JAMB UTME - Biology - 2000

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Gibberellins are plant hormones that play an important role in regulating growth and development. One of the growth activities in plants that is brought about by gibberellins is cell elongation. Gibberellins stimulate the elongation of cells in the stem and leaves, leading to an increase in plant height and leaf size. This is important for plant growth and development, as it allows the plant to reach for sunlight and compete with other plants for resources. While gibberellins do not directly cause rapid cell division or tropic response, they can indirectly influence these processes through their effects on cell elongation and other aspects of plant growth. Therefore, the correct answer to the question is "cell elongation."

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For growth to occur in organisms, the rate of anabolism must exceed that of catabolism. Anabolism is the process of building complex molecules from simpler ones, while catabolism is the breakdown of complex molecules into simpler ones. In order for an organism to grow, it needs to produce more complex molecules (such as proteins and DNA) than it breaks down. This requires a net energy input, which is obtained from food. Therefore, food storage must be high enough to provide the necessary energy and building blocks for anabolism, but it is not the determining factor for growth.

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The pollutants that contribute to the depletion of the ozone layer in the atmosphere are chlorofluorocarbons (CFCs). CFCs are synthetic organic compounds containing chlorine, fluorine, and carbon. They are used as refrigerants, propellants in aerosol cans, and in the production of foam products. When CFCs are released into the atmosphere, they rise to the stratosphere and are broken down by ultraviolet radiation, releasing chlorine atoms. These chlorine atoms then react with ozone molecules, breaking them down and depleting the ozone layer.

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Coelom is absent in the class of animals termed coelenterata, also known as cnidarians. Cnidarians are a diverse group of aquatic animals that include jellyfish, corals, and sea anemones. They have a simple body plan with two cell layers, an outer epidermis and an inner gastrodermis, separated by a jelly-like layer called mesoglea. They do not have a true body cavity or coelom. Instead, their digestive and reproductive organs are suspended in the gastrovascular cavity, which functions both for digestion and distribution of nutrients throughout the body. This cavity is lined by gastrodermis, which performs both digestive and absorptive functions. In contrast, the other animal groups listed, Mollusca, Reptilia, and Arthropoda, all have a true coelom, which is a fluid-filled body cavity completely lined by mesoderm, the middle layer of cells in the embryo. This coelom allows for more complex body structures and organ systems to develop, and also serves as a space for circulation of fluids and other substances in the body.

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Short-sightedness, also known as myopia, occurs when the eye is too long or the cornea is too curved, causing distant objects to appear blurry. To correct this, a lens with a negative or concave curvature is needed to diverge the light before it enters the eye, allowing distant objects to be seen clearly. Therefore, the correct option is a concave lens.

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The chamber of the mammalian heart with the thickest wall is the left ventricle. This is because the left ventricle is responsible for pumping oxygen-rich blood to the rest of the body, so it needs to generate more forceful contractions than the other chambers. The thick wall of the left ventricle is made up of strong muscle tissue that allows it to contract with enough force to push blood through the systemic circulation, which is the circulation of blood throughout the body. The right ventricle, on the other hand, has a thinner wall because it only needs to pump blood to the lungs, which are nearby and don't require as much force.

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The adaptation of animals to aquatic habitats are characteristics or features that help them survive and thrive in water. Out of the options listed, the adaptation of animals to aquatic habitats includes "Gills, streamlined bodies and lateral lines." Gills are used by aquatic animals to extract oxygen from the water. Streamlined bodies reduce drag and make it easier to swim through the water, while lateral lines help animals sense movement and vibrations in the water. These adaptations are particularly useful for fish, which are the primary group of animals that have these characteristics. The other options may be adaptations of animals to other environments, but they are not specific to aquatic habitats. For example, lungs are an adaptation to life on land, while scaly skin is an adaptation to life in arid environments. Spiracles are openings on the bodies of insects that are used for breathing, but they are not adaptations to aquatic environments.

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The set of fins that control steering, balancing, and changing direction and pitch in fish is the pectoral and pelvic fins. These fins are located on the sides of the fish and are responsible for controlling the fish's movement and direction in the water. The dorsal and anal fins are primarily used for stability and propulsion, while the caudal fin (tail fin) is used for propulsion and speed. However, the pectoral and pelvic fins play a crucial role in the fish's ability to turn and maneuver through the water.

