WAEC SSCE - Biology - 2016

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A noticeable physical appearance of individuals of the same species is called morphological variation. It refers to the observable differences in the physical features or characteristics of individuals within a species. Morphological variation can include differences in size, shape, color, texture, or other physical traits that can be visually distinguished. For example, some animals may have different patterns of stripes or spots, or different shapes of their horns or antlers. Plants may have different leaf shapes or flower colors. Morphological variation can be influenced by genetic factors, environmental conditions, or a combination of both. It is important in helping scientists classify and identify species and subspecies, as well as in understanding evolutionary relationships between different groups of organisms.

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Flaccidity in plants refers to a state in which the plant cells lose their water content and become soft and limp. This happens when there is a loss of water in the plant, either due to a lack of water supply or excessive water loss through transpiration. This loss of water causes the cell to shrink and lose its turgidity, resulting in the plant becoming wilted. As a result of the loss of turgor pressure, the plant may not be able to carry out important functions such as photosynthesis and nutrient uptake. Therefore, the correct answer to the question is wilting.

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A blend of inherited and acquired characteristics shows variation. Inherited characteristics are passed down from parents to offspring through genetic material, while acquired characteristics are developed through an individual's life experiences and interactions with the environment. Variation refers to differences that exist among individuals of the same species, and this variation can be due to both genetic and environmental factors. Therefore, a blend of inherited and acquired characteristics contributes to the observed variation among individuals of a species.

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Guard cells are located in the epidermis of the leaves. The epidermis is the outermost layer of cells that covers the entire surface of the leaf, and the guard cells are specialized cells that are located in the stomata, which are tiny openings on the underside of the leaf that allow for gas exchange. The guard cells can change shape to open or close the stomata, which helps to regulate the amount of water and gases that enter and exit the leaf.

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Sneezing is NOT a voluntary action. Sneezing is a reflex action, which means it happens automatically in response to an irritation or stimulation of the nasal passages. When the nasal lining detects irritants like dust, pollen, or bacteria, it sends a signal to the brainstem, which triggers a series of involuntary muscle contractions that force air out of the nose and mouth. Sneezing is a natural defense mechanism of the body that helps to remove irritants and protect the respiratory system. Unlike stealing, fighting, and cheating, which are deliberate and intentional actions that require a decision and choice, sneezing is not under conscious control and cannot be stopped voluntarily. Therefore, sneezing is NOT a voluntary action.

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A pandemic is an outbreak of disease that is widespread, affecting a large region or even multiple continents. It is characterized by the spread of the disease across a large population, with high rates of infection and transmission from person to person. Unlike an epidemic, which is typically limited to a specific region or community, a pandemic has the potential to affect millions of people around the world. Pandemics are often caused by the emergence of new strains of infectious diseases or the spread of existing diseases to new populations.

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The term used to describe the maintenance of a constant internal environment in an organism is "homeostasis". Homeostasis is the process by which an organism maintains stable internal conditions necessary for survival, despite changes in the external environment. It involves the regulation of various physiological variables such as body temperature, pH, blood glucose levels, and water balance. Homeostasis is essential for the proper functioning of cells, tissues, and organs in the body, and it is maintained through various feedback mechanisms that operate within the body.

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The blood group of the parents can be determined using the principle of codominance and the possible genotypes of the parents. Each parent contributes one allele to their offspring, and the offspring's blood group is determined by the combination of the two alleles received from their parents. Since the offspring have blood groups AB, BB, BO and AO, we can deduce that one of the parents must have contributed an A allele and the other parent contributed a B allele. This is because the blood groups AB, BB and AO all have either an A or B allele, while the blood group BO has an O allele from each parent. Therefore, the possible genotypes of the parents are IAIA and IBIO, IAIB and IBIB, or IAIB and IBIO, where IA and IB represent the A and B alleles respectively, and IO represents the O allele. The only genotype combination that can produce offspring with blood groups AB, BB, BO and AO is IAIB and IBIO. Therefore, the blood group of the parents is AB and BO.

