JAMB UTME - Biology - 2002

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Charles Darwin's theory of evolution suggests that the most successful organisms are those that best adapt to their environment. He proposed that living organisms compete with each other for resources, such as food, water, and shelter. Organisms with traits that make them better suited to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring. This process, called natural selection, leads to the gradual change and evolution of species over time. Darwin did not suggest that the struggle for existence among living organisms is sporadic or that organs of the body which are not regularly used by an organism will disappear. He also did not believe that any traits acquired by an organism during its lifetime could be passed on to its offspring, as those traits would not be encoded in the organism's genes.

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To calculate the density of plants in the field, we need to divide the number of observed plants by the area of the quadrat used. In this case, we observed 48 water leaf plants in a 2m2 quadrat. So, the density of water leaf plants in the field is: 48/2 = 24 plants per m2 However, none of the answer options match with this calculation. To obtain one of the answer options, we need to divide the observed number of plants by the area of one quadrat, which is 2m2, and then multiply it by the number of quadrats in one m2. For example, if we divide the observed number of plants (48) by the area of one quadrat (2m2), we get: 48/2 = 24 plants per 2m2 To convert this to the density per m2, we need to multiply it by the number of 2m2 quadrats in one m2, which is 0.5 (since 1m2 is equal to 0.5 times 2m2). Therefore, the density of water leaf plants in the field is: 24 x 0.5 = 12 plants per m2 This calculation matches with.2 per m2. Therefore, the answer is 1.2 per m2.

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The parameters of size, height, weight, and color in a population of living things are examples of continuous variation. Continuous variation is a type of variation in which individuals in a population vary within a range, and the variation can be measured quantitatively. In other words, the variation is not discrete or grouped into distinct categories, but rather exists along a continuous spectrum. Height, weight, and size, for example, can vary continuously from very small to very large, with many intermediate values in between. Color can also vary continuously, such as shades of skin color in humans. This type of variation can be influenced by both genetic and environmental factors.

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The term that best fits the description of "a step in the movement of energy through an ecosystem" is trophic level. A trophic level is a position in a food chain or food web that shows the organism's feeding relationship with other organisms in an ecosystem. The trophic level of an organism is determined by its source of energy and nutrients. The first trophic level consists of primary producers, which convert sunlight into energy through photosynthesis. The second trophic level consists of primary consumers, which feed on the primary producers. The third trophic level consists of secondary consumers, which feed on the primary consumers, and so on. Each trophic level represents a step in the transfer of energy and nutrients through an ecosystem. The other terms are related to the concept of trophic levels but do not fully encompass the idea of "a step in the movement of energy through an ecosystem." A food chain is a linear sequence of organisms that shows how energy and nutrients are transferred from one organism to another. A food web is a more complex representation of the feeding relationships in an ecosystem, with many interconnected food chains. A pyramid of numbers shows the number of organisms at each trophic level in an ecosystem, but it does not necessarily indicate the flow of energy.

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Animals aestivate when the environment in which they live becomes hot and dry. Aestivation is a type of dormancy that animals enter in response to environmental conditions such as high temperatures and low humidity. During aestivation, animals reduce their metabolic rate and become inactive, conserving their energy and water until more favorable conditions return. Aestivation is often seen in animals that live in arid regions with unpredictable rainfall patterns, such as certain species of snails, frogs, and tortoises.

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Plants prevent overcrowding through efficient seed dispersal mechanisms. When plants produce seeds, they need to ensure that these seeds are carried away from the parent plant to a new location where they can germinate and grow without competing with the parent plant for resources like water, nutrients, and sunlight. Different plants have evolved various strategies to disperse their seeds effectively, such as wind dispersal, animal dispersal, and self-dispersal. These mechanisms help to ensure that new plants can grow in areas with enough resources to support them, reducing overcrowding and competition among plants. Therefore, seed dispersal is the most efficient way for plants to prevent overcrowding.

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The structure found only in plant cells are the cell wall and chloroplasts. The cell wall is a rigid structure that surrounds the plant cell and provides it with support and protection. It is made up of cellulose, which is a carbohydrate that is not found in animal cells. Chloroplasts are organelles that are responsible for photosynthesis, the process by which plants make their food. They contain chlorophyll, a green pigment that absorbs light energy and converts it into chemical energy that can be used by the plant. Neither the cell wall nor chloroplasts are found in animal cells, which only have a cell membrane and cytoplasm. Chromatin and nucleolus are structures found in the nucleus of both plant and animal cells. Lysosomes are organelles found in animal cells, but they are not unique to them as some protists also have lysosomes.

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The organ located within the duodenal loop in mammals is the pancreas. The pancreas is a glandular organ that is part of both the digestive and endocrine systems. It is located in the upper abdomen and lies within the curvature of the duodenum, which is the first part of the small intestine. The pancreas produces digestive enzymes that are released into the duodenum to help break down food, especially fats and proteins. Additionally, the pancreas secretes hormones such as insulin and glucagon, which help regulate blood sugar levels.

