JAMB UTME - Biology - 1993

Détails de la réponse

When it is cold, the blood vessels of the skin constrict to reduce the amount of blood flowing to the skin. This is a mechanism to conserve heat and maintain the body's internal temperature. When the blood vessels constrict, less blood flows to the skin and more blood is redirected to internal organs, which helps to keep them warm. This is why people may experience a pale, cool skin when exposed to cold temperatures.

Détails de la réponse

The group of plants that produces naked seeds is conifers. Conifers are a group of plants that includes trees and shrubs with needle-like or scale-like leaves. They produce cones that contain the male and female reproductive structures, and these cones protect the seeds until they are mature. Unlike flowering plants, conifers do not produce fruit to protect their seeds, hence the term "naked seeds".

Détails de la réponse

Carnivorous plants are usually found in areas where insects are abundant. This is because these plants have adapted to grow in nutrient-poor soils by evolving the ability to trap and digest insects in order to obtain the necessary nutrients such as nitrogen and phosphorus. Insects are a rich source of these nutrients, and so the presence of an abundance of insects in an area is beneficial for the survival of carnivorous plants.

Détails de la réponse

The correct order of the vertebrae along the spinal column is "Atlas → axis → cervical → thoracic → lumbar → sacral". The atlas is the first cervical vertebra, followed by the axis which is the second cervical vertebra. After that, there are several cervical vertebrae, followed by thoracic, lumbar, and sacral vertebrae. The sacrum is formed by the fusion of five vertebrae and is followed by the coccyx, which is formed by the fusion of three to five small vertebrae.

Détails de la réponse

The end products of the digestion of fats and oils in mammals are fatty acids and glycerin. During digestion, fats and oils are broken down by enzymes called lipases, which break them down into their constituent parts of fatty acids and glycerin. These end products can then be absorbed into the bloodstream and transported to cells throughout the body to be used for energy or stored as fat.

Détails de la réponse

The option that is common to both sporophytes and gametophytes of a fern is chloroplasts. Chloroplasts are organelles found in plant cells and some algae that are responsible for photosynthesis. Both sporophytes and gametophytes in ferns have chloroplasts which enable them to produce food (carbohydrates) through photosynthesis. Rhizoids are root-like structures that are found in gametophytes of ferns, while roots are only found in sporophytes. Leaves are also only found in sporophytes of ferns. Therefore, chloroplast is the correct answer.

Détails de la réponse

Détails de la réponse

The butterfly is of great economic importance because it plays a vital role in the pollination of flowers of crops and other plants. Butterflies have long, slender tongues that can reach deep into flowers to suck nectar. In the process of collecting nectar, the butterfly transfers pollen from the male flower part (stamen) to the female flower part (pistil) of the same or different flowers, resulting in fertilization and fruit or seed production. This makes butterflies important pollinators that contribute to the growth and productivity of many plant species, including those that are economically important to humans.

Détails de la réponse

The main function of the petal of a flower is to attract pollination agents. Petals are often brightly colored and have distinctive shapes to attract pollinators such as insects, birds, and bats. The scent of the petals also helps in attracting these pollinators. When the pollinator lands on the petals, it picks up or deposits pollen, which helps in the reproduction of the plant. Therefore, petals play a crucial role in the process of pollination and the reproductive success of the plant.

Détails de la réponse

The highest accumulation of a non-biodegradable substance would occur in the trophic level of tertiary consumers. This is because non-biodegradable substances, such as heavy metals or persistent organic pollutants, tend to accumulate in the bodies of organisms over time, and as we move up the food chain, the concentration of these substances becomes increasingly magnified. Tertiary consumers are at the top of the food chain, and thus, they accumulate the highest concentrations of non-biodegradable substances.

Détails de la réponse

Manufactured food in the plant is transported through the phloem. Phloem is a specialized tissue in plants responsible for the transportation of nutrients, including the carbohydrates produced by photosynthesis, from the leaves to other parts of the plant where they are needed for growth and energy. This process is called translocation and is powered by the pressure flow mechanism, which involves the active transport of sugars from source to sink tissues. In contrast, the xylem is responsible for transporting water and minerals from the roots to the rest of the plant. The cambium is a tissue responsible for secondary growth, while the cortex is a tissue located in the outermost layer of the stem or root.

