JAMB UTME - Biology - 2011

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

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The cross of a red-flowered plant with a white-flowered plant producing a pink-flowered plant is an example of incomplete dominance. Incomplete dominance is a type of genetic inheritance in which the phenotype of the offspring is a blend of the phenotypes of the parents. In this case, the phenotype (appearance) of the pink-flowered plant is a blend of the red and white flower color of the parents. Codominance, on the other hand, is a type of genetic inheritance in which both dominant alleles (versions of a gene) are expressed equally and independently in the phenotype of the offspring. In this case, both the red and white flower color would be present in the phenotype of the offspring, but they would not blend to form a new color. Mutation is a change in the DNA sequence of an organism, which can result in changes to the phenotype. Linkage refers to the close physical proximity of genes on a chromosome and the tendency for them to be passed on together. Neither of these concepts is directly relevant to the cross of the red-flowered and white-flowered plants producing a pink-flowered plant. Therefore, the cross of the red-flowered and white-flowered plants producing a pink-flowered plant is an example of incomplete dominance.

The wings of a bat and those of a bird are examples of

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The wings of a bat and those of a bird are examples of convergent evolution. Convergent evolution is when two unrelated species develop similar adaptations to their environments, even though they evolved independently from each other. In this case, the wings of bats and birds both evolved to help them fly, but the wings of bats and birds are not related to each other, as bats are mammals and birds are a separate class of vertebrates. This shows that evolution can lead to similar solutions in different species when they face similar challenges in their environments.

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

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The theory of "Use and Disuse" was not considered by Charles Darwin in his evolutionary theory. This theory was proposed by Jean-Baptiste Lamarck, a French biologist who lived before Darwin. Lamarck's theory stated that traits developed during an organism's lifetime could be passed down to its offspring. For example, a giraffe's neck would become longer over time as the giraffe stretched its neck to reach higher leaves, and this longer neck would be passed down to its offspring. In contrast, Darwin's theory of evolution through natural selection emphasized the role of variation, competition, and survival of the fittest in driving evolution. Darwin observed that individuals within a population vary in their traits, and that some of these traits are more advantageous in a given environment. Those individuals with advantageous traits are more likely to survive and reproduce, passing their advantageous traits on to their offspring. Over time, this process of natural selection can lead to the evolution of new species.

The inheritable characters that are determined by a gene located on the X-chromosome is

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The inheritable characters that are determined by a gene located on the X-chromosome are referred to as sex-linked. This means that the gene responsible for a particular trait is located on the X chromosome, which is one of the two sex chromosomes (the other being the Y chromosome). In humans, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). Because females have two copies of the X chromosome, they have two copies of any gene located on the X chromosome. This means that if one copy of a gene on the X chromosome is faulty, they have a second, normal copy to compensate. In contrast, males only have one copy of the X chromosome, so if a gene on the X chromosome is faulty, they do not have a second, normal copy to compensate. This can result in certain traits being more commonly seen in males. Sex-linked traits can be either dominant or recessive. A dominant trait is one that will be expressed if a person has at least one copy of the dominant allele (version of a gene). A recessive trait is only expressed if a person has two copies of the recessive allele. In the case of sex-linked traits, because males only have one X chromosome, a dominant trait will always be expressed, while a recessive trait will only be expressed if both copies of the X chromosome carry the recessive allele.

The vector of the malaria parasite is

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The vector of the malaria parasite is the female Anophelous mosquito. The malaria parasite needs a host to survive and reproduce, and the female Anophelous mosquito provides that host. When the mosquito feeds on the blood of an infected person, it ingests the malaria parasite along with the blood. The parasite then multiplies within the mosquito and eventually moves to the mosquito's salivary glands. When the mosquito bites another person, it injects saliva containing the malaria parasite into that person's bloodstream, thus spreading the disease. Male Culex mosquitoes do not transmit malaria, and female Aedes and Culex mosquitoes may transmit other diseases but not malaria.

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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. During this phase, the parasite multiplies in liver cells and forms thousands of merozoites, which are released into the bloodstream to infect red blood cells. This is the first phase of the malaria parasite's life cycle within the human body and is crucial for the subsequent development of the disease.

