JAMB UTME - Biology - 1989

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Genotype refers to the genetic makeup of an organism, specifically the combination of alleles that an individual has inherited from its parents. Alleles are the different versions of a gene that code for a particular trait. When an organism has two alleles that are the same, the genotype is described as homozygous. This means that the individual has inherited identical alleles from its parents for a particular trait. For example, in pea plants, there are two possible alleles for flower color: purple (P) and white (p). If a pea plant inherits two purple alleles (PP) from its parents, it is homozygous for flower color. Similarly, if it inherits two white alleles (pp), it is also homozygous for flower color. In contrast, if an organism has two different alleles for a particular trait, the genotype is described as heterozygous. This means that the individual has inherited two different alleles for a particular gene from its parents. For example, if a pea plant inherits one purple allele (P) and one white allele (p) from its parents, it is heterozygous for flower color (Pp). Therefore, when the two alleles present in an organism are of the same type, the genotype is described as homozygous.

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The sex-linked character among the given options is color blindness. Sex-linked traits are the traits that are carried on the sex chromosomes (X and Y chromosomes). In humans, the sex chromosomes are XX in females and XY in males. Since males have only one X chromosome, they are more likely to express the traits carried on the X chromosome. Color blindness is a recessive trait that is carried on the X chromosome. Therefore, males have a higher chance of expressing color blindness than females. Sickle-cell anaemia is an autosomal recessive trait, meaning it is not carried on the sex chromosomes. Tongue rolling and skin color are also not sex-linked traits and are not determined by the sex chromosomes.

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A corn differs from a bulb in that its stem is the main food storage organ. In corn plants, the stem is modified to form the edible kernel that serves as the main food storage organ. On the other hand, a bulb is an underground stem that is modified for food storage and is typically round or oval in shape. The bulb has concentric layers of fleshy storage leaves, while corn does not have any fleshy layers. Additionally, corn does not have a flattened disc-shaped stem, no buds in the axils of the leaves, and no adventitious roots.

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In a dicotyledonous stem, each companion cell is found beside the sieve tube. Sieve tubes are a type of specialized plant cell that forms a part of the phloem, which is responsible for transporting sugars and other organic compounds throughout the plant. Companion cells are a type of plant cell that are closely associated with sieve tube cells. They are responsible for supporting the sieve tube cells and facilitating the movement of sugars and other organic compounds through the phloem. During development, the companion cells and sieve tube cells are derived from the same mother cell. As they mature, the companion cells remain closely associated with the sieve tube cells and are always found adjacent to them. This close association allows the companion cells to provide the sieve tube cells with the energy and nutrients they need to carry out their transport function. Therefore, the correct answer to the question is the sieve tube, as each companion cell is found beside it in the dicotyledonous stem.

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A characteristic of the phylum Coelenterata is that they possess a gut with a single opening. Coelenterates, also known as cnidarians, are a group of aquatic animals that includes jellyfish, coral, and sea anemones. Their gut has a single opening, which functions as both a mouth and an anus. This means that food enters and waste leaves through the same opening. This type of digestive system is called a gastrovascular cavity, and it is a defining characteristic of the phylum Coelenterata. The other options are not characteristics of Coelenterates - most of them are marine is true but not specific to Coelenterates, they do not possess numerous pores on their body, and they are not bilaterally symmetrical.

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If a healthy potted plant is continuously kept in dim light, the rate of photosynthesis will decrease as the plant will receive less light energy for photosynthesis. This means that the plant will produce less oxygen and release less carbon dioxide, which are the byproducts of photosynthesis. As a result, the rate of respiration will also decrease because the plant needs less energy from glucose to carry out cellular functions. If the plant is kept in extremely dim light, it may not have enough energy from photosynthesis to carry out respiration, which could lead to the plant's death. However, if the light level is just reduced, the plant will adjust to the new level of light and maintain a balance between the rate of photosynthesis and respiration. In this case, the plant will take in less carbon dioxide and release less oxygen, and its overall growth may slow down due to the decreased energy from photosynthesis.