Détails de la réponse

Détails de la réponse

Détails de la réponse

Détails de la réponse

Plants adapted for life in salty marshes are called halophytes. Halophytes are plants that are adapted to grow in soils that have high salt concentrations, such as those found in salt marshes, mangrove swamps, and other coastal areas. They have unique adaptations that allow them to take up and tolerate salt, such as specialized salt glands and the ability to store excess salt in their tissues. These adaptations enable halophytes to survive and thrive in environments where other plants would perish due to the high salt concentrations.

Détails de la réponse

The diastema is labelled as part 3. A diastema is a gap or space between two teeth, often seen in mammals with elongated canines such as dogs or in some primates. In the case of the labelled image, the diastema is the gap between the canine tooth (part 2) and the first premolar tooth (part 4). This gap in the teeth allows for a larger range of motion of the jaw and can help in grasping and tearing food.

Détails de la réponse

The instrument that is NOT used in measuring abiotic factors in any habitat is "Microscope". A microscope is an instrument used to observe and magnify small objects that are not visible to the naked eye, but it is not used for measuring abiotic factors such as temperature, humidity, and wind direction, which are physical and chemical factors in the environment. The instruments used for measuring abiotic factors are a thermometer for temperature, a hygrometer for humidity, and a wind vane for wind direction.

Détails de la réponse

Détails de la réponse

Détails de la réponse

Flame cells are the excretory system of flatworms. Flatworms do not have a true circulatory or respiratory system, and so they rely on a network of flame cells to filter out waste products and excess water from their bodies. These specialized cells are located on the sides of the flatworms' bodies and contain tiny hair-like structures called cilia. The cilia beat in a coordinated manner to create a current of fluid that draws waste products and excess water into the flame cells. The waste products are then eliminated from the body through tiny openings called nephridiopores.

Détails de la réponse

Détails de la réponse

The autonomic nervous system in mammals is responsible for controlling involuntary functions such as heart rate, digestion, and breathing. It consists of two main components: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system prepares the body for "fight or flight" responses in times of stress, while the parasympathetic nervous system helps to regulate the body's "rest and digest" responses. Together, these systems work to maintain homeostasis in the body.

Détails de la réponse

During conjugation in Paramecium, the micronuclei of two individuals undergo meiosis to produce haploid micronuclei, which then undergo mitosis to form four haploid micronuclei in each cell. One of the haploid micronuclei in each cell is exchanged between the two conjugating individuals, and the exchanged micronuclei fuse with the micronuclei of the recipient individual, resulting in the formation of a diploid micronucleus. This process results in genetic recombination. Therefore, the statement that is true of the process of conjugation in Paramecium is that each micronucleus divides twice.

Détails de la réponse

The most important physical factor which affects an organism living in the intertidal zone of the seashore is wave action. The intertidal zone is the area between the highest tide and the lowest tide. Organisms that live in this zone must be able to withstand exposure to air and water, as well as the constant pounding of waves. The strength of the waves and the frequency with which they occur can affect an organism's ability to feed, reproduce, and maintain its position on the shore. Therefore, wave action is the most important physical factor that influences the distribution and abundance of intertidal organisms.

Détails de la réponse

Détails de la réponse

Détails de la réponse

The response shown by the tips of the root and shoot of a plant to the stimulus of gravity is called geotropism. Geotropism is the growth of a plant in response to gravity. The roots of the plant show positive geotropism and grow towards the direction of gravity, i.e., downwards, while the shoot of the plant shows negative geotropism and grows against the direction of gravity, i.e., upwards. This response helps the plant to anchor itself in the soil and grow towards the source of light for photosynthesis.