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The distribution of vegetation zones is determined by temperature, light, rain, and humidity. Temperature affects the type of vegetation that can grow in a particular area; areas with colder temperatures usually have different vegetation than areas with warmer temperatures. Light also affects vegetation distribution; areas with more sunlight tend to have different vegetation than areas with less sunlight. Rain and humidity affect the availability of water for plant growth, which can determine the types of vegetation that can thrive in an area. Areas with more rain and humidity tend to have different vegetation than areas with less rain and humidity. Overall, these four factors interact to determine the distribution of vegetation zones around the world.

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Peripheral arrangement of vascular tissues in dicots is a characteristic of the internal structure of the stem. In dicot stems, vascular bundles (collections of xylem and phloem tissues) are arranged in a circular pattern around the edge of the stem, forming a ring. This arrangement is known as a peripheral vascular arrangement and is characteristic of dicot stems. The peripheral arrangement of vascular tissues helps to provide structural support to the stem and allows for efficient transport of water, minerals, and nutrients throughout the plant. Therefore, the peripheral arrangement of vascular tissues is a feature of the internal structure of the stem in dicots.

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All humans and many other primates can be typed for the ABO blood group. There are four principal types: A, B, AB, and O. There are two antigens and two antibodies that are mostly responsible for the ABO types. The specific combination of these four components determines an individual's type in most cases

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Ecological succession refers to the gradual and predictable process of change in the composition of species in an ecosystem over time. In general, ecological succession tends to lead to an increase in species diversity, meaning that more and more different types of organisms become established and thrive within the ecosystem. This is because ecological succession typically begins with the colonization of the area by a relatively small number of pioneering species that are well-suited to the harsh conditions of the newly-formed or disturbed environment. Over time, these species modify the environment in ways that make it more hospitable to other, less hardy species, which then begin to colonize the area as well. As this process continues, the number and variety of species within the ecosystem tends to increase, leading to greater overall diversity. Of course, there are many factors that can influence the course and outcome of ecological succession, and not all successions will result in the same patterns of species diversity. However, in general, an increase in species diversity is one of the most common and noticeable outcomes of ecological succession.

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The reason for the colour changes in a certain savanna grasshopper is that it is adapting to changes in its environment and avoiding predation. During the rainy season, the grass is green and lush, and the grasshopper's green colouration helps it blend in with its surroundings and avoid being spotted by predators. In the dry season, the grass dries up and turns brown, and the grasshopper changes to a brown colour to blend in with its new surroundings. After dry season bush fires, the grass is burned, and the grasshopper changes to a black colour to blend in with the burnt surroundings. This helps it avoid being seen by predators that might be searching for prey in the burnt area. Therefore, the reason for the colour changes in this savanna grasshopper is that it is adapting to changes in its environment and avoiding predation. By changing its colour to match its surroundings, the grasshopper is better able to hide from predators and increase its chances of survival.

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The soil becomes toxic to plants when the concentration of its essential elements is in the range labelled IV. In soil, there is an optimal concentration range of essential elements that supports plant growth and development. When the concentration of essential elements exceeds the optimal range, it can become toxic to plants and adversely affect their growth and survival. The range labelled IV refers to the concentration range where the essential elements become excessively high, resulting in toxicity for plants. Therefore, it is important to maintain the optimal range of essential elements in the soil for healthy plant growth.

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Serum differs from blood plasma because it lacks the blood protein fibrinogen. Both serum and blood plasma are components of blood that are obtained when blood is separated by centrifugation. However, plasma contains all the proteins normally found in blood, including fibrinogen, while serum is the fluid that remains after the blood has clotted and the fibrinogen has been removed. Therefore, while blood plasma contains fibrinogen and other blood proteins, serum lacks fibrinogen, which is why it is often used for diagnostic tests that require the measurement of blood clotting ability. Serum also lacks blood cells, but this is true of both serum and plasma, as these are removed during the centrifugation process.

