WAEC SSCE - Biology - 2022 (Objective)

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Higher and more complex animals like birds and mammals can reproduce only by sexual means.

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Protease J would react with the particular illustrated substance because enzymes are specific in their action. Enzymes are biological catalysts that facilitate chemical reactions in living organisms. Each enzyme is designed to catalyze a specific reaction by binding to a specific substrate, which is the substance it acts upon. This specificity is crucial for enzyme function and efficiency. In the given scenario, protease J is a type of enzyme that specifically acts on proteins. Proteases are responsible for breaking down proteins into smaller peptides or individual amino acids. When protease J encounters the illustrated substance, which represents a food substance, it is likely a protein-based food. Protease J has a specific structure that allows it to bind to the protein molecules present in the food substance. Once bound, protease J catalyzes the hydrolysis reaction, breaking the protein into smaller components. This process is highly specific to proteins and does not occur with other types of food substances. Therefore, the reason protease J would react with the particular illustrated substance is because enzymes, including proteases, are specific in their action. They recognize and interact with specific substrates, enabling the catalysis of specific chemical reactions.

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The pyramid that is not used in ecology is the pyramid of organisms. This is because the other three options - energy, numbers, and biomass - are the three main types of ecological pyramids that are commonly used to describe different aspects of ecosystems. The pyramid of energy shows the flow of energy through an ecosystem and how much energy is transferred from one trophic level to another. It typically has a triangular shape, with the primary producers at the base and the top predators at the apex. The pyramid of numbers shows the relative number of individual organisms at each trophic level of an ecosystem. This pyramid can have different shapes, depending on the ecosystem being studied. The pyramid of biomass shows the total amount of living organic matter, or biomass, at each trophic level of an ecosystem. This pyramid can also have different shapes, depending on the ecosystem being studied. In contrast, the pyramid of organisms is not commonly used in ecology because it is difficult to measure and does not provide as much information about the structure and function of an ecosystem as the other three types of pyramids.

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The region of a plant stem in which cells divide to increase its diameter is called the cambium. The cambium is a thin layer of meristematic cells located between the xylem and phloem in the stem and root of a plant. It produces new cells that differentiate into secondary xylem (wood) towards the inside and secondary phloem (inner bark) towards the outside of the stem. The cambium is responsible for the radial growth of the plant, which increases the diameter of the stem over time.

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The organelles in cells that are commonly known as suicidal bags are called lysosomes. Lysosomes are small, spherical organelles that are surrounded by a membrane and contain powerful digestive enzymes. These enzymes are capable of breaking down a wide variety of biomolecules, including proteins, carbohydrates, nucleic acids, and lipids. The term "suicidal bags" refers to the fact that lysosomes have the ability to destroy themselves, as well as other parts of the cell. If a lysosome's membrane is damaged, its digestive enzymes can leak out and damage other organelles, ultimately leading to the death of the cell. Lysosomes play an essential role in maintaining the health and function of cells. They are responsible for breaking down and recycling old or damaged organelles, as well as foreign substances that may have entered the cell. Without lysosomes, cells would quickly become overloaded with waste and eventually die.

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The statement "males are never carriers since they only receive one sex chromosome" is not correct when talking about sex-linked traits. Sex-linked traits are genetic traits that are carried on the sex chromosomes, specifically the X and Y chromosomes. In humans, females have two X chromosomes (XX) while males have one X and one Y chromosome (XY). Since sex-linked traits are located on the X chromosome, they can be inherited differently between males and females. Females can be carriers of sex-linked traits because they have two X chromosomes. If a female inherits a defective allele for a sex-linked trait from one parent but a normal allele from the other parent, she can be heterozygous for the trait. In this case, she carries the defective allele but does not express the trait herself. However, she can pass it on to her offspring, both male and female. On the other hand, males have only one X chromosome. If a male inherits a defective allele for a sex-linked trait on his X chromosome, he will express that trait since he does not have another copy of the X chromosome to mask the effects of the defective allele. Therefore, males are more likely to exhibit sex-linked traits compared to females. In summary, the statement that males are never carriers since they only receive one sex chromosome is incorrect. Females can be carriers of sex-linked traits, while males are more likely to express the trait if they inherit a defective allele on their single X chromosome.

