JAMB UTME - Biology - 1995

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When a tall plant and a dwarf plant are crossed, the resulting F1 generation is always tall because the tall trait is dominant over the dwarf trait. When the F1 generation is allowed to self-pollinate, the resulting F2 generation will have a 3:1 ratio of tall to dwarf plants. This is because each F1 plant carries one dominant tall allele and one recessive dwarf allele. Using a Punnett square to represent the possible genotypes of the F2 generation, we can see that out of 4 possible combinations, only 1 combination (Tt x Tt) will result in a dwarf plant (genotype tt). This gives us a probability of 1/4 or 25% chance of a dwarf offspring. If we have 120 F2 plants, we can expect 25% or 0.25 of them to be dwarf. To find out how many that is, we can multiply 120 by 0.25 to get 30 dwarf plants. Therefore, the answer is 30, and this is because of the 3:1 ratio and the laws of probability.

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Human height is an example of a feature that depends on both genetic and environmental factors. Genes play a crucial role in determining the potential height that an individual can reach, but environmental factors also influence how much of this potential is realized. The genetic factors that contribute to height include multiple genes that interact with each other to determine an individual's height potential. However, environmental factors such as nutrition, exercise, and overall health can also impact height by affecting bone growth, development, and overall health. For example, a person with genes that give them the potential for tall height may not reach their full height potential if they suffer from malnutrition or other health problems during childhood. Therefore, human height is an example of a feature that depends on both genetic and environmental factors.

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During respiration, air circulates round plant tissues via the intercellular spaces. Intercellular spaces are the spaces that exist between plant cells. They provide a pathway for the exchange of gases, such as oxygen and carbon dioxide, between the plant cells and the environment. These spaces are particularly important in the process of respiration because they facilitate the diffusion of gases necessary for the release of energy from food molecules. The other options listed (lenticels, stomata, guard cells) are all involved in the exchange of gases in plants, but they do not play a role in air circulation around plant tissues during respiration.

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The DNA molecule is a chain of repeating nucleotides. Each nucleotide is made up of a nitrogenous base, a sugar molecule, and a phosphate group. These nucleotides are linked together in a specific sequence to form a long chain, which is the DNA molecule. The nitrogenous bases in the nucleotides are adenine (A), thymine (T), cytosine (C), and guanine (G), and the sequence of these bases determines the genetic information stored in the DNA molecule.

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The slender, long and slightly curved beak of the sun-bird is an adaptation for feeding on nectar. The sun-bird's beak has evolved to fit perfectly into the long and narrow tubes of flowers, where it feeds on the nectar using its long tongue. This allows the sun-bird to obtain nectar from flowers that other birds may not be able to access.

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Secondary thickening in dicotyledonous stem is controlled by the cambium. The cambium is a type of meristem, which is a specialized tissue that is responsible for the growth and development of plants. The cambium is located between the xylem and phloem tissues in the stem, and it is responsible for the production of new xylem and phloem cells during secondary growth. As the cambium produces new xylem and phloem cells, the stem increases in diameter, resulting in secondary thickening. The pericycle is a layer of cells in the root that is responsible for the initiation of lateral roots, but it is not involved in secondary thickening in the stem.

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Organelles are specialized structures inside cells that perform specific functions. Respiration and photosynthesis are two processes that are related to energy production in cells. Respiration involves the breakdown of glucose to release energy, while photosynthesis involves the conversion of light energy into chemical energy. The organelles that are involved in respiration are the mitochondria, which are responsible for generating ATP (the energy currency of cells) through the breakdown of glucose. Therefore, cells that are actively respiring will have a high number of mitochondria. Photosynthesis, on the other hand, occurs in chloroplasts. Chloroplasts contain the pigment chlorophyll, which is responsible for capturing light energy and converting it into chemical energy through a series of reactions. Therefore, cells that are actively photosynthesizing will have a high number of chloroplasts. Therefore, the answer is Mitochondria and Chloroplasts (Option B) because they are the organelles involved in the processes of respiration and photosynthesis, respectively. Nucleolus and centrioles (Option A), lysosomes and ribosomes (Option C), and Golgi apparatus and endoplasmic reticulum (Option D) are involved in other cellular processes such as DNA replication, protein synthesis, and cellular transport, but not directly in respiration and photosynthesis.

