JAMB UTME - Biology - 2010
Pregunta 1 Informe
Use the diagram above to answer this question.The main function of the feathers covering the part labelled is to
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The feathers covering the part labelled in the diagram are located on the bird's body and their main function is to serve as an insulator to maintain body heat. Birds are warm-blooded animals, which means they need to maintain a constant body temperature to survive. Feathers are excellent insulators, and they help to trap body heat close to the skin. This is especially important for birds that live in colder environments or migrate to colder regions. While feathers do have other functions, such as providing lift for flight or displaying attractive colors for mating purposes, the primary function of the feathers covering the body is to provide insulation and help maintain body heat. Feathers can also help protect the skin from sun exposure and other environmental factors, but preventing ectoparasites from attacking the animal is not the main function of the feathers in this location.
Pregunta 2 Informe
In the diagram, which of the animals represents the oldest creatures in terms of evolutionary history?
Detalles de la respuesta
Based on the diagram, the animal that represents the oldest creatures in terms of evolutionary history is option I, which is the jellyfish. Jellyfish are known to have existed for over 500 million years, making them one of the oldest multicellular organisms still in existence today.
Pregunta 3 Informe
Circulation of blood to all parts of the body except the lungs is through
Detalles de la respuesta
The circulation of blood to all parts of the body except the lungs is through the systemic circulation. The circulatory system is responsible for the transportation of blood throughout the body, delivering oxygen and nutrients to tissues and organs and removing waste products. The circulatory system has two main circuits: the pulmonary circulation and the systemic circulation. The pulmonary circulation is responsible for carrying deoxygenated blood from the heart to the lungs, where it picks up oxygen and returns to the heart. In contrast, the systemic circulation carries oxygenated blood from the heart to all parts of the body except the lungs, and returns deoxygenated blood back to the heart. Therefore, the circulation of blood to all parts of the body except the lungs is through the systemic circulation. The systemic circulation involves the arteries, capillaries, and veins that carry blood to and from the body's tissues and organs. In summary, systemic circulation is the circuit of the circulatory system that delivers oxygenated blood to all parts of the body except the lungs.
Pregunta 4 Informe
Low annual rainfall, sparse vegetation , high diurnal temperatures and cold nights are characteristic features of the
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Pregunta 5 Informe
The average number of individuals of a species per unit area of the habitat is the
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The average number of individuals of a species per unit area of the habitat is known as population density. This term refers to the number of individuals of a particular species living in a specific area, such as per square mile or per hectare. Population density is an important ecological concept because it provides insight into the size and distribution of a population within an ecosystem, which can help scientists and researchers better understand how the population interacts with its environment and other species.
Pregunta 6 Informe
The activity of an organism which affects the survival of another organism in the same habitat constitutes
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The activity of an organism that affects the survival of another organism in the same habitat is called a biotic factor. Biotic factors are living things that directly or indirectly affect the distribution and abundance of other organisms in their environment. They include things like predation, competition, symbiosis, and disease. In this case, the activity of one organism is directly affecting the survival of another organism. For example, if one species of animal preys on another species of animal, the predator's activity is a biotic factor that affects the survival of the prey. Similarly, if one plant species competes with another plant species for sunlight, nutrients, or water, the competition is a biotic factor that affects the distribution and abundance of both species. Edaphic factors, abiotic factors, and physiographic factors are all different types of non-living environmental factors that can also affect the distribution and abundance of organisms, but they do not involve the activity of other living things in the same way that biotic factors do.
Pregunta 7 Informe
I. Stomata → Spirogyro II. Alveoli → Earthworm III. Malpighian tubule → Mammal IV. Contractile vacuole → Protozoa.
Which of the above structures is correctly matched with the organisms in which it is found?
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Pregunta 8 Informe
Use the diagram above to answer this question.
In which plantation are all the trees between the height of 2-4m?
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Pregunta 9 Informe
Mycorrhizae promote plant growth by
Detalles de la respuesta
Mycorrhizae are symbiotic associations between fungi and plant roots. They promote plant growth by absorbing inorganic nutrients, such as phosphorus and nitrogen, from the soil and transferring them to the plant. This enables the plant to grow faster and larger. The fungi also help to protect the plant from certain soil-borne pathogens and pests, which can help to prevent damage and disease. Overall, mycorrhizae serve as important partners to plants, contributing to their health and productivity in a number of ways.
