WAEC SSCE - Biology - 2019

Maelezo ya Majibu

Maelezo ya Majibu

Maelezo ya Majibu

The function of the part labelled II is that it controls many involuntary actions of the body. The part labelled II refers to the medulla oblongata, which is a part of the brainstem that connects the brain to the spinal cord. The medulla oblongata plays a crucial role in regulating various vital involuntary functions of the body, such as blood pressure, breathing, heart rate, and digestion. It also controls reflexes such as coughing, sneezing, and vomiting. Additionally, the medulla oblongata helps to regulate the body's internal environment by controlling the levels of certain chemicals in the blood, such as oxygen, carbon dioxide, and hydrogen ions. Therefore, the correct answer is that the medulla oblongata controls many involuntary actions of the body.

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The role that is not performed by a government agency responsible for forest maintenance is regulating mining activities in the forest. A government agency responsible for forest maintenance is tasked with managing and protecting forest resources in a sustainable manner. This includes activities such as regulating the harvest of timber and poaching, creating and managing forest reserves, and tracking the movement of timber, wood, and wildlife. However, regulating mining activities in the forest is not typically a responsibility of a government agency responsible for forest maintenance. This is usually the responsibility of a separate agency, such as a department of mining or natural resources. Mining activities can have a significant impact on forest ecosystems, including deforestation, soil erosion, and water pollution. As a result, regulating mining activities in the forest requires specialized expertise and resources, which are often not within the purview of a government agency responsible for forest maintenance. Therefore, the role that is not typically performed by a government agency responsible for forest maintenance is regulating mining activities in the forest.

Maelezo ya Majibu

Maelezo ya Majibu

The salinity of a brackish habitat can vary depending on the amount of freshwater and saltwater that mix together in that environment. Brackish water is a mixture of freshwater and saltwater, which can occur in estuaries, mangrove swamps, and other coastal areas. The salinity of the habitat may increase during the dry season when the water evaporates and the salt concentration becomes more concentrated. Conversely, it may decrease when there is a lot of rainfall and freshwater flows into the habitat, diluting the saltwater. Therefore, the correct answer is that the salinity of a brackish habitat increases during the dry season.

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The digestion of proteins starts in the stomach. When we eat protein-rich foods such as meat, eggs, or dairy products, the proteins are broken down into smaller units called amino acids. This process of breaking down proteins into smaller units is called digestion. In the stomach, proteins are mixed with gastric juices that contain hydrochloric acid and a digestive enzyme called pepsin. The hydrochloric acid helps to break down the proteins into smaller units, while pepsin cuts the proteins into even smaller pieces. Once the proteins have been broken down into smaller units, they move into the small intestine, where they are further broken down into individual amino acids by digestive enzymes produced by the pancreas and the small intestine. In summary, the digestion of proteins starts in the stomach, where they are broken down into smaller units by the action of gastric juices containing hydrochloric acid and pepsin. The smaller units are then further broken down into individual amino acids in the small intestine.

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The factor "Mitosis" is not a source of variation in living organisms. Variation in living organisms refers to differences between individuals within a population. There are several sources of variation, including inheritance and the environment. Inheritance refers to the transfer of genetic information from parents to offspring through the genes they pass on. The environment also plays a role in determining the traits and characteristics of an organism, through factors such as diet, temperature, and exposure to toxins. Mitosis, on the other hand, is a type of cell division that results in the formation of two identical daughter cells, each with the same genetic information as the parent cell. Mitosis is not a source of variation because it simply results in the duplication of existing genetic information, rather than the introduction of new or different genetic information.

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The form of energy utilized during photosynthesis is "solar" energy. Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in glucose and other organic compounds. This process takes place in specialized organelles called chloroplasts, which contain chlorophyll, a pigment that absorbs light energy. The light energy is used to power a series of chemical reactions that convert carbon dioxide and water into glucose and oxygen. Therefore, the energy used during photosynthesis is solar energy, which is captured by chlorophyll and converted into chemical energy.

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The nucleotide that is not found in DNA molecules is uracil. DNA (deoxyribonucleic acid) is a type of nucleic acid that contains the genetic instructions used in the development and function of all living organisms. DNA is made up of repeating units called nucleotides, which consist of a sugar molecule (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), or thymine (T). Uracil (U) is a nitrogenous base that is similar in structure to thymine, but it does not occur in DNA. Instead, uracil is found in RNA (ribonucleic acid), which is another type of nucleic acid that is involved in the synthesis of proteins. RNA is similar to DNA in many ways, but it contains a different sugar molecule (ribose) and can have uracil in place of thymine. This difference in nucleotide composition allows RNA to perform a range of functions that are distinct from those of DNA. Therefore, the nucleotide that is not found in DNA molecules is uracil. The other three nucleotides - adenine, cytosine, and guanine - are all found in DNA.

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The rate of diffusion of molecules between two media will be higher if the difference in concentration of the two media is high. Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration until they reach equilibrium. The rate of diffusion is directly proportional to the concentration gradient, which is the difference in concentration between the two regions. If the concentration gradient is high, that means there is a large difference in concentration between the two regions, which creates a steeper gradient for molecules to move down. As a result, the rate of diffusion will be faster because the molecules will move more rapidly to reach equilibrium. On the other hand, if the concentration gradient is low or negligible, that means there is little or no difference in concentration between the two regions, and the gradient for molecules to move down is less steep. Consequently, the rate of diffusion will be slower as the movement of molecules will be less rapid. If there is no difference in concentration between the two media, there will be no concentration gradient and no movement of molecules, and therefore, no diffusion.