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The diseases caused by bacteria are infections that can affect different parts of our body. Some common bacterial diseases are tuberculosis, gonorrhea, syphilis, and cholera. Tuberculosis is a bacterial disease that mainly affects the lungs, causing a persistent cough, fever, and weight loss. It can also spread to other parts of the body and can be life-threatening if not treated promptly. Gonorrhea is a sexually transmitted bacterial infection that can affect both men and women. It can cause painful urination, discharge, and pelvic pain, and if left untreated, it can lead to infertility. Syphilis is another sexually transmitted bacterial infection that can have serious consequences if left untreated. It can cause a range of symptoms, including sores, rashes, fever, and fatigue, and if left untreated, it can lead to severe damage to the heart, brain, and other organs. Cholera is a bacterial infection that is usually spread through contaminated food or water. It can cause severe diarrhea, vomiting, and dehydration, and if left untreated, it can be fatal. AIDS, on the other hand, is not caused by bacteria but by a virus called HIV. It attacks the immune system and can lead to a range of complications, including infections, cancers, and neurological disorders.

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Filariasis is transmitted through mosquito bite. Mosquitoes that carry the microscopic worms responsible for filariasis can transmit the disease to humans when they bite to feed on blood. The worms then infect the lymphatic system, leading to swelling and blockages. The other diseases listed - typhus, plague, and schistosomiasis - are transmitted through other means, such as fleas, rodents, and contaminated water.

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The depth of illumination in a water body can be measured with a secchi disc. A secchi disc is a simple tool used to measure water transparency or turbidity in a water body. It consists of a circular disc that is divided into quadrants and painted in alternating black and white colors. The disc is lowered into the water until it can no longer be seen, and the depth at which it disappears from view is recorded. This depth is known as the secchi depth and is used to determine the transparency of the water. The deeper the secchi depth, the clearer the water, and the shallower the secchi depth, the more turbid or cloudy the water. A photometer is a device used to measure the intensity of light, a hydrometer is used to measure the density of liquids, and an anemometer is used to measure wind speed.

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The ion that is involved in the conduction of the nerve impulse is K+ (potassium ion). Nerve impulses are electrical signals that travel along the axons of neurons, allowing for communication between different parts of the nervous system. These signals are generated by a flow of ions across the cell membrane of the neuron. When the neuron is at rest, the concentration of K+ ions is higher inside the cell, while the concentration of Na+ ions is higher outside the cell. When a nerve impulse is generated, there is a rapid influx of Na+ ions into the cell, followed by a rapid efflux of K+ ions out of the cell. This change in ion concentration causes a change in the electrical potential of the cell membrane, which propagates along the axon as the nerve impulse. Therefore, K+ ions are involved in the conduction of the nerve impulse by participating in the rapid efflux of ions out of the neuron during the generation of the electrical signal.

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The equation 2H2 → 2H2 + O2(g) represents the decomposition of water into hydrogen and oxygen gases during the light-dependent stage of photosynthesis. For this reaction to occur, light energy and chlorophyll must be present. Light energy is required to excite the electrons in the chlorophyll molecule, which are then used to split the water molecule into its component parts of hydrogen and oxygen. Enzymes are not required for this reaction to occur. Therefore, the correct answer is: Light energy and chlorophyll.

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The part of the brain responsible for controlling the process of walking is the cerebellum. The cerebellum is located at the base of the brain and is involved in coordinating voluntary movements such as posture, balance, and coordination. It receives sensory information from the body and uses this information to adjust and refine motor movements, including walking. Therefore, the cerebellum is essential for maintaining smooth and coordinated movements during walking.

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The excretory structure in the earthworm is the nephridium. Earthworms have numerous nephridia, which are responsible for filtering out waste materials from the coelomic fluid and expelling them through tiny pores on the body surface called nephridiopores. The nephridia also help to regulate the osmotic balance of the earthworm's body fluids.