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The thin and lanky growth of seedlings in rice field with reddish leaves and poor root development indicates a deficiency in a nutrient in the soil. Among the given options, the nutrient most likely lacking in the soil is phosphorus. This is because phosphorus is essential for root growth, stem strength and the development of healthy leaves. A deficiency in phosphorus can lead to stunted growth and discoloured leaves. Therefore, if the soil lacks phosphorus, the seedlings in the rice field will show the symptoms described.

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Aged erythrocytes (red blood cells) are dissolved in the liver. The liver breaks down these old and damaged cells and recycles their components, such as iron and amino acids, for the production of new red blood cells. This process also helps to remove waste products, like bilirubin, from the bloodstream. The pancreas, lymph nodes, and kidneys are not directly involved in this process.

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The components of castor oil seed and the maize grain are similar EXCEPT for the number of cotyledons. Cotyledons are embryonic leaves that are present in the seeds of flowering plants. They are the first leaves to emerge from the germinating seed and play an important role in providing nutrients to the developing embryo. In general, there are two types of seeds based on the number of cotyledons they have: monocotyledonous (one cotyledon) and dicotyledonous (two cotyledons). The maize grain is a monocotyledonous seed, meaning it has only one cotyledon, while the castor oil seed is a dicotyledonous seed, meaning it has two cotyledons. This is the main difference between the two seeds, and it affects the way they develop and the nutrients they store. The location of the embryo, the number of radicles, and the number of plumules are all similar in castor oil seed and maize grain, as they are both seeds of flowering plants and share common characteristics.

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Crop rotation is a farming practice where different crops are grown on the same land in a planned sequence over several growing seasons. Farmers practise crop rotation for several reasons, but one of the main benefits is that it helps to conserve soil fertility. Different crops have different nutrient requirements and some crops are better at fixing nitrogen in the soil than others. When crops are rotated, the soil is able to maintain its nutrient balance and structure, preventing soil depletion and ensuring that it remains fertile. This means that the soil is able to support healthy plant growth and produce higher yields, which is important for the sustainability of agriculture. Crop rotation also helps to prevent soil erosion by reducing the likelihood of soil becoming compacted and allowing it to hold more moisture. Additionally, planting different crops can help to control pests and diseases, as some pests and diseases are specific to certain crops. By rotating crops, farmers can disrupt the pest and disease life cycles and reduce the need for pesticides and other chemical interventions. Therefore, farmers practise crop rotation primarily to maintain soil fertility, but it also has other benefits such as preventing soil erosion and controlling pests and diseases.

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A multinucleate body without internal cell boundaries is a characteristic of fungi. Fungi are a group of eukaryotic organisms that include yeasts, molds, and mushrooms. They are characterized by their filamentous structure, which consists of long, branching threads called hyphae. These hyphae can be divided into cells by internal cell walls, called septa, which have pores that allow for the movement of nutrients and other molecules. However, some fungi, such as those in the Zygomycota phylum, lack these internal cell walls and are multinucleate, meaning that they contain multiple nuclei within a single, continuous cytoplasmic mass. These fungi are referred to as coenocytic fungi and are characterized by their large, multinucleate hyphae. This lack of internal cell boundaries allows for efficient nutrient transport and distribution throughout the fungal body. It also allows for rapid growth and adaptation to changing environmental conditions.

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The way of controlling bilharzia that can result in pollution is applying chemicals to kill the snails. Bilharzia is a disease caused by a parasitic worm that spends part of its lifecycle in freshwater snails. One of the ways of controlling bilharzia is by applying chemicals to kill the snails and break their life cycle. However, the use of chemical molluscicides can result in pollution of the water bodies. When chemicals are applied in large quantities, they can accumulate in the water and become toxic to aquatic life, including fish and other aquatic organisms. In addition, some molluscicides contain persistent organic pollutants that can remain in the water for long periods and accumulate in the food chain, posing a risk to human health. Therefore, while applying chemicals to kill the snails may be an effective way of controlling bilharzia, it can also result in pollution of the water bodies, making it a potential environmental hazard.