Pregunta 10 Informe
The primary structure responsible for pumping blood for circulation through the mammalian circulatory systems is the
Detalles de la respuesta
The primary structure responsible for pumping blood for circulation through the mammalian circulatory system is the left ventricle. The heart has four chambers: the right and left atria, and the right and left ventricles. The right ventricle pumps blood to the lungs, while the left ventricle pumps oxygenated blood to the rest of the body through the arteries. The left ventricle is responsible for generating the force required to pump blood throughout the entire body, making it the primary pumping structure of the heart.
Pregunta 11 Informe
The barrier between maternal and foetal blood is the
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The barrier between maternal and foetal blood is the placenta. The placenta is a temporary organ that develops during pregnancy and connects the developing fetus to the uterine wall of the mother. It allows for the exchange of nutrients, oxygen, and waste products between the mother and the developing fetus, while preventing the mixing of their bloodstreams. The placenta acts as a filter and a barrier, preventing harmful substances such as bacteria and large molecules from passing from the mother's bloodstream to the fetus, thus protecting the developing fetus from infection and other harm.
Pregunta 12 Informe
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Thyroxine and adrenalin are hormones that control behavioral patterns. Hormones are chemical messengers produced by the endocrine glands and they help regulate various bodily functions. Thyroxine is produced by the thyroid gland and regulates metabolism, growth, and development, while adrenaline is produced by the adrenal gland and is responsible for the fight or flight response in stressful situations. Both hormones play a role in controlling an organism's behavioral patterns. For example, adrenaline can cause an increase in heart rate and alertness, preparing an organism to respond to a potential threat. Thyroxine can affect an organism's mood and energy levels, influencing their behavior.
Pregunta 13 Informe
Which of the following groups of cells is devoid of true nuclei
Detalles de la respuesta
The correct answer is "monera." Monera is a kingdom of living organisms that includes bacteria and cyanobacteria. These cells lack a true nucleus, which means their genetic material is not enclosed in a membrane-bound nucleus like in eukaryotic cells. Instead, the genetic material is located in the cytoplasm of the cell. Algae, fungi, and viruses, on the other hand, all have true nuclei.
Pregunta 14 Informe
Chemosynthetic organisms are capable of manufacturing their food from simple inorganic substances through the process of
Detalles de la respuesta
Chemosynthetic organisms are capable of manufacturing their food from simple inorganic substances through the process of oxidation. Chemosynthesis is a process by which some organisms, such as bacteria, obtain energy by breaking down inorganic molecules such as hydrogen sulfide, ammonia or methane. These organisms use the energy generated by the oxidation of these compounds to create organic compounds such as sugars or amino acids that can be used as food. During the process of chemosynthesis, inorganic compounds are oxidized, meaning that they lose electrons. This process releases energy that is then used to build organic compounds. Chemosynthesis is an important process in environments where sunlight is not available, such as deep-sea hydrothermal vents or caves. Denitrification, reduction, and phosphorylation are not involved in the process of chemosynthesis. Denitrification is the process by which some bacteria convert nitrates into nitrogen gas, while reduction involves the gain of electrons by a molecule. Phosphorylation is the process by which phosphate is added to a molecule to create a high-energy compound.
Pregunta 15 Informe
If both parents are heterozygous for a trait, the probability that an offspring will be recessive for that trait is
Detalles de la respuesta
If both parents are heterozygous for a trait, the probability that an offspring will be recessive for that trait is 1/4 or 25%. Heterozygous means that an individual has two different alleles (versions of a gene) for a particular trait. One allele is dominant, and the other allele is recessive. The dominant allele is expressed in the phenotype, or physical appearance, of the individual, while the recessive allele is only expressed in the phenotype if the individual has two copies of the recessive allele. When two heterozygous parents (Aa x Aa) have offspring, each parent can pass on either the dominant allele (A) or the recessive allele (a) to their offspring. The possible combinations of alleles that can be passed on from each parent are: AA, Aa, aA, and aa. Only the aa genotype results in the recessive trait being expressed in the offspring's phenotype. The probability of an offspring inheriting an a allele from one parent is 1/2, and the probability of inheriting an a allele from the other parent is also 1/2. Therefore, the probability of an offspring inheriting two a alleles (aa genotype) is the product of these probabilities, which is 1/2 x 1/2 = 1/4 or 25%.
Pregunta 16 Informe
Use the diagram above to answer this question.
With respect to their decreasing dependence on aquatic conditions for reproduction, which of the following is the correct arrangement of the animals represented?