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One common characteristic of fungi, algae, mosses, and ferns is that they produce spores that are dispersed. Spores are tiny structures that are capable of growing into a new organism under the right conditions. They are produced in large numbers and can be dispersed by various means, such as wind, water, or animals. Fungi, algae, mosses, and ferns all produce spores as part of their life cycle. The spores allow these organisms to spread and colonize new areas. Once the spores find a suitable environment, they can germinate and grow into new individuals. This method of reproduction through spores is different from sexual reproduction by conjugation, which involves the fusion of gametes to form a new individual. It is also different from the alternation of generations, which is a life cycle where an organism alternates between a haploid and diploid phase. Finally, not all of these organisms possess chlorophyll in their tissues. Only algae possess chlorophyll, which allows them to perform photosynthesis.

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Among the given options, the vertebrate whose skin functions as a respiratory surface is the frog. Frogs are amphibians, and they have a moist and permeable skin that allows for the exchange of gases such as oxygen and carbon dioxide. Oxygen is absorbed into the bloodstream through the skin, while carbon dioxide is released out of the body through the same skin. This is possible because their skin is thin and moist, making it an ideal respiratory surface for the frog.

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The end product of glycolysis in plants and animals is pyruvic acid. Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells, where glucose is converted into pyruvate through a series of enzymatic reactions. Pyruvate is a key intermediate in cellular respiration, which further undergoes oxidative decarboxylation to produce acetyl-CoA, the starting point for the citric acid cycle.

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The colour of the ventral (underside) surface of a fish is lighter than that of the dorsal (upper) surface mainly as an adaptation for camouflage. The lighter ventral coloration helps the fish blend in with the brighter water surface when viewed from below, making it less visible to predators. This is a common adaptation seen in many aquatic animals, including fish, to increase their chances of survival in their environment.

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The type of placentation shown in the question is "marginal". This is because the ovules are borne on the margin or edge of the ovary, with a single ovule attached to each placenta.

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During the bending of the arm, the biceps muscles contract and the triceps muscles relax. The biceps muscle is located in the front of the upper arm and is responsible for bending the elbow, while the triceps muscle is located at the back of the upper arm and is responsible for straightening the arm. When you bend your arm, the biceps muscle contracts and pulls on the forearm bone, causing it to move towards the upper arm bone, while the triceps muscle relaxes and allows the movement to occur smoothly.

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A measure for the control of bilharzia is the application of molluscicides in water bodies. Bilharzia, also known as schistosomiasis, is a parasitic disease that is transmitted through water snails. These snails release parasitic larvae into the water, which can penetrate the skin of people who come into contact with the contaminated water. Molluscicides are chemicals that are specifically designed to kill snails and their larvae in water bodies, thus preventing the spread of the disease. Other measures, such as cutting low brushes around homes or screening windows and doors with mosquito nets, may help to control other diseases but are not effective against bilharzia. Similarly, the application of herbicides in water bodies is not an effective measure for controlling bilharzia.

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Colonization of a bare rock surface is termed primary succession. Primary succession refers to the process of ecological succession that occurs in an area where there was no previous soil or vegetation, such as a bare rock surface, glacier retreat, or lava flow. In these areas, the first organisms to colonize are usually bacteria, lichens, and mosses that can survive in harsh conditions and break down the rock surface to create soil. As the soil layer builds up and organic matter accumulates, larger plants such as grasses and shrubs can begin to grow, which in turn attracts animals and insects. Over time, the ecosystem becomes more complex and diverse, with different species competing and interacting with each other. Therefore, the colonization of a bare rock surface is an example of primary succession, which is a process of ecological change that occurs in areas where there was no previous soil or vegetation.

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In a food chain involving a primary producer, a primary consumer, and a secondary consumer, energy is transferred from one level to the next. The primary producer, such as plants, uses the sun's energy to make food. The primary consumer, such as a herbivore, eats the plants, and in doing so, they obtain some of the energy that was stored in the plants. The secondary consumer, such as a carnivore, eats the primary consumer, and in doing so, they obtain some of the energy that was stored in the herbivore. However, not all of the energy is transferred from one level to the next. Some of the energy is lost as heat or used up by the organism in its daily activities. Therefore, the secondary consumer gets only a small portion of the energy contained in the primary producer. So, option D is the correct answer.

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A person with type O blood can donate to a patient with type A because the donor's blood lacks antigens. Blood type is determined by the presence or absence of certain antigens on the surface of red blood cells. Type O blood does not have A or B antigens, whereas type A blood has A antigens. Therefore, type O blood can be safely transfused to someone with type A blood, as the donor's blood will not trigger an immune response in the recipient due to the lack of antigens.