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Succession is the process of gradual change in the species composition of a community over time. It can be primary, which occurs in a newly formed habitat without any pre-existing organisms, or secondary, which occurs in a disturbed habitat where some organisms already exist. One of the main biological associations that contribute directly to succession in a community is competition. Competition occurs when two or more organisms require the same resources such as food, water, light, or space. As the community develops, the competition for resources becomes more intense, leading to the dominance of certain species over others. This dominance results in changes in the community structure and composition, as some species become more successful at obtaining resources than others. This can lead to a shift in the dominant species as the community develops, a process known as ecological succession. Predation, parasitism, and commensalism are not direct contributors to succession. Although they can affect the distribution and abundance of species in a community, they do not directly influence the order in which different species replace each other during succession. Therefore, the correct answer is option A - competition.

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The feature that is not an adaptation is: - Hairy structures on the leaves to reduce water loss Explanation: Adaptations are traits that have evolved over time in response to environmental pressures. They provide an advantage to the organism in its environment, increasing its chances of survival and reproduction. Breathing roots for entry air, flowers raised above water to attract pollinators, and spongy tissues containing gases for buoyancy are all adaptations. However, hairy structures on the leaves to reduce water loss are not necessarily adaptations. While they may help reduce water loss in some environments, they are not always present in all plants and may not confer a significant advantage in all environments. Therefore, this feature cannot be considered a universal adaptation.

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Based on the diagrams, the answer is III and I. The process involves the fusion of two cells: one with a large vesicle (cell P) and another with a smaller vesicle (cell Q). The fusion of these two cells allows the contents of the larger vesicle to be released and processed by the enzymes in the smaller vesicle. In more detail, the process involves the fusion of the membrane of the large vesicle (III) with the membrane of the smaller vesicle (I). This fusion creates a pore that allows the contents of the large vesicle to enter the smaller vesicle. The enzymes in the smaller vesicle then process the contents of the large vesicle, and the resulting molecules are released from the smaller vesicle through its membrane (II). Therefore, the parts of P and Q that fuse to complete the biological process are III and I.

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A group of organisms of the same species living in a particular place is known as a population. Population refers to a group of individuals of the same species that live in the same area at the same time and have the potential to interbreed. For example, a population of fish in a pond, a population of deer in a forest, or a population of bacteria in a petri dish. Populations can vary in size and can be affected by factors such as birth and death rates, immigration, and emigration. Understanding populations is important in ecology, as it can help us understand how populations interact with each other and their environment, and how they change over time.

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The practice that will not maintain soil fertility is "tendency of becoming waterlogged". When soil becomes waterlogged, it means it is excessively saturated with water, leading to low oxygen content. This condition does not support the growth of beneficial soil microorganisms that are essential for soil fertility. It also leads to the leaching of important nutrients from the soil. Therefore, it is necessary to avoid this practice and implement soil management techniques such as crop rotation, intercropping, mulching, and organic fertilization to maintain soil fertility.

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An evidence of the occurrence of photosynthesis in an experiment is the release of oxygen. During photosynthesis, plants and other photosynthetic organisms use energy from sunlight to convert carbon dioxide and water into oxygen and glucose (a type of sugar). The oxygen produced by photosynthesis is released into the atmosphere as a waste product. While the other options listed - release of carbon dioxide, formation of water molecules, and formation and release of fructose - are all part of the chemical reactions that occur during photosynthesis, they are not necessarily evidence of the occurrence of photosynthesis. For example, the release of carbon dioxide could be a result of cellular respiration (the process by which cells release energy from glucose), rather than photosynthesis. Similarly, the formation of water molecules and fructose could occur in other metabolic pathways, not just photosynthesis. Therefore, the most specific and direct evidence of the occurrence of photosynthesis in an experiment is the release of oxygen.

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The process that brings about the shrinking of a spirogyra cell when placed in a strong solution is plasmolysis. Plasmolysis is a phenomenon that occurs when a plant cell is placed in a hypertonic solution (a solution with a higher concentration of solutes than the cell). Water moves out of the cell through osmosis, causing the cell membrane to shrink away from the cell wall. In the case of spirogyra, a freshwater green algae, when it is placed in a strong salt solution, water moves out of the cell through osmosis, causing the cell membrane to shrink away from the cell wall, and the cell becomes flaccid. This process is called plasmolysis. Therefore, the process that brings about the shrinking of a spirogyra cell when placed in a strong solution is plasmolysis.

