WAEC SSCE - Biology - 2017

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Drought can result in food shortage. Drought is a prolonged period of dry weather that can lead to a shortage of water for plants, which can cause crops to fail and result in a shortage of food for both humans and animals. In areas where agriculture is heavily dependent on rain, drought can have a significant impact on food production and lead to food shortages. Low rate of reproduction, emigration, and topography are not directly related to food shortage. However, factors such as population growth and migration patterns can indirectly affect food production and availability. The shape and elevation of the land, or topography, can also impact agriculture, but it is not a direct cause of food shortage.

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Soil permeability refers to how easily water passes through the soil. It is a measure of the rate at which water can move through soil pores or spaces between soil particles. Soils with high permeability allow water to pass through quickly, while soils with low permeability restrict the movement of water. Permeability is determined by various factors, such as soil texture, structure, compaction, and organic matter content. Coarse-textured soils with larger pore spaces, such as sandy soils, generally have high permeability, while fine-textured soils with smaller pore spaces, such as clay soils, have low permeability. Soil permeability is an important property that affects plant growth and water availability, as it influences the rate at which water can move through soil and reach plant roots.

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More accurate comparisons of trophic levels is not associated with pyramids of energy. Pyramids of energy are graphical representations of the flow of energy through an ecosystem, showing the amount of energy transferred from one trophic level to the next. While pyramids can be used to compare the efficiency of energy transfer between trophic levels and make comparisons of pyramids for different ecosystems, they do not necessarily provide more accurate comparisons of trophic levels. The accuracy of the comparison depends on various factors such as the method used to measure the energy flow and the precision of the data used to construct the pyramid.

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The part labelled I in the human sperm diagram is the acrosome. The acrosome is a specialized structure that covers the head of the sperm. It contains digestive enzymes that are necessary for the sperm to penetrate the protective layers of the egg during fertilization. When the sperm reaches the egg, the acrosome releases these enzymes, which break down the outer membrane of the egg and allow the sperm to enter and fertilize it. Therefore, the acrosome is a critical structure in the process of fertilization and is responsible for facilitating the fusion of the sperm and egg.

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When viewing an object that is close to the human eye, the eye lens becomes fat. The process of changing the shape of the eye lens to focus on objects at different distances is called accommodation. When the eye is focusing on a nearby object, the ciliary muscles in the eye contract, which causes the suspensory ligaments to relax. This, in turn, allows the eye lens to become more rounded and thicker, which increases its refractive power. The increased curvature of the eye lens allows the eye to bend the light more, so that the light rays converge and focus on the retina, producing a clear and sharp image. This process of accommodation is necessary to see objects clearly at different distances, and it is an automatic process controlled by the brain. Therefore, when viewing an object that is close to the human eye, the eye lens becomes fat to focus the light rays and produce a clear image on the retina.

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The pyramid of energy gives the most accurate picture of the relationships between the various trophic levels in a food chain. This is because energy is lost at each level due to metabolic processes, so there is less energy available to the organisms at higher trophic levels. Therefore, the pyramid of energy shows the decreasing amount of energy available at each level, with the producers at the bottom and the top predators at the top. This pyramid provides a clearer and more accurate representation of the energy flow through a food chain than other pyramids, such as those based on numbers or biomass. This is because energy flow is a unidirectional process, and it reflects the actual transfer of energy from one trophic level to another in a food chain.

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The Pancreas serves as both an endocrine gland and an exocrine gland. An endocrine gland is a gland that produces hormones and releases them into the bloodstream to regulate various bodily functions. The Pancreas produces hormones such as insulin and glucagon which regulate the body's blood sugar levels. On the other hand, an exocrine gland is a gland that releases substances through ducts directly into a target organ or tissue. The Pancreas also has exocrine functions, as it releases digestive enzymes into the small intestine to help break down food. So, the Pancreas has both endocrine and exocrine functions.

