JAMB UTME - Biology - 2016

The sequence of the one-way gaseous exchange mechanism in a fish is

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The adaptive importance of the nuptial flight from termite colonies is to

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The theory of use and disuse of organs was promulgated by

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In which of the following groups of vertebrates is parental care mostly exhibited?

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Parental care is mostly exhibited in the group of vertebrates known as Mammals. Mammals are a class of vertebrate animals that have several unique characteristics that make them well-suited to exhibit parental care. First and foremost, mammals give birth to live young, which requires a significant investment of time and energy on the part of the mother. Additionally, most mammalian mothers produce milk to feed their offspring, which requires further investment of energy and resources. Furthermore, mammalian offspring are generally born in a relatively undeveloped state and require a significant amount of care and nurturing in order to survive. This often involves extended periods of maternal care, as well as, in some species, the active participation of the father or other family members in raising the offspring. In contrast, while some birds (Aves) and some reptiles (Reptilia) exhibit parental care, it is generally not as extensive or prolonged as that seen in mammals. Amphibians (Amphibia), on the other hand, typically do not exhibit parental care beyond depositing eggs in suitable locations. Therefore, based on these characteristics, it can be concluded that parental care is mostly exhibited in Mammals.

Which of the following is NOT a method of conserving wild life?

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Indiscriminate poaching is not a method of conserving wildlife. In fact, it is one of the main threats to wildlife populations. Poaching involves the illegal killing, hunting, or capture of wildlife for commercial or personal gain, often resulting in the depletion of populations of endangered or threatened species. Conservation is the practice of protecting and preserving natural resources, including wildlife, and it requires the implementation of measures that help to sustain and improve wildlife populations. Indiscriminate poaching, on the other hand, undermines conservation efforts by removing animals from their natural habitats and disrupting the ecological balance. In order to conserve wildlife, various methods can be employed, such as establishing zoological gardens, enacting wildlife conservation laws, and establishing game reserves. These measures help to protect wildlife by creating safe habitats for them to live, regulating human activities that may harm them, and promoting their overall well-being.

Strong short and concical beak to pick and crush seeds is an adaptive feature of

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The strong, short, and conical beak adapted for picking and crushing seeds is a feature of the weaver bird. Weaver birds are small, seed-eating birds that use their strong and conical beaks to pick and crush the hard outer shell of seeds. This type of beak is specially adapted to allow the bird to crack open seeds and extract the nutritious inner contents. Unlike ducks, owls, and hawks, which have different types of beaks that are adapted for catching and eating prey, the weaver bird's beak is uniquely suited to its seed-based diet. This is an example of how an organism's physical features can evolve over time to help it survive and thrive in its environment.

The movement response of a cockroach away from a light source is

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The movement response of a cockroach away from a light source is called negative phototaxis. Phototaxis refers to the movement of an organism in response to light, and "negative" indicates that the movement is away from the light source. In other words, the cockroach is trying to escape the light and move into a darker area. This is a common behavior among many species of insects, as they are often attracted to dark, sheltered places for safety and protection.

Which of the following conditions is NOT necessary for photosynthesis to take place?

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Seed plants are divided into

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Seed plants are divided into two main groups: angiosperms and gymnosperms. Angiosperms are flowering plants that produce seeds inside a protective fruit. This group includes a wide variety of plants, such as roses, lilies, tomatoes, and oak trees. Gymnosperms are non-flowering plants that produce seeds without a protective covering. This group includes conifers, such as pine trees, and cycads, which are a type of primitive seed plant. So, in summary, seed plants can be classified into angiosperms and gymnosperms based on the type of seed and its protective covering.

The part of the mammalian ear responsible for the maintenance of balance is the

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The part of the mammalian ear responsible for the maintenance of balance is the vestibular system. The vestibular system is located in the inner ear and consists of three semicircular canals and the utricle and saccule. These organs work together to sense changes in head position and movement, and then send signals to the brain that help us maintain our balance. Essentially, the vestibular system acts like a built-in level that helps us stay upright and steady, even when we're moving around or being jostled.