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Double fertilization is a unique feature of angiosperms. Angiosperms are flowering plants, which are characterized by their flowers and fruits. Double fertilization is a process that occurs during the formation of seeds in angiosperms, where two sperm cells from the pollen tube fertilize two different cells in the female gametophyte. One sperm cell fertilizes the egg cell, forming a zygote that will develop into an embryo, while the other sperm cell fertilizes the central cell, forming the endosperm, which is a nutrient-rich tissue that provides nourishment to the developing embryo. This unique process of double fertilization is not found in bryophytes, pteridophytes, or algae. In these other groups of plants, fertilization occurs through a single sperm cell that fuses with the egg cell, forming a zygote. The endosperm is formed either by cell division of the zygote or by the fusion of the sperm cell with a separate cell in the female gametophyte. Therefore, double fertilization is a key characteristic that sets angiosperms apart from other groups of plants. It allows for the efficient use of resources and the production of seeds with a high nutrient content, which contributes to the success and diversity of angiosperms in many different environments.

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Fruit enlargement can be induced by spraying the young ovary with auxin, cytokinin, and gibberellin. These three hormones work together to stimulate cell division, elongation, and differentiation, leading to fruit growth and development. Auxin promotes cell division and expansion, cytokinin promotes cell division, and gibberellin promotes cell elongation. By applying these hormones to the young ovary, the fruit can be induced to grow larger than it would under normal circumstances. The other options do not include the necessary combination of hormones to induce fruit enlargement.

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Crop rotation is a farming practice where different crops are grown on the same land in a planned sequence over several growing seasons. Farmers practise crop rotation for several reasons, but one of the main benefits is that it helps to conserve soil fertility. Different crops have different nutrient requirements and some crops are better at fixing nitrogen in the soil than others. When crops are rotated, the soil is able to maintain its nutrient balance and structure, preventing soil depletion and ensuring that it remains fertile. This means that the soil is able to support healthy plant growth and produce higher yields, which is important for the sustainability of agriculture. Crop rotation also helps to prevent soil erosion by reducing the likelihood of soil becoming compacted and allowing it to hold more moisture. Additionally, planting different crops can help to control pests and diseases, as some pests and diseases are specific to certain crops. By rotating crops, farmers can disrupt the pest and disease life cycles and reduce the need for pesticides and other chemical interventions. Therefore, farmers practise crop rotation primarily to maintain soil fertility, but it also has other benefits such as preventing soil erosion and controlling pests and diseases.

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The LEAST efficient energy transfer link in an ecosystem is from the secondary consumers to decomposers. This is because secondary consumers, such as carnivores, receive only a small fraction of the energy that their prey originally obtained from the producers (plants or algae). This is due to the fact that energy is lost at each step of the food chain through processes such as respiration, movement, and waste production. When secondary consumers are consumed by decomposers, even less energy is transferred due to the fact that the energy in their bodies has already been used and broken down. Therefore, this link in the food chain is the least efficient in terms of energy transfer.

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Lichen is an example of a symbiotic association between a fungus and an alga or a cyanobacterium. The fungus provides a structure for the partnership, while the alga or cyanobacterium provides the food through photosynthesis. The partnership is so close that lichen is often described as a single organism, even though it is made up of two different types of organisms. Lichens can be found in a variety of environments, from the arctic tundra to the rainforest, and are important as indicators of air quality and ecosystem health.

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The habitat in which plants will show xeromorphic features most prominently is habitat X. Xeromorphic features refer to adaptations in plants that help them survive in dry environments, such as deserts. Examples of xeromorphic features include reduced leaf size, thick cuticles, and deep root systems. Habitat X is likely to be a dry and arid environment, which would favor the development of xeromorphic features in plants. In contrast, habitats R, P, and Q may have different environmental conditions that do not necessarily require xeromorphic adaptations in plants.

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The characteristic feature of exponential increase in population is associated with binary fission. Binary fission is a type of asexual reproduction that occurs in single-celled organisms, where the parent cell divides into two identical daughter cells. Each daughter cell can then divide into two more daughter cells, and the process repeats itself. This type of reproduction allows for rapid population growth since each division leads to a doubling of the population size. In contrast, sexual reproduction, budding, and vegetative propagation do not necessarily lead to exponential population growth.