The fallacy in Lamarck's evolutionary theory was the assumption that

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The fallacy in Lamarck's evolutionary theory was the assumption that acquired traits are heritable. Lamarck's theory of evolution, proposed in the early 19th century, was based on the idea that organisms could acquire new traits during their lifetime through use or disuse of body parts. For example, Lamarck believed that giraffes evolved long necks because they stretched to reach leaves on tall trees, and that this acquired trait was passed on to their offspring. However, we now know that acquired traits are generally not heritable. The genetic material that is passed on from one generation to the next is not affected by the use or disuse of body parts during an organism's lifetime. Instead, genetic variation arises through random mutations and other mechanisms, which are then subject to natural selection based on their fitness in a particular environment. In addition to the fallacy of heritability of acquired traits, Lamarck's theory also failed to take into account the role of natural selection in shaping evolutionary change. Nevertheless, Lamarck's ideas were an important step towards the development of modern evolutionary theory, and many of his observations about the diversity and adaptation of living organisms continue to inform our understanding of the natural world.

Which of the following instruments is used to measure relative humidity?

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A hygrometer is used to measure relative humidity. Relative humidity is the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature. It is expressed as a percentage. A hygrometer works by measuring the difference between the temperature of the air and the temperature of a substance, such as a wet bulb, that is in contact with the air. The difference between the two temperatures is used to calculate the relative humidity of the air. In simple terms, a hygrometer helps us determine the level of moisture in the air, which can affect comfort and health, as well as preservation of certain items.

Lack of space in a population could lead to an increase in

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When a population lacks sufficient space, it can lead to an increase in disease rate. This is because when individuals live in close proximity to each other, infectious diseases can easily spread from person to person. This is particularly true for respiratory illnesses that can be spread through the air, such as the common cold, flu, and COVID-19. Additionally, lack of space can lead to poor hygiene conditions, which can further increase the risk of disease transmission. In contrast, lack of space is not likely to directly cause an increase in water scarcity, drought, or birth rate.

Which of the following is a feature of the population pyramid of a developing country?

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The vascular tissues in higher plants are responsible for

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The movement response of a cockroach away from a light source can be described as

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The movement response of a cockroach away from a light source can be described as negative phototaxis. This means that the cockroach is moving in the opposite direction of the light source. It is important to note that this response is not due to the cockroach trying to avoid the light itself, but rather because the cockroach is programmed to prefer dark environments for survival.

Which of the following can cause shrinkage of living cells?

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A hypertonic solution can cause shrinkage of living cells. Hypertonic refers to a solution with a higher concentration of solutes (such as salt) compared to the inside of a living cell. When a living cell is placed in a hypertonic solution, water from inside the cell will move out of the cell through osmosis in an attempt to balance the concentration of solutes. This causes the cell to lose water and shrink in size, leading to a process called plasmolysis. In contrast, an isotonic solution has the same concentration of solutes as the inside of a living cell, so there is no net movement of water in or out of the cell. A hypotonic solution has a lower concentration of solutes compared to the inside of a living cell, causing water to move into the cell and potentially causing it to burst or undergo lysis. Deionized water, which has had its ions removed, is hypotonic in nature and can cause lysis of living cells when they are placed in it. Therefore, the correct option that can cause shrinkage of living cells is "hypertonic solution."

The adaptive importance of nuptial flight from termite colonies is to

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The adaptive importance of nuptial flight from termite colonies is to "disperse the reproductives in order to establish new colonies." During nuptial flight, winged reproductive termites leave their original colony in large numbers to mate and start new colonies. This strategy allows for genetic diversity and prevents inbreeding, as the reproductives from different colonies come together to mate. Once mated, the winged termites land, shed their wings, and establish new colonies where they become the king and queen of the new termite colony. This ensures the survival and expansion of the termite population, as well as the colonization of new habitats. Providing food for other animals during the early rains or expelling the reproductives to provide enough food for other members are not the adaptive importance of nuptial flight from termite colonies. The former refers to the ecological role of termites in the food chain, while the latter is not a biologically accurate explanation for nuptial flight.

Use the diagram above to answer this question.