If the cross of a red-flowered plant with a white flowered plant produces a pink flowered plant, this is an example of

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This is an example of incomplete dominance. In incomplete dominance, the offspring of two different parental plants exhibit a phenotype that is a mix of the traits from both parents. In this case, the red-flowered plant and the white-flowered plant have produced a pink-flowered plant that has inherited traits from both parents and expressed a new phenotype that is a mix of the two.

When a cell is placed in solution and the size of the cell increases, the concentration of solution is said to be

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When a cell is placed in a solution and the size of the cell increases, the concentration of the solution can be described as hypotonic. This means that the solution has a lower concentration of solutes (dissolved particles) compared to the inside of the cell. As a result, water molecules move into the cell in an attempt to balance the concentration of solutes on both sides of the cell membrane. This influx of water can cause the cell to swell and potentially burst, a process known as lysis. In contrast, if the solution has a higher concentration of solutes than the inside of the cell, it is considered hypertonic, and water will move out of the cell, causing it to shrink. If the concentrations are balanced, the solution is isotonic, and there is no net movement of water across the cell membrane.

Which of the following animals has homodont dentition?

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Lizard has homodont dentition. Homodont dentition refers to having teeth that are all the same shape and size. In other words, each tooth is interchangeable and performs the same function as any other tooth in the mouth. Out of the given options, lizards have homodont dentition. This means that all of their teeth are the same shape and size and can be used interchangeably for catching and crushing prey. In contrast, rats, humans, and pigeons have heterodont dentition, which means that their teeth are different shapes and sizes and perform different functions in the mouth. For example, human teeth are specialized for cutting, tearing, and grinding different types of food, while pigeon beaks are adapted for picking and pecking seeds.

The function of the red head in male Agama lizards is to

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The function of the red head in male Agama lizards is to attract female lizards for mating purposes. The red head is a visual signal that helps the male lizard stand out and show off to potential mates. This is a way for the male to show that he is healthy and strong, and therefore a good choice for mating. This colorful display is an important part of the mating ritual for Agama lizards, and it helps the male to attract a female and increase his chances of reproducing.

The arrangement of ovules attached to the sides of a syncarpous ovary with a single chamber is referred to as

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The arrangement of ovules attached to the sides of a syncarpous ovary with a single chamber is referred to as parietal placentation. In parietal placentation, the ovules are attached to the inner wall, or parietal tissue, of the ovary, forming a line or several lines along the edges of the ovary chamber. This is in contrast to axile placentation, where the ovules are attached to a central axis in the ovary, or free-central placentation, where the ovules are attached to a central column in a free-standing manner. Parietal placentation is commonly found in plants with syncarpous ovaries, such as the tomato and the apple, and is thought to be an adaptation that allows for efficient use of space within the ovary while still ensuring adequate attachment and nourishment of the developing ovules.

Which of these organisms partly digest its food extracellularly?

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Termites partly digest their food extracellularly. Termites are insects that feed on wood and other cellulose-based materials. Unlike other insects, such as houseflies and mosquitoes, termites have a unique digestive system that allows them to partially digest their food outside of their bodies. This is made possible by the presence of microorganisms, such as protozoa and bacteria, in the termite's gut. These microorganisms break down the cellulose in the wood and release simple sugars and other nutrients, which are then absorbed by the termite. This extracellular digestion allows termites to efficiently break down tough plant material and extract the nutrients they need to survive. By relying on their gut microbes to do some of the heavy lifting, termites are able to survive on a diet that would otherwise be indigestible.

Which of the following organs regulates the levels of water. salts, hydrogen ions, and urea in the mammals?

