JAMB UTME - Biology - 1994

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In Amoeba, osmoregulation is carried out by the contractile vacuole. The contractile vacuole is responsible for regulating the water balance and maintaining homeostasis by expelling excess water that is constantly taken up by the cell through osmosis. When the contractile vacuole fills with water, it contracts and expels the excess water out of the cell, thus preventing it from bursting due to excess water intake.

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When a short-sighted person views a distant object without spectacles, the image is formed in front of the retina. In a short-sighted eye, the eyeball is too long or the cornea is too curved, which causes the image to be focused in front of the retina instead of directly on it. This results in a blurry image when looking at distant objects. Spectacles or contact lenses can correct this by refracting the light before it enters the eye, so that the image is focused directly on the retina.

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The answer is viruses. Viruses are considered the smallest living organisms because they possess some characteristics of living things such as the ability to replicate and evolve, but they also possess characteristics of non-living matter such as the inability to carry out metabolic processes on their own and the need to infect a host cell to replicate.

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The phenomenon by which an animal goes into a state of dormancy during the dry season is called aestivation. Aestivation is the opposite of hibernation, which is a state of dormancy that animals enter during the cold winter months to conserve energy. During aestivation, an animal enters a state of dormancy during the hot, dry months of the year, typically in response to the lack of water and food. During aestivation, an animal reduces its metabolic rate, and its body temperature drops to conserve energy and water. This allows the animal to survive the harsh environmental conditions until the weather becomes more favorable. Many animals, including snails, tortoises, and certain species of frogs and lungfish, use aestivation as a survival strategy during the dry season. Therefore, the correct answer is "aestivation."

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The fleshy base of a flower to which the different floral parts are attached is known as the Receptacle. The receptacle is an enlarged end of the flower stalk that supports the flower's reproductive structures, such as the sepals, petals, stamens, and pistils. The receptacle is an essential part of the flower's structure as it provides support to the different floral parts and aids in the process of pollination and reproduction.

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People who suck petrol with their mouths run the risk of increasing the concentration of lead in their blood. This is because petrol (or gasoline) contains lead, which can be absorbed into the bloodstream when it is ingested or inhaled. Lead is a toxic heavy metal that can cause serious health problems, particularly in children and pregnant women. It can damage the nervous system, affect brain development, and lead to other health issues such as anemia, kidney damage, and reproductive problems. Therefore, it is very important to avoid ingesting or inhaling petrol, and to always use appropriate safety measures when handling it.

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The differences and similarities among living things account for diversity and evolution. Living things can be very different from one another in terms of their physical characteristics, behaviors, and habitats. However, they also share many common features, such as the ability to reproduce and the need for food and water. These differences and similarities provide the basis for the process of evolution, which occurs over many generations as organisms with advantageous traits are more likely to survive and reproduce. The process of evolution leads to the development of new species and the diversity of life on Earth. While competition can also play a role in the survival of individual organisms, it is not directly related to the overall diversity and evolution of living things. Finally, stability is not necessarily a direct outcome of the differences and similarities among living things, as changes can occur over time due to environmental factors, genetic mutations, or other factors.

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Breathing root is an adaptation for survival in the mangrove swamp. The mangrove swamp is a harsh environment characterized by waterlogged soil that is deficient in oxygen. Breathing roots, also known as pneumatophores, are specialized roots that emerge from the water and allow the mangrove tree to obtain oxygen from the air. These roots are characterized by a spongy tissue that has numerous tiny pores, called lenticels, which allow for gas exchange between the air and the root. The roots also have a unique architecture that allows them to anchor the tree in the soft and unstable soil of the mangrove swamp. The breathing roots, therefore, play a critical role in the survival of mangrove trees in this unique habitat.

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Ptyalin is an enzyme found in saliva that helps break down starch into simple sugars. An increase in the concentration of acid is likely to decrease the activity of ptyalin. This is because ptyalin functions optimally in a slightly alkaline environment (pH 6.7-7.0). An increase in acid concentration in the mouth can lower the pH, making the environment more acidic, and disrupting the enzyme's function. This is why sour or acidic foods can sometimes impair the breakdown of starch in the mouth.