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The probability of having a girl or a boy is always the same in each birth and is 1/2 or 50-50. Therefore, the probability of having a girl in the fifth birth is also 1/2 or 50-50, regardless of the gender of the previous children. This is because the gender of the previous children does not affect the gender of the next child since each birth is an independent event. So, the answer is 1/2 or 50-50.

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A tapeworm exhibits a parasitic mode of nutrition. This means that it feeds off the nutrients of another living organism, known as the host, to survive and grow. Tapeworms attach themselves to the inner lining of the host's intestines, and absorb the nutrients from the food that the host has eaten, depriving the host of these nutrients. This type of feeding is different from holozoic nutrition, which involves the intake of solid food and the digestion of that food within the organism's body.

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The feature of the caste system of bees and termites is that the workers are sterile. In these social insects, individuals are specialized and divided into castes based on their roles in the colony. The workers are responsible for tasks such as foraging, nest maintenance, and care of the young. They are also usually smaller in size and sterile, meaning they cannot reproduce. The queens and kings are larger in size and are responsible for reproduction. Nuptial flight, where the reproductive individuals leave the colony to mate and form new colonies, is typically performed by the queens and kings.

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In this scenario, the boy has one X chromosome and one Y chromosome. As the Y chromosome does not carry the allele for colour blindness, only the X chromosome determines whether he is colour blind or not. He has one Xn allele, which is the recessive allele for colour blindness. As a result, the boy is colour-blind. Therefore, the correct answer is "be colour-blind".

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One adaptation of life on trees by monkeys is the possession of digits that are opposable. This means that their thumbs (and sometimes their big toes) can move and touch the other digits on the same hand or foot, allowing them to grip branches and manipulate objects while moving through the trees. This adaptation gives monkeys more dexterity and flexibility, which is crucial for their survival in their arboreal environment.

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The capture and digestion of insects by a pitcher plant is a special form of nutrition termed "heterotrophic". Heterotrophic nutrition is a type of nutrition in which organisms cannot produce their own food and obtain nutrients by consuming other organisms. In the case of pitcher plants, they are unable to obtain essential nutrients such as nitrogen from the soil, so they have evolved to capture and digest insects to obtain these nutrients. The pitcher plant lures insects into its slippery, waxy, downward-sloping leaves, where they become trapped and are digested by enzymes produced by the plant. This unique adaptation allows the pitcher plant to survive in nutrient-poor environments.

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When a marine fish is taken from the ocean and put in a tank of fresh water, it dies after a short period because the body cells of the fish swell and burst as a result of the hypotonic fresh water. The cells of the fish are adapted to a high concentration of saltwater, and when they are placed in freshwater, which has a lower salt concentration, water moves into the cells of the fish through osmosis. This causes the cells to swell and burst, leading to the death of the fish.

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Both an amoeba and an unlaid chicken egg are single cells. An amoeba is a single-celled organism that belongs to the kingdom Protista. It is a type of unicellular organism that moves by extending pseudopods, which are temporary projections of the cell membrane and cytoplasm. An unlaid chicken egg is also a single cell. Before an egg is laid by a chicken, it consists of a single cell called a zygote. This zygote contains all the genetic material necessary to form a fully developed chicken. As the egg is incubated, the zygote undergoes cell division and differentiation, forming various tissues and organs until it becomes a fully formed chick. So, while an amoeba and an unlaid chicken egg are very different from each other, they both start as a single cell.

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The pair of organs that is located in the anterior half of the mammalian body cavity is the heart and the lungs. The body cavity of mammals is divided into two main parts, the anterior and posterior cavities. The anterior cavity contains the thoracic cavity and the abdominopelvic cavity. The thoracic cavity is located in the anterior half of the body cavity and contains the heart and lungs. The heart is a muscular organ that pumps blood throughout the body, and it is located in the mediastinum, a cavity in the thorax. The lungs are a pair of organs responsible for respiration, located on either side of the heart within the thoracic cavity. Therefore, the correct answer is "Lungs and Heart."

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This experimental set-up is designed to demonstrate a specific concept related to photosynthesis. To answer this question, we need to analyze each option and choose the one that is consistent with the experimental set-up. -: "Light is necessary for photosynthesis." This is a valid statement, but it doesn't tell us whether the experimental set-up can be used to demonstrate this concept. We cannot determine the correct answer solely based on this statement. -: "Oxygen is necessary for photosynthesis." This is incorrect because oxygen is actually a product of photosynthesis, not a requirement. -: "Photosynthesis occurs in the leaves of plants." This is a general statement about photosynthesis, but it doesn't tell us whether the experimental set-up can be used to demonstrate this concept. We cannot determine the correct answer solely based on this statement. -: "Carbon (IV) oxide is necessary for photosynthesis." This is the correct answer. The experimental set-up involves placing a plant in a sealed container with a light source and a solution of sodium hydroxide. The sodium hydroxide solution absorbs carbon dioxide produced by the plant during photosynthesis, creating a vacuum. This vacuum can be measured, and it provides evidence that the plant is producing carbon dioxide during photosynthesis. Therefore, the experimental set-up demonstrates that carbon dioxide is necessary for photosynthesis. So, the main label we can associate with this question is "Photosynthesis: demonstrating the necessity of carbon dioxide".