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The organ that regulates the levels of water, salts, hydrogen ions, and urea in mammals is the kidney. The kidney is a vital organ responsible for filtering waste products from the blood and producing urine, which is then excreted out of the body. The kidney achieves this through a complex system of tubules and nephrons that filter the blood and reabsorb necessary substances while eliminating excess water and waste products such as urea. The kidney's primary role is to maintain the body's homeostasis, which involves regulating the levels of water, salts, hydrogen ions, and urea in the body. The kidney helps to balance the amount of water in the body by regulating the production and excretion of urine. The kidney also regulates the levels of salts, such as sodium, potassium, and calcium, in the body to ensure they remain within a healthy range. Additionally, the kidney helps to regulate the body's pH level by controlling the levels of hydrogen ions in the blood. Finally, the kidney eliminates excess urea, a waste product produced by the breakdown of proteins in the body, by filtering it out of the blood and excreting it in the urine. In summary, the kidney is the organ that regulates the levels of water, salts, hydrogen ions, and urea in mammals. It achieves this through a complex system of tubules and nephrons that filter the blood and reabsorb necessary substances while eliminating excess water and waste products such as urea.

A collection of population of all living organisms that exist in a habitat is referred to as

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The collection of all living organisms that exist in a specific habitat is referred to as a community. A community is made up of populations of different species that interact with one another and share the same living space. For example, a community of living organisms in a forest might include trees, birds, insects, mammals, and other species that live together in that particular habitat. An ecosystem, on the other hand, includes not just living organisms but also their physical environment and the interactions between them. This can include things like soil, water, sunlight, and weather patterns, as well as the various species that live in the ecosystem. A niche refers to the role or position that a particular species occupies within an ecosystem, including the specific conditions that it needs to survive and thrive. Finally, the environment refers to the physical and biological factors that make up a particular habitat or ecosystem, including the abiotic (non-living) factors like temperature, moisture, and sunlight, as well as the biotic (living) factors like other species and food sources.

The pathogen that cause smallpox is

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Smallpox is caused by a virus called variola, which is a member of the poxvirus family. Poxviruses are large, complex viruses that can cause a range of diseases in animals and humans. Smallpox is a highly contagious disease that was once widespread throughout the world, but has now been eradicated through a global vaccination campaign. The virus spreads from person to person through the air, and can cause a rash, high fever, and other symptoms.

The micro-organisms that causes Typhoid disease is

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The micro-organism that causes Typhoid disease is Salmonella typhi. Typhoid fever is a serious illness caused by the Salmonella typhi bacteria. The bacteria is spread through contaminated food and water, and is most common in areas with poor sanitation and hygiene. When a person ingests food or water that is contaminated with the bacteria, it can multiply in the small intestine and then spread to other parts of the body, such as the bloodstream and the lymphatic system. This can cause a range of symptoms, including fever, abdominal pain, diarrhea or constipation, and a rash. Typhoid fever can be treated with antibiotics, but it's important to get medical attention as soon as possible to avoid complications. Good hygiene and safe food and water practices can help prevent the spread of the bacteria.

The movement of blood between the heart and all other parts of the body besides the lung is known as

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The movement of blood between the heart and all other parts of the body besides the lung is known as systemic circulation. In the systemic circulation, blood carries oxygen and nutrients from the heart to the body's tissues and organs, and returns carbon dioxide and waste products back to the heart. The heart pumps the blood to the rest of the body through arteries, and the blood returns to the heart through veins. This circulation system helps to distribute oxygen and nutrients to the body's cells and to remove waste products.

The insects in which the maxillae are modified into a long coiled proboscis is

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An example of a non-bio degrable pollutants is

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An example of a non-biodegradable pollutant is ceramics. Ceramics are materials that are made from non-organic substances such as clay, porcelain, and cement. These materials are resistant to decomposition by bacteria and other microorganisms, which means they do not break down easily in the environment. As a result, when ceramics are disposed of improperly, they can accumulate in the environment and cause pollution. Unlike biodegradable pollutants such as dung and wood, which can be broken down by natural processes and recycled back into the environment, ceramics and other non-biodegradable pollutants persist in the environment for a very long time. This can lead to a range of environmental problems, including the contamination of soil, water, and air, as well as harm to wildlife and human health. Therefore, it is important to properly dispose of non-biodegradable materials like ceramics through recycling or other appropriate waste management practices.