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Decomposers are organisms that break down dead organic matter into simpler inorganic substances. From the given options, the set that is made up of decomposers is "Mushroom, rhizophus and bacteria." Mushrooms are fungi that play a significant role in breaking down dead organic matter in the environment. They secrete enzymes that digest organic matter and convert it into simpler inorganic compounds. Rhizophus is a type of fungi that is also involved in the decomposition of dead organic matter. Bacteria are another group of decomposers that play an essential role in the breakdown of dead organic matter. They can break down complex organic compounds into simpler inorganic compounds. On the other hand, earthworms, nematodes, and platyhelminthes are not decomposers. Earthworms feed on organic matter, but they are not decomposers as they do not break down the organic matter into inorganic substances. Nematodes and platyhelminthes are also not decomposers but rather are considered as consumers in the food chain, feeding on other organisms. Therefore, the correct answer is "Mushroom, rhizophus and bacteria."

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The correct order in an evolutionary sequence for the following plant groups is: Bacteria → algae → mosses → ferns → seed plants. This sequence represents the evolution of plant life on Earth, starting with the earliest forms of bacteria that lived in the water. Over time, algae evolved from bacteria and were the first photosynthetic organisms that produced oxygen as a byproduct of their metabolism. Mosses evolved from algae and were the first land plants to develop structures that allowed them to survive on dry land. Ferns evolved from mosses and were the first plants to develop vascular tissue, which allowed them to grow taller and transport water and nutrients more efficiently. Finally, seed plants evolved from ferns and were the first plants to produce seeds, which provided a protective covering for the embryo and allowed for more efficient reproduction and dispersal. Therefore, the correct option is: Bacteria → algae → mosses → ferns → seed plants.

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In a drought situation, plants can suffer from water stress, which means they don't have enough water to carry out their normal functions. This can lead to a variety of negative effects, one of which is reduced biochemical activities. This is because water is essential for many of the biochemical reactions that occur within a plant, such as photosynthesis, the process by which plants convert sunlight into energy. When water is scarce, the plant's ability to carry out these reactions is limited, which can cause it to slow down or even stop growing altogether. Additionally, without enough water, the plant may not be able to absorb and transport nutrients properly, which can further reduce its overall health and productivity. Therefore, the answer to the question is reduced biochemical activities.

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The part of the brain that controls heart beat and breathing is the medulla oblongata. The medulla oblongata is located in the brainstem, which connects the brain to the spinal cord. It is responsible for controlling several involuntary functions, including heart rate, breathing rate, and blood pressure. The medulla oblongata contains specialized neurons that form the respiratory and cardiovascular centers. These centers respond to changes in carbon dioxide, oxygen, and pH levels in the blood, as well as to signals from other parts of the body. For example, if carbon dioxide levels in the blood rise, the respiratory center in the medulla oblongata will increase breathing rate to remove excess carbon dioxide. Similarly, if blood pressure drops, the cardiovascular center will increase heart rate to maintain blood flow to the body. Overall, the medulla oblongata plays a critical role in maintaining homeostasis and ensuring that the body's essential functions, such as breathing and heart rate, are properly regulated.

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The membrane surrounding the vacuole in a plant cell is called the "tonoplast". The vacuole is an organelle found in plant cells that stores water, nutrients, and waste products. The tonoplast is a selectively permeable membrane that encloses the vacuole and regulates the exchange of materials between the cytoplasm and the vacuole. It is composed of lipids and proteins and helps to maintain the structural integrity of the cell. The tonoplast is different from the plasma membrane, which surrounds the entire cell and controls the movement of substances in and out of the cell.