The gas evolved in the process is

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In an experiment to determine the percentage of humus and water in a soil sample, the following results were obtained

Weight of the evaporating basin alone = 80.5g

Weight of basin and soil = 101.5g

Weight after drying the soil in the oven = 99.0g

Weight of basin and roasted soil = 95.5g

The percentage of humus in the soil sample is

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Mass of Soil = 101.5 - 80.5 = 21.0g
Mass of humus = (99.0 - 95.5)g = 3.5g
% of humus = \(\frac{3.5}{21.0} \times \frac{100}{1}}
= 16.7%

Use the following information to answer the question below.

I. Test tube containing cane sugar and water . ll. Test tube containing cane sugar and diluted acid. III. Test tube containing cane sugar and its degrading enzyme .

In which of the test tubes will glucose be detected after complete hydrolysis?

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Glucose will be detected after complete hydrolysis in test tubes ll and lll. Cane sugar, also known as sucrose, is a type of sugar that is made up of glucose and fructose molecules. In test tube l, which contains cane sugar and water, no hydrolysis will occur because water alone does not contain the necessary enzymes to break down the sucrose molecules into glucose and fructose. In test tube ll, which contains cane sugar and diluted acid, the acid will help to break down the sucrose molecules into glucose and fructose through a process called hydrolysis. The acid acts as a catalyst, speeding up the hydrolysis reaction and breaking the bonds between the glucose and fructose molecules. In test tube lll, which contains cane sugar and its degrading enzyme, the enzyme will help to break down the sucrose molecules into glucose and fructose through hydrolysis. Enzymes are naturally occurring proteins that function as catalysts, speeding up chemical reactions and breaking down complex molecules into simpler ones. Therefore, glucose will be detected after complete hydrolysis in both test tubes ll and lll, but not in test tube l.

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. This system is located in the inner ear and consists of three semicircular canals and the otolith organs (utricle and saccule). These structures contain hair cells that are sensitive to the movement of fluid in the canals and the shifting of otoliths in response to movement. The vestibular system provides the brain with information about the body's position and movement in space, allowing us to maintain our balance and coordinate our movements. It also plays a role in spatial orientation, motion sickness, and other sensory and motor functions.

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

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The sequence of the one-way gaseous exchange mechanism in a fish is: mouth → gills → operculum. Fish breathe by taking in water through their mouth and passing it over their gills. The gills are the organs responsible for extracting oxygen from the water and releasing carbon dioxide. Once the water passes over the gills, it is expelled through an opening on the side of the fish's body called the operculum. The operculum helps to regulate the flow of water over the gills and also protects them from damage. Therefore, the correct sequence of the one-way gaseous exchange mechanism in a fish is mouth → gills → operculum.

Use the following information to answer the question below.

I. Test tube containing cane sugar and water . ll. Test tube containing cane sugar and diluted acid. III. Test tube containing cane sugar and its degrading enzyme .

The enzyme involved in the hydrolysis is

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The enzyme involved in the hydrolysis of cane sugar is sucrase. Hydrolysis is the chemical process of breaking down a larger molecule into smaller molecules by adding water. In the case of cane sugar (sucrose), hydrolysis involves breaking the bond between glucose and fructose molecules with the addition of a water molecule. This reaction is catalyzed by an enzyme called sucrase, which is found in the small intestine of animals and in some microorganisms. When cane sugar is exposed to sucrase, it is broken down into glucose and fructose, which can then be absorbed and used by the body for energy. The other enzymes listed (rennin, erepsin, and maltase) are involved in the digestion of other types of molecules, such as milk proteins, peptides, and maltose, respectively.

Use the diagram above to answer this question.

The experimental set-up above is used to demonstrate the process of

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I. Parasitism → Sundew. ll. Autotrophism →Amoeba. III. Saprophytism → Alga. IV Heterotrophism → Agama.Which of the above modes of nutrition is correctly matched with the organism that exhibits it?