Which of the following protects the essential parts of the flower at bud stage?

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The sepals protect the essential parts of the flower at the bud stage. Sepals are the leaf-like structures located at the base of the flower that enclose and protect the flower bud before it blooms. They are usually green, but can also be colored like petals in some flowers. The sepals provide a protective layer around the developing flower, shielding it from damage, drying out or getting eaten by insects. Once the flower is ready to bloom, the sepals usually open up or fall off, allowing the petals to emerge and the reproductive structures (stamens and carpels) to be exposed for pollination. In some flowers, the sepals remain attached and become a part of the flower structure. However, their primary function is to protect the flower bud and ensure the successful development of the reproductive parts.

The activity of ptyalin is likely to decrease with an increase in the concentration of

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The activity of ptyalin, which is an enzyme responsible for breaking down starch into simpler sugars, is likely to decrease with an increase in the concentration of acid. This is because ptyalin works best in a slightly alkaline environment, which means that it is most effective at breaking down starch when the pH is between 6.7 and 7.0. When acid is added to this environment, the pH decreases and becomes more acidic, which can denature or deactivate the enzyme. Therefore, an increase in the concentration of acid can disrupt the optimal pH range for ptyalin, causing a decrease in its activity and effectiveness in breaking down starch.

The path followed by air as it passes through the lungs in mammals

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When mammals breathe in, air enters through the nostrils and flows into the nasal cavity. The air is then filtered, warmed, and humidified by the mucous membranes and tiny hairs inside the nasal cavity.
From there, the air travels down the pharynx, a tube that connects the nasal cavity to the larynx. The larynx is where the vocal cords are located and it also acts as a valve to prevent food and liquid from entering the lungs.
After passing through the larynx, the air enters the trachea, which is also known as the windpipe. The trachea is a tube made of rings of cartilage that keeps it open. The trachea branches into two tubes called bronchi, one leading to the left lung and one to the right lung.
Inside the lungs, the bronchi continue to divide into smaller and smaller tubes called bronchioles. These bronchioles eventually lead to tiny air sacs called alveoli, which are surrounded by tiny blood vessels called capillaries.
It is at the alveoli where the exchange of gases occurs. Oxygen from the air diffuses through the walls of the alveoli and into the capillaries, where it binds to red blood cells and is transported throughout the body. At the same time, carbon dioxide from the body diffuses from the capillaries into the alveoli, where it is exhaled out of the body when we breathe out.
Therefore, the path followed by air as it passes through the lungs in mammals is: nostrils → nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

The ability of a living organism to detect and respond to changes in the environment is referred to as

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The ability of a living organism to detect and respond to changes in the environment is referred to as irritability. Irritability is a basic property of living organisms, allowing them to sense changes in their environment and respond accordingly. This can take many forms, such as plants bending towards light, animals moving away from a stimulus that causes pain, or even single-celled organisms changing direction in response to a chemical gradient. Essentially, irritability is a way for organisms to adapt and survive in their environment by detecting and responding to stimuli.

The ability of a Chameleons to change its colour rapidly is an adaptation for

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The ability of chameleons to change their color rapidly is an adaptation for escaping detection. Chameleons are known for their ability to change their skin color to blend in with their surroundings. This helps them to avoid predators, such as birds and snakes, that might otherwise detect them and try to eat them. For example, if a chameleon is sitting on a brown branch, it can change its skin color to brown to blend in with the branch, making it harder for predators to see it. Similarly, if a chameleon is on a green leaf, it can change its skin color to green to blend in with the leaf, making it harder for predators to detect it. So, the ability to change color rapidly is an important adaptation that helps chameleons to avoid being eaten, and survive in their environment. While chameleons may also use color changes for other purposes, such as communication or attracting a mate, the primary purpose of their color-changing ability is to escape detection from predators.

