JAMB UTME - Biology - 2021

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The plants that grow in deserts or very dry areas are referred to as "xerophytes."

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The TRUE statement regarding the process of conjugation in Paramecium is that each micronucleus divides twice. During conjugation in Paramecium, two individuals exchange genetic material through their micronuclei. The micronucleus in each individual undergoes meiosis to produce four haploid nuclei. Three of these nuclei disintegrate, while the remaining haploid nucleus undergoes mitosis twice to form two nuclei. One of these nuclei becomes the new micronucleus, while the other forms the new macronucleus. Therefore, the correct option is: Each micronucleus divides twice.

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In lab, we used Benedict's reagent to test for one particular reducing sugar: glucose. 

Benedict's reagent starts out aqua-blue. As it is heated in the presence of reducing sugars, it turns yellow to orange.

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Vascular tissue is comprised of the xylem and the phloem, the main transport systems of plants.

xylem, plant vascular tissue that conveys water and dissolved minerals from the roots to the rest of the plant and also provides physical support.

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Aged erythrocytes, or red blood cells, are destroyed in the liver and spleen. The liver is primarily responsible for the breakdown of hemoglobin from old red blood cells, while the spleen is responsible for the removal of the remaining cell debris. The pancreas and kidneys are not directly involved in the destruction of red blood cells, and while the lymph nodes play a role in the immune system, they are not a site of red blood cell destruction.

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The complementary strand of a DNA strand with base sequence TCA is AGT. In DNA, each nucleotide base pairs with a specific partner: adenine (A) with thymine (T) and guanine (G) with cytosine (C). The base pairing rules dictate that the complementary strand of a DNA strand with base sequence TCA would have a base sequence of AGT, because adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). Therefore, the correct answer is AGT.

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In mammals(humans), the process of olfaction begins when volatile molecules enter the nasal cavity and activate receptors in the olfactory epithelium (OE). The olfactory receptor (OR) proteins are located in hair-like projections of the olfactory sensory neurons (OSNs).

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When a Spirogyra cell is immersed in a salt solution more concentrated than its cell sap, it loses water and shrivels. This is because of the process of osmosis, where water moves from an area of low solute concentration to an area of high solute concentration. In this case, the salt solution outside the cell has a higher solute concentration than the cell sap inside the Spirogyra cell, so water moves out of the cell, causing it to lose water and shrink.

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The organ that produces both hormones and enzymes is the pancreas.

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The culture bottle must be darkened to prevent photosynthesis in the root. This is because photosynthesis in the root can lead to the production of oxygen, which can cause oxidation and breakdown of the mineral elements. By darkening the culture bottle, the root is deprived of light, which in turn prevents photosynthesis and ensures the mineral elements remain intact. Additionally, preventing algal growth in the culture solution may also be a reason to darken the bottle, but the primary reason is to prevent photosynthesis in the root.

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The measure for the control of bilharzia is the application of molluscicides in water bodies. Molluscicides are chemicals that are used to kill snails, which are intermediate hosts for the parasites that cause bilharzia. Cutting low bushes around homes may reduce the risk of exposure to ticks that transmit other diseases, but it is not an effective measure for the control of bilharzia. Screening windows and doors with mosquito nets is a measure for the prevention of malaria, which is caused by a different parasite that is transmitted by mosquitoes. Application of herbicides in water bodies is not a recommended measure for the control of bilharzia as it can have negative impacts on the aquatic ecosystem.

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The appendicular skeleton includes the bones of the shoulder girdle, the upper limbs, the pelvic girdle, and the lower limbs.

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The movement of part of a plant in response to external stimulus of no particular direction is called nastic movement. Nastic movements are non-directional responses to stimuli such as touch, vibration, or changes in temperature or humidity. These movements are generally not dependent on the direction of the stimulus, and they occur in response to a wide range of stimuli. Examples of nastic movements include the opening and closing of flowers, the folding of leaves in response to touch or changes in temperature, and the movement of tendrils in climbing plants.

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The villus in the small intestine is significant because it increases the surface area for absorption. The villi are finger-like projections that line the inner surface of the small intestine, and they greatly increase the surface area available for the absorption of nutrients from digested food. Each villus contains a network of capillaries and a lacteal, which absorb and transport nutrients into the bloodstream and lymphatic system, respectively. This increased surface area is essential for efficient absorption of nutrients, such as carbohydrates, proteins, and lipids, that are necessary for growth and maintenance of the body.

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The mutation theory of organic evolution was propounded by Hugo de Vries.

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Low mortality rate, high birth rate, high immigration rate and low emigration rate are causes for rapid over-crowding.

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In the mammalian respiratory system, exchange of gases occurs in the alveoli, which are tiny air sacs located at the end of the bronchioles in the lungs. The alveoli are surrounded by capillaries and it is here that oxygen from inhaled air diffuses across the alveolar walls and into the bloodstream, while carbon dioxide from the bloodstream diffuses across the alveolar walls and into the lungs to be exhaled.

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The blood circulation in a mammal is said to be double because it passes twice through the heart in a complete circuit. This means that blood is pumped from the heart to the lungs to pick up oxygen and release carbon dioxide, and then back to the heart before being pumped out to the rest of the body. This is called the pulmonary circulation. The blood then returns to the heart and is pumped out to the body in what is called systemic circulation. This process of double circulation ensures that the oxygenated blood is efficiently distributed to all parts of the body, allowing for proper bodily function.

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he functional group in a food chain include:

Primary producer → Primary consumer → Secondary consumer

Grass, grasshopper, toad, snake, hawk

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Stomata allow a plant to take in carbon dioxide, which is needed for photosynthesis. They also help to reduce water loss.