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The function of the villi in the alimentary canal is to increase the surface area for absorption. Villi are small, finger-like projections that protrude from the lining of the small intestine. They increase the surface area of the small intestine, allowing for greater absorption of nutrients from digested food. The increased surface area of the villi provides a larger area for the absorption of nutrients such as carbohydrates, proteins, and lipids. The nutrients are then transported to the bloodstream to be used by the body for energy and other functions.

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Special modification which enable an organism to survive in its habitat is known as adaptation. Adaptation is a biological process in which an organism undergoes certain physical or behavioral changes that make it better suited to survive and reproduce in its environment. These modifications can be structural, physiological or behavioral and may occur over long periods of time through natural selection or quickly through genetic mutations. Adaptation helps organisms to cope with changes in their environment, increases their chances of survival, and enables them to exploit available resources for their own benefit.

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Cockroaches are the insects in which group instinct is not displayed. Cockroaches are not social insects, they do not live in large organized groups like the other options. Cockroaches are mainly solitary insects and they do not work together as a group to build nests or collect food.

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Scientists who study genetics are known as geneticists. Genetics is the branch of biology that deals with the study of genes, heredity, and genetic variation in living organisms. Geneticists use various techniques and tools to study DNA, mutations, gene expression, and genetic disorders. They also work on developing new methods to understand genetic mechanisms and how they can be used in fields such as medicine, agriculture, and biotechnology.

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The rational and prudent use of natural resources is known as conservation. It involves the sustainable use and management of natural resources to ensure their availability for future generations. Conservation involves the protection, preservation, and management of natural resources, including water, air, land, and wildlife, to ensure their long-term viability. It aims to maintain the balance between human needs and the protection of the environment. Conservation practices can include measures such as reducing waste, recycling, using renewable resources, and protecting natural habitats. By conserving natural resources, we can ensure that they are available for future generations to use and enjoy, while also minimizing the negative impact of human activities on the environment.

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The phenomenon in the diagram is eutrophication. Eutrophication is a process that occurs when excessive nutrients, such as nitrates, are added to a water body. These nutrients promote the growth of algae and other aquatic plants, which can lead to an increase in organic matter in the water. As the organic matter decomposes, it consumes oxygen, which can lead to hypoxia (low oxygen levels) in the water. This can be harmful to fish and other aquatic life, and can even lead to the death of these organisms. Therefore, eutrophication can have negative impacts on aquatic ecosystems and water quality.

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The function of the villi in the alimentary canal is to increase the surface area for absorption of nutrients. Villi are tiny, finger-like projections that line the small intestine. They are covered in microvilli, which are even smaller projections. Together, villi and microvilli create a large surface area in the small intestine, which helps to maximize the absorption of nutrients from food. As food passes through the small intestine, the villi and microvilli trap and absorb nutrients such as sugars, amino acids, and fatty acids, which are then transported into the bloodstream and carried to the rest of the body. Without the villi, the surface area for absorption would be greatly reduced, and the body would not be able to extract as many nutrients from the food that is eaten. Therefore, the function of the villi in the alimentary canal is to increase the surface area for absorption.

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All of the natural resources listed can be conserved through various methods and practices. However, if we had to choose one resource that cannot be fully conserved, it would be air. While efforts can be made to reduce air pollution, it is not possible to completely eliminate all sources of air pollution. Additionally, air is a constantly moving and changing resource, making it difficult to control and manage in the same way as other resources. Therefore, while efforts can be made to minimize negative impacts on air quality, it cannot be fully conserved in the same way as other natural resources.

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The correct order for testing a leaf for starch is: III, I, II, and IV. First, the leaf is placed in boiling water to kill the cells and denature the enzymes that could break down starch. Next, the decolorizing step removes chlorophyll from the leaf, making it easier to observe the presence of starch. Then, the leaf is rinsed with warm water to soften it and make it easier to spread. Finally, iodine solution is added to the leaf, and if starch is present, the iodine will react with the starch, turning it blue-black.