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Deficiency in insulin could lead to diabetes. Insulin is a hormone produced by the pancreas that helps regulate the amount of glucose (sugar) in the blood. In people with diabetes, the pancreas either does not produce enough insulin or the body cannot effectively use the insulin that is produced. When there is not enough insulin in the body, glucose builds up in the bloodstream instead of being absorbed by cells to provide energy. This can lead to high blood sugar levels, which can cause a range of health problems over time, including damage to the kidneys, nerves, eyes, and cardiovascular system. Therefore, insulin plays a crucial role in regulating blood sugar levels, and a deficiency in insulin can lead to diabetes.

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In the pyramid of energy illustrated above, the organism with the least amount of transferred energy is the bird. The pyramid of energy is a graphical representation of the flow of energy in an ecosystem. It shows the amount of energy that is transferred from one trophic level to another in the form of food. At each level, some energy is lost in the form of heat or used for metabolic processes, so the amount of energy available to the next level is always less than the previous level. In the given pyramid, the producers (Spirogyra) have the most energy, and energy decreases as we move up the pyramid through the different trophic levels. The tadpole and fish have more energy than the bird because they are at lower trophic levels and have more energy available to them from the producers. The bird, being at the highest trophic level, has the least amount of energy because it has to expend energy to hunt and consume prey, and much of the energy in the prey is lost as heat or used for metabolic processes before it reaches the bird. Therefore, the bird has the least amount of transferred energy in the given pyramid of energy.

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The heart can beat continuously without being fatigued because it is composed of cardiac muscle. The heart is a special type of muscle called cardiac muscle. Cardiac muscle is different from skeletal muscle and smooth muscle in that it has unique properties that allow it to contract and relax repeatedly without becoming fatigued. One of the key differences between cardiac muscle and other types of muscle is that cardiac muscle has its own intrinsic electrical conduction system, which generates electrical signals that coordinate the contraction and relaxation of the heart. This allows the heart to beat continuously without relying on signals from the nervous system, which can become fatigued. In addition, cardiac muscle also has a high number of mitochondria, which are the energy-producing structures in cells. This allows cardiac muscle to produce energy continuously, enabling it to maintain its rhythmic contractions. In summary, the heart can beat continuously without being fatigued because it is composed of a unique type of muscle called cardiac muscle, which has its own intrinsic electrical conduction system and a high number of mitochondria.

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Organisms in an ecosystem are usually grouped according to their trophic level into producers and consumers. Producers, also known as autotrophs, are organisms that are capable of producing their food using energy from the sun (photosynthesis) or chemical energy (chemosynthesis). Examples of producers include plants, algae, and some bacteria. They form the base of the food chain in an ecosystem. Consumers, on the other hand, are organisms that cannot produce their food and rely on other organisms for their energy. They are classified into different levels, also known as trophic levels, based on the source of their food. The primary consumers, also known as herbivores, eat plants and other producers. The secondary consumers, or carnivores, eat herbivores, while the tertiary consumers, or top carnivores, eat other carnivores. By grouping organisms into producers and consumers based on their trophic level, ecologists can study the flow of energy and nutrients through an ecosystem. This information can be used to understand how changes in one part of the ecosystem can affect other parts and to make predictions about the impact of human activities on the environment.

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Tooth decay is usually caused by the bacteria in our mouth that metabolize sugar and other carbohydrates from our food and produce acids that damage the enamel of our teeth. These bacteria live in our mouth and form a sticky film on our teeth called plaque. When we eat sugary or starchy foods, the bacteria in the plaque use them as fuel to produce acids. Over time, these acids can dissolve the minerals in our tooth enamel, leading to cavities and decay. So, it's important to maintain good oral hygiene, limit sugary foods, and visit a dentist regularly to prevent tooth decay. Eating proteinous foods does not directly cause tooth decay, but neglecting oral hygiene after eating such foods can lead to plaque formation and eventually tooth decay.

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Maelezo ya Majibu

An example of organ level of organization is the kidney. The organ level of organization is the level at which different tissues come together to form organs that perform specific functions in the body. The kidney is an organ that is made up of different types of tissues, including epithelial tissue, connective tissue, and muscle tissue. These tissues work together to perform the vital function of filtering waste products from the blood and regulating the body's fluid balance. The kidney contains functional units called nephrons that consist of various structures such as the glomerulus, proximal tubule, loop of Henle, and distal tubule, each with a specific function. Therefore, the kidney is an excellent example of the organ level of organization in the body.

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The conversion of ammonium salts into nitrates is called nitrification. Nitrification is a process in the nitrogen cycle in which ammonia (NH3) is oxidized to nitrite (NO2-) and then to nitrate (NO3-) by bacteria. This process occurs in soil, water, and wastewater treatment plants, where bacteria play a crucial role in converting ammonium ions (NH4+) into nitrates (NO3-), which can be used by plants as a source of nitrogen. The first step in nitrification is the conversion of ammonium ions into nitrite ions by bacteria called Nitrosomonas. The second step is the conversion of nitrite ions into nitrate ions by bacteria called Nitrobacter. This process releases energy that the bacteria use for their metabolism. Nitrification is important because it provides a source of nitrogen for plants and other organisms that cannot fix nitrogen from the air. It also helps to reduce the amount of ammonium ions in the soil, which can be toxic to plants at high concentrations. The process of nitrification is also a key step in the removal of nitrogen from wastewater treatment plants before it is discharged into the environment.

