JAMB UTME - Biology - 2008

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The transmission of impulses along a nerve fibre is characterized by electrical and ionic changes. When a nerve impulse is generated, there is a temporary reversal in the electrical charge across the cell membrane, causing a wave of electrical current to travel along the nerve fibre. This electrical signal opens up voltage-gated ion channels in the membrane, allowing ions to flow in and out of the cell, which creates a flow of electrical current. This ionic exchange produces a new electrical signal in the next section of the membrane, allowing the impulse to travel down the nerve fibre. Therefore, electrical and ionic changes are the main characteristics of the transmission of impulses along a nerve fibre.

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The graph represents two lines, one for body temperature in "l" and another for body temperature in "ll" over a period of time. The lines fluctuate up and down in response to changes in external temperature. Therefore, it can be appropriately deduced that external temperatures affect the body temperature of l and ll.

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Bacteria are unicellular microorganisms that exist in different shapes and arrangements. Streptococci are a type of bacteria that are arranged in chains, as the name suggests. These bacteria are spherical or oval-shaped and occur in chains due to their mode of cell division. Streptococci are known to cause a variety of infections in humans, including strep throat, pneumonia, and meningitis.

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The zone between the epidermis and the pericycle in a dicotyledonous stem is known as the cortex. The cortex is composed of several layers of parenchyma cells, which store food and provide mechanical support to the stem. It also contains collenchyma cells, which provide additional support to the stem. The cortex is important for the exchange of gases and water between the stem and the environment.

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The easiest way to establish the level of pollution in a local stream is to measure the level of oxygen. Oxygen is essential for the survival of aquatic life, and the presence of pollutants in the water can decrease the amount of dissolved oxygen. By measuring the oxygen level, we can determine if the water is polluted or not. If the oxygen level is low, it indicates that there is pollution in the water, and the quality of the water is poor. Carbon (IV) oxide, ammonia, and alkalinity are also important parameters to measure, but they may not provide a clear indication of pollution as their levels can fluctuate due to natural processes.

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The population size of species II on the 20th day is 200. This is because the line representing species II intersects the y-axis at 200, indicating the initial population size, and then crosses the x-axis at the 20th day, showing that the population size has reached zero. Therefore, the population size of species II on the 20th day is 200.

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The ability of a chameleon to change its color is an adaptive feature for defense. Chameleons can change their color to blend in with their surroundings, making it harder for predators to spot them. Additionally, they can change their color to reflect their mood or to communicate with other chameleons, but defense is the primary reason for their color-changing ability. By blending in with their environment, chameleons can avoid being seen and increase their chances of survival.

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The vessel that carries blood from l to ll is the pulmonary artery. This is because the pulmonary artery is the vessel that carries deoxygenated blood from the heart to the lungs, where it gets oxygenated. The oxygenated blood is then carried back to the heart by the pulmonary vein. The carotid artery and jugular vein are not involved in this specific circulation pathway.

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Bush burning has major consequences on an ecosystem, one of which is the loss of biological diversity. This is because bush burning destroys habitats and food sources for organisms, resulting in a decline in their population. Additionally, bush burning can also lead to the loss of soil fertility as it destroys the organic matter that supports plant growth. The burning of plants can also release carbon dioxide into the atmosphere, contributing to climate change. Therefore, bush burning can have significant negative impacts on the environment and should be avoided where possible.

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The most advanced evolutionary development in plants is the development of flowers. Flowers are the reproductive structures of angiosperms (flowering plants), which are the most diverse and advanced group of plants. Flowers have evolved to attract pollinators, which aid in fertilization and increase genetic diversity. Therefore, the development of flowers is considered an advanced evolutionary adaptation in plants.

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The type of reproduction illustrated in IV is budding. Budding is a form of asexual reproduction in which a new individual develops from an outgrowth or bud from the parent organism. In the diagram, a small outgrowth or bud is developing from the parent organism, which will eventually detach and become a new individual. This process is characteristic of organisms like hydra, yeast, and some sponges.

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The association that is an example of mutualism is hydra viridis and zoochlorellae. In mutualism, both organisms benefit from the relationship. Hydra viridis, a freshwater invertebrate, harbors zoochlorellae, which are single-celled green algae that live inside its cells. The algae produce food through photosynthesis, which benefits both the algae and the hydra. The hydra, in turn, provides a protected environment and nutrients to the algae. Therefore, both organisms benefit from the association, making it an example of mutualism. The other options are not examples of mutualism; they are parasitic or commensal relationships.

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Insectivorous plants, as the name suggests, feed on insects. These plants trap and kill insects using different mechanisms, such as sticky surfaces or snap traps. Once the prey is captured, the plant releases enzymes that digest the insect's body and extract nutrients, including nitrogen. Therefore, the correct answer is nitrogen.