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The association between two organisms in which one of the organisms gains while the other loses is referred to as parasitism. In parasitism, the organism that benefits is called the parasite, while the other organism, which is harmed, is called the host. The parasite gains some form of benefit from the host, such as food, shelter, or nutrients, while the host is often weakened or damaged by the relationship. This can lead to negative effects on the host's health, survival, or reproductive success. Parasitism is different from other types of symbiotic relationships like mutualism, commensalism, and saprophytism because in those relationships, both organisms benefit or at least one organism is not harmed. In parasitism, however, one organism benefits at the expense of the other.

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Glucose is not usually present in the urine of a healthy person. Glucose is a type of sugar that is normally present in the blood, but it is typically filtered out by the kidneys and reabsorbed back into the bloodstream. If there is too much glucose in the blood, such as in the case of diabetes, the kidneys may not be able to reabsorb all of it and some may end up in the urine. This is why glucose is sometimes present in the urine of people with diabetes, but it is not typically present in the urine of healthy individuals. On the other hand, urea, mineral salts, and water are all normally present in the urine of healthy people. Urea is a waste product that is produced when the body breaks down protein, and it is filtered out of the blood by the kidneys and excreted in the urine. Mineral salts such as sodium, potassium, and calcium are also filtered out of the blood by the kidneys and excreted in the urine, along with excess water.

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The source of the nitrates in the diagram is fertilizers. Fertilizers contain nitrogen, which is an essential nutrient for plant growth. When fertilizers are applied in excess, the nitrogen can leach into the surrounding soil and eventually into nearby water bodies, leading to an increase in nitrate levels in the water. This excess nitrogen can cause an overgrowth of algae and other aquatic plants, leading to a decrease in oxygen levels in the water, which can harm fish and other aquatic life. Therefore, it is important to use fertilizers judiciously and avoid over-application to prevent nitrate pollution in water bodies.

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Overcrowding in a population does not result in commensalism. Commensalism is a type of symbiotic relationship between two species where one species benefits while the other is neither harmed nor benefited. Overcrowding, on the other hand, can lead to competition for resources, such as food, water, and shelter, among individuals of the same species. It can also increase the transmission of diseases and parasites, resulting in death or migration of some individuals from the population. Therefore, overcrowding can have significant impacts on population dynamics, but it does not lead to commensalism.

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The direction of wind is determined by a wind vane. A wind vane is a weather instrument that shows the direction of the wind. It consists of a pointer that freely rotates on a vertical axis and always points into the wind. The wind direction is indicated by the end of the pointer that is opposite the arrow.

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Genotypes 1 and 11 are carriers of color blindness. This is because color blindness is a recessive trait that is carried on the X chromosome. In this cross, the male is color blind because he only has one X chromosome, and it carries the recessive gene for color blindness. The female is not color blind because she has two X chromosomes, and she would need to have two copies of the recessive gene to be color blind. Genotype 1 represents the X chromosome that the color blind male passes on to his daughters, and genotype 11 represents the X chromosome that the normal female passes on to her sons. Since both of these genotypes carry one copy of the recessive gene for color blindness, they are carriers of the trait. Genotype 111 represents the X chromosome that the normal female passes on to her daughters. Since this X chromosome does not carry the recessive gene for color blindness, genotype 111 is not a carrier of the trait. Therefore, the correct answer is 1 and 11 only.

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The kidney is not an organ of the digestive system. While all the other options listed (oesophagus, pancreas, and stomach) are part of the digestive system, the kidney is not involved in the digestion or absorption of nutrients from food. The kidney is part of the excretory system and is responsible for filtering waste products from the blood and producing urine.

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The phenomenon in the diagram shows an increase in the growth of algae and other aquatic plants due to an increase in nitrates in the water. One cause that could lead to this phenomenon is the dumping of sewage into the water bodies. Sewage contains high levels of nutrients, including nitrates, which when discharged into water bodies can cause an increase in the growth of algae and other aquatic plants. This increase in growth can lead to eutrophication, a process where the excessive growth of algae and other aquatic plants reduces oxygen levels in the water, leading to the death of aquatic organisms. Therefore, the dumping of sewage into water bodies can have serious negative impacts on the health of the ecosystem and human activities that depend on it.