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To focus on a distant object, the ciliary muscle of the eye relaxes, and the eye lens gets thinner. The ciliary muscle is a ring of muscle fibers that surrounds the lens of the eye, and it helps to change the shape of the lens to adjust the focus. When we look at a distant object, the ciliary muscle relaxes, causing the suspensory ligaments to pull on the lens and make it thinner. This allows the lens to refract the light less and focus the light on the retina at the back of the eye. This process is called accommodation, and it enables us to see objects clearly at different distances. So, the correct answer is that the ciliary muscle of the eye relaxes, and the eye lens gets thinner to focus on a distant object.

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The yellow and black stripes on the body of wasps is an example of "warning coloration". Warning coloration, also known as aposematism, is a type of protective mechanism used by animals to warn potential predators that they are harmful, poisonous, or dangerous to consume. Animals that display warning coloration often have bright, vibrant, and easily identifiable markings or patterns, such as stripes, spots, or bold coloration. In the case of wasps, the bright yellow and black stripes on their bodies serve as a warning to predators that they are equipped with a powerful stinger and can defend themselves if threatened. These markings help to deter predators from attacking, which reduces the risk of injury or death to the wasp. Other examples of animals that use warning coloration include poison dart frogs, monarch butterflies, and skunks. These animals have evolved to use bright colors or strong odors as a signal to potential predators that they are not to be messed with. By doing so, they increase their chances of survival in the wild.

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The part labelled I in a cell is the centromere. The centromere is a specialized region on a chromosome where the two identical sister chromatids are joined together. During cell division, the spindle fibers attach to the centromere and pull the sister chromatids apart, ensuring that each new cell receives one complete set of chromosomes. Therefore, the centromere plays a crucial role in cell division and the distribution of genetic material to the daughter cells.

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Individuals with blood group AB can donate blood to individuals with blood group AB only. This is because blood group AB contains both A and B antigens on the surface of the red blood cells, and therefore does not produce antibodies against either A or B blood types. As a result, individuals with blood group AB can receive blood from any blood type that does not have antibodies against them, which is only the blood group AB. On the other hand, individuals with blood group O are known as universal donors because they do not have A or B antigens on their red blood cells, and therefore their blood can be donated to individuals with any blood type.

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Maelezo ya Majibu

The stage of cell division illustrated in the diagram is Metaphase. Metaphase is the second stage of mitosis, which is the process of cell division that results in the formation of two daughter cells from a single parent cell. In metaphase, the chromosomes, which were duplicated in the previous stage (prophase), line up along the equator of the cell, called the metaphase plate. In the diagram, we can see that the chromosomes are aligned in the middle of the cell, which is characteristic of metaphase. The spindle fibers, which attach to the centromeres of the chromosomes and pull them apart in the next stage (anaphase), are also visible in the diagram. During metaphase, the chromosomes are at their most condensed and visible under a microscope. This allows for the accurate separation of genetic material between the two daughter cells during the subsequent stages of cell division. After metaphase, the cell progresses to anaphase, where the spindle fibers pull the sister chromatids of each chromosome apart to opposite poles of the cell. Finally, in telophase, the cell divides into two daughter cells, each with its own set of chromosomes.

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In a complete dominance monohybrid cross between a pure breeding yellow-flowered plant Y and a pure breeding white-flowered plant y, the result of the first filial generation is 100% yellow flowers. This is because yellow flower color is dominant over white flower color, and the Y allele is dominant over the y allele. As a result, all the offspring in the first generation, also known as the F1 generation, will have one Y allele from the yellow-flowered parent and one y allele from the white-flowered parent, making them all yellow-flowered heterozygotes. However, if we cross the F1 generation plants with each other, we will get a 3:1 ratio of yellow to white flowers in the second filial generation (F2), because the yellow-flowered heterozygotes can produce both yellow and white-flowered offspring.

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The part labelled I in the diagram above is the cerebrum. The cerebrum is the largest part of the brain and is responsible for many important functions, such as consciousness, sensation, movement, perception, and learning. It is divided into two hemispheres, the left and right hemispheres, which are connected by a bundle of nerve fibers called the corpus callosum. The cerebrum is also divided into four lobes: the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe. Each lobe is responsible for different functions, such as motor control, sensory processing, language, memory, and visual perception. The cerebrum is one of the most complex and important organs in the human body, and its functions are essential for our daily lives and interactions with the world around us.

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The correct answer is "homeostasis." Homeostasis refers to the process of maintaining a stable and consistent internal environment within an organism. This is important because cells and organs require a specific environment to function properly, and changes to that environment can disrupt the organism's ability to survive. Homeostasis is achieved through various mechanisms that monitor and regulate important physiological parameters such as temperature, pH, and nutrient levels. For example, the body may sweat to cool down when it gets too hot, or shiver to generate heat when it gets too cold. Similarly, the body may release hormones to regulate blood sugar levels, or increase breathing rate to remove excess carbon dioxide. Overall, homeostasis is a complex and dynamic process that allows organisms to adapt to changing environmental conditions and maintain a stable internal environment that supports optimal physiological function.