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Exhaled air differs from inhaled air in that it usually has more carbon dioxide and more water vapor. When we breathe in, we inhale oxygen and exhale carbon dioxide. The exhaled air also contains moisture from the lungs, which can make it slightly warmer and more humid than the inhaled air. Therefore, the correct option is "usually has more water vapor" and "less amount of oxygen".

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The fin that is mainly used for balancing in fish is the dorsal fin. The dorsal fin is located on the top of the fish's body and helps to keep the fish stable while swimming. It also helps to prevent the fish from rolling over in the water. While the other fins, such as the pectoral, caudal, and anal fins, also assist in swimming and maneuvering, the dorsal fin specifically plays a role in balancing the fish.

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The part labelled I in the diagram refers to the "lag phase". The lag phase is the first phase of bacterial growth where the bacteria are adjusting to their new environment, synthesizing new components and increasing in size, but not yet dividing. During this phase, there is little to no increase in the number of bacteria. Once the bacteria have adapted and are ready to divide, they enter the log phase, which is the phase of rapid exponential growth.

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When a plant parenchyma cell becomes turgid, it also acts as a supporting tissue. Turgidity refers to the state of the cell when it is fully hydrated and swollen, which causes it to be rigid and provide structural support to the plant. When a plant cell loses water and becomes flaccid, it cannot provide support to the plant. The presence of crystals or pigmentation in the cell does not necessarily affect its ability to act as a supporting tissue.

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Among the given options, "class" is the most inclusive taxon in terms of the number of individuals it includes. Taxonomy is the science of naming and classifying living organisms. Organisms are classified into different groups based on their characteristics, and each of these groups is called a taxon. The taxonomic hierarchy consists of several levels or ranks, with each level representing a different degree of similarity and relatedness among the organisms. Starting from the most inclusive to the least inclusive, the taxonomic hierarchy goes like this: kingdom, phylum, class, order, family, genus, and species. The "class" is a higher taxonomic rank or category than "order," "family," or "species." It is a group of related orders, and each class is made up of one or more orders. Thus, a class includes many orders, families, and species. For instance, the class "Mammalia" includes many orders such as primates, carnivores, rodents, and whales, among others. Each of these orders, in turn, includes several families, and each family includes several species. Therefore, "class" is the most inclusive of the given options.

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The possession of amniotic eggs is the most important characteristic that makes reptiles conquer terrestrial habitats. The amniotic egg is an egg with a protective membrane that allows the embryo to develop in a self-contained aquatic environment, without the need for the egg to be laid in water. This adaptation allows reptiles to lay their eggs on land, which increases their chances of survival since the eggs are protected from water-borne predators. The amniotic egg also allows reptiles to live in areas that are far away from water bodies. This adaptation, therefore, allows reptiles to occupy terrestrial habitats where they can move around freely, hunt, and reproduce.

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The edge of a freshwater habitat, such as a stream or pond, is called the "littoral zone." This is the shallow area where light penetrates all the way to the bottom, allowing aquatic plants to grow and providing habitat for a variety of animals, such as insects, fish, and amphibians. The littoral zone is an important part of the freshwater ecosystem, and plays a crucial role in nutrient cycling and maintaining water quality.

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The major adaptive feature of endoparasites is the presence of piercing mouthparts. Endoparasites are parasites that live inside the body of their host, and to survive, they need to feed on the host's tissues or blood. The piercing mouthparts allow them to attach themselves to the host's tissues and feed on their fluids. This feature is an adaptation that helps endoparasites to obtain their necessary nutrients from their host while avoiding detection and expulsion by the host's immune system.

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The part labelled IV in the diagram indicates that the yeast population has reached its maximum size. This is because the growth curve of the yeast population reaches a plateau at this point, which suggests that the population has reached its carrying capacity and can no longer sustain further growth.

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Water reabsorption takes place in regions lll and lV of the nephron. The loop of Henle, located in regions l and ll, is responsible for the concentration of the urine by establishing an osmotic gradient in the medulla of the kidney. The collecting duct, located in regions lll and lV, is where the final adjustment of urine concentration occurs, and this is where water is reabsorbed back into the bloodstream. Therefore, the correct answer is lll and lV.

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volume of air in the soil = (350 + 500) - 800
= 850 - 800 = 50 cm3
% of air in the soil = (volume of air)/total volume x (100)/1 = (50)/800 x 100 = 6.25%

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Radial symmetry is a feature common to coelenterates. Coelenterates are a group of aquatic animals that include jellyfish, coral, and sea anemones. They exhibit radial symmetry, which means their body parts are arranged around a central axis like spokes on a wheel. This allows them to move in any direction and efficiently capture prey from any angle.

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The Rhesus factor of blood was first identified in a category of monkeys.

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Natural selection is the natural process that produces adaptive evolutionary changes. It is the process where organisms that are better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring. Over time, this can lead to changes in the frequency of traits within a population, which can result in the development of new species. Therefore, natural selection is a fundamental mechanism of evolution.

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