation of generations, where two distinct phases, gametophyte and sporophyte, alternate in a regular pattern.

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The process that can best be used to determine the relative amounts of the different soil particles in a soil sample is sedimentation. Sedimentation is the process by which soil particles settle to the bottom of a container due to the force of gravity. The different soil particles settle at different rates, depending on their size, shape, and density. By allowing the soil sample to settle for a specific amount of time and then measuring the depth of each layer of settled particles, the relative amounts of sand, silt, and clay in the soil can be determined. This information is important in assessing the quality and potential use of the soil.

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Oozing out of water from the leaves of plants in a humid environment is known as guttation. Guttation occurs when the roots of a plant absorb more water than the plant can transpire through its leaves. The excess water pressure forces water out of special pores called hydathodes, located on the tips or edges of leaves. The water that is exuded through these pores can contain sugars, amino acids, and minerals dissolved in it. Guttation usually occurs in plants during the night or early morning when the humidity is high and the soil is moist.

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Viruses differ from all forms of life because they require other living cells to multiply. Unlike living organisms that can reproduce on their own, viruses need a host cell to reproduce and multiply. They invade host cells and take over their machinery to produce more viruses, which ultimately kills the host cell. While viruses can cause infectious diseases, they do not have a thick cell wall, nor do they feed on waste products of other organisms, further distinguishing them from living organisms.

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Sudan III solution is used to detect the presence of fats in food substances. When a few drops of Sudan III solution are added to a food substance and a red coloration is obtained, it indicates the presence of fats in the food. Therefore, the food substance tested in this scenario contains fat.

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The long neck in giraffes is used to illustrate the theory of natural selection. According to this theory, individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring. In the case of giraffes, those with longer necks were better able to reach high leaves for food, and therefore had a greater chance of survival and reproduction. Over time, this led to the development of longer necks in giraffes through natural selection.

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The most important pollutant of the marine environment in Nigeria is oil. Nigeria is a major oil-producing country, and oil spills from oil exploration, transportation, and processing activities have caused significant damage to the marine environment. These oil spills release toxic chemicals and pollutants into the water, affecting marine life, ecosystems, and the livelihoods of people who depend on the sea for their sustenance. In addition to oil spills, other pollutants such as sewage, insecticides, and inorganic fertilizers can also contribute to marine pollution, but the impact of oil spills is considered to be the most significant in Nigeria.

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Annelids differ from nematodes because they possess a metamerically segmented body, which means their body is divided into numerous similar segments. On the other hand, nematodes do not have segmented bodies. Annelids also possess a complete digestive system, which means they have a mouth and an anus, whereas nematodes have a tubular digestive system with only one opening, which serves both as mouth and anus. Although both annelids and nematodes are bilaterally symmetrical and triploblastic, these characteristics are not the primary features that differentiate them from each other.

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The element that is essential for the coagulation of blood is calcium. Calcium plays a crucial role in blood coagulation by activating several enzymes and proteins that ultimately lead to the formation of a clot. Without calcium, the blood would not be able to clot properly, which could result in excessive bleeding. Potassium, phosphorus, and iron are also important minerals for the human body, but they do not play a direct role in blood coagulation.

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Coconut and oil palm fruits can be grouped as drupes. A drupe is a type of fruit that has a fleshy outer layer (exocarp), a hard pit or shell (endocarp) surrounding the seed, and a middle layer of flesh (mesocarp). Examples of other drupe fruits include peaches, plums, cherries, and mangoes. In the case of coconut and oil palm fruits, the hard shell (endocarp) is what we commonly refer to as the "coconut shell" or "palm kernel". Inside this shell, there is a layer of flesh (mesocarp) and a seed or nut (endocarp) that is often used to produce oil.

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The statement is incorrect. The appendicular skeleton is composed of the bones of the limbs and the girdles that attach the limbs to the axial skeleton. The pectoral girdle, consisting of the scapula and clavicle, is part of the appendicular skeleton, but it only makes up a small portion of it. The rest of the appendicular skeleton includes the pelvic girdle and the bones of the forelimbs and hindlimbs. Therefore, the correct option is "pelvic girdle, fore and hind limbs."

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The youngest plant tissue is meristem. Meristem is a type of tissue in plants consisting of undifferentiated cells that can divide to produce new cells. These new cells can differentiate into any other type of plant cell, including those found in the other tissues mentioned (phloem, epidermis, xylem). Therefore, meristem is the starting point for the growth of new plant tissues and organs.