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The structure that will NOT be found in the nucleus of a cell is lysosome. The nucleus is a membrane-bound organelle found in eukaryotic cells that contains genetic material in the form of DNA. It is typically surrounded by a double membrane called the nuclear envelope, which has pores that allow for the exchange of materials between the nucleus and the cytoplasm. The nucleolus is a substructure within the nucleus that is involved in the production of ribosomes. It is made up of proteins and RNA, and is not surrounded by a membrane. Centrioles are cylindrical structures made up of microtubules that play a role in cell division. They are found in pairs, and are typically located near the nucleus of the cell. Lysosomes, on the other hand, are membrane-bound organelles that contain digestive enzymes. They are involved in breaking down and recycling cellular waste and foreign materials that have been taken up by the cell. Therefore, of the structures listed, lysosome is the one that will NOT be found in the nucleus of a cell. The other structures, including DNA, nucleolus, and centrioles, are all either found within the nucleus or in close proximity to it.

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The underground storage stems that grow horizontally in the soil are called "rhizomes." Rhizomes are a type of stem that grow underground and horizontally, sending out roots and shoots from nodes along their length. They store nutrients and energy for the plant, which can help it survive adverse conditions such as drought or cold temperatures. Examples of plants that have rhizomes include ginger, bamboo, and some types of grasses. Because they grow horizontally, rhizomes can also help plants spread and colonize new areas.

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The main function of the amniotic fluid is for the protection of the foetus from shock. The amniotic fluid is a clear, colorless liquid that surrounds the foetus during pregnancy. It acts as a cushion to protect the foetus from any external pressure or shocks that might occur during pregnancy. The amniotic fluid also helps to regulate the temperature around the foetus and provides a medium for the foetus to move and develop. Additionally, the amniotic fluid also plays a role in the development of the foetus's respiratory and digestive systems. However, its primary function is to protect the foetus from any physical shocks or bumps that might occur inside the mother's womb. Therefore, the correct answer is that the main function of the amniotic fluid is for the protection of the foetus from shock.

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The major mineral present in the shell of molluscs is Calcium. Molluscs are a group of organisms that includes snails, clams, and mussels. Their shells serve as a protective covering and are made of calcium carbonate, which is a mineral that is abundant in seawater. Calcium is essential for the formation and hardening of the shells and is continuously incorporated into the shells as the mollusc grows. This helps to maintain the strength and structural integrity of the shell and provides protection from predators, extreme temperatures, and other environmental factors.

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Muscle fatigue in the body of an athlete is due to the "accumulation of lactic acid". When an athlete engages in intense physical activity, their muscles require a large amount of energy to contract and relax rapidly. This energy is supplied by a process called cellular respiration, which involves the breakdown of glucose to produce ATP (adenosine triphosphate), the main source of energy for muscle contraction. However, during intense exercise, the body may not be able to supply enough oxygen to the muscles to sustain cellular respiration. In the absence of oxygen, the body switches to a different metabolic pathway called anaerobic respiration, which produces energy more quickly but also generates lactic acid as a byproduct. As lactic acid accumulates in the muscles, it can lead to a drop in pH, which can interfere with the chemical reactions required for muscle contraction. This can cause the muscles to become fatigued, making it more difficult for the athlete to continue exercising at a high level of intensity. In summary, muscle fatigue in athletes is caused by the accumulation of lactic acid in the muscles, which can interfere with the chemical reactions required for muscle contraction. This buildup of lactic acid is a result of the switch to anaerobic respiration during intense exercise, which occurs when there is not enough oxygen available to sustain cellular respiration.

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The resource that is renewable is trees. Renewable resources are resources that can be replenished naturally over time, either through natural processes or human intervention. Trees are a renewable resource because they can be replanted and grown again after they are harvested for wood or other products. When forests are managed sustainably, meaning they are harvested in a way that does not exceed the forest's ability to regenerate, trees can provide an ongoing supply of wood products without depleting the resource. On the other hand, petroleum, coal, and iron are non-renewable resources. These resources are finite and can only be extracted from the earth's crust once. Once they are extracted and used, they cannot be replenished. As a result, they are considered non-renewable resources. Therefore, the resource that is renewable is trees.

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The biological importance of the dance by the worker honeybee is that it signals the availability of food. Honeybees are social insects that live in large colonies. They have a complex system of communication that allows them to share information about the location of food sources. When a worker honeybee finds a food source, such as a flower, it performs a dance to communicate the location of the food to other worker bees in the colony. The dance involves a series of movements that indicate the direction and distance of the food source relative to the colony. By performing this dance, the worker bee is able to alert other worker bees to the availability of food, which helps to ensure that the colony has access to a reliable source of nutrition. In summary, the biological importance of the dance by the worker honeybee is that it signals the availability of food, allowing other worker bees in the colony to be alerted to its presence and ensuring the colony has access to a reliable source of nutrition.