The bacteria that is found in the root nodules of leguminous plants is

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Which of the organisms represent are notable agricultural pests

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The theory of natural selection was postulated by

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The theory of natural selection was postulated by Charles Darwin. He proposed that organisms with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring. Over time, this process leads to the evolution of new species. This concept is known as natural selection because the environment "selects" which individuals are better adapted to survive and reproduce. Darwin developed this theory after observing the diversity of life during his travels on the HMS Beagle, and conducting experiments on plant and animal breeding. His book "On the Origin of Species" was published in 1859 and became one of the most influential scientific works in history, revolutionizing our understanding of life and the natural world.

An example of an endospermous seed is

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An example of an endospermous seed is the maize grain. Endosperm is the tissue within the seed of a flowering plant that provides nutrients to the developing embryo. In endospermous seeds like maize, the endosperm is the primary source of food for the embryo. As the maize grain develops, the endosperm grows and stores starch and other nutrients, which are used by the embryo for growth and development when the seed germinates. So, the maize grain is a good example of an endospermous seed because it relies on the endosperm for its initial growth and development.

The largest amount of yolk is found in the egg of

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The largest amount of yolk is found in the eggs of birds, also known as Aves. Birds lay eggs that are designed to provide nourishment for their developing embryos. The yolk is one of the main sources of nutrition for the embryo and is rich in proteins, lipids, and other nutrients. In bird eggs, the yolk is typically large and round, and makes up the majority of the egg's volume. In contrast, the eggs of reptiles, amphibians, and fish often have smaller yolks that are not as rich in nutrients. These eggs are usually designed to be laid in water or moist environments where the developing embryo can receive nutrients from the surrounding environment. So in short, if you want to find the largest amount of yolk, look for bird eggs!

Which of the following theories was NOT considered by Darwin in his evolutionary theory?

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The theory that was not considered by Darwin in his evolutionary theory is "use and disuse." Darwin's theory of evolution is based on the idea of natural selection, which states that organisms that are better adapted to their environment are more likely to survive and reproduce. The key factors in natural selection are variation, survival of the fittest, and competition. Use and disuse refers to the idea that certain body parts or traits become stronger or weaker depending on how much they are used. This theory was popular before Darwin and was considered to be a way that species could change over time. However, Darwin rejected this idea and instead emphasized the role of natural selection. In conclusion, "use and disuse" was not considered by Darwin in his theory of evolution, as he instead focused on the role of natural selection in shaping species over time.

The type of asexual reproduction that is common to both Paramecium and Protists is

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The type of asexual reproduction that is common to both Paramecium and Protists is binary fission. Binary fission is a simple process of cell division in which a single cell divides into two identical daughter cells. This is the most common method of asexual reproduction in single-celled organisms like Paramecium and Protists. During binary fission, the parent cell grows and replicates its DNA, then the cell membrane and cell wall divide, forming two separate cells. Each daughter cell gets a complete copy of the parent's genetic material and is an exact copy of the original cell. This allows the organism to rapidly increase its population without having to go through the time and energy-intensive process of sexual reproduction.

In the nitrogen cycle, the nitrates in the soil are converted to atmospheric nitrogen by

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The nitrates in the soil are converted to atmospheric nitrogen by denitrifying bacteria. The nitrogen cycle is a continuous process where nitrogen moves between the atmosphere, soil, and living organisms. Nitrates are produced in the soil through the process of nitrification, where nitrogen-fixing bacteria convert atmospheric nitrogen into nitrates. However, these nitrates can then be converted back into atmospheric nitrogen by another type of bacteria called denitrifying bacteria. Denitrifying bacteria are responsible for breaking down nitrates into nitrogen gas, which is then released back into the atmosphere. This process helps to maintain a balance of nitrogen in the ecosystem and ensures that plants and other living organisms have access to the nitrates they need for growth.

