JAMB UTME - Biology - 2006

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The two normal types of sex chromosomes are XX and XY. Sex chromosomes determine the biological sex of an individual. Females have two X chromosomes (XX), while males have one X chromosome and one Y chromosome (XY). During sexual reproduction, each parent contributes one sex chromosome, either an X or a Y, to their offspring. If an individual inherits an X chromosome from both parents, they will be female (XX), while if they inherit an X chromosome from their mother and a Y chromosome from their father, they will be male (XY). Therefore, the two normal types of sex chromosomes are XX and XY.

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The chamber of the heart that receives oxygenated blood from the lungs in a rabbit is the left auricle. The left auricle receives oxygen-rich blood from the lungs and pumps it into the left ventricle, which then pumps it out to the rest of the body. The right atrium, on the other hand, receives deoxygenated blood from the body and pumps it to the lungs for oxygenation.

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The diagram is illustrating sexual reproduction in option I. In this option, there are two different individuals, one male and one female, each contributing genetic material to create offspring. The male and female individuals are indicated by the labels "♂" and "♀" respectively. The fusion of the male and female gametes (sperm and egg) produces a zygote, which then develops into an offspring with a unique combination of genetic material from both parents. This process is characteristic of sexual reproduction. Therefore, option I is the correct answer.

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A population that doubles in size at constant intervals is an indication of exponential growth. Exponential growth refers to a pattern of growth where a population increases at a constant rate over time, resulting in a J-shaped curve. In this type of growth, the population size doubles after a fixed time period, such as every year or every generation. This pattern of growth is often seen in populations that have abundant resources and few limiting factors. However, exponential growth cannot continue indefinitely, as resources eventually become limited and environmental factors begin to exert greater pressures on the population.

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Climax communities in a biotic succession are usually characterized by a stable composition of plant and animal species. In a biotic succession, different species of plants and animals gradually replace each other over time as the environment changes. As these changes occur, the communities that inhabit the area also change until a stable endpoint is reached, which is known as the climax community. The climax community is characterized by a relatively stable composition of plant and animal species, where the dominant species have become well adapted to the environment and are able to maintain their populations. While some changes may still occur within the community, they are generally minor and do not significantly alter the overall composition of the community. The other options are not correct because they suggest that the climax community is constantly changing or undergoing rapid changes, which is not the case. While there may be some minor changes over time, the overall composition of the community remains relatively stable.

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The change in the length of the neck of the giraffes shown in the diagram was brought about by natural selection. Over time, giraffes with longer necks were better able to reach food sources that were higher up in trees, giving them a survival advantage over giraffes with shorter necks. These longer-necked giraffes were then more likely to survive and reproduce, passing on their longer-necked traits to their offspring. This process of natural selection gradually led to the evolution of longer necks in giraffes over many generations. Geographical isolation, predation, and symbiosis may also play a role in evolution, but in this particular case, the lengthening of the giraffe necks was primarily driven by natural selection.

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The economic importance of the larva in the diagram is that it feeds on the leaves of crops. The larva shown in the diagram is a pest insect that is known to feed on the leaves of crops such as cotton and soybeans. When large populations of these larvae are present, they can cause significant damage to the crops, which can result in lower crop yields and financial losses for farmers. Therefore, the economic importance of this larva lies in its ability to cause damage to crops, which can have a negative impact on the economy of areas that rely on agriculture.

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An organism that exhibits extracellular digestion is Rhizopus. Rhizopus is a type of fungus that obtains nutrients by secreting enzymes outside its body to break down organic matter. The enzymes break down complex molecules, such as carbohydrates and proteins, into simpler molecules, such as glucose and amino acids, which the fungus can then absorb and use as a source of energy. This process is called extracellular digestion because it takes place outside the organism's body. In contrast, intracellular digestion takes place within the organism's body. Therefore, Rhizopus is an example of an organism that exhibits extracellular digestion.

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The primitive feature of the coelenterates is the possession of radial symmetry. Radial symmetry means that the body of the organism is arranged in a circular or radial pattern around a central axis. This is different from bilateral symmetry where the body is divided into two mirror-image halves. Radial symmetry is considered primitive because it is found in many of the earliest forms of animals and is a less complex form of symmetry. The possession of radial symmetry in coelenterates allows for equal access to the environment in all directions and also enables them to capture prey from any direction.

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Fish have the most simple structured heart among the given options. The fish heart consists of two chambers, an atrium and a ventricle. The atrium receives deoxygenated blood from the body and pumps it into the ventricle, which in turn pumps the blood to the gills for oxygenation. This is in contrast to the more complex heart structures of the other options, which have more chambers and a more sophisticated system for circulating oxygenated blood throughout the body.