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Tall trees with unbranched trunks which grow above the upper storey of the forest are commonly referred to as emergents. Emergents are a type of tree that grow above the canopy layer of a forest. They typically have unbranched trunks with a small crown of leaves at the top, which allows them to access more sunlight and better compete for resources. Emergents are found in tropical rainforests, where they can grow up to 70 meters or more in height. Emergent trees play an important role in the ecosystem by providing habitat and food for a variety of animals, as well as helping to regulate the climate by absorbing carbon dioxide from the atmosphere. Because they grow above the canopy layer, they also have a unique view of the forest and provide a different perspective on the ecosystem as a whole. Therefore, tall trees with unbranched trunks which grow above the upper storey of the forest are commonly referred to as emergents.

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The specific role of a species within its environment is known as its niche. A niche refers to the way an organism interacts with its environment, including the biotic (living) and abiotic (non-living) factors. It describes the specific set of resources that a species needs to survive, grow, and reproduce, as well as its interactions with other species, such as predation, competition, and mutualism. The niche of a species is determined by a combination of its physical and biological requirements, such as food, water, shelter, temperature, and reproduction. For example, the niche of a hummingbird includes feeding on nectar from flowers and hovering in mid-air to collect it, which requires specialized beaks and wings. The concept of niche is important in ecology because it helps to explain how different species coexist in the same ecosystem without competing for the same resources. Each species occupies a unique niche that allows it to avoid competition with other species and to use the resources available in a specific way. If two species have the same niche, they will compete for the same resources, and one may be driven to extinction or forced to evolve to occupy a different niche.

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The complex relationship between the members of a community and their physical environment is known as Ecology. Ecology is the study of the interactions between living organisms and their environment. It looks at how plants, animals, and other organisms depend on each other and their surroundings for survival. The physical environment includes things like air, water, soil, and climate. Ecologists study the flow of energy and matter through these relationships, as well as how different species adapt to changes in their environment. In simple terms, ecology is about understanding how all the parts of an ecosystem (a community of living and nonliving things) fit together and depend on each other.

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The cross between RrTt and rrtt will result in 50% of the offspring being tall with red fruits. The capital R and T represent dominant alleles for red colour and tallness, respectively, while the small r and t represent recessive alleles for white colour and shortness, respectively. When RrTt (heterozygous for both traits) is crossed with rrtt (homozygous recessive for both traits), the possible gametes for RrTt are RT, Rt, rT, and rt, while the gametes for rrtt are rt only. When the gametes combine, we get the following possible genotypes for the offspring: RT, Rt, rT, and rt. Of these, RT and rT will result in tall plants because they contain at least one dominant allele for tallness, while Rt and rt will result in short plants. Similarly, the genotypes RT and Rt will result in red fruits, while rT and rt will result in white fruits because red color is dominant over white. So, the possible genotypes for the offspring are: RT, Rt, rT, and rt, with the phenotypic ratio being 1:1:1:1 for tall with red fruits, tall with white fruits, short with red fruits, and short with white fruits, respectively. Therefore, 50% of the offspring will be tall with red fruits, which is the correct answer.

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Cholera is mostly spread by contaminated water. Cholera is a bacterial infection that affects the small intestine, and it is caused by the bacterium Vibrio cholerae. When a person consumes contaminated water or food, they can become infected with the bacterium and develop cholera. Cholera can spread quickly and easily in areas with poor sanitation and hygiene practices. When people use contaminated water sources for drinking, cooking, or washing, they can become infected with cholera. Additionally, cholera can be spread through the fecal-oral route, which means that if an infected person does not practice good hygiene, they can spread the bacterium to others through their feces. In summary, cholera is mostly spread by contaminated water, and it can also be spread through poor hygiene practices and the fecal-oral route. It is important to practice good sanitation and hygiene practices to prevent the spread of cholera.

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Anaerobic respiration in the organism illustrated in the diagram above produces carbon dioxide and ethanol. Anaerobic respiration is a type of cellular respiration that occurs in the absence of oxygen. It is also known as fermentation and is an important metabolic pathway in some organisms, such as yeasts and bacteria. During anaerobic respiration, glucose is broken down into pyruvate, which is then converted into ethanol and carbon dioxide in the absence of oxygen. The process of anaerobic respiration produces energy in the form of ATP, which the organism can use for various cellular activities. The production of ethanol and carbon dioxide during anaerobic respiration is also used in various industrial processes, such as brewing and baking. Overall, anaerobic respiration is a crucial process that enables some organisms to survive and thrive in environments where oxygen is limited.

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a.

b. The five parts of the alimentary canal of an earthworm are:

1. Mouth
2. Pharynx
3. Esophagus
4. Crop
5. Gizzard
6. Intestine
7. Anus

c. Six ways by which water could be polluted by agricultural practices are:

1. Excessive use of fertilizers and pesticides, which can leach into groundwater or runoff into nearby water sources.
2. Manure and waste runoff from animal farms, which can contain harmful pathogens and nutrients that can cause eutrophication.
3. Soil erosion from farming activities, which can deposit sediment and other contaminants into waterways.
4. Irrigation practices that use water inefficiently, leading to increased water usage and depletion of water sources.
5. Deforestation and land conversion for agriculture, which can impact the natural water cycle and lead to reduced water quality and quantity.
6. Contamination of water sources from machinery or storage facilities used in agricultural activities.

d. The life cycle of a housefly includes the following stages:

1. Egg: The female housefly lays eggs on decaying organic matter or animal waste.
2. Larva: The eggs hatch into larvae, also known as maggots, which feed on the decaying matter and grow rapidly.
3. Pupa: After several days, the mature larvae form a pupa, which is a protective coc

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b. The five parts of the alimentary canal of an earthworm are the mouth, pharynx, esophagus, crop, and gizzard.

c. Six ways by which water could be polluted by agricultural activities are:

1. Runoff from fields carrying pesticides and fertilizers into nearby water bodies.
2. Livestock waste and manure runoff into rivers and streams.
3. Leaching of nutrients and chemicals from fields into groundwater.
4. Erosion from tilled fields, which can carry sediment and nutrients into waterways.
5. Irrigation runoff carrying chemicals and salts.
6. Discharge of untreated or poorly treated agricultural wastewater into surface waters.

d. The life cycle of a housefly involves four stages: egg, larva, pupa, and adult. Adult female houseflies lay eggs on organic matter such as garbage, animal waste, or decaying food. The eggs hatch into larvae, commonly known as maggots, which feed on the organic matter for several days. The larvae then move to a dry location to pupate, forming a hard outer casing known as a puparium. Within the puparium, the larvae transform into an adult fly. The adult emerges from the puparium, mate, and begin the cycle anew.

e. Hypogeal germination is a type of seed germination where the cotyledons (seed leaves) remain below the soil surface. In a mature maize seedling, the embryo is located at the base of the kernel, and the radicle (embryonic root) emerges first during germination. The radicle grows downward, elongates, and forms lateral roots. The shoot also emerges from the embryo and grows upward, carrying the plumule (embryonic shoot) and the first true leaves above the soil surface. The diagram of hypogeal germination in a mature maize seedling should show the radicle, the embryonic shoot, the first true leaves, the kernel, and the soil.

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a.(i) The type of genetic cross is a dihybrid cross, as the parents differ in two traits (tallness and flower color).

a.(ii) One reason for this answer is that the parents are homozygous for their respective traits, which allows for a clear separation of the traits in the offspring and enables the determination of the mode of inheritance.

b.(i) Evolution is the process of change in the heritable characteristics of populations over successive generations, which can result in the development of new species from existing ones.

b.(ii) The phenotypic ratio of the F2 generation can be determined using a Punnett square or a forked-line diagram. In this case, a Punnett square can be used to show the possible combinations of alleles in the F2 generation:

The phenotypic ratio of the F2 generation is 9:3:3:1, which means that 9/16 of the offspring will be tall and red, 3/16 will be tall and white, 3/16 will be dwarf and red, and 1/16 will be dwarf and white.

b.(iii) To calculate the number of tall and white flowers in the F2 generation, we need to know the total number of offspring. In this case, the total number of F2 offspring is given as 160. From the phenotypic ratio, we know that 9/16 of the offspring will be tall, which is approximately 90 (9/16 x 160). Similarly, 3/16 of the offspring will be white, which is approximately 30 (3/16 x 160). Therefore, in the F2 generation, we would expect to obtain approximately 90 tall flowers and 30 white flowers.

Maelezo ya Majibu

a. (i) Lightning plays an important role in the nitrogen cycle because it helps to convert atmospheric nitrogen gas into reactive forms that can be used by plants and other organisms. This process, known as nitrogen fixation, is essential for the functioning of ecosystems.

(ii) Nitrosomonas is a type of bacterium that plays a key role in the nitrogen cycle by converting ammonia into nitrite, a more reactive form of nitrogen. This process is called nitrification and is important for the functioning of ecosystems.

(iii) Azotobacter is another type of bacterium that plays an important role in the nitrogen cycle by converting nitrates into nitrogen gas, a process known as denitrification. This helps to regulate the amount of nitrogen in the ecosystem and maintain balance.

b. (i) The excretory organ in insects is the Malpighian tubules.

(ii) The excretory organ in earthworms is the nephridia.

c. (i) Hepatitis is a medical condition in which the liver becomes inflamed. It can be caused by a variety of factors, including viral infections, alcohol abuse, and certain medications. Symptoms of hepatitis can include fatigue, jaundice, abdominal pain, and loss of appetite.

(ii) Kidney stones are hard deposits of minerals and salts that form in the kidneys. They can cause pain and discomfort as they move through the urinary tract, and can also lead to more serious health problems if left untreated. Symptoms of kidney stones include severe pain in the back or side, nausea, and frequent urination.

d. (i) Three effects of lack of sense receptors in the skin to humans include: decreased ability to feel touch, temperature, and pain; decreased ability to detect and respond to changes in the environment; and increased risk of injury and skin damage.

(ii) The three layers of the epidermis in the skin of humans are: the stratum corneum, the stratum granulosum, and the stratum basal.

e. (i) Metamorphosis is the process of transformation that some species of animals undergo during their development, in which they change from one form to another.

(ii)

• Grasshopper: incomplete metamorphosis
• Cockroach: incomplete metamorphosis
• Butterfly: complete metamorphosis
• Mosquito: complete metamorphosis
• Housefly: complete metamorphosis

Incomplete metamorphosis involves gradual changes from one form to another, without a pupal stage. Complete metamorphosis involves a transformation from a larval form to a pupal form, followed by the emergence of an adult form.