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Pregunta 17 Informe
The chromosome number of a cell before and after the process of meiosis is conventionally represented as
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The chromosome number of a cell before and after the process of meiosis is conventionally represented as "2n → n". This means that the cell starts with a diploid number of chromosomes (2n), which is reduced by half through the process of meiosis, resulting in haploid daughter cells with half the number of chromosomes as the parent cell. So, "2n → n" represents the reduction in chromosome number from diploid to haploid during meiosis.
Pregunta 18 Informe
A food chain always begins with a
Detalles de la respuesta
A food chain always begins with a "producer" (as stated in). Producers are organisms that make their own food using sunlight, water, and carbon dioxide through the process of photosynthesis. They are usually green plants or algae that use chlorophyll to capture sunlight and convert it into energy. In a food chain, producers are eaten by primary consumers, which are then eaten by secondary consumers, and so on. Decomposers, which break down dead organisms and waste material, also play a crucial role in food chains, but they do not typically serve as the starting point of a food chain. Therefore, a food chain always begins with a producer, as they are the first level of the chain, providing the basis of the energy and nutrients that support all other organisms in the ecosystem.
Pregunta 19 Informe
The protozoan plasmodium falciparum is transmitted by
Detalles de la respuesta
The protozoan Plasmodium falciparum is transmitted by female Anopheles mosquitoes. Plasmodium falciparum is the causative agent of the most severe form of malaria in humans. The parasite is transmitted through the bite of an infected female Anopheles mosquito, which injects the Plasmodium falciparum sporozoites (the infective form of the parasite) into the bloodstream of a human host. Once in the human bloodstream, the sporozoites travel to the liver, where they mature and multiply, then enter the red blood cells, causing them to rupture and release more parasites into the bloodstream. This process leads to the characteristic symptoms of malaria, such as fever, chills, and flu-like illness. Therefore, the correct answer is female Anopheles mosquitoes as they are the vectors responsible for transmitting the protozoan Plasmodium falciparum.
Pregunta 20 Informe
The outer layer of the kidney where the Bowman's capsules are found is the
Detalles de la respuesta
The outer layer of the kidney where the Bowman's capsules are found is called the cortex. This is the layer of the kidney that contains the renal corpuscles, including the glomerulus and Bowman's capsule, where the process of filtration of blood takes place. The cortex also contains the convoluted tubules, which are responsible for reabsorbing nutrients and water back into the bloodstream. The other options, pelvis, medulla, and pyramid, are different regions within the kidney, but they are not the location of the Bowman's capsules.
Pregunta 21 Informe
The oily substance that lubricates the mammalian hair to keep it flexible and water repellent is secreted by the
Detalles de la respuesta
The oily substance that lubricates mammalian hair is secreted by the sebaceous glands. These glands are located in the skin and produce sebum, an oily substance that helps to keep the hair flexible and water repellent. Sebum also has antibacterial properties and helps to prevent the hair and skin from drying out.
Pregunta 22 Informe
Which of the following is NOT a function of the nucleus of a cell?
Detalles de la respuesta
The function that is NOT associated with the nucleus of a cell is that it is not a reservoir of energy for the cell. The nucleus is a membrane-bound organelle that contains the cell's genetic material, including DNA and RNA. It is often referred to as the "control center" of the cell because it regulates gene expression and controls the cell's growth and reproduction. One of the main functions of the nucleus is to store and carry hereditary information in the form of DNA, which is organized into structures called chromosomes. During cell division, the nucleus divides and the chromosomes are replicated and distributed to each daughter cell. The nucleus also plays a crucial role in protein synthesis by translating genetic information into messenger RNA (mRNA), which is then transported to the ribosomes in the cytoplasm, where it is used to manufacture proteins. Overall, the nucleus is a vital organelle that controls the life processes of the cell and ensures the accurate transmission of genetic information from one generation of cells to the next.
Pregunta 23 Informe
Use the diagram above to answer this question.
During photosynthesis, the arrow labelled ll represents the
Detalles de la respuesta
The arrow labelled ll in the diagram refers to the release of oxygen as a by-product during photosynthesis. This occurs in the light-dependent reaction stage of photosynthesis where light energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH. As a result of this process, oxygen is produced and released into the atmosphere as a by-product.