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An example of a filter -feeding animal is

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An example of a filter-feeding animal is a whale. Filter-feeding is a method of feeding where an animal passes water through a specialized structure to filter out small organisms like plankton, krill, and small fish. Whales have a specialized structure in their mouth called baleen plates which act like a filter. They take in a large amount of water and then force the water back out through the baleen, trapping small organisms inside their mouth which they then swallow. This allows whales to feed on a huge amount of small organisms at once. On the other hand, sharks, butterflies, and mosquitoes do not filter-feed. Sharks are carnivorous predators that catch their prey using their sharp teeth, butterflies are nectar feeders and they have a long tube-like structure called proboscis which they use to suck the nectar from flowers, and mosquitoes are blood feeders, where they insert their proboscis into the skin of animals to extract blood.

During blood transfusion, agglutination may occur as a result of the reaction between

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During blood transfusion, agglutination can occur due to the reaction between contrasting antigens and antibodies. Antigens are proteins found on the surface of red blood cells, which help identify them as belonging to the individual's own body. Antibodies are proteins in the plasma of the blood that help to recognize and fight foreign substances such as bacteria, viruses, and other substances. When a person receives a blood transfusion, their immune system may recognize the antigens on the red blood cells of the donated blood as foreign and produce antibodies against them. If the donated blood contains antigens that are different from the recipient's own blood, the antibodies produced by the recipient's immune system will bind to these foreign antigens, causing agglutination or clumping of the red blood cells. This agglutination can block blood vessels and prevent oxygen from reaching the body's tissues, causing serious health problems. Therefore, it is essential to match the blood types of the donor and recipient before a blood transfusion to prevent agglutination and other adverse reactions. This involves testing the blood for the presence of specific antigens and antibodies, and selecting compatible blood types to ensure a safe and successful transfusion.

In nature, plants and animals are perpetually engaged in mutualism because

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Plants and animals are engaged in mutualism because they help each other survive and thrive. For example, plants provide food and oxygen for animals to breathe, while animals help pollinate plants and spread their seeds. This relationship is beneficial for both the plants and animals, and it helps them both to survive and grow. The relationship between plants and animals in nature is a good example of mutualism, where both species help each other and benefit from each other.

The conversion of a nutrient into a molecule in the body of a consumer is referred to as

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The conversion of a nutrient into a molecule in the body of a consumer is referred to as assimilation. Assimilation is the process by which organisms convert the nutrients they absorb into the molecules they need for energy, growth, and maintenance. In animals, assimilation typically occurs in the digestive tract after the food has been broken down by digestion and absorbed into the bloodstream. Nutrients such as glucose, amino acids, and fatty acids are taken up by cells throughout the body and used to synthesize new proteins, carbohydrates, and fats, as well as to produce energy through cellular respiration. Thus, assimilation is a crucial part of the nutrient cycle and is essential for the growth, development, and survival of living organisms.

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. In many species of lizards, males use bright colors or elaborate displays to attract females during the mating season. The red head of male Agama lizards is one such example of a male display that is used to attract females. During the breeding season, male Agama lizards will often perch on high rocks or other elevated surfaces, where they can display their brightly colored heads to passing females. The red coloration is thought to be a signal of the male's overall health and genetic quality, which is an important factor in female mate choice. While the red head may make the male more conspicuous to predators, it is not believed to serve a primary function in predator avoidance or concealment. Similarly, while male lizards may engage in aggressive displays to defend their territory from other males, this behavior is not typically associated with the red head coloration. Instead, the primary function of the red head is to attract mates and increase the male's reproductive success.

Seed plants are divided into

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Seed plants are divided into two main groups: "angiosperms and gymnosperms". Gymnosperms are plants whose seeds are not enclosed in an ovary or fruit. Examples of gymnosperms include conifers, cycads, and ginkgos. Angiosperms, on the other hand, are plants whose seeds are enclosed in an ovary or fruit. This group includes most of the plants that people are familiar with, such as flowers, trees, and grasses. Angiosperms are further divided into two main subgroups: "monocotyledons and dicotyledons". These subgroups are based on the number of cotyledons (embryonic leaves) present in the plant's seed. Monocots have one cotyledon, while dicots have two. The division of seed plants into these groups is based on their morphology, anatomy, and reproductive characteristics.

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Dracunculiasis, also known as Guinea worm disease, is a parasitic infection that is caused by drinking contaminated water. Specifically, the disease is contracted by drinking water that contains tiny crustaceans called copepods that have been infected with Guinea worm larvae. Once ingested, the larvae mature into adult worms that can grow up to 3 feet long and cause painful symptoms such as blistering, fever, and nausea. Therefore, the correct answer is drinking contaminated water. It cannot be contracted through eating contaminated food, bathing in contaminated water or bites of blackfly.