Maelezo ya Majibu

(a)

i)

Kingdom and Class of Organism from which Specimen H (quill feather) could be Obtained:

Kingdom -->Animalia

Class --> Aves

(ii)

Location on the Body of Organism from which Specimen H (quill feather) could be Obtained: Wing (s) or tail(s).

(iii)

Example of Organism from which Specimen H (quill feather) could be Obtained Chicken, pigeon, domestic fowl, cock, hen, vulture, ostrich, duck, gull.

(b)

(i) Differences between Specimens H & J:

ii)

Similarities between Specimen and J:

- They both possess point attachment; they both posses apex

- They both have margin

- Both have glossy surface.

(c)

Functions of specimen H (quill feather) and Specimen J (palm frond) to the organism that posses them

Specimen H:

-Flight/flying

- Insulation

-Camouflage

- Sexual / courtship display

- Protection

- Waterproof

- Gives shape.

Specimen J: Photosynthesis manufacture of food /transpiration. gaseous exchange.                                                                                                                                         

(d)

Observable Features that Adapt Specimens H and J to their Functions:

Specimen H (quill feather):

- Strong and firm, to beat against air/wind/protection/insulation

-Hollow shaft / rachis/light weight; for buoyancy

- Interlocking barbules/closely packed barbs for upthrust, color for camouflage 

- Courtship display/identification

- Glossy surface for waterproof.

Specimen J (Palm frond):

- Green colour for photosynthesis

- Veins; for conduct / transport of water/nutrient / food

- Glossy/waxy surface; makes it waterproof.

Maelezo ya Majibu

a. Five vertebrae in mammals with their corresponding locations are:
1. Cervical vertebrae - located in the neck region
2. Thoracic vertebrae - located in the chest region
3. Lumbar vertebrae - located in the lower back region
4. Sacral vertebrae - located in the pelvic region
5. Coccygeal vertebrae - located in the tail region

b. The functions of the following parts in a dicotyledonous leaf are:
(i) Palisade - responsible for photosynthesis by containing chloroplasts and maximizing exposure to light.
(ii) Vascular bundle - responsible for transporting water, minerals, and food throughout the leaf.
(iii) Epidermis - provides protection to the leaf and prevents water loss through the cuticle.

c. The functions of the following parts in the stem of a flowering plant are:
(i) Sieve tube - responsible for transporting sugars and nutrients throughout the plant.
(ii) Cortex - stores food and water, and provides support to the stem.
(iii) Pith - stores and transports nutrients and water, and provides support to the stem.

d. Two external structural differences between the stem and root of a maize seedling are:
1. The stem is above the ground, while the root is below the ground.
2. The stem has buds or leaves, while the root does not.

Two internal structural differences between the stem and root of a maize seedling are:
1. The stem has a vascular bundle arranged in a circular pattern, while the root has a radial pattern.
2. The stem has more collenchyma and sclerenchyma tissue for support, while the root has more parenchyma tissue for absorption.

Maelezo ya Majibu

a.

(i) Here is the completed table with the respiratory surface of each organism:

(ii) Five characteristic features of respiratory surfaces in organisms are:

1. They are thin: This allows for efficient diffusion of gases across the surface.
2. They are moist: Moist surfaces help dissolve gases, which makes it easier for them to diffuse across the surface.
3. They have a large surface area: A larger surface area means more gases can be exchanged at a faster rate.
4. They are in contact with the environment: This allows for the exchange of gases between the organism and the environment.
5. They are adapted to the organism's environment: Respiratory surfaces are adapted to the organism's habitat and way of life.

b.

Tilapia is a freshwater fish that has a respiratory organ called the gills. Here is a drawing of the gills in Tilapia, labeled fully:

The gills are located on both sides of the fish's head and are covered by a bony plate called the operculum. Water flows over the gills, and oxygen is absorbed into the bloodstream while carbon dioxide is released into the water. The gills have many tiny filaments that increase the surface area for gas exchange, and they are highly vascularized to maximize the uptake of oxygen.

Maelezo ya Majibu

a. Three features of the small intestine that increase the rate of absorption of digested food are:

1. Villi - finger-like projections on the lining of the small intestine that increase surface area for absorption.

2. Microvilli - smaller projections on the surface of the villi that further increase surface area.

3. Blood capillaries and lacteals - blood vessels and lymphatic vessels that absorb nutrients and transport them to other parts of the body.

b. Glucose formed in a plant during photosynthesis is used for energy or stored as starch for later use. The glucose is transported to different parts of the plant through the phloem tissue.

c. The mode of feeding in each of the following organisms are:

(i) Euglena - Euglena is a mixotrophic organism, meaning it can make its own food through photosynthesis or consume other organisms for nutrients through phagocytosis.