The relationship between a termite and the protozoam in its intestine is described as

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The relationship between a termite and the protozoa in its intestine is described as symbiosis. Symbiosis is a type of interaction between two different species that live together in a close and mutually beneficial relationship. In the case of termites and protozoa, the termite provides a suitable environment for the protozoa to live in, while the protozoa help to digest the cellulose in the wood that termites eat. This mutualistic relationship benefits both the termite and the protozoa, and neither of them would be able to survive without the other.

The rate of transpiration is NOT affected by

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Fibrinogen and prothrombin play important roles in the

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Fibrinogen and prothrombin are two important proteins in the blood that play a crucial role in the clotting of blood. When there is an injury or damage to a blood vessel, the body's natural response is to stop the bleeding. Fibrinogen and prothrombin are both involved in a complex chain of events that result in the formation of a blood clot. First, prothrombin is converted into an enzyme called thrombin. Thrombin then converts fibrinogen into fibrin, which forms a mesh-like network of fibers that traps blood cells and forms a clot to stop the bleeding. Without fibrinogen and prothrombin, the blood would not be able to clot properly, leading to severe bleeding and potential loss of life. In summary, fibrinogen and prothrombin are essential proteins that help to ensure that blood can clot effectively and prevent excessive bleeding in response to injury or damage.

Exo-erythrocytic phase of the life cycle of malaria parasite occurs in the

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The exo-erythrocytic phase of the life cycle of the malaria parasite occurs in the liver of humans. After a mosquito infected with the malaria parasite bites a human, the parasite enters the bloodstream and eventually makes its way to the liver. Once inside the liver cells, the parasite undergoes a period of growth and replication, known as the exo-erythrocytic phase. During this phase, the parasite multiplies within the liver cells and forms many daughter parasites, which are released back into the bloodstream. These daughter parasites then invade red blood cells and begin the next phase of the malaria life cycle. So, to summarize, the exo-erythrocytic phase of the malaria parasite occurs in the liver of humans, where the parasite multiplies and prepares to infect red blood cells, leading to the onset of clinical symptoms associated with malaria.

Which of the following plant hormone is responsible for ripening of fruits?

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The plant hormone that is responsible for ripening of fruits is ethylene. Ethylene is a gaseous hormone that is naturally produced by plants, including fruits, during their growth and development. It is released in higher amounts as the fruit reaches maturity and signals the fruit to begin the ripening process. The ripening process includes changes in the color, texture, and flavor of the fruit, as well as the breakdown of starches and other complex molecules into simple sugars. Ethylene helps to activate enzymes in the fruit that are responsible for these changes, which leads to the softening of

The vector for the malaria parasite is a

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The vector for the malaria parasite is the female Anopheles mosquito. A vector is an organism that carries and transmits a disease from one host to another. In the case of malaria, the disease is caused by a parasite called Plasmodium and it is transmitted to humans through the bite of a female Anopheles mosquito. The female mosquito takes in the parasite when it bites an infected person and then passes it on to another person when it bites again. So, the female Anopheles mosquito acts as the vector for the malaria parasite, spreading the disease from person to person.

The importance of the mouth-brooding behaviour in Tilapia is that it

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The path followed by air as it passes through the lungs in mammals is

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The path followed by air as it passes through the lungs in mammals is trachea ⇢ bronchi ⇢ bronchioles ⇢ alveoli. When a person inhales, air enters the body through the nose or mouth and travels down the trachea (windpipe). The trachea branches into two main air passages called bronchi, which enter the lungs. The bronchi then branch into smaller tubes called bronchioles, which lead to clusters of tiny air sacs called alveoli. The alveoli are where gas exchange between the air and the bloodstream occurs. Oxygen from the air enters the bloodstream and is transported to the body's cells, while carbon dioxide from the bloodstream enters the alveoli to be exhaled.