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The lateral meristem in flowering plants is found in the cambium. The cambium is a thin layer of tissue that is responsible for secondary growth in plants, allowing them to increase in diameter. The lateral meristem is the region of the cambium that actively produces new cells, causing the stem or root to grow wider. The cambium is located between the xylem and phloem tissues, and it is responsible for the formation of the secondary xylem and phloem. This process is called secondary growth and it helps to thicken the stem and roots, providing additional support and allowing for the transport of more water and nutrients.

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The function of the villi in the alimentary canal is to increase the surface area for absorption. The villi are tiny finger-like projections that line the small intestine. They increase the surface area available for absorption of nutrients, such as carbohydrates, proteins, and fats, by up to 600 times. The villi are covered with microvilli, which further increase the surface area. This allows for more efficient absorption of nutrients into the bloodstream, which is then transported to the rest of the body for energy and growth.

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Saprophitism is the relationship that does not involve two organisms. Saprophitism is a type of relationship between an organism and dead or decaying organic matter. The organism involved in saprophitism is known as a saprophyte or saprobe, and it feeds on dead or decaying organic matter. This type of relationship is important in the ecosystem because it helps to break down dead organic matter and recycle nutrients back into the environment. In contrast, the other relationships listed - commensalism, symbiosis, and parasitism - all involve two organisms. Commensalism is a relationship in which one organism benefits and the other is neither helped nor harmed. Symbiosis is a relationship in which two organisms live in close association with each other and both benefit. Parasitism is a relationship in which one organism benefits at the expense of the other. In summary, saprophitism is a relationship between an organism and dead or decaying organic matter, and is the only relationship listed that does not involve two organisms.

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In ecology, a community refers to groups of different organisms living in a habitat. A community is a set of populations of different species living and interacting in a particular place at the same time. These populations interact with each other in different ways such as competition, predation, and mutualism, and their interactions can have significant effects on the entire ecosystem. Therefore, the community is an important level of organization in ecology, which helps us understand the complex relationships among different species and their impact on the environment.

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Capillarity of soil refers to how well water rises up in the soil due to the attraction between the soil particles and water molecules. It is the ability of the soil to hold water against the force of gravity. When the soil is dry, it creates a suction force that pulls water from wetter areas towards it, which is known as capillary action. This process helps to provide water to plants and other organisms living in the soil.

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The diagram is depicting a feedback loop for the regulation of blood glucose levels. The number 11 represents insulin, a hormone that signals the body's cells to take up glucose from the blood. Therefore, a decrease in the number of insulin (11) would lead to a decrease in the uptake of glucose by cells and an increase in the concentration of glucose in the blood, a condition known as hyperglycemia. This would not result in an increase in urine production, energy production, or a decreased population, but could lead to decreased immunity over time if left uncontrolled. Therefore, the correct answer is "decreased immunity".

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The organ responsible for the production of insulin is the pancreas. Insulin is a hormone that regulates the amount of glucose in the blood. When glucose levels rise in the blood after eating, the pancreas produces and releases insulin to help cells in the body absorb and use the glucose for energy or store it for later use. Therefore, Pancreas is the correct answer.

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Conservation is the practice of protecting and preserving natural resources, including habitats and wildlife, for the benefit of both present and future generations. Out of the options listed, protecting endangered species is the action that supports conservation. This is because it involves taking measures to prevent the extinction of species that are at risk, thereby preserving the biodiversity of the ecosystem. By protecting endangered species, we are helping to maintain a healthy balance in the ecosystem and ensuring the survival of the natural resources that we rely on.

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The inability of an organism to adapt to its habitat can lead to extinction. Adaptation is the process by which an organism becomes better suited to its environment, through changes in its physical or behavioral traits. Adaptation enables organisms to survive and reproduce in their habitat, and is a key driver of evolution. However, if an organism is unable to adapt to changes in its habitat, it may become less well-suited to its environment, and may not be able to survive or reproduce. This can eventually lead to the extinction of the species. Extinction refers to the complete disappearance of a species from the earth, either through natural causes or as a result of human activities such as habitat destruction, pollution, and climate change. Extinction can have significant ecological and economic impacts, as it can disrupt food webs, reduce biodiversity, and affect ecosystem services.