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The part of the mammalian skin involved in temperature regulation is the sweat gland. Sweat glands are responsible for producing sweat, which is a liquid that is released through the skin's surface to help cool down the body. As the sweat evaporates, it takes away heat from the body and helps to lower the body's temperature. Therefore, the sweat gland plays an essential role in the body's thermoregulation.

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The importance of the association between the fungus and the algae in the diagram is that the fungus obtains oxygen and carbohydrates from the algae. The association between the fungus and the algae is called a mutualistic relationship, which means that both organisms benefit from the relationship. In this case, the algae photosynthesize and produce carbohydrates using energy from the sun. Some of these carbohydrates are transferred to the fungus, which cannot photosynthesize on its own. In return, the fungus provides a protected environment for the algae to grow and reproduce. The fungus also absorbs minerals and water from the surrounding soil and makes them available to the algae. Therefore, the main benefit that the fungus receives from the association with the algae is a source of energy in the form of carbohydrates and oxygen.

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In the diagram, structures used for offense and defense are labelled as i and ii. Structure i represents the canines, which are long and pointed teeth used for biting and tearing prey or for self-defense. They are prominent in carnivorous animals like lions, tigers, and wolves. Structure ii represents the horns, which are bony protrusions that grow from the heads of certain mammals like antelopes, cattle, and sheep. Horns are primarily used for defense against predators, rivals, and in some cases, for fighting over mates. Structures iii and iv are not associated with either offense or defense in this diagram. Structure iii represents the molars, which are broad teeth used for grinding food. Structure iv represents the nasal cavity, which is an air-filled space in the skull that connects the nostrils to the respiratory system.

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The answer is that both the nervous and endocrine systems involve the use of chemical substances. The nervous system uses neurotransmitters to transmit signals between neurons, while the endocrine system uses hormones to transmit signals throughout the body via the bloodstream. Both systems use chemical messengers to communicate with target cells, tissues, and organs, and to regulate a variety of bodily functions.

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Mendel's second law of inheritance states that alleles segregate independently during the formation of gametes. This means that during the formation of sex cells (sperm or egg cells), the two copies of a gene separate from each other randomly, so each gamete receives only one copy of the gene. This random separation of alleles means that different traits are inherited independently of each other. For example, the inheritance of a gene for flower color does not affect the inheritance of a gene for plant height. This is why Mendel's second law is also called the law of independent assortment.

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Night blindness results from a deficiency of Vitamin A. Vitamin A is essential for good vision, especially in low light conditions. It is required for the proper functioning of the retina, the part of the eye that senses light and helps us see. When the body does not get enough Vitamin A, the retina cannot function properly, leading to night blindness. Night blindness is a condition where the affected person has difficulty seeing in low light conditions, such as at dusk or in dimly lit rooms. It can also lead to other vision problems, such as a decreased ability to see contrasting colors or an increased sensitivity to glare. Vitamin E, Vitamin K, and Vitamin C are important for other bodily functions, but not for vision.

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The evidence that supports the advancement of ferns over mosses is derived from comparative anatomy. Comparative anatomy is the study of the similarities and differences in the structures of different organisms. Scientists have studied the anatomy of both mosses and ferns and have found that ferns have more advanced structures than mosses. For example, ferns have vascular tissue, which allows them to transport water and nutrients more efficiently than mosses. They also have more complex leaves and root systems than mosses, which allows them to grow larger and compete more effectively for resources. In contrast, mosses lack true roots, stems, and leaves, and their bodies are relatively simple. While mosses play an important role in ecosystems and have unique adaptations that allow them to survive in harsh environments, they are generally considered to be less advanced than ferns and other plants with more complex structures. Therefore, the evidence that supports the advancement of ferns over mosses is derived from comparative anatomy.

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The intensity of competition among animals in a given area will increase with an increase in population size. Competition occurs when two or more individuals require the same limited resources such as food, water, and shelter. When the population size increases, there are more individuals competing for these limited resources, which leads to increased competition. In this situation, individuals must compete more fiercely to obtain the resources they need to survive, which may lead to a decline in individual fitness, health and survival. In contrast, if the population size decreases, the intensity of competition will likely decrease as there are fewer individuals competing for the same resources. Therefore, the intensity of competition among animals in a given area will increase with an increase in population size.

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In the diagram, the structure labelled I is sensitive to light and touch. Structure I represents the eye, which is the organ of sight in animals. The eye is sensitive to light and is responsible for vision. Additionally, the eye is also sensitive to touch and is protected by eyelids and eyelashes, which help to keep out foreign particles and other irritants. Therefore, the structure labelled I is sensitive to both light and touch. The other options are incorrect as they suggest that the structure is sensitive to chemicals only or light only, which is not true for the eye.