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The labelled part that provides a surface for the attachment of the triceps is part III. The triceps muscle is located at the back of the upper arm and is responsible for extending the arm at the elbow joint. It has three heads, and the long head of the triceps attaches to the scapula bone and the lateral and medial heads attach to the humerus bone of the upper arm. Part III of the diagram represents the humerus bone, and the bony protrusion on the back of the bone is called the olecranon process. This process provides a surface for the attachment of the tendon of the triceps muscle, allowing it to extend and straighten the arm at the elbow joint.

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The group of animals that do not possess a nervous system is Porifera. Porifera, also known as sponges, are simple, multicellular animals that lack organs and tissues. They do not have a true nervous system but can react to physical and chemical stimuli through specialized cells called choanocytes. These cells help in filtering water and capturing food particles, and they also respond to changes in the water flow and chemical composition. However, Porifera do not have a centralized nervous system like other animals and thus cannot process information or respond to stimuli in the same way.

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The group of organisms that do not have members that can be called autotrophs is Fungi. Autotrophs are organisms that are able to synthesize their own food using simple inorganic substances and an external energy source, such as sunlight. Autotrophs include plants, some protists, and some bacteria. Fungi, on the other hand, are heterotrophic organisms that obtain their nutrition by decomposing dead organic matter or by forming mutualistic relationships with other organisms. They do not have the ability to carry out photosynthesis or produce their own food, and therefore cannot be called autotrophs. In summary, fungi are not autotrophs, while protists, mosses, and Chlorophyta all have members that can be considered autotrophs.

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The pair of organisms that is in a mutualistic relationship is the Hermit crab and Sea anemone. In this relationship, the hermit crab provides protection and transportation for the sea anemone, while the sea anemone provides the hermit crab with defense against predators. The sea anemone attaches itself to the shell of the hermit crab and uses its stinging tentacles to deter potential predators. In return, the hermit crab provides the sea anemone with food and a means of transportation to new food sources. Therefore, the hermit crab and sea anemone have a mutualistic relationship because both organisms benefit from the interaction.

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The organism that can carry out both autotrophic and heterotrophic modes of nutrition is Euglena. Euglena is a unicellular organism that belongs to the kingdom Protista. It has a unique feature of having both plant-like and animal-like characteristics. Like plants, Euglena can carry out photosynthesis using chloroplasts to produce their food. In this mode, they are autotrophic. However, Euglena can also feed on organic matter in their environment when sunlight is not available for photosynthesis. In this mode, they are heterotrophic. Euglena can engulf food particles using their flexible pellicle and form a food vacuole for digestion. This ability to switch between autotrophic and heterotrophic modes of nutrition makes Euglena a very adaptable and versatile organism. It allows them to survive in different environments where sunlight and organic matter are not always available.

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Petroleum is a resource that cannot be renewed. Petroleum, also known as crude oil, is a fossil fuel that was formed millions of years ago from the remains of plants and animals. It is a non-renewable resource because it takes millions of years to form and cannot be replenished at the same rate it is being used. Once all the petroleum reserves have been extracted, there will be no more left. This is in contrast to renewable resources such as air, food crops, and soil, which can be replenished naturally over time.

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The function of the teeth labelled X is for tearing and grasping. The teeth labelled X are the canine teeth, which are the sharp, pointed teeth located next to the incisors in both jaws. The canine teeth are adapted for grasping and tearing food, and they play an important role in feeding on prey and in processing tough or fibrous foods. For example, in carnivorous animals, the canines are used for seizing and killing prey, while in omnivorous or herbivorous animals, the canines are used for tearing and shredding tough plant material, such as leaves or stems. The canines are also important in social interactions, such as aggression or threat displays. Therefore, the function of the teeth labelled X is for tearing and grasping, making them an essential part of the dentition of many animals.