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P - sperm cell:

III. Nucleus     IV. Mitochondria

Q- Egg cell: 

I. Nucleus       II. Cytoplasm.

Sperm-egg fusion is a cell-cell membrane fusion event essential for the propagation of sexually reproducing organisms.

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Proteases are enzymes that break down proteins into smaller molecules called amino acids. The food substances depicted in diagrams K, L, M, and N are all proteins. Therefore, when protease J reacts with any of these food substances, the end product would be amino acids. During the reaction, the protease J breaks down the protein in the food substance into individual amino acids by breaking the peptide bonds between them. This process is called hydrolysis, and it requires the addition of water molecules to break the bonds. Fatty acids and glucose are not end products of the breakdown of proteins by proteases. Fatty acids are the building blocks of lipids, while glucose is a type of sugar. Water is not an end product either; it is required in the hydrolysis reaction to break the peptide bonds between amino acids. Therefore, the correct answer is option C - amino acids.

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The possible genotypes of the original plants could be TT and Tt. In this scenario, we are crossing two tall plants, which means they both have the allele for tall height (T). When these two plants are crossed, their offspring in the F1 generation will all be tall because they inherit a copy of the tall allele from each parent (Tt). Now, when the F1 plants are selfed, meaning they are allowed to reproduce with each other, the resulting F2 generation shows a mixture of tall and short plants. This indicates that there is a presence of a recessive allele for short height (t). To have a mixture of tall and short plants in the F2 generation, the original plants must have been heterozygous for the height trait. This means that one parent carried two copies of the tall allele (TT), while the other parent carried one copy of the tall allele and one copy of the short allele (Tt). When these plants are crossed, there is a 25% chance of producing offspring with the genotype TT (tall), a 50% chance of producing offspring with the genotype Tt (tall), and a 25% chance of producing offspring with the genotype tt (short). Therefore, the possible genotypes of the original plants are TT and Tt, where TT represents a homozygous tall genotype and Tt represents a heterozygous tall genotype.

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The position occupied by each of the organisms J, K, L, M, and N in the food chain is known as the trophic level. Trophic levels refer to the hierarchical levels of the food chain, where each level represents a different group of organisms that have similar functions in the transfer of energy and nutrients from one level to the next. The first level of the trophic level comprises producers, which are usually plants that produce their food using photosynthesis. The second level is occupied by primary consumers, which are herbivores that feed on the producers. The third level consists of secondary consumers, which are carnivores that feed on the primary consumers, and so on. Each level of the trophic level represents a different level of energy transfer and nutrient cycling in the ecosystem.

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The organ level of organization in living things is found in the kidney. An organ is a group of tissues that work together to perform a specific function in the body. The kidney is an example of an organ because it is made up of different types of tissues that work together to filter and remove waste products from the blood, regulate fluid balance, and maintain electrolyte balance. In contrast, a waterleaf plant is made up of different types of tissues, but does not have organs like the kidney. A virus particle is not considered a living organism and does not have levels of organization like living things. Spermatozoon is a single cell and is not considered an organ or a level of organization.

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The major source of vitamin A are egg yolk, carrot, and palm oil. Vitamin A is a fat-soluble vitamin that is essential for maintaining healthy vision, skin, and immune function. It is also important for the normal growth and development of cells and tissues in the body. Egg yolk is a good source of vitamin A because it contains carotenoids, which are converted into vitamin A in the body. Carrots are also a rich source of carotenoids, particularly beta-carotene, which the body can convert into vitamin A. Palm oil is another source of carotenoids and is commonly used in many countries as a cooking oil and food ingredient. While other foods may contain some amount of vitamin A, such as liver, green vegetables, and milk, they are not considered to be as rich a source as egg yolk, carrot, and palm oil. Therefore, egg yolk, carrot, and palm oil are considered the major sources of vitamin A in the diet.

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The process by which the amount of water and solutes in the blood is controlled is called osmoregulation. Osmoregulation is the process by which living organisms maintain a balance of water and solutes within their bodies. In animals, the kidneys play a crucial role in osmoregulation, regulating the concentration of solutes such as sodium and potassium ions in the blood, as well as the amount of water that is retained or excreted. In plants, osmoregulation involves the movement of water and solutes in and out of the plant cells to maintain turgor pressure, which helps keep the plant rigid and upright. Therefore, the correct answer is osmoregulation.