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The term associated with natural selection is "survival of the fittest." Natural selection is the process by which certain traits that are advantageous for survival become more common in a population over time. This occurs through the differential survival and reproduction of individuals with those traits. The concept of "fitness" refers to an organism's ability to survive and reproduce in its environment, based on its inherited traits. Those with higher fitness are more likely to survive and pass on their advantageous traits to their offspring, while those with lower fitness are less likely to survive and reproduce. Therefore, "survival of the fittest" refers to the idea that the most well-adapted individuals are the ones most likely to survive and pass on their genes to the next generation, leading to evolution over time.

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The function of the villi in the alimentary canal is to increase the surface area for absorption. Villi are finger-like projections found on the inner lining of the small intestine. They increase the surface area of the small intestine, which allows for more efficient absorption of nutrients from food. The villi are covered in microvilli, which are even smaller projections that further increase the surface area for absorption. The increased surface area provided by the villi and microvilli allows for a greater amount of nutrients to be absorbed into the bloodstream.

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The cells and tissues of the nose, throat, chest, diaphragm, and lungs form the respiratory system. The respiratory system is responsible for taking in oxygen from the air and eliminating carbon dioxide from the body. The process of respiration occurs through the exchange of gases in the lungs, which is facilitated by the respiratory system. Therefore, the correct option is respiratory.

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(a)(i) Agglutination

Agglutination is the clumping together of red blood cells that occurs when incompatible bloods are mixed during transfusion. It is caused by a reaction between the antigens on the donor's red cells and the corresponding antibodies in the recipient's plasma.

(a)(ii) Blood transfusion compatibility

A tick means the transfusion is safe (no agglutination); a cross means agglutination occurs.

Group O is the universal donor (can give blood to all groups) and group AB is the universal recipient (can receive from all groups).

(b) Adaptations for obtaining food

(i) Mosquito larva: it has a breathing siphon so it can hang at the water surface, and tufts of mouth brushes that beat to create currents which sweep tiny food particles and micro-organisms in the water into its mouth (filter feeding).

(ii) Dodder plant: it is a parasite with no chlorophyll; it twines around a host plant and develops haustoria (suckers) that penetrate the host's tissues to absorb ready-made food and water.

(iii) Grasshopper: it has strong biting and chewing mouthparts (hard mandibles and maxillae) that cut and grind plant material, suiting its herbivorous diet.

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(a) Two differences between tactic and nastic movements

(b) Two examples each

• (i) Tactic movement: Euglena and Chlamydomonas (also Amoeba, Paramecium).
• (ii) Nastic movement: Mimosa pudica (sensitive plant) and the flower of Portulaca (also the Venus fly-trap).

(c)(i) Three ways of caring for the mammalian skin

1. Bathe (wash) the skin regularly with soap and clean water.
2. Wear clean, well-aired clothing.
3. Eat a balanced diet rich in vitamins and treat cuts or skin infections promptly.

(c)(ii) Three stimuli to which the mammalian skin is sensitive: touch (pressure), temperature (heat and cold) and pain.

(d) Five effects of high temperature on a terrestrial habitat

1. It increases the rate of evaporation and transpiration, drying out the soil and plants.
2. It lowers the humidity of the air.
3. It causes wilting and can kill plants and seedlings.
4. It forces some animals to burrow, become nocturnal or migrate (aestivate) to avoid the heat.
5. It speeds up decay of organic matter and reduces the water available to organisms.

(e)(i) What is courtship behaviour?

Courtship behaviour is the special pattern of actions carried out by animals (usually the male) to attract a mate of the opposite sex and prepare for mating.

(e)(ii) Three courtship behaviours: display of bright colours or plumage (as in the peacock); special calls, songs or sounds; special dances or movements (and the offering of food or nest material).

(f) Three organisms that carry out holozoic nutrition: human being, dog and Amoeba.

(g) How fingerprinting is used to detect crime

Every person has a unique pattern of ridges on the fingertips that never changes through life. At a crime scene the finger marks (prints) left on surfaces are dusted, lifted and compared with the fingerprints of suspects. If a suspect's fingerprint pattern matches the print found at the scene, it is strong evidence that the person was present, so the criminal can be identified.