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From the distribution shown in the diagram, we can decide that species IV is the one whose distribution is not dependent on rainfall. Species IV is found in all three locations, regardless of the amount of rainfall, whereas the other three species are restricted to specific areas based on rainfall levels. This suggests that species IV may have adaptations that allow it to tolerate a wider range of environmental conditions than the other species. However, we cannot make any conclusions about the rainfall preferences of the other species based on this diagram, as their distributions are not as clear-cut. While species III seems to be most abundant in the location with the highest rainfall, it is also found in the other two locations. Similarly, while species I and II are more restricted in their distributions, we cannot definitively say whether they prefer moderate to high rainfall or constant rainfall based on this diagram alone.

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A plant that exhibits the type of reproduction shown in IV is bryophyllum. Bryophyllum is a type of plant that reproduces asexually through the production of vegetative propagules, which are plant structures that can grow into new individuals. In bryophyllum, the vegetative propagules develop from the edges of the leaves, and each propagule can grow into a new plant. The diagram is likely showing the reproductive structure of a flowering plant, but the structure labelled IV is similar to the reproductive structures found in bryophyllum leaves. In bryophyllum, the leaf margins produce small plantlets that eventually grow roots and develop into new plants.

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The soil type that contains nutrients which are not readily available for plants is clayey soil. Clayey soil is composed of small mineral particles that are tightly packed together, which can make it difficult for plant roots to penetrate and absorb nutrients. This type of soil has a high capacity to retain water and nutrients, but the nutrients are often bound to the clay particles and not easily available for plants to use. In contrast, sandy soil has larger mineral particles that do not tightly pack together, which can allow for easy water and nutrient movement but also leads to rapid drainage and nutrient leaching. Loamy soil is a mixture of sand, silt, and clay and is often considered the ideal soil type for plant growth because it provides good water and nutrient retention while also allowing for good drainage and aeration. Alluvial soil is formed by the deposition of sediment by a river or stream and can have a mixture of sand, silt, and clay. The nutrient availability in alluvial soil can vary depending on the specific composition of the soil.

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The mammalian vein that starts with and ends in a capillary network is the hepatic portal vein. The hepatic portal vein is responsible for carrying blood from the gastrointestinal tract, pancreas, and spleen to the liver. It starts in capillaries that are present in the walls of the digestive tract and ends in the capillary network of the liver. The blood that flows through this vein is rich in nutrients and other substances that have been absorbed from the intestines and processed by the pancreas. The other options are not correct because they do not start and end in capillary networks. The pulmonary vein carries oxygenated blood from the lungs to the heart and does not start in a capillary network. The mesenteric vein drains blood from the intestines but does not end in a capillary network. The renal vein carries blood from the kidneys to the heart and does not start in a capillary network.

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The causative agent of typhoid fever is Salmonella. Salmonella typhi is the specific bacterium responsible for causing typhoid fever, which is a bacterial infection that is spread through contaminated food or water. The bacteria can survive in water or soil for several weeks and can be transmitted from person to person through contact with feces or urine of an infected individual. Symptoms of typhoid fever include fever, headache, stomach pain, and diarrhea. It is important to seek medical treatment if you suspect you have typhoid fever as it can lead to serious complications if left untreated.

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Grasses recover quickly from bushfires in the savanna because of their fibrous roots. Grasses have a root system that is made up of many thin, branching roots that spread out near the surface of the soil. These roots help grasses to quickly absorb nutrients and water after a fire. Fibrous roots also allow grasses to quickly send up new shoots from the base of the plant, even if the aboveground part of the plant has been burned away. This allows grasses to quickly recover and grow again after a fire. In contrast, succulent stems or perennating organs, which are options mentioned in the question, are not typically associated with the ability of grasses to recover after a fire.

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In the diagram, the variation illustration is morphological. Morphological variation refers to differences in physical characteristics or traits among individuals of a species. In the diagram, the variation is shown through differences in the size, shape, and coloration of the beetles. These physical differences are morphological in nature and can be used to distinguish one type of beetle from another. The other options are not applicable to the illustration shown in the diagram. Discontinuous variation refers to traits that are either present or absent, such as blood type, and is not applicable to morphological differences between beetles. Physiological variation refers to differences in the internal functions of an organism, such as metabolism or hormone production, and is not visible in the diagram. Biochemical variation refers to differences in the chemical composition of an organism, such as enzymes or proteins, and is also not visible in the diagram.

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The part of the mammalian skin involved in excretion is the sweat glands. Sweat glands are responsible for producing sweat, which contains water, salt, and other waste products such as urea and ammonia. These waste products are eliminated from the body through the skin via the sweat glands. Sweat glands help to regulate body temperature and maintain electrolyte balance by excreting excess water and salt from the body. Therefore, the sweat glands play an essential role in the excretion of waste products from the body through the skin.