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The parts labelled I and II make up the Malpighian body. The Malpighian body is a structure found in the kidney that is responsible for filtering blood and forming urine. It is made up of two main parts: the glomerulus and Bowman's capsule. The glomerulus is a small network of blood vessels that allows for the filtration of blood. It is located within Bowman's capsule, which is a cup-shaped structure that surrounds the glomerulus and collects the filtered blood and other fluids. Together, the glomerulus and Bowman's capsule make up the Malpighian body, which is the functional unit of the kidney responsible for filtration and urine formation.

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The mutation theory of organic evolution was propounded by Hugo de Vries. Hugo de Vries was a Dutch botanist who lived from 1848 to 1935. He was one of the first scientists to study the genetics of plants and proposed the mutation theory of organic evolution in the early 1900s. The mutation theory states that new species arise from sudden, heritable changes in the genetic material (mutations) that occur spontaneously rather than through gradual accumulation of small changes as proposed by Charles Darwin's theory of natural selection. De Vries believed that these mutations were responsible for the sudden appearance of new species in the fossil record and that they could occur rapidly and independently of natural selection. He conducted experiments on plant breeding and found evidence to support his theory. Although the mutation theory was initially met with skepticism, it has since become an important aspect of modern evolutionary theory. Today, we know that mutations do play a role in the origin of new species, and scientists continue to study the mechanisms of mutation and their effects on evolution.

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Feathers in birds are structural features that are adapted for uses other than water conservation. While feathers do provide some insulation and protection against water, their main function is for flight and display. Feathers are highly specialized structures that have evolved to provide lift and allow birds to fly through the air. They are also used for mating displays, camouflage, and communication. Succulent stems, scales in animals, and spines in plants are all adaptations for water conservation. Succulent stems store water, scales in animals reduce water loss by covering the skin, and spines in plants reduce water loss by protecting against herbivory. Therefore, feathers in birds are the structural features in the given options that are adapted for uses other than water conservation.

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Bacteria in the large intestine of humans are important in the synthesis of vitamins K and B2. The large intestine, also known as the colon, is the final part of the digestive system. It is home to trillions of bacteria, collectively known as the gut microbiota. These bacteria perform a number of important functions in the body, including aiding in digestion, modulating the immune system, and synthesizing vitamins. One of the most important roles of gut bacteria is the synthesis of vitamins K and B2. Vitamin K is essential for blood clotting and bone health, while vitamin B2, also known as riboflavin, is important for energy production and maintaining healthy skin, eyes, and nervous system. While humans cannot synthesize these vitamins on their own, certain bacteria in the large intestine have the ability to produce them. These bacteria break down undigested food particles and produce the vitamins as byproducts, which can then be absorbed by the body. Therefore, bacteria in the large intestine of humans play an important role in the synthesis of vitamins K and B2, which are essential for various bodily functions.

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The secretion of the growth hormone occurs in the head region of the human body. More specifically, the growth hormone is produced and secreted by the pituitary gland, which is located at the base of the brain in the head region. The pituitary gland is a small gland that plays a major role in regulating various bodily functions, including growth, metabolism, and reproduction. The growth hormone is essential for proper growth and development in children, and also plays a role in maintaining healthy body composition and metabolism in adults. It stimulates the production of insulin-like growth factor-1 (IGF-1) in the liver, which is responsible for promoting the growth and replication of cells throughout the body. While the growth hormone is primarily produced and secreted in the head region, its effects are felt throughout the body, including in the waist, neck, and gonads.

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The male Agama lizard with the brightest head color is typically the dominant one in the group. This means that it has the highest rank and most control over resources and mating opportunities within the group. Other males may exhibit less bright head colors and defer to the dominant male, allowing it to maintain its status as the leader of the group. Therefore, the brightness of the head color is an important visual signal used in social communication and hierarchy establishment among male Agama lizards.

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The part of the brain that controls body posture in mammals is the cerebellum. The cerebellum is a part of the brain located at the base of the skull, underneath the cerebrum. It is responsible for coordinating movements and maintaining balance and posture. It receives information from the sensory systems in the body, as well as from other parts of the brain, and uses this information to regulate muscle activity and adjust body posture. When the cerebellum is damaged or not functioning properly, a person may experience difficulty with coordination, balance, and maintaining posture. This can lead to problems with movement, such as tremors, unsteadiness, and difficulty walking. Therefore, the cerebellum is the part of the brain that plays a key role in controlling body posture in mammals.