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(a) Organs of the alimentary canal of humans, in sequence

1. Mouth (buccal cavity)
2. Pharynx
3. Oesophagus (gullet)
4. Stomach
5. Small intestine (duodenum, then ileum)
6. Large intestine (colon)
7. Rectum
8. Anus

(b) Bird versus human alimentary canal

(i) Three structural differences

(ii) Three structural similarities

1. Both have a mouth for taking in food.
2. Both have an oesophagus leading to the stomach.
3. Both have a small and large intestine for digestion and absorption.

(c) How the dentition of herbivores is adapted for feeding

Herbivores have wide, chisel-like incisors that bite and crop grass and leaves. The canines are reduced or absent, leaving a gap (diastema) in which the tongue turns and rolls food. The premolars and molars are broad with ridged (interlocking) grinding surfaces and grow continuously to replace the wear caused by chewing tough, fibrous plant material. The lower jaw also moves sideways so the ridged cheek teeth grind the food thoroughly.

(d) Two roles of the pancreas in digestion

• It secretes pancreatic juice containing digestive enzymes (amylase, trypsin and lipase) that act on carbohydrates, proteins and fats.
• It secretes sodium hydrogen carbonate (an alkali) that neutralises the acidic food arriving from the stomach, giving the enzymes the right pH.

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(a)(i) Three forms in which living cells exist

1. As single, free-living (unicellular) organisms.
2. As a colony of cells.
3. As part of a many-celled (multicellular) organism (in tissues).

(a)(ii) One example each

• Unicellular (single cell): Amoeba (or Euglena, Paramecium).
• Colony: Volvox (or Spirogyra as a filament).
• Multicellular: a human being (or a maize plant).

(b) A diagram 6 to 10 cm long of a typical plant cell is required, labelling: cell wall, cell membrane, cytoplasm, nucleus, large central vacuole, chloroplast and (if shown) mitochondria.

(c)(i) Three differences between a plant cell and an animal cell

(c)(ii) Three similarities between a plant cell and an animal cell

1. Both have a cell membrane.
2. Both have cytoplasm.
3. Both have a nucleus (and mitochondria).

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(a)(i) What is a habitat?

A habitat is the natural place or environment where an organism (plant or animal) lives, feeds and reproduces, for example a pond, a forest or the soil.

(a)(ii) Three roles of a decomposer in an ecosystem

• It breaks down dead plants and animals and other organic waste, so it clears the environment of dead matter.
• It releases (recycles) mineral nutrients such as nitrogen and carbon back into the soil, water and air for reuse by plants.
• It keeps the nutrient cycles going, so producers can continue to obtain the raw materials they need.

(b) Energy flow in a freshwater habitat

Energy from the Sun is trapped by producers (green water plants and algae/phytoplankton) during photosynthesis and stored as chemical energy in their food. This energy passes to primary consumers (herbivores such as water fleas and small fish) when they eat the plants, and then to secondary and tertiary consumers (larger fish and birds) along the food chain. At each transfer (trophic level) much of the energy is lost as heat during respiration and in undigested waste, so less energy is available at each higher level. Decomposers finally break down all dead organisms and release the remaining energy as heat. Energy therefore flows in one direction only, from the Sun through the organisms and out as heat, and is not recycled.

(c)(i) Three harmful effects of microorganisms to plants

1. They cause plant diseases such as leaf spot, blight and wilt.
2. They cause rotting and spoilage of fruits, tubers and stored produce.
3. They cause galls or decay that reduce crop yield.

(c)(ii) Six beneficial effects of microorganisms to humans

1. They decay dead matter and recycle nutrients, keeping the environment clean.
2. They fix atmospheric nitrogen, enriching the soil for crops.
3. They are used in making foods such as bread, yoghurt, cheese and local drinks (fermentation).
4. They are used to produce antibiotics such as penicillin.
5. Bacteria in the gut help in digestion and make some vitamins.
6. They are used in sewage treatment and in producing alcohol and other industrial products.