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In a pyramid of numbers, the number of individuals at each trophic level is represented. The base of the pyramid represents the primary producers, which are the organisms that are capable of producing their own food. As we move up the pyramid, the number of individuals decreases because each successive trophic level depends on the trophic level below it for energy. Therefore, the organisms with the least number of individuals in a pyramid of numbers are the highest-level consumers, which are the tertiary consumers. These organisms are at the top of the food chain and usually have the fewest number of individuals because they require the most energy to survive.

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The sex-linked defect in which very slight cut produces severe bleeding is known as haemophilia. Haemophilia is a genetic disorder that affects the blood's ability to clot. It is caused by a deficiency in one of the blood clotting factors, specifically factor VIII (hemophilia A) or factor IX (hemophilia B). Haemophilia is an X-linked recessive disorder, which means it primarily affects males. Females can be carriers of the gene but are usually not affected because they have two X chromosomes and the mutation typically only affects one. People with haemophilia experience prolonged bleeding after injury or surgery, as their blood does not clot properly. They may also experience spontaneous bleeding into joints and muscles, which can cause pain and permanent damage. Treatment for haemophilia involves replacement therapy, where the missing clotting factor is injected into the bloodstream to prevent bleeding.

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The red coloration on the head of a male lizard helps it to secure its mate. Many species of lizards exhibit sexual dimorphism, meaning that males and females have distinct physical differences. In some cases, males may have brightly colored patches or markings on their bodies that help them attract a mate or signal their dominance to other males. In the case of the red coloration on the head of a male lizard, this is likely a visual cue that is used to attract a female mate. The red color may signal to females that the male is healthy, strong, and capable of providing good genes for their offspring. In some species, the intensity of the red coloration may even be linked to the male's social status, with dominant males exhibiting more vivid coloration than subordinate males. While the red coloration on the head of a male lizard may make it more conspicuous to predators, it is unlikely to be used for camouflage or defense. Instead, its primary function is likely related to mating and reproduction. Based on the given options, the best answer is to secure its mate, as this is the most likely function of the red coloration on the head of a male lizard.

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People with sickle-cell anemia have hemoglobin S and are homozygous recessive. Sickle-cell anemia is an autosomal recessive genetic disorder caused by a mutation in the HBB gene that produces hemoglobin S. When an individual inherits two copies of the mutated gene (one from each parent), they have sickle-cell anemia. Individuals who are heterozygous (carrying one normal and one mutated gene) are carriers of the disorder but do not have the disease itself.

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Ecological succession is the gradual process of change in the species structure of a given area over time. The succession begins with a pioneer community and continues until a climax community is formed. The climax community is the stable end point of ecological succession, which is reached when the ecosystem has achieved a state of equilibrium with the environment. It is composed of a diverse set of species that are well adapted to the prevailing environmental conditions and are in a state of balance with each other. Therefore, the correct answer is "climax community".

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A circulatory system that does not allow mixing of oxygenated and de-oxygenated blood in mammalian heart is referred to as closed. The closed circulatory system is one in which blood is pumped through the vessels by the heart and remains confined within a continuous system of vessels. In mammals, the heart has four chambers: two atria and two ventricles, and there is no direct communication between the two sides of the heart. The right side of the heart receives de-oxygenated blood from the body and pumps it to the lungs for oxygenation, while the left side of the heart receives oxygenated blood from the lungs and pumps it to the body. Therefore, there is no mixing of oxygenated and de-oxygenated blood in the mammalian heart, and this is what makes it a closed circulatory system.

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The process by which a red blood cell placed in distilled water absorbs water until it bursts and releases its contents into the surrounding solution is known as haemolysis. When a red blood cell is placed in a hypotonic solution, such as distilled water, water molecules move into the cell by the process of osmosis. This causes the cell to swell and become more turgid, which means that it is under increased pressure from the internal water content. If this pressure becomes too great, the cell membrane can rupture, releasing the cell contents into the surrounding solution. This process is known as haemolysis. Plasmolysis, on the other hand, is the opposite process that occurs when a plant cell is placed in a hypertonic solution. In this case, water moves out of the cell by osmosis, causing the cell to shrink and the cell membrane to pull away from the cell wall. Turgidity is a term used to describe the state of being swollen and firm due to internal water pressure. This term can be used to describe both plant and animal cells, but it does not specifically refer to the process of haemolysis. Based on the given options, the best answer for the process described is haemolysis, as it specifically refers to the bursting of a red blood cell due to the influx of water.