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The cell organelle that is the site for the production of ATP is the mitochondrion. ATP stands for Adenosine Triphosphate, which is the energy currency of the cell. Mitochondria are known as the powerhouses of the cell because they are responsible for producing ATP through a process called cellular respiration. During cellular respiration, the mitochondria break down glucose and other molecules to release energy, which is stored in ATP molecules. The energy produced by the mitochondria is used by the cell to carry out various metabolic processes, including growth, repair, and movement. Therefore, the mitochondria play a crucial role in providing energy to the cell and are essential for the survival and functioning of the cell.

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The substance that is greater in concentration in the part labeled IV when compared to that part labeled I is Urea. The urinary tubule is a part of the renal system and is responsible for filtering waste products from the blood and reabsorbing important substances back into the bloodstream. In the diagram, the part labeled I represents the beginning of the urinary tubule, where the blood is filtered to remove waste products. The part labeled IV represents the end of the tubule, where the final concentration of waste products is determined. Urea is a waste product produced by the liver and is present in high concentrations in the blood. As the blood passes through the urinary tubule, some of the urea is reabsorbed back into the bloodstream, but most of it continues to be filtered and concentrated in the part labeled IV. The concentration of urea in the part labeled IV is therefore greater than that in the part labeled I. Lipids, glucose, and uric acid are not primarily waste products of the renal system, but they can be filtered and reabsorbed in small amounts along with urea and other waste products.

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Deforestation is not a practice used in conserving water. The opposite of deforestation is reforestation, which is a practice used in conserving water. Deforestation involves cutting down trees and removing forests, which can negatively impact the water cycle and lead to decreased water availability in the area. Reforestation, on the other hand, involves planting new trees and increasing forest cover, which can help improve water retention in the soil and promote a healthier water cycle. Afforestation and damming are also practices used in conserving water. Afforestation involves planting new trees to increase forest cover, while damming involves building structures such as dams to store water and regulate its flow. Both of these practices can help conserve water and improve water management in an area.

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The organism that cannot exist freely on its own is Plasmodium. Plasmodium is a parasitic protozoan that causes malaria in humans. It cannot survive outside of its host, which is typically a mosquito or a human. Plasmodium has a complex life cycle that involves both sexual and asexual reproduction, and it requires a specific set of environmental conditions to complete its life cycle. Once inside the host, the parasite invades the host's red blood cells and feeds on hemoglobin, which can cause severe anemia and other complications. Therefore, Plasmodium is entirely dependent on its host for survival and cannot exist freely on its own.

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Genotype is involved in mutation. A mutation is a change in the DNA sequence of a gene. The DNA sequence of a gene determines the gene's function, and this function is known as the gene's genotype. So, when a mutation occurs in a gene, it changes the gene's genotype and can result in a different phenotype, which is the observable physical or functional characteristic of an organism that is determined by its genotype. Therefore, it is incorrect to say that the genotype is not involved in mutation.

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The function associated with calcium in plants is the formation of the cell wall. Calcium is an important nutrient that is required for the proper development and strengthening of the cell wall in plant cells. It plays a crucial role in the formation of pectin, a component of the cell wall that helps to hold the cell walls of adjacent cells together. This allows the plant to maintain its structure and also helps to protect it from environmental stresses like wind and water. Additionally, calcium helps to regulate the transport of other nutrients and water into and out of the cell, and it is involved in the activation of enzymes that are important for growth and development.

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The natural dwelling place of an organism is called its habitat. Habitat refers to the specific place or environment where an organism lives and obtains the resources it needs to survive, such as food, water, shelter, and space. It is the natural home or living place of an organism where it carries out its life activities. For example, the habitat of a fish may be a freshwater pond or river, while the habitat of a bird may be a forest or a grassland. The characteristics of the habitat, such as temperature, humidity, soil type, and the presence of other organisms, can affect the survival and reproduction of the organism. Therefore, habitat is an important concept in ecology and biology, as it plays a crucial role in determining the distribution and abundance of species in an ecosystem.