The crossing of individuals of the same species with different genetic characters is

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The crossing of individuals of the same species with different genetic characters is called crossbreeding. It involves mating two organisms with different genetic traits or characteristics to create offspring with a combination of traits from both parents. This process is commonly used in agriculture and animal breeding to produce offspring with desirable traits, such as increased resistance to disease, larger size, or higher productivity. Crossbreeding can lead to a more diverse gene pool within a population and improve the overall fitness and adaptability of a species. However, it is important to carefully consider the genetic traits of both parents to ensure the health and viability of the offspring.

The hereditary characters in plants and animals are located on the

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The hereditary characters in plants and animals are located on the chromosome. Chromosomes are long, coiled strands of DNA that contain the genes that carry the instructions for making an organism. Genes are specific sequences of DNA that contain the instructions for making a particular trait, like eye color or height. The chromosomes and genes are located in the nucleus of a cell, which is the control center of the cell. The nucleus contains most of the cell's DNA and is where many of the cell's functions are regulated.

Which of the following pairs are social insects?

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Which of the following can cause shrinkage of living cells?

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A hypertonic solution can cause shrinkage of living cells. When a living cell is placed in a hypertonic solution, which is a solution with a higher concentration of solutes (such as salt or sugar) than the cell's cytoplasm, water molecules will move out of the cell through the process of osmosis. This is because water moves from an area of low solute concentration to an area of high solute concentration. As a result, the cell loses water and can shrink or shrivel up, which is known as plasmolysis. In contrast, an isotonic solution has the same concentration of solutes as the cell's cytoplasm, so there is no net movement of water in or out of the cell. A hypotonic solution has a lower concentration of solutes than the cell's cytoplasm, causing water to move into the cell, potentially leading to swelling or bursting of the cell. Deionized water, which has had its ions removed, can also cause cells to swell or burst due to the lack of solutes.

which of the following is an agent of a sexually transmitted disease?

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Treponema pallidum is an agent of a sexually transmitted disease. Sexually transmitted diseases (STDs) are infections that are spread through sexual contact. Treponema pallidum is a bacterium that causes syphilis, a type of STD. Syphilis is typically transmitted through direct contact with a syphilis sore during sexual activity. The other options you listed are not sexually transmitted diseases: - Entamoeba histolytica is a parasite that causes amoebic dysentery, which is an infection of the intestines. - Salmonella typhi is a bacterium that causes typhoid fever, which is a serious illness spread through contaminated food and water. - Clostridium tetani is a bacterium that causes tetanus, which is a serious illness resulting from a bacterial infection in a wound. So, in summary, Treponema pallidum is an agent of a sexually transmitted disease, while the other options you listed are not associated with STDs.

When sickle cell carrier marries a normal woman, the probability of them having a normal offspring is

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When a person has sickle cell trait (i.e., is a carrier), it means they have one copy of the sickle cell gene and one copy of the normal gene. If a person with sickle cell trait marries a normal woman who has two copies of the normal gene, their offspring have a 50% chance of inheriting the sickle cell gene from the carrier parent and a 50% chance of inheriting the normal gene from the normal parent. Therefore, the probability of the offspring being a carrier of sickle cell trait (i.e., having one copy of the sickle cell gene and one copy of the normal gene) is 50%. The probability of the offspring having two copies of the normal gene and not having sickle cell trait is also 50%. It's worth noting that if both parents have sickle cell trait, their offspring have a 25% chance of inheriting two copies of the sickle cell gene and having sickle cell disease, a 50% chance of inheriting one copy of the sickle cell gene and being a carrier, and a 25% chance of inheriting two copies of the normal gene and not having sickle cell trait or disease.