The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.

The Malpighian tubules are tubular structures that are free floating in the haemolymph and function as excretory and osmoregulatory organs of insects. 

 Contractile vacuoles (in the cells of the lower organisms) protect a cell from absorbing too much water and potentially exploding by excreting excess water.

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Percentage of water content (retained= Waterabsorbed        ∗100

                                                                                  Weightofsoil

→ 50−35∗100    

         50    

= 30%     

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The animal is likely to be a lizard. Lizards have scales, teeth, nares (nostrils), and a backbone. Toads have dry, bumpy skin instead of scales, birds have feathers instead of scales and nares, and rats have fur instead of scales and lack visible nares.

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When the original king and queen of termites die, they are usually replaced by adult reproductives from the same colony. These replacement reproductive termites are commonly referred to as "secondary reproductives." These secondary reproductives are typically young adult termites that have not yet developed the full reproductive capabilities of the primary king and queen. However, under certain circumstances, other options such as adopting a king and queen from another colony or feeding adult workers to breed may also occur, depending on the species of termite and the specific conditions of the colony.

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The two key cations involved in the action potential of nervous transmissions are Na+ (Sodium) and K+ (Potassium).

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Flatworms and roundworms are said to be invertebrates because they have no backbones. Invertebrates are animals that lack a vertebral column or backbone. This distinguishes them from vertebrates, which have a backbone composed of individual vertebrae. Flatworms and roundworms are both examples of invertebrates, as they lack a backbone. Their small size, ability to live inside other organisms, or unicellularity do not determine their classification as invertebrates.

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The correct sequence of the movement of urea during urine formation is: - glomerulus --> Bowman's capsule --> convoluted tubule --> Henle's loop --> collecting tubule. is the correct sequence of events that occur during urine formation in the kidneys. The blood enters the glomerulus where filtration occurs and the filtrate moves into the Bowman's capsule. From there, the filtrate moves into the convoluted tubule, then into the Henle's loop and finally into the collecting tubule. During this process, urea and other waste products are removed from the blood and excreted in the urine.

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A freshwater plant such as water lily can solve the problem of buoyancy by the possession of aerenchyma tissues. These are spongy tissues that contain air spaces, which provide buoyancy to the plant and help it float on the surface of the water. Aerenchyma tissues also facilitate the transport of gases, such as oxygen, from the leaves to the roots of the plant, which is important for respiration. Dissected leaves, thin cell walls of the epidermis, and water-repelling epidermis do not directly contribute to the buoyancy of the plant.

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Evolutionary sequence in vertebrates: Fishes → Amphibians → Reptiles → Birds → Mammals.

IV → III → II → I

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The blood vessel which carries blood from the alimentary canal to the liver is the hepatic portal vein.

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People with type AB+ blood are universal recipients because they have no antibodies to A, B or Rh in their blood and can receive red blood cells from a donor of any blood type.

Donors with blood type AB can donate to recipients with blood type AB only.

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The total number of plant species in the population study is: 15 (Guinea grass) + 5 (Ipomoea spp) + 7 (Sida spp) + 23 (Imperata spp) = 50 The percentage of occurrence of Imperata spp is: (23 / 50) x 100% = 46% Therefore, the correct answer is option (C) 46%.

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People who suck petrol with their mouths run the risk of increasing the concentration of lead in their blood. Lead is a highly toxic substance that can cause serious health problems, including damage to the nervous system, kidneys, and reproductive system. It can also lead to developmental and behavioral problems, especially in children. Therefore, it is important to avoid exposing yourself to lead in any form, including through inhalation or ingestion of gasoline fumes.

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Nitrogen is not typically regarded as a pollutant on land or in the air, as it is a natural component of the atmosphere and essential to plant growth. However, excessive use of nitrogen-containing fertilizers can lead to water pollution. Smoke, noise, and sulfur dioxide are often considered pollutants. Smoke can be harmful to human health and contribute to air pollution. Noise pollution can be harmful to both humans and wildlife, and sulfur dioxide can contribute to acid rain and air pollution.

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The most abundant group of organisms in the animal kingdom is Insecta. Insects are a class of invertebrates within the phylum Arthropoda and they make up approximately 80% of all known animal species.

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The likely reason the marine fish died after being put in a tank of fresh water is that the body cells of the fish swelled and burst as a result of the hypotonic freshwater. Marine fish are adapted to live in saltwater, which is hypertonic compared to their body fluids. As a result, their cells are adapted to pump out excess water and retain salt. When they are placed in freshwater, which is hypotonic compared to their body fluids, water rushes into their cells, causing them to swell and eventually burst. This can lead to a range of problems, including organ failure and death. Therefore, it's important to acclimate fish properly before transferring them to a new tank or environment.

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The correct sequence of the one-way gaseous exchange mechanism in a fish is: - Mouth --> Gills --> Operculum Fish use their mouths to take in oxygen-rich water, which then passes through the gills, where the oxygen is extracted and carbon dioxide is released. The oxygen then diffuses into the bloodstream through the thin walls of the capillaries in the gills, while carbon dioxide diffuses out of the bloodstream and into the water. Finally, the water exits the fish's body through the operculum, which is a bony plate that covers the gills and helps to regulate water flow over them.

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Wind-pollinated flowers:

• No bright colors, special odors, or nectar.
• Small.
• Most have no petals.
• Stamens and stigmas exposed to air currents.
• Large amount of pollen.
• Pollen smooth, light, easily airborne.
• Stigma feathery to catch pollen from wind.

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