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When two heterozygous parents (Aa x Aa) are crossed, their genotypes can be represented as follows: AA Aa Aa aa Each parent can produce two types of gametes: A and a. The possible genotypes of the offspring can be obtained by combining the gametes from each parent. The possible genotypes of the offspring are: AA, Aa, Aa, aa. Only the offspring with the genotype aa will exhibit the recessive trait phenotypically. Therefore, the proportion of the offspring that will exhibit the recessive condition is 1/4.

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The transect method involves the study of a particular area by recording all the living organisms within a specific line or area. The highest number of species are most likely to be recorded in areas with high biodiversity. In this case, the tropical rain forest has the highest biodiversity among the options listed and is home to a vast array of plant and animal species. Therefore, the student is likely to record the highest number of species in a tropical rain forest.

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A person that is obese must avoid meals containing margarine and butter. This is because margarine and butter contain high amounts of saturated and trans fats, which can increase cholesterol levels in the body and lead to weight gain. Obesity is a condition where a person has an excessive amount of body fat, and it is often caused by consuming too many calories and not engaging in enough physical activity. Therefore, avoiding foods high in saturated and trans fats can be an important part of a weight loss or management plan for someone who is obese. The other food options listed, such as carrots and oranges, beef and beans, and rice and yam, do not necessarily need to be avoided by someone who is obese as they can be part of a healthy and balanced diet.

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In corns, food is usually stored in the stems. Corns are thick, swollen, modified underground stems of plants. They are used by plants as a means of storing nutrients, especially carbohydrates, which can be used during periods of low growth or unfavorable conditions. Storing food in the stems allows the plant to easily access the nutrients when needed for growth and development.

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The structure that is common in the embryos of mammals, amphibians, birds, fishes, and reptiles and which is an evidence of their common ancestry is the gill-slits. Gill-slits are openings found in the pharynx region of the embryos of these animals. Although these structures have different functions in different groups of animals, their presence in the embryos of different vertebrates is a clear indication of their shared evolutionary history. The gill-slits develop into different structures in different animals, for example, in fishes they develop into gills, in reptiles, birds and mammals, they develop into different structures like the middle ear cavity, parathyroid gland, and thymus gland.

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Genetic counseling is important when a marriage is planned between an Rh-negative (Rh-) woman and an Rh-positive (Rh+) man. This is because when an Rh- woman and an Rh+ man have a child, there is a chance that the child will inherit the Rh+ factor from the father and the Rh- factor from the mother. If this happens, the mother's immune system may produce antibodies against the Rh+ factor in the child's blood, which can cause hemolytic disease of the newborn (HDN) in subsequent pregnancies. Genetic counseling can help these couples understand their risks and options for preventing HDN, such as Rh immunoglobulin injections. It is important to note that genetic counseling can be helpful for any couple planning to have children, regardless of their Rh status.

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The answer to the given question is "discoid and enucleated." Erythrocytes, commonly known as red blood cells, and leukocytes, also known as white blood cells, are two main types of blood cells. Erythrocytes are responsible for carrying oxygen to different parts of the body, while leukocytes are responsible for protecting the body from infection and disease. At maturity, erythrocytes lack a nucleus and other organelles. This allows them to carry more oxygen and have a flexible, discoid shape, which helps them to pass through narrow capillaries. On the other hand, leukocytes have a nucleus and are more flexible, amoeboid-shaped, which enables them to move and migrate in response to infections and injuries. Therefore, the correct answer is "discoid and enucleated."

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Flagella are whip-like structures that help organisms move. The animals that move by means of flagella are Chlamydomonas and Euglena. Chlamydomonas is a unicellular green alga, and Euglena is a unicellular flagellate. Both of these organisms use flagella to swim through their environment.

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To select and retain the desirable trait of large body size which a farmer has observed in his herd, the farmer needs to inbreed the animals in his herd. Inbreeding refers to the breeding of closely related animals. By mating closely related animals, the farmer increases the likelihood of offspring inheriting desirable traits, such as large body size, from both parents. Over time, the frequency of the desired genes will increase in the population, leading to more animals with the desirable trait. However, inbreeding can also increase the frequency of harmful recessive genes, which can lead to health problems in the offspring. Therefore, careful selection of animals for breeding is necessary to avoid harmful effects of inbreeding.

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The carnassial teeth of a carnivorous animal consist of the last upper premolar and the first lower molar. These teeth are specialized for shearing and slicing meat. They have sharp, blade-like edges that fit together like scissors, allowing the animal to efficiently cut through flesh and bone.

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Tissue respiration refers to the process by which cells break down glucose molecules to release energy that can be used by the body. This energy is necessary for all metabolic processes that keep the body functioning properly. Therefore, the main importance of tissue respiration is the release of energy that is used by the body.