Détails de la réponse

Members of the phylum Protozoa use the contractile vacuole to remove excess water. Protozoa are unicellular organisms that are found in various habitats such as freshwater, marine water, and soil. They need to maintain a balance of water and solutes in their cytoplasm to carry out various cellular functions. The contractile vacuole is a specialized organelle that helps in regulating this balance by collecting excess water and expelling it out of the cell through a pore. This helps in preventing the cell from bursting due to excess water intake, which is important for the survival of the organism.

Détails de la réponse

The path that sound entering the human ear follows is: ear drum → ossicles → oval window. When sound waves enter the ear, they travel down the ear canal and strike the eardrum, causing it to vibrate. These vibrations are then transmitted through three tiny bones in the middle ear, known as the ossicles, which amplify and transmit the sound to the oval window. The oval window, a membrane-covered opening in the cochlea, then vibrates, which stimulates the fluid inside the cochlea, producing nerve impulses that the brain interprets as sound.

Détails de la réponse

The presence of a black precipitate after boiling a solution of a food substance with osmic acid indicates the presence of fats and oils. Osmic acid is a chemical reagent that is used to detect the presence of unsaturated lipids, such as fats and oils, which react with osmic acid to form a black precipitate. This reaction is a specific test for the presence of fats and oils and is commonly used in food analysis.

Détails de la réponse

The term used to describe the sum total of biotic and abiotic factors in the environment of the organism is "ecosystem". An ecosystem consists of all the living organisms in a particular area, along with their physical environment, including water, air, soil, and other non-living factors. The ecosystem is a dynamic system in which living organisms interact with each other and their environment. It involves the flow of energy and matter, and the cycling of nutrients among the living and non-living components of the ecosystem.

Détails de la réponse

Glycogen is a type of carbohydrate that is used as an energy source and stored in the liver and muscles of animals. Therefore, the organism that would store glycogen is the Rattus, which is a type of rodent commonly known as a rat. The other options, Spirogyra and Chlamydomonas, are both types of algae and do not have the ability to store glycogen. Magnifera, on the other hand, is the scientific name for mango, which is a fruit and not an organism that would store glycogen.

Détails de la réponse

The units of inheritance, which are genes, are situated on chromosomes. Chromosomes are long, coiled-up strands of DNA (deoxyribonucleic acid) molecules that carry an organism's genetic information. Genes are specific sections of DNA that encode for particular traits or characteristics of an organism, such as eye color or height. When cells divide, the chromosomes replicate and the copies are distributed to the daughter cells, ensuring that each new cell receives a complete set of genetic information.

Détails de la réponse

Abiotic factors are non-living components of an ecosystem that affect living organisms. Temperature and rainfall are two important abiotic factors that affect all plants and animals in a habitat. Temperature affects the rate of metabolic processes in plants and animals, while rainfall affects the availability of water, which is essential for survival. Therefore, fluctuations in temperature and rainfall can have significant impacts on the distribution and abundance of species in a given ecosystem. Other abiotic factors such as salinity and wind direction may also be important depending on the specific habitat.

Détails de la réponse

Détails de la réponse

Détails de la réponse

Interveinal chlorosis is a condition in plants where the leaf tissue between the veins turns yellow while the veins remain green. This condition is usually associated with the deficiency of magnesium. Magnesium is an important element for plant growth and is necessary for chlorophyll production, which gives plants their green color. When magnesium is deficient, the plant cannot produce enough chlorophyll, leading to the yellowing of the leaves.

Détails de la réponse

Détails de la réponse

Soil fertility can be conserved and renewed by crop rotation and cover crops. Crop rotation involves changing the crop planted in a particular field each growing season, which helps to prevent depletion of soil nutrients and build up of soil-borne pests and diseases. Cover crops are crops that are grown specifically to protect and enrich the soil rather than for harvest. They help to reduce soil erosion, add organic matter to the soil, and fix nitrogen from the atmosphere, which can improve soil fertility. Together, these practices help to maintain and improve soil fertility over time, which is important for sustainable agriculture.