Pregunta 24 Informe
A pair of genes that control a trait is referred to as
Detalles de la respuesta
A pair of genes that control a trait is referred to as "alleles" (as stated in). An allele is a specific version of a gene, which determines a particular trait or characteristic. Each individual organism inherits two alleles for each gene, one from each parent, and the combination of these alleles determines the organism's phenotype, or observable traits. In genetics, alleles can be dominant or recessive. A dominant allele is expressed when an individual has either one or two copies of the allele, while a recessive allele is only expressed when an individual has two copies of the allele. A hybrid, on the other hand, refers to an offspring of two different species or varieties, or of genetically dissimilar parents. It is not a term that describes a pair of genes that control a trait. Therefore, a pair of genes that control a trait is referred to as alleles, which can be dominant or recessive.
Pregunta 25 Informe
The blood component that has the greatest affinity for oxygen is the
Detalles de la respuesta
The blood component that has the greatest affinity for oxygen is the erythrocytes, also known as red blood cells. These cells contain a protein called hemoglobin which binds to oxygen molecules in the lungs and carries them to tissues throughout the body. Hemoglobin is a highly specialized molecule that can bind up to four oxygen molecules at a time, and it is the primary means by which oxygen is transported in the bloodstream. Therefore, erythrocytes play a vital role in delivering oxygen to the body's tissues and organs.
Pregunta 26 Informe
Which of the following organisms is mainly found in the marine habitat?
Detalles de la respuesta
The organism mainly found in the marine habitat is the dogfish. Dogfish is a type of shark that lives in the ocean. Achatina is a type of land snail, Tilapia is a type of freshwater fish, and tortoise is a land animal.
Pregunta 27 Informe
If both parents are heterozygous for a trait, the probability that an offspring will be recessive for that trait is
Detalles de la respuesta
If both parents are heterozygous for a trait, it means that each parent has one dominant allele and one recessive allele for that trait. When these two parents mate, their offspring have a 25% chance of inheriting two recessive alleles (one from each parent), which will result in the expression of the recessive trait. This means that the probability that an offspring will be recessive for that trait is 1/4 or 25%. Therefore, option C (1/4) is the correct answer.
Pregunta 28 Informe
When the mixture of a food substance and Benedict's solution was warmed, the solution changed from blue to black-red. This indicates the presence of
Detalles de la respuesta
The presence of reducing sugar is indicated by a change in color from blue to black-red when a food substance is mixed with Benedict's solution and heated. Benedict's solution is a chemical reagent used to detect the presence of reducing sugars, such as glucose, fructose, and maltose. When Benedict's solution is mixed with a food substance containing reducing sugar and heated, a chemical reaction takes place, causing the solution to change color from blue to green, yellow, orange, or red, depending on the amount of reducing sugar present. If the amount of reducing sugar is high, the solution may turn brick-red or even black-red in color. This color change is due to the reduction of copper ions in the Benedict's solution to copper oxide, which is a black or reddish-brown solid. In contrast, fatty acids, sucrose, and amino acids do not react with Benedict's solution, and therefore, do not cause a color change from blue to black-red when mixed with the solution and heated.
Pregunta 29 Informe
Use the diagram above to answer this question.
Which of the following is a true feature of plantation ll?
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Pregunta 30 Informe
The flippers of a whale and the fins of a fish are examples of
Detalles de la respuesta
The flippers of a whale and the fins of a fish are examples of convergent evolution (comme l'). Convergent evolution is a process in which two or more unrelated species evolve similar traits or characteristics independently in response to similar environmental pressures or challenges. In the case of the flippers of a whale and the fins of a fish, both of these species have evolved appendages that allow them to move through water efficiently, even though their evolutionary lineages are not closely related. Divergent evolution, on the other hand, refers to the process by which closely related species evolve different traits or characteristics in response to different environmental pressures. Coevolution refers to the process by which two or more species evolve in response to each other, with each species exerting selective pressures on the other. Continuous variation refers to the variation that occurs within a population due to the combined influence of genetic and environmental factors.
Pregunta 31 Informe
The sheet of muscle that separates the thoracic and the abdominal cavities is the
Detalles de la respuesta
The sheet of muscle that separates the thoracic and abdominal cavities is called the diaphragm. The diaphragm is a thin, dome-shaped muscle that separates the chest cavity (thorax) from the abdominal cavity. It plays an important role in breathing, as it contracts and relaxes to create changes in pressure that help to move air in and out of the lungs. In addition to its role in breathing, the diaphragm also plays a role in the function of several other organs located in the thoracic and abdominal cavities, such as the heart, liver, and spleen. It also helps to maintain the position of the stomach and intestines. Overall, the diaphragm is a vital muscle that is essential for breathing and the proper functioning of several other organs in the body.