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A cross between an albino female and a genetically normal male will result in offspring that are all phenotypically normal, but all of them will be carriers of the albino gene. Albinism is a genetic condition that is inherited in an autosomal recessive manner, which means that an individual must inherit two copies of the gene to express the albino phenotype. The albino female has two copies of the albino gene, while the genetically normal male has two copies of the normal gene. During fertilization, each parent contributes one copy of their genes to their offspring. Therefore, all the offspring will receive one copy of the normal gene from the father and one copy of the albino gene from the mother, making them carriers of the albino gene. However, since they only have one copy of the albino gene, they will not express the albino phenotype and will be phenotypically normal. If two of these carriers mate, they will have a 25% chance of producing albino offspring.

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Out of the options given, grasshopper pests would have the least destructive impact on animal life and balance in nature. While grasshopper pests can cause damage to crops and vegetation, they do not have as significant an impact on the overall ecosystem as the other options. Chemical pollution, forest fires, and oil spillage can all have devastating effects on the environment, including the loss of habitat, destruction of food sources, and the deaths of many animals. Chemical pollution can cause long-term damage to soil and water, leading to the death of plants and animals. Forest fires can destroy large areas of habitat, leading to the displacement or death of many animals, and it can take years for the ecosystem to fully recover. Oil spillage can lead to the death of marine life and the contamination of habitats, affecting the entire food chain. In contrast, grasshopper pests, while problematic for agriculture, are a natural part of the ecosystem and can actually be beneficial in some cases. They serve as a food source for many predators, and their consumption of vegetation can stimulate plant growth and diversity. Therefore, based on the information provided, grasshopper pests would have the least destructive impact on animal life and balance in nature compared to the other options.

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The feature associated with monocots is: one seed leaf, parallel venation of leaves, and petals in threes or a multiple of three. Monocots and dicots are two major classes of flowering plants. Monocots have one seed leaf, while dicots have two. Monocots also have parallel venation of leaves, meaning the veins run parallel to each other, while dicots have net-veined leaves. Additionally, the flowers of monocots have petals in threes or a multiple of three, while in dicots, the floral parts are in fours or fives. Therefore, the features of one seed leaf, parallel venation of leaves, and petals in threes or a multiple of three are all associated with monocots.

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Complex social behavior and organization are mostly found in mammals. Mammals are warm-blooded animals that have fur or hair, and most of them give birth to live young. Many mammals, such as primates, elephants, whales, dolphins, and some rodents, live in complex social groups and have well-defined social structures. They exhibit behaviors such as cooperation, communication, and division of labor, which are important for their survival and reproduction. In contrast, while some insects, birds, and reptiles also display social behavior, it is generally less complex than that found in mammals.

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The adaptation of buttress roots is typical of tropical rainforest species. Buttress roots are large, flat roots that extend from the base of the trunk and provide additional support to the tree. They are a common adaptation in tropical rainforests, where trees must be able to support themselves in shallow soils with high rainfall and wind. The large surface area of buttress roots also helps to absorb nutrients from the thin topsoil found in these environments. Few stomata is an adaptation found in desert plants that helps reduce water loss. Thick bark is an adaptation found in trees in dry, cold, or fire-prone environments that provides protection from the elements. Reduced leaves is an adaptation found in plants in arid environments that helps reduce water loss through transpiration. Therefore, buttress roots are the adaptation of tropical rainforest species that help them thrive in their unique environment.

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The inner ear contains two main organs, the cochlea and the semi-circular canals. The cochlea is responsible for hearing, and it contains hair cells that respond to sound vibrations and transmit them to the brain. The semi-circular canals are responsible for balance and detecting head movements. They are three fluid-filled canals that are oriented in different planes, and when the head moves, the fluid inside the canals moves, which stimulates hair cells that send signals to the brain. Therefore, the cochlea and semi-circular canals are the two main organs of the inner ear that are responsible for hearing and balance.