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A virus is a tiny infectious particle that can only replicate inside a host cell. Although viruses share some similarities with living organisms, they are not considered living entities because they cannot carry out their own metabolism and reproduction outside of a host cell. Out of the given options, viruses have one feature in common with animal cells: DNA. Both viruses and animal cells contain genetic material in the form of DNA, which carries the genetic information necessary for the development and function of an organism or virus. However, viruses differ from animal cells in the way that their DNA is packaged and structured. While animal cells have a defined nucleus that houses their DNA and other organelles, viruses do not have a nucleus or any organelles. Instead, a virus consists of a protein coat that encloses its genetic material, which may be DNA or RNA. Viruses also lack cytoplasm, which is the gel-like substance that fills the cell and surrounds its organelles. Glycogen, a complex carbohydrate that stores energy in animal cells, is also not typically found in viruses. Therefore, the answer is DNA (Option B) as it is the only feature that viruses have in common with animal cells out of the given options.

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Vitamin K plays an important role in blood clotting. When we get injured and start bleeding, vitamin K helps to activate certain proteins in our blood that are responsible for clotting and stopping the bleeding. Without enough vitamin K, our blood would not be able to clot properly, leading to excessive bleeding and other complications. Vitamin K is found in a variety of foods such as leafy greens, broccoli, and liver. Additionally, newborns are often given a vitamin K shot to prevent bleeding complications since they may not have enough vitamin K in their bodies yet.

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Maelezo ya Majibu

The gland directly affecting metabolic rate, growth and development is the thyroid gland. This gland is located in the neck and produces hormones that regulate various body functions including heart rate, blood pressure, and body temperature. The hormones produced by the thyroid gland, such as thyroxine, help to control the rate at which the body uses energy, affecting metabolism and growth. Therefore, the thyroid gland plays an important role in maintaining overall health and well-being.

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The mammalian organ that acts as both a digestive and an endocrine organ is the pancreas. The pancreas is located in the abdomen, behind the stomach, and is responsible for producing digestive enzymes that are released into the small intestine to aid in the digestion of food. Additionally, the pancreas produces hormones such as insulin and glucagon, which regulate blood sugar levels and play a role in metabolism. This dual function makes the pancreas a crucial organ in the body's digestive and endocrine systems.

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The sex of a fetus is determined during fertilization. Fertilization is the process where a sperm cell from the male combines with an egg cell from the female to form a zygote, which develops into an embryo and eventually a fetus. The sperm cell carries either an X or Y chromosome, while the egg cell carries an X chromosome. If a sperm carrying an X chromosome fertilizes the egg, the resulting zygote will have two X chromosomes and develop into a female fetus. On the other hand, if a sperm carrying a Y chromosome fertilizes the egg, the resulting zygote will have one X and one Y chromosome and develop into a male fetus. Therefore, the sex of a fetus is determined by the combination of sex chromosomes from the sperm and egg during fertilization.

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The specific number of chromosomes in each somatic cell is represented by "2N". "2N" stands for "diploid number," which refers to the number of chromosomes found in somatic cells, or non-reproductive cells, in an organism. The diploid number is the total number of chromosome pairs that an organism has, with one chromosome from each pair inherited from each parent. For example, humans have a diploid number of 46, which means that they have 23 pairs of chromosomes in each somatic cell. Each chromosome in a pair carries similar genetic information, although there may be slight differences in the alleles present on each chromosome. In contrast, "N" represents the haploid number, which is half the number of chromosomes found in somatic cells. Haploid cells are found in the reproductive organs and contain only one set of chromosomes. When two haploid cells combine during fertilization, they form a diploid cell with the full complement of chromosomes.

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When a healthy shoot of a flowering plant is illuminated from one side, auxins accumulate on the non-illuminated side of the shoot. Auxin is a plant hormone that controls various aspects of plant growth and development. One of the effects of auxin is to promote cell elongation, which causes the shoot to bend towards the light source. When light shines on one side of the shoot, the auxins on that side are destroyed, and the auxins on the other side accumulate. This creates a concentration gradient of auxin, with higher levels on the non-illuminated side, causing the shoot to bend towards the light source.