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The anatomical evidence usually used in support of the evolutionary relationship among whales, humans, birds, and dogs is the possession of pentadactyl limb. A pentadactyl limb is a limb with five digits, such as the hand of a human, wing of a bird, flipper of a whale, and paw of a dog. This similarity in limb structure suggests that these animals shared a common ancestor at some point in their evolutionary history. This is an example of homology, which is the similarity in structure due to a common ancestry.

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Carbondioxide is the waste product that is excreted through the stomata and lenticels in plants. During photosynthesis, plants take in carbon dioxide from the atmosphere and use it to produce glucose and oxygen. However, during respiration, plants release carbon dioxide as a waste product, which needs to be removed from the plant's body. The stomata and lenticels are specialized structures in plants that allow for gas exchange, and carbon dioxide is one of the gases that can diffuse out of the plant's body through these structures. In contrast, alkaloids, tannins, and anthocyanins are not waste products that are excreted through the stomata and lenticels. Alkaloids and tannins are secondary metabolites that play important roles in plant defense against herbivores and pathogens, while anthocyanins are pigments that give fruits and flowers their vibrant colors.

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Green plants are distinguished from other living organisms by their ability to manufacture their own food through the process of photosynthesis. They contain a green pigment called chlorophyll that enables them to capture light energy from the sun, carbon dioxide from the air, and water from the soil to produce glucose (a simple sugar) and oxygen. This process occurs in the chloroplasts of plant cells and is responsible for producing the organic matter that forms the basis of the food web on earth. Unlike animals and other organisms, plants do not need to consume other organisms for energy because they are able to produce their own food.

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The soil swallowed by the earthworm to form the worm cast is grouped up in the gizzard. Earthworms are known for their ability to consume large amounts of soil and organic matter, digesting it in their digestive tract and excreting it as nutrient-rich castings. As the earthworm consumes soil, it is ground up and mixed with digestive fluids in the muscular gizzard. The gizzard is a specialized part of the earthworm's digestive system that is responsible for breaking down food, particularly coarse particles like soil and plant matter. It contains tough, muscular walls that contract and grind the soil and organic matter, breaking it down into smaller pieces that can be more easily digested in the intestine. As the soil is ground up in the gizzard, it is mixed with digestive fluids and formed into pellets, which are then passed through the intestine and out of the earthworm's body as worm castings. These castings are rich in nutrients like nitrogen, phosphorus, and potassium, making them an important component of healthy soil. Based on the given options, the best answer is the gizzard, as this is the specific part of the earthworm's digestive system where soil is ground up and mixed with digestive fluids to form worm castings.

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The part labelled J is most likely a manometer. A manometer is an instrument used for measuring pressure, particularly in gases. It consists of a U-shaped tube filled with a liquid, such as mercury or water, and the pressure difference between two sources is measured by the difference in height between the two arms of the tube. A porosimeter is used to measure the pore size distribution of a porous material, such as soil or rock. A potometer is a device used to measure the rate of water uptake by a plant, which is important for studying plant physiology and water use efficiency. An auxanometer is used to measure the rate of growth of a plant or part of a plant, typically by measuring the movement of a lever or other indicator as the plant grows. Based on the context of the question and the options given, the part labelled J is most likely a manometer, as it is being used to measure pressure.

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The phloem parenchyma is a type of plant tissue that plays a role in food storage. Specifically, it stores carbohydrates (such as sugars) that are produced during photosynthesis in the leaves. These stored carbohydrates can then be transported to other parts of the plant that need them for energy or growth. The phloem parenchyma does not support the stem or produce the sieve tube, and it is not involved in transporting water.