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During binary fission in lower organisms, the nucleus undergoes mitosis. Mitosis is the process of cell division where a single cell divides into two identical daughter cells, each containing a copy of the original cell's DNA. In binary fission, the cell replicates its DNA and then divides into two daughter cells, each with a single copy of the DNA. This process is similar to mitosis in eukaryotic cells, but occurs without the formation of a spindle apparatus.

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A band of connective tissue linking two bones in a joint is known as a "ligament". Ligaments connect bones to other bones and help to stabilize and strengthen joints. They are made up of strong, flexible fibers that allow for movement while also preventing bones from moving too far or becoming dislocated. For example, the anterior cruciate ligament (ACL) is an important ligament in the knee that helps to keep the knee joint stable during activities such as running and jumping.

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Fossil records found in sedimentary rocks offer some explanation for the theory of evolution because the deposits have remains of organisms characteristic of when they were formed. This means that scientists can observe changes in the characteristics of organisms over time by comparing fossils in different strata. These changes provide evidence of evolution and support the theory that organisms change over time to adapt to their environment. The fossils found in sedimentary rocks can also provide information about extinct organisms and their relationships to modern organisms, allowing scientists to understand the history of life on Earth.

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The part of the stomach nearer the gullet is called the cardiac sphincter. This is the muscular valve that controls the opening between the esophagus (gullet) and the stomach, allowing food to pass from the esophagus into the stomach and preventing stomach acid and other contents from flowing back up into the esophagus. The cardiac sphincter is located at the top of the stomach, near the esophagus, and is also known as the gastroesophageal sphincter.

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An instrument used to measure the speed of wind is called an anemometer. It has cups that rotate when exposed to wind, and the rotation speed is proportional to the wind speed. Therefore, an anemometer measures the wind speed in terms of rotations per minute (RPM) or meters per second (m/s).

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The largest amount of yolk is found in the eggs of reptiles. This is because reptiles are oviparous, which means that their young develop in eggs outside of the mother's body. The large amount of yolk in the egg provides the developing embryo with the nutrients it needs to grow and develop until it is ready to hatch. Mammals, fish, and amphibians have different reproductive strategies, and their eggs do not contain as much yolk as reptiles.

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Sorus and indusium perform similar functions. Sorus is a cluster of sporangia (structures that produce and contain spores) found on the underside of fern leaves. Indusium is a thin membrane-like structure that covers the sorus and helps to protect and disperse the spores. Both sorus and indusium are involved in the reproduction of ferns. Sorus produces the spores and indusium helps to protect and disperse them.

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The situation described, where different species compete for a limited resource, is an example of interspecific competition. In this case, toads and lizards are competing for a limited amount of food, which means that the individuals of one species may have an advantage over the other in obtaining the necessary resources. This competition may lead to changes in the population size or behavior of each species, as they try to adapt to the availability of resources.

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The Southern Guinea Savanna and Northern Guinea Savanna are two types of savannas in West Africa. The Southern Guinea Savanna differs from the Northern Guinea Savanna in that it has more rainfall and taller grasses. This makes the Southern Guinea Savanna more suitable for grazing animals, as the tall grasses provide more food, while the Northern Guinea Savanna is more suitable for crops due to its lower rainfall and shorter grasses.

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Birds excrete a nitrogenous substance that is different from mammals because they conserve water by producing a solid, pasty material that contains very little water. This substance is called uric acid. Uric acid is a nitrogenous waste product that is produced by the liver, released into the bloodstream, and then excreted by the kidneys into the cloaca, which is the common exit point for the urinary, digestive, and reproductive systems in birds. Unlike mammals, birds do not convert ammonia to urea, which requires more water to excrete. Instead, birds convert ammonia directly to uric acid, which is less toxic and requires very little water to excrete. This allows birds to conserve water in their bodies, which is important for their survival in dry environments.

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The ability of the eye to adjust its focus to both near and distant objects is known as accommodation. The lens of the eye changes shape to focus on nearby objects, which is referred to as accommodation, while for distant objects the lens flattens out. The other options are related to the eye, but do not specifically refer to the ability to focus on both near and distant objects. Refraction refers to the bending of light as it passes through the eye, hypermetropia is a condition where distant objects are seen more clearly than nearby objects, and image formation refers to the process by which an image is formed on the retina.

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Companion cells are part of the phloem in plants. They are specialized parenchymal cells that are closely associated with sieve tube elements in the phloem. They are responsible for loading sugars and other organic compounds into the sieve tube elements for long-distance transport throughout the plant. The phloem is one of the two types of vascular tissue in plants, the other being xylem. Xylem is responsible for transporting water and minerals from the roots to the rest of the plant. The pericycle is a layer of cells in the roots that gives rise to lateral roots, while the pith is the central, often spongy, tissue of stems and roots.