In which of the following species is the biomass of an individual the smallest ?

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An example of an endospermous seed is

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An example of an endospermous seed is "maize grain." Endospermous seeds are those that have a food storage tissue called "endosperm" that nourishes the developing embryo of the seed. In the case of maize grain, the endosperm is the starchy part of the seed that we eat as cornmeal, cornstarch, or popcorn. During seed development, the endosperm is formed when the female reproductive cell (the egg) is fertilized by the male reproductive cell (the sperm). The endosperm provides nutrients for the embryo until it is able to photosynthesize on its own after germination. Cashew nut, cotton seed, and bean seed are not examples of endospermous seeds, as they have different mechanisms for storing and providing nutrients to the developing embryo.

In mammals, the exchange of nutrients and metabolic products occurs in the

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The bright coloured eye spots on the wings of moth are an example of

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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 fission. Fission is a type of asexual reproduction in which an organism divides into two or more parts, each of which grows into a new individual. In Paramecium, a single-celled organism, fission occurs when the cell divides into two daughter cells, each with a complete set of genetic information. Similarly, in some protists, fission occurs when the organism splits into two or more daughter cells. Budding is another type of asexual reproduction in which a new organism grows out of the body of the parent organism. Sporulation is a process by which an organism produces spores, which can grow into new individuals. Fragmentation is a type of asexual reproduction in which a parent organism breaks into two or more pieces, each of which can grow into a new individual. However, these types of reproduction are not common to both Paramecium and protists.

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Which of the organisms represented are notable agricultural pests?

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In which of the following biomes is the south western part of Nigeria located?

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The southwestern part of Nigeria is located in the tropical rainforest biome. A biome is a large geographical region characterized by a particular type of climate and vegetation. The tropical rainforest biome is found near the equator and is characterized by high temperatures and high rainfall throughout the year. This combination of warm, wet conditions creates an environment that is ideal for the growth of lush, diverse vegetation, including tall trees, shrubs, and vines. In contrast, temperate forests are found in regions with more moderate climates and are characterized by trees that lose their leaves in the fall. Tropical woodlands are found in regions that receive less rainfall than tropical rainforests and are characterized by more sparse vegetation. Deserts are found in regions that receive very little rainfall and are characterized by harsh, arid conditions and limited vegetation. So, the southwestern part of Nigeria, which is located near the equator, is best characterized as a tropical rainforest biome.

Millet , sorghum, maize and onions are common crops growth in Nigeria in the

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Millet, sorghum, maize and onions are common crops grown in Nigeria in the sudan savanna. The sudan savanna is a type of grassland that is found in West Africa and is known for its hot, dry climate and fertile soil. This makes it an ideal place for growing crops like millet, sorghum, maize and onions, which are all well adapted to the conditions in the sudan savanna. These crops provide food for the local people and are important for the economy of Nigeria.

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

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Parental care is mostly exhibited in Mammals (Mammalia). Mammals are unique among the vertebrates because they have mammary glands that produce milk to nourish their offspring. Parental care in mammals begins before birth with the development of the fetus inside the mother's uterus, where it receives nutrients and oxygen through the placenta. After birth, mammalian mothers provide their young with milk, warmth, and protection until they are able to fend for themselves. Mammalian fathers also play an important role in parental care. In many mammal species, fathers provide food, protection, and even grooming to their offspring. For example, male lions protect their cubs from predators while the mother is hunting, and male gorillas carry and play with their infants. While some species of reptiles, amphibians, and birds also exhibit parental care, it is not as extensive or complex as in mammals. In these groups, parental care may include behaviors such as guarding the eggs or young, providing food, or teaching the offspring how to find food and defend themselves. However, most reptiles, amphibians, and birds do not have specialized organs to produce milk or the ability to carry and nurse their young, which limits the extent of their parental care.

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

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Which of the following is true of leucocytes?