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The pancreatic juice contains the enzymes amylopsin, steapsin, and trypsinogen. The pancreas is an organ located near the stomach that produces pancreatic juice, which contains several digestive enzymes that aid in the digestion of food. Amylopsin is an enzyme that breaks down carbohydrates like starch into smaller molecules such as glucose. Steapsin is an enzyme that helps in the digestion of fats by breaking them down into smaller fatty acids and glycerol. Trypsinogen is an enzyme that is converted into trypsin, which helps in the digestion of proteins by breaking them down into smaller peptides. Therefore, based on the options provided, the correct answer is that the pancreatic juice contains the enzymes amylopsin, steapsin, and trypsinogen, which aid in the digestion of carbohydrates, fats, and proteins, respectively.

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Among the given options, the ecological factor that exerts the greatest influence on the structure of the profiles is climatic. The climate of a region, which includes temperature, precipitation, humidity, wind, and other weather conditions, has a significant impact on the biotic and abiotic factors that make up the ecosystem. Climatic factors affect the rate of weathering and erosion of rocks and soils, which in turn affects the nature of the soil profiles. Temperature and precipitation, for example, can impact the rate of decomposition of organic matter in the soil, which can affect the nutrient content and fertility of the soil. Wind can also play a role in shaping the physical structure of the soil. Additionally, climatic factors also influence the distribution and abundance of different plant and animal species within an ecosystem. Different species have different adaptations to climatic conditions, and these adaptations can shape the composition and structure of the ecosystem. Overall, climatic factors have a broad and far-reaching impact on the structure of the profiles, making them the most influential among the given options.

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Sulphur dioxide is a dangerous product of coal burning. When coal is burned, it releases sulphur dioxide, a gas that can cause serious health and environmental problems. Sulphur dioxide can react with other chemicals in the air to form acid rain, which can damage crops, forests, and waterways. In addition, sulphur dioxide can cause respiratory problems in humans, including asthma and bronchitis. It is therefore important to control the amount of sulphur dioxide released during coal burning through the use of pollution control technologies.

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The irreversible life process by which new protoplasm is added to increase the size and weight of an organism is known as growth. During growth, an organism's cells divide and differentiate, which allows the organism to increase in size and complexity. This process is usually accompanied by an increase in weight, as the organism accumulates new biomass. Anabolism and catabolism are two processes involved in metabolism, which refers to the chemical processes that occur within an organism to maintain life. Anabolism is the process of building up complex molecules from simpler ones, while catabolism is the process of breaking down complex molecules into simpler ones to release energy. Development refers to the process of a single-celled zygote becoming a fully-formed organism, including both growth and differentiation. Therefore, growth is a part of development, but the two terms are not interchangeable.

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The type of joint at the point labelled 5 is a hinge joint. A hinge joint is a type of joint that allows for movement in only one plane, like a door hinge. It consists of two bones that are connected by a strong ligament, which allows for movement back and forth in a single direction. The joint at point 5 appears to be between two long bones and allows for movement in one plane only, suggesting that it is a hinge joint. In contrast, a ball and socket joint allows for movement in multiple planes and directions, like the shoulder joint. A pivot joint allows for rotational movement around a central axis, like the joint between the atlas and axis vertebrae in the neck. A gliding joint allows for sliding movements between flat surfaces of bones, like the joint between the carpal bones of the wrist. Therefore, based on the location and type of movement, the joint at the point labelled 5 is most likely a hinge joint.

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The phylum Annelida have members with both internal and external segmentation. Annelids are commonly referred to as segmented worms, and they have a well-defined body composed of multiple segments. Each segment of the body has its own set of muscles and nerves, and the segmentation allows for greater flexibility and movement. Annelids also have internal segmentation, with each segment containing its own set of organs such as the digestive, circulatory, and reproductive systems. Examples of annelids include earthworms, leeches, and polychaete worms.

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Among the given options, syphilis is the disease that can be caused by a bacterium. Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. It is usually spread through sexual contact, but can also be passed on from mother to child during pregnancy or childbirth. The symptoms of syphilis can vary widely, but usually, the infection progresses through several stages, including the development of a painless sore or ulcer at the site of infection, followed by a rash, fever, and swollen lymph nodes. If left untreated, syphilis can cause serious complications, such as damage to the heart, brain, and other organs. Ringworm is caused by a fungal infection, while poliomyelitis is caused by a virus. Malaria is caused by a parasite that is transmitted through the bite of infected mosquitoes.

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