Pregunta 32 Informe
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In the male reproductive system of a mammal, sperm is stored in the epididymis. The epididymis is a coiled tube that lies on the surface of each testis. After the sperm are produced in the seminiferous tubules of the testes, they move to the epididymis, where they mature and are stored until ejaculation. During ejaculation, the sperm are propelled through the vas deferens and into the urethra for expulsion from the body.
Pregunta 33 Informe
The two halves of the pelvic girdle are joined together at the
Detalles de la respuesta
The two halves of the pelvic girdle are joined together at the pubic symphysis. The pelvic girdle is a ring of bones that connects the vertebral column to the lower limbs. It consists of two hip bones, each of which is made up of three fused bones: the ilium, ischium, and pubis. The pubic symphysis is a cartilaginous joint that connects the two pubic bones anteriorly, forming the front part of the pelvic girdle. It is a strong joint that provides stability to the pelvis and allows for a small amount of movement during childbirth.
Pregunta 34 Informe
I. Adoption of appropriate nocturnal habits ll. Burrowing lll. Adjusting their internal body temperature. IV Possession of many sweat pores.
Which of the above are ways in which desert animals adapt to extreme heat of the environment?
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Pregunta 35 Informe
A dilute solution of phenylthiocarbamide tastes bitter to some people and is tasteless to others. This is an example of
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Pregunta 36 Informe
Use the diagram above to answer this question.
Based on the shape and structure of the beak and feet, the bird represented is likely to feed mainly on
Detalles de la respuesta
The bird in the diagram has a short, stout beak and strong, sharp claws. This suggests that the bird is adapted for feeding on hard, tough food items like seeds. The shape of the beak is not suited for tearing flesh, and the presence of claws indicates that the bird is likely to perch on branches and use its feet to hold onto food items while it eats. Therefore, the bird is likely to feed mainly on seeds.
Pregunta 37 Informe
The main distinguishing features between the soldier termite and other members of the caste are the
Detalles de la respuesta
Soldier termites have distinguishing features that set them apart from other members of the termite colony. They do not have wings, and their mandibles (mouthparts) are very strong and developed, allowing them to defend the colony from predators. They also have a large head, which contains the muscles needed to operate their mandibles. Therefore, the correct option is "absence of wings, possession of strong mandibles and a large head."
Pregunta 38 Informe
Parental care is exhibited by
Detalles de la respuesta
Parental care is exhibited by birds. Parental care refers to the behavior of adult animals towards their offspring to ensure their survival and well-being. In birds, parental care involves activities such as incubation of eggs, protection of eggs and chicks from predators, feeding and nurturing of chicks, and teaching them important survival skills. This behavior is crucial for the survival and successful reproduction of bird species.
Pregunta 39 Informe
The vector for yellow fever is
Detalles de la respuesta
The vector for yellow fever is the Aedes mosquito. A vector is an organism that transmits a disease from one host to another. In the case of yellow fever, the Aedes mosquito becomes infected with the virus when it feeds on an infected human or monkey. The virus then multiplies in the mosquito and can be transmitted to another human or monkey when the mosquito feeds again.
Pregunta 40 Informe
The dominant phase in the life cycle of a fern is the?
Detalles de la respuesta
The dominant phase in the life cycle of a fern is the sporophyte. This is because the sporophyte is the diploid phase, which means that it has two sets of chromosomes. The sporophyte is the leafy plant that we see when we look at a fern, and it is the stage that produces spores through meiosis. The spores then develop into the haploid gametophyte stage, which is much smaller and is not visible to the naked eye. The gametophyte produces gametes (sperm and eggs) that then fuse to form the diploid zygote, which develops into the sporophyte.
Pregunta 41 Informe
Which of the following stimuli is likely to elicit a nastic response in an organism?
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Pregunta 42 Informe
Which of the following characterizes a mature plant cell?
Detalles de la respuesta
The characteristic that characterizes a mature plant cell is that the cell wall is made up of cellulose. Plant cells have several features that distinguish them from animal cells, including the presence of a cell wall made up of cellulose. This cell wall provides structural support to the cell and helps to maintain the shape of the plant tissue. As the plant cell matures, the cell wall becomes thicker and more rigid, allowing the cell to withstand the mechanical stresses of growth and development. While the nucleus is an important organelle in both plant and animal cells, its position and shape can vary depending on the cell type and developmental stage. The cytoplasm also fills up the entire cell space in both plant and animal cells. Therefore, neither of these characteristics is unique to a mature plant cell.