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The role of the Golgi complex in a eukaryotic cell is to transport organic materials in and out of the cell. The Golgi complex is responsible for processing, sorting, and modifying proteins and lipids that have been synthesized in the endoplasmic reticulum (ER). It then packages and transports these modified molecules to their final destinations, either within the cell or outside of it. This process involves the formation of vesicles that bud off from the Golgi complex and carry their cargo to their intended target. In summary, the Golgi complex acts as a kind of post office for the cell, ensuring that the right molecules get to the right place at the right time.

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Water is formed during tissue respiration as a result of the reduction of oxygen by hydrogen. In the process of respiration, oxygen is used to break down glucose molecules to release energy, which is then used by the cell for various functions. During this process, electrons and hydrogen ions are transferred from glucose to oxygen molecules, which combines with hydrogen ions to form water molecules. The chemical equation for respiration can be summarized as: glucose + oxygen → carbon dioxide + water + energy. This means that water is produced as a byproduct of the cellular respiration process. It's important to note that water is essential for the respiration process, as it helps to transport electrons and protons during the various stages of respiration. The breakdown of water molecules does not occur during tissue respiration, and the reduction of carbon dioxide is not directly involved in the formation of water.

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Water is necessary for a germinating seed because it activates the enzymes required for the process of germination. Enzymes are molecules that help to speed up chemical reactions, and they are essential for the breakdown of stored food in the seed to provide energy for the growing embryo. However, these enzymes are inactive when the seed is dry, and they can only become active when they come into contact with water. Without water, the enzymes cannot work, and the seed cannot germinate. Therefore, water is crucial for the process of germination to occur.

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The organ that produces both hormones and enzymes is the pancreas. The pancreas is a gland located in the abdomen that plays an important role in digestion and glucose metabolism. It produces digestive enzymes, such as amylase and lipase, which are released into the small intestine to break down carbohydrates, proteins, and fats. It also produces hormones, such as insulin and glucagon, which regulate blood sugar levels. Insulin helps to lower blood sugar levels by facilitating the uptake of glucose by cells, while glucagon raises blood sugar levels by stimulating the liver to release stored glucose. Therefore, the pancreas serves a dual function in the body, producing both enzymes and hormones.

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The dominant phase in the life cycle of a bryophyte is the gametophyte. A bryophyte is a type of non-vascular plant that includes mosses, liverworts, and hornworts. In their life cycle, bryophytes alternate between two distinct phases: the gametophyte phase and the sporophyte phase. The gametophyte is the dominant phase in the bryophyte life cycle, as it is the phase that performs most of the plant's functions, including photosynthesis and reproduction. The gametophyte produces gametes (sperm and egg cells) which, after fertilization, develop into sporophytes. The sporophyte is a short-lived phase in the bryophyte life cycle that produces spores, which then grow into new gametophytes, completing the cycle. Therefore, the dominant phase in the life cycle of a bryophyte is the gametophyte.

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A unique characteristic that distinguishes the class of vertebrates represented in the diagram from other vertebrates is the presence of a covering of feathers. Feathers are a defining characteristic of birds, which are members of the class Aves. While other vertebrates, such as reptiles and some mammals, may have scales or hair, feathers are unique to birds. Feathers play a critical role in flight and insulation, making them essential to the survival of birds in their environments. Two pairs of limbs and scales on the lower legs are not unique to this class of vertebrates and can be found in other groups. A pair of wings is also not unique, as bats have wings but are not birds. Therefore, the presence of feathers is the distinguishing characteristic of birds in this diagram.

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The organ situated in the pericardial cavity of a mammal is the heart. The pericardial cavity is a fluid-filled space that surrounds and protects the heart, which is the central organ of the circulatory system. The heart is responsible for pumping blood throughout the body, delivering oxygen and nutrients to cells and tissues and removing waste products. It is a muscular organ that contracts and relaxes in a rhythmic pattern to create the force needed to circulate blood. The heart is divided into four chambers: the left and right atria and the left and right ventricles. The atria receive blood from the body and lungs, while the ventricles pump blood out of the heart to the rest of the body. The heart is one of the most important organs in the body, and its proper functioning is critical to maintaining overall health and wellness. Any problems with the heart, such as arrhythmias, blockages, or disease, can have serious consequences for the body's ability to function properly. Therefore, it is important to take good care of the heart through a healthy lifestyle, regular exercise, and medical check-ups.

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The characteristic that best exemplifies the evolutionary advancement of mammals over other vertebrates is the viviparous mode of reproduction. Viviparity is a reproductive adaptation where the developing embryo is retained within the mother's uterus and receives nutrients and oxygen from the mother's blood. This adaptation enables mammals to have a more intimate and efficient transfer of nutrients and gases to the developing offspring, leading to a higher rate of survival compared to other vertebrates. In contrast, other vertebrates such as reptiles and birds lay eggs that have to be incubated and protected outside the mother's body, which increases the risk of predation and dehydration for the developing embryo.