Détails de la réponse

The spores of mucor are dispersed by the wind. Mucor is a type of fungi that reproduces asexually by producing large numbers of spores. These spores are light and small, and they can be easily carried away by the wind to new locations. This is known as wind dispersal, and it is a common way that many types of fungi and plants spread their spores or seeds to new areas. Therefore, is the correct answer.

Détails de la réponse

Carbon monoxide poisons tissue by combining with haemoglobin. Carbon monoxide has a greater affinity for haemoglobin than oxygen does, meaning it can bind with haemoglobin molecules in the blood more easily. This reduces the amount of haemoglobin available to carry oxygen to the body's tissues. As a result, the body's tissues are deprived of oxygen, which can lead to tissue damage or death. This is why carbon monoxide is sometimes referred to as the "silent killer" – it is odorless, colorless, and tasteless, making it difficult to detect without special equipment.

Détails de la réponse

Cold-blooded animals are referred to as poikilothermic. This means that their body temperature is not internally regulated and varies with the temperature of their environment. In other words, their body temperature is not constant, and they are unable to maintain a steady internal temperature like warm-blooded animals. Examples of cold-blooded animals include reptiles, amphibians, and fish.

Détails de la réponse

The bright colours of the comb and feathers in the peacock are for courtship purposes. Peacock feathers are a classic example of sexual selection, where males develop traits that are attractive to females for the purposes of mating. The bright colors of the feathers and the elaborate courtship displays performed by male peacocks are intended to attract the attention of females and increase the likelihood of successful mating. The colors and displays are not for defense or camouflage, but rather to increase reproductive success.

Détails de la réponse

The cotyledons in H are carried above the soil because the hypocotyl grows faster than the epicotyl. The hypocotyl is the embryonic stem of the plant and is responsible for pushing the cotyledons out of the soil. As it grows, it elongates and lifts the cotyledons, exposing them to light for photosynthesis. This process is known as hypocotyl elongation, and it allows the plant to establish itself and start growing towards maturity.

Détails de la réponse

The pancreas is an important organ in the human body that produces insulin, a hormone that regulates the level of sugar in the blood. When the pancreas is surgically removed, the body loses its ability to produce insulin, and as a result, the level of sugar in the blood increases. This condition is called diabetes, which can lead to various complications if not managed properly. Therefore, option A is the correct answer. The other options are not related to the function of the pancreas, and thus, they are incorrect.

Détails de la réponse

Tongue rolling is an example of discontinuous variation observed in man. Discontinuous variation refers to distinct categories or traits that are either present or absent in a population. In the case of tongue rolling, some individuals can roll their tongues while others cannot, making it a clear example of a trait that is either present or absent without any intermediate variations. This is different from continuous variation, which refers to traits that vary along a continuum, such as height or body weight.

Détails de la réponse

The most successful group of animals in terms of diversity of species is Arthropoda. Arthropods include insects, spiders, crustaceans, and other groups, and they have been able to colonize virtually every habitat on Earth, from deep ocean trenches to mountaintops, and from rainforests to deserts. Arthropods make up more than 80% of all known living animal species, which is an impressive feat and the reason why they are considered the most successful group of animals.

Détails de la réponse

Bryophytes differ from pteridophytes in their dependency on water for reproduction. Bryophytes, which include mosses and liverworts, are small, non-vascular plants that require water for the sperm to swim to the egg. Pteridophytes, which include ferns and horsetails, have a vascular system that allows them to transport water and nutrients and do not require water for the sperm to swim to the egg. Other options are not the distinguishing features between bryophytes and pteridophytes.

Détails de la réponse

Lichens would be the first colonizers in an ecological succession changing rocks to soil. Lichens are symbiotic organisms that consist of a fungus and an alga or cyanobacterium. They are able to grow on bare rocks and start breaking them down into soil by secreting acids that dissolve the rock surface. The breakdown of rocks and the accumulation of organic matter in the lichen thalli contribute to the formation of soil. This process is the first step in ecological succession, where plants and other organisms gradually colonize a barren area and change its ecological community over time.

Détails de la réponse