Pregunta 43 Informe
The part of the human gut that has an acidic content is the
Detalles de la respuesta
The part of the human gut that has an acidic content is the stomach. The stomach is a muscular organ located between the esophagus and the small intestine. It receives food from the esophagus and releases acidic digestive juices, including hydrochloric acid, which lower the pH of the stomach contents to between 1.5 and 3.5. The acidic environment in the stomach helps to break down food particles into smaller molecules, such as proteins and carbohydrates, and also helps to kill harmful bacteria and other microorganisms that may be present in the food. After the food has been partially digested in the stomach, it passes into the duodenum, which is the first part of the small intestine. The duodenum has a slightly alkaline environment, which helps to neutralize the acidic stomach contents and prepare the food for further digestion in the small intestine. The ileum and colon, which are part of the large intestine, have a neutral to slightly acidic pH.
Pregunta 44 Informe
The mode of nutrition of sun dew and bladder wort can be described as
Detalles de la respuesta
The mode of nutrition of sundew and bladderwort can be described as holozoic. This means that they obtain their nutrients by trapping and digesting small organisms like insects. These carnivorous plants have evolved specialized structures such as sticky hairs, and bladder-like traps that capture the prey. They then use enzymes to break down the organic material of the prey into smaller molecules that they can absorb and use as nutrients. This is different from autotrophic plants, which can produce their own food through photosynthesis, and from saprophytic organisms, which obtain their nutrients from decaying organic matter. Chemosynthetic organisms manufacture their food from simple inorganic substances.
Pregunta 45 Informe
Which of the following is lacking in the diet of a person with kwashiorkor?
Detalles de la respuesta
A person with kwashiorkor lacks sufficient protein in their diet. Kwashiorkor is a type of malnutrition that occurs when a person's diet is deficient in protein. Protein is important for the growth and repair of tissues in the body, and a lack of protein can lead to a range of symptoms including muscle wasting, stunted growth, and edema (swelling). Carbohydrates, minerals, and vitamins are also important nutrients, but they are not lacking specifically in kwashiorkor. Carbohydrates provide energy to the body, while minerals and vitamins are needed in small amounts to support a range of bodily functions. However, a deficiency in any of these nutrients can lead to other types of malnutrition and health problems. In summary, a lack of protein is the primary nutrient deficiency in kwashiorkor, and it is important to ensure that individuals with this condition receive sufficient protein in their diet to prevent further complications.
Pregunta 46 Informe
Yeast respires anaerobically to convert simple sugar to carbon (IV) oxide and
Detalles de la respuesta
Yeast is capable of two types of respiration: aerobic and anaerobic. In the absence of oxygen, yeast carries out anaerobic respiration, also known as fermentation, to produce energy. During this process, yeast converts simple sugar into carbon dioxide and alcohol. Therefore, the answer is alcohol.
Pregunta 47 Informe
Use the diagram above to answer this question.
The movement of material in the xylem and phloem tissues of the plant are represented by the arrows labelled
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Pregunta 48 Informe
Which of the following is true of the transverse section of a dicot system?
Detalles de la respuesta
The correct option is "the xylem is more interiorly located than the phloem." In a dicot stem, the vascular bundles are arranged in a ring-like structure, with the xylem located towards the center and the phloem towards the periphery. This arrangement is called a "closed" vascular system, in contrast to the "open" vascular system of monocots. The cambium, a layer of meristematic cells that gives rise to new xylem and phloem, lies between the xylem and phloem in the vascular bundles. The cortex is the outermost layer of the stem, while the epidermis is the outermost layer of cells that covers the stem.
Pregunta 49 Informe
At what stage in the life history of a mammal is the sex of an individual set?
Detalles de la respuesta
The stage in the life history of a mammal at which the sex of an individual is set is "at conception" (as stated in). The sex of a mammal, like other animals, is determined by the chromosomes inherited from its parents. Female mammals have two X chromosomes (XX), while male mammals have one X and one Y chromosome (XY). The sex of the individual is determined at the moment of fertilization, when the sperm from the male parent (which carries either an X or a Y chromosome) fuses with the egg from the female parent (which always carries an X chromosome) to form a zygote. Therefore, the sex of an individual mammal is determined at conception, before birth or any other stages in the life history of the mammal. Puberty and adolescence are stages in the life history of a mammal where sexual characteristics become more apparent, but the sex of the individual has already been determined at conception.