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The gradual cumulative, adaptive and heritable changes in an organism over a long period of time resulting in new species is called organic evolution. Organic evolution is the process by which species of living organisms change over time through a combination of genetic variation and natural selection. Over many generations, small changes in the traits of an organism accumulate, leading to new, distinct species that are better adapted to their environment. This process can take hundreds or thousands of years and is driven by the survival and reproduction of organisms that have traits that give them an advantage in their environment.

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Deamination of amino acids in the liver produces urea. When proteins are broken down in the body, the amino acids are transported to the liver for processing. In the liver, enzymes remove the amino group from the amino acids, a process called deamination. This produces ammonia, which is toxic to the body. To get rid of the ammonia, the liver converts it into a less toxic compound called urea, which can be safely transported to the kidneys for excretion in urine. Therefore, the liver plays a crucial role in removing excess nitrogen from the body, and the production of urea is an important part of this process.

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The complex energy-rich organic matter which living organisms need for life is food. Food provides the energy and nutrients that living organisms need to carry out their metabolic processes, grow, and reproduce. Food contains various molecules such as carbohydrates, proteins, and fats that the body breaks down into simpler forms through digestion and then utilizes to provide energy and building blocks for the body's cells. Without food, organisms would not be able to survive as they would not have the necessary energy and resources to carry out life-sustaining activities.

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The development of the pentadactyl limb is one of the structural adaptations of mammals for movement on land. This means that mammals have five digits (fingers or toes) on each limb, which allows for a wide range of movement and the ability to grasp and manipulate objects. This adaptation helps mammals to move more effectively on land, allowing them to climb, run, jump, and perform other movements necessary for survival.

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The processes associated with photosynthesis are I, III, and IV only. During photosynthesis, energy from sunlight is absorbed by specialized pigment molecules in plant cells called chlorophyll. This energy is then used to convert carbon dioxide from the air and water from the soil into glucose, a simple sugar molecule that is used for energy and as a building block for other organic molecules. Oxygen is also produced as a by-product of this process and is released into the air. Therefore, options I, III, and IV are the correct processes associated with photosynthesis as carbon dioxide is not evolved during this process.

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The establishment of game reserves and parks is a method of conserving natural resources. Game reserves and parks are protected areas where wildlife and their habitats are preserved and protected. These areas are set aside to conserve biodiversity and protect rare and endangered species. By preserving these habitats, game reserves and parks help to conserve the ecosystem and the natural resources within it. The other options listed are not directly related to the establishment of game reserves and parks. Cultivating game involves raising and breeding game animals for hunting or other purposes, while controlling pollution involves reducing and managing environmental pollution. Cultural awareness refers to promoting understanding and appreciation of different cultures and traditions.

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An example of osmosis in plants is the absorption of water from the soil by the root. Osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration through a selectively permeable membrane. In plants, the root hairs, which are thin extensions of the root, have a higher concentration of solutes (dissolved substances) than the surrounding soil. As a result, water moves from the area of high water concentration in the soil to the area of low water concentration in the root hairs via osmosis. This is an essential process for the plant to absorb the water and nutrients it needs for growth and survival.

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The characteristic that is NOT associated with social insects is "All members are identical". In social insects, there is division of labor where each member of the colony has a specific task to perform, such as foraging, building the nest, caring for the young, or defending the colony. The members dwell in the same habitat, which is typically the nest or colony, and some members protect the queen, who is responsible for producing offspring. However, social insects are not identical. They may have different physical characteristics or perform different tasks within the colony. For example, in a bee colony, worker bees are physically different from drones, and they have different roles and responsibilities within the colony. Similarly, in an ant colony, soldiers are larger and have a different body shape than workers. In summary, social insects are not identical, but they do exhibit division of labor, live in the same habitat, and have some members that protect the queen.

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(a) Instruments for collecting organisms

• (i) Soil organisms from a soil sample: a Tullgren funnel (Baermann funnel is used for aquatic/moist soil organisms).
• (ii) Tiny insects from a leaf or stem: a pooter (aspirator).