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An economic importance of the organism represented by IV is that

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The interaction of a community of organisms with its abiotic environment constitutes

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The interaction of a community of organisms with its abiotic environment constitutes an ecosystem. An ecosystem is a biological community of interacting organisms and their physical environment. It includes living things like plants, animals, and microorganisms, as well as non-living things like water, soil, and air. Ecosystems can vary in size from small ponds to large forests or even the entire planet. Every ecosystem has a complex web of interactions between the living and non-living components, such as the flow of energy and nutrients. For example, plants use energy from the sun to produce food through photosynthesis, which is then consumed by herbivores, which are then eaten by carnivores. Meanwhile, nutrients in the soil and water are cycled through the ecosystem by decomposers like bacteria and fungi. Therefore, the correct answer is option C: an ecosystem.

Habitats are generally classified into

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Habitats are generally classified into two categories: aquatic and terrestrial. Aquatic habitats include all types of water bodies such as oceans, rivers, lakes, ponds, and wetlands. These habitats are characterized by their water-based environment, which can vary in temperature, salinity, and depth. Aquatic habitats are home to a diverse range of plant and animal species that have adapted to living in water. Terrestrial habitats include all land-based environments such as deserts, forests, grasslands, tundra, and mountains. These habitats are characterized by their soil-based environment, which can vary in temperature, moisture, and nutrient content. Terrestrial habitats are home to a wide range of plant and animal species that have adapted to living on land. Therefore, the correct answer is option B: aquatic and terrestrial.

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

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The ability of living organisms to detect and respond to changes in the environment is called "irritability." This refers to the ability of an organism to detect and respond to stimuli from the environment, such as light, temperature, touch, or sound. For example, if you touch a hot stove, your body's ability to feel the heat and quickly move your hand away is an example of irritability. Similarly, a plant's ability to grow towards light is also an example of irritability, as it responds to the stimulus of light to orient its growth. Other terms listed in the options have different meanings. "Locomotion" refers to an organism's ability to move from one place to another, while "growth" refers to an organism's increase in size or complexity over time. "Taxis" refers to a type of movement in response to a stimulus, such as the movement of bacteria towards a food source or away from a harmful substance.

The number of alleles controlling blood groups in humans

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Which of the following groups of environmental factors are density-dependent?

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Food, predation, disease, and accumulation of metabolites are density-dependent environmental factors. Density-dependent factors are those that become more influential as the population size of a species increases. For example, as a population grows, there may be increased competition for limited food resources, an increase in the spread of disease, and a buildup of waste products, which can all have a negative impact on the population. These factors can limit the growth of a population and help to maintain a balance in the ecosystem.

In mammals, the exchange of nutrients and metabolic products occurs in the

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

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The path that air follows as it passes through the lungs in mammals is: trachea → bronchi → bronchioles → alveoli. When we inhale, air enters through the nostrils and travels down the throat and into the trachea, which is also known as the windpipe. The trachea then splits into two bronchi, one for each lung. The bronchi further divide into smaller bronchioles, which continue to branch into even smaller tubes. Eventually, the bronchioles lead to tiny air sacs called alveoli, which are the site of gas exchange. When we breathe in, oxygen from the air is diffused into the blood vessels surrounding the alveoli, while carbon dioxide from the blood is diffused into the alveoli to be exhaled out of the body. This process is called respiration and is necessary for the body to receive oxygen and get rid of carbon dioxide.

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

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The organ that regulates the levels of water, salts, hydrogen ions, and urea in the mammalian blood is the Kidney. The kidney is an important organ responsible for filtering the blood and removing waste products such as urea, excess salts, and hydrogen ions. It also regulates the amount of water in the body by either retaining it or excreting it in the urine, depending on the body's needs. The kidneys work by filtering blood through tiny structures called nephrons, which remove waste products and excess fluids from the blood. The filtered blood is then returned to circulation, while the waste products are excreted as urine. The kidney also plays a crucial role in maintaining the body's acid-base balance by regulating the levels of hydrogen ions in the blood. If the blood becomes too acidic or too alkaline, the kidneys adjust the levels of hydrogen ions in the blood to bring it back into balance. In summary, the kidney is the organ that regulates the levels of water, salts, hydrogen ions, and urea in the mammalian blood by filtering the blood, removing waste products, and regulating the amount of water in the body.