(ii) Spirogyra - Spirogyra is an autotrophic organism that produces its own food through photosynthesis.

d. Three characteristics of an Estuarine habitat are:

1. Salinity gradient - Estuaries are characterized by a gradient of salinity due to mixing of freshwater and saltwater.

2. High productivity - The high nutrient levels in estuaries support high rates of primary production.

3. Biodiversity - Estuaries are home to a diverse range of plant and animal species adapted to the changing environmental conditions.

e. Three differences between an aquatic habitat and a terrestrial habitat are:

1. Aquatic habitats are characterized by the presence of water, while terrestrial habitats are not.

2. Aquatic habitats have lower oxygen levels, while terrestrial habitats have higher oxygen levels.

3. Aquatic habitats have different temperature ranges and light levels compared to terrestrial habitats.

Maelezo ya Majibu

a) The branch of Biology that involves the use of specimens A, B, C, D, E, and F is Zoology, which is the study of animals.
b) The functions of specimens A, B, C, D, E, and F are:
- Specimen A: Could be used for the study of the anatomy and physiology of the respiratory system.
- Specimen B: Could be used to study the anatomy and morphology of a specific type of insect.
- Specimen C: Could be used for the study of plant anatomy and morphology.
- Specimen D: Could be used for the study of mammalian anatomy and physiology.
- Specimen E: Could be used for the study of marine invertebrates.
- Specimen F: Could be used for the study of bird anatomy and morphology.
c) Specimen B could be used for the study of insect anatomy and morphology, while specimen D could be used for the study of mammalian anatomy and physiology. For example, Specimen D could be used to study the respiratory and digestive systems of mammals.
d) As an AI language model, I am unable to create drawings. However, I can describe how to make a drawing of specimen D. Specimen D is a mammal, so the drawing should depict the anatomy of a mammal, with labels for the various organs and body parts.
e) Two organisms associated with the use of specimen D are humans and chimpanzees. Two organisms associated with the use of specimen F are eagles and penguins. Specimen D is a mammal, and humans and chimpanzees are also mammals. Specimen F is a bird, and eagles and penguins are both birds.

Maelezo ya Majibu

a)

(i) The possible genotypes of their offspring can be determined using a Punnett square. The female heterozygote for sickle cell has the genotype HbA HbS, and the sickler has the genotype HbS HbS.

The possible genotypes of their offspring are HbA HbS (sickle cell trait) and HbS HbS (sickle cell disease).

(ii) The phenotypic ratio of the offspring can be determined from the Punnett square as follows:

• 50% of the offspring will have sickle cell disease (HbS HbS).
• 50% of the offspring will have sickle cell trait (HbA HbS).

b)

A Rhesus negative woman who marries a Rhesus positive man is at risk of developing Rhesus incompatibility. During her first pregnancy, if the fetus is Rhesus positive, some of the fetal blood cells may enter her bloodstream and stimulate her immune system to produce antibodies against the Rhesus factor. In her second pregnancy, if the fetus is also Rhesus positive, her antibodies may cross the placenta and attack the fetal red blood cells, leading to hemolysis (breakdown of red blood cells) and anemia (low levels of red blood cells). This condition is known as hemolytic disease of the newborn (HDN) and can lead to serious complications, including brain damage and even death.

c)

Two examples of features in animals that support Lamarck's theory of use and disuse of body parts are:

• The long neck of giraffes: According to Lamarck's theory, giraffes developed long necks because they stretched their necks to reach higher leaves on trees, and this stretching caused their necks to become longer over time. However, this theory has been disproven by modern genetics, which shows that the long neck of giraffes is actually the result of natural selection acting on random genetic variations.
• The reduced hindlimbs of snakes: According to Lamarck's theory, snakes lost their hindlimbs because they no longer needed them for locomotion, and the disuse of these limbs caused them to gradually shrink and disappear. However, this theory has also been disproven by modern genetics, which shows that the loss of hindlimbs in snakes is actually the result of genetic mutations that have been selected for over time.

d)

Three structures in mammals that are vestigial are:

• The appendix: This is a small pouch attached to the large intestine that may have played a role in digestion in our distant ancestors. However, in modern humans, the appendix appears to have no function and can even cause health problems if it becomes

Maelezo ya Majibu

a. (i) Five challenges that make conservation of resources difficult are:

1. Economic development and population growth leading to increased demand for natural resources.
2. Climate change and its impacts on ecosystems and biodiversity.
3. Deforestation and loss of habitats for wildlife.
4. Overfishing and depletion of marine resources.
5. Corruption and lack of enforcement of conservation laws and regulations.

(ii) Ways by which the Government of a country ensures conservation of natural resources are:

1. Enacting and enforcing laws and regulations that protect natural resources.
2. Implementing sustainable use policies, such as quotas and catch limits for fishing.
3. Designating protected areas, such as national parks and wildlife reserves.
4. Supporting research and monitoring programs to better understand and manage natural resources.
5. Engaging local communities and stakeholders in conservation efforts.

b. An endangered species is a type of organism that is at risk of extinction due to a decline in its population size or range. These species are considered to be in danger of disappearing permanently, and conservation efforts are needed to protect them and their habitats.

c. (i) The blood group genotype of the child with blood group O is ii (homozygous recessive).

(ii) The possible blood group genotypes of the father are:

1. IAi (homozygous dominant)
2. I Ai (heterozygous)
3. IBi (homozygous dominant)

d. Three reasons why genetic variation is important to plants are:

1. Adaptation to changing environmental conditions: Genetic variation allows plants to adapt to changing environmental conditions, such as changes in temperature, rainfall, and soil quality. This helps them to survive and thrive in different environments.
2. Increased resistance to pests and diseases: Genetic variation can increase a plant's resistance to pests and diseases, as some individuals may have genetic traits that make them more resistant to certain threats.
3. Improved crop yields: Genetic variation can lead to the development of new crop varieties that have improved yields, better quality, and greater resistance to pests and diseases. This can help to increase food production and improve food security.