(b) Diagram of the pooter

A labelled drawing (6 cm to 8 cm long) of a pooter should be made showing: a small glass or plastic collecting jar (bottle) closed with a rubber bung, through which pass two tubes; the inlet tube (mouth of which is placed over the insect), the suction (mouth) tube through which the collector sucks air, and a piece of fine gauze / muslin tied over the inner end of the suction tube to prevent the insect from being sucked into the mouth. When air is sucked, the insect is drawn through the inlet tube into the jar.

(c) Relationship between symbiotic organisms

Symbiosis is a close association between two different organisms living together. Three examples:

• Lichen (alga and fungus): the alga carries out photosynthesis and provides food for both partners, while the fungus absorbs and stores water and mineral salts and provides anchorage and protection for the alga. Both benefit (mutualism).
• Rhizobium bacteria in the root nodules of leguminous plants: the bacteria fix atmospheric nitrogen into nitrates for the plant, and the plant supplies the bacteria with food and shelter. Both benefit.
• Sea anemone and hermit crab: the sea anemone rides on the crab's shell; its stinging tentacles protect the crab from enemies, while the crab carries the anemone to new feeding grounds and shares scraps of food. Both benefit.

(Others: ruminants and cellulose-digesting bacteria in their gut; Paramecium and Zoochlorella.)

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(a)(i) Classification of living things

Classification is the arrangement of living things into groups on the basis of their similarities and differences, so that related organisms are placed together.

(a)(ii) Scientist

Carolus Linnaeus (Carl Linnaeus) developed the binomial system of nomenclature.

(a)(iii) Three reasons why classification is necessary

• It makes the study of the very large number of living things easier and more orderly.
• It shows the relationships and possible evolutionary links between organisms.
• It gives each organism a single, universally accepted scientific name, avoiding the confusion of different common names.

(a)(iv) Seven major groups in order of hierarchy

1. Kingdom
2. Phylum (Division in plants)
3. Class
4. Order
5. Family
6. Genus
7. Species

(b) Features viruses share

(i) With living things:

• They possess genetic material (DNA or RNA / nucleic acid).
• They can reproduce (multiply), but only inside a living host cell.
• They can mutate and show variation.

(ii) With non-living things:

• They can be crystallised and stored like chemicals.
• They do not feed, respire, grow or carry out metabolism on their own (no cellular structure or protoplasm).

(c) Viral diseases

• (i) Plants: tobacco mosaic disease and cassava mosaic disease (leaf curl / maize streak also acceptable).
• (ii) Humans: measles and poliomyelitis (others: HIV/AIDS, smallpox, chicken pox, yellow fever, influenza).

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(a) Four characteristics of enzymes

• They are proteins.
• They act as biological catalysts, speeding up reactions without being used up.
• They are specific, each enzyme acting on only one substrate (or one type of reaction).
• They are affected by temperature and are denatured (destroyed) by high temperature.
• They work best at a particular (optimum) pH and temperature.
• They are required in very small amounts.

(b) Digestive enzymes of the duodenum

(Any two of the above are acceptable.)

(c)(i) Importance of chlorophyll

Chlorophyll traps (absorbs) light energy from the sun and uses it to manufacture food during photosynthesis.

(c)(ii) Two macroelements needed for chlorophyll formation

Magnesium and nitrogen (iron is also required for its synthesis).

(c)(iii) Deficiency symptoms

• Magnesium deficiency: yellowing of leaves (chlorosis), especially between the veins, and stunted growth.
• Nitrogen deficiency: yellowing of older leaves, poor stunted growth and small size.

(d) Testing for starch in a leaf

1. Dip the leaf in boiling water for about a minute to kill the cells and stop chemical activity.
2. Boil the leaf in ethanol (alcohol) in a water bath to remove the chlorophyll (decolourise it). Do not heat alcohol directly over a flame because it is flammable.
3. Dip the softened, brittle leaf in warm water to soften it.
4. Spread the leaf on a white tile and add drops of iodine solution over it.
5. Observation: the leaf turns blue-black where starch is present. A brown/yellow colour shows starch is absent.

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