29 reviewed questions with answers and explanations.
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The association between a leguminous plant and Rhizobium bacteria in its root nodules is known as
D: symbiosis
Rhizobium bacteria in legume root nodules obtain carbon compounds and a suitable habitat from the plant. In return, nitrogen fixation supplies nitrogen compounds useful to the plant. This is a mutualistic symbiosis.
AI-reviewed · source checkedWhich option combines the usual aquatic and terrestrial habitats of amphibians?
B: in water and on moist land
Amphibians are commonly associated with aquatic habitats and moist land. Their skin and, in many species, reproduction depend on moisture, making dry terrestrial conditions less suitable for typical amphibian activity.
AI-reviewed · source checkedViviparity occurs mainly in the
A: mammals
Live birth is characteristic of most mammals, including marsupials and placental mammals. Egg-laying monotremes are exceptions. Some reptiles and amphibians also bear live young, so the feature is not exclusive to mammals.
AI-reviewed · source checkedThe jointed structure in insects that bears organs which are sensitive to touch, smell and vibration is the
C: antenna
An insect antenna bears sensory receptors that can detect chemicals, touch and movement or vibration. The paired antennae are jointed appendages on the head.
AI-reviewed · source checkedWater fleas, wood lice and barnacles belong to the group
B: crustacea
Water fleas, woodlice and barnacles are crustaceans despite their very different appearances and habitats. Woodlice are terrestrial members of the group, while barnacles are highly modified attached forms.
AI-reviewed · source checkedThe mode of feeding in Amoeba and Hydra is
A: heterotrophic
Amoeba and Hydra obtain organic food from other organisms. This makes their feeding heterotrophic, rather than producing organic food from inorganic carbon by photosynthesis.
AI-reviewed · source checkedWhich of the following organisms does not exist as a single free living cell?
B: Volvox
Volvox normally forms a coordinated spherical group of many cells. The other listed organisms are commonly represented by single free-living cells, making Volvox the exception.
AI-reviewed · source checkedIn the fern structure shown, II and III respectively are
Which major brain division contains networks central to conscious learning and memory?
C: cerebrum
The cerebrum contains networks central to learning and memory, including cortical and associated structures. Different kinds of memory involve several interconnected regions rather than one isolated point.
AI-reviewed · source checkedUrea formation occurs in the
B: liver
The liver converts nitrogen from amino-acid breakdown into urea through the urea cycle. The kidneys then remove much of that urea from the blood in urine.
AI-reviewed · source checkedIn the egg section, the structure that helps hold the yolk in position is labelled
The carbon dioxide produced during aerobic tissue respiration can be identified by its visible reaction with a solution of
A: calcium hydroxide
Carbon dioxide reacts with calcium hydroxide solution, or limewater, to form a cloudy calcium carbonate precipitate. This visible change can identify the carbon dioxide released during aerobic respiration.
AI-reviewed · source checkedThe enzyme invertase will hydrolyze sucrose to give
C: glucose and fructose
Sucrose contains glucose and fructose joined by a glycosidic bond. Invertase catalyses hydrolysis of that bond, releasing one glucose molecule and one fructose molecule.
AI-reviewed · source checkedWhen yeast respires anaerobically, it converts simple sugar to carbon (IV) oxide and
C: alcohol
During alcoholic fermentation, yeast converts sugars into ethanol and carbon dioxide while regenerating NAD+ so glycolysis can continue. Ethanol is the alcohol referred to in the options.
AI-reviewed · source checkedWhich listed blood cells play the main cellular role in transporting oxygen and carbon dioxide in mammals?
D: erythrocytes
Erythrocytes contain haemoglobin, which transports most blood oxygen and part of the carbon dioxide. They also help convert carbon dioxide into bicarbonate, much of which is carried in plasma.
AI-reviewed · source checkedThe veins of the leaf are formed by the
A: vascular bundles
Leaf veins contain vascular bundles with xylem and phloem. These tissues carry water, minerals and organic solutes and also contribute support to the leaf.
AI-reviewed · source checkedA specimen turns blue-black when iodine solution is added. This indicates the presence of
B: Starch
Iodine forms a blue-black complex with starch, particularly the helical amylose component. The other listed sugars do not give this characteristic starch-test colour.
AI-reviewed · source checkedThe vertebra shown belongs to which region?
Blood vessels pass through the small opening labelled
A garden sample contains 15 guinea-grass plants, 5 Ipomoea, 7 Sida and 23 Imperata plants. What percentage of the counted plants are Imperata?
C: 46%
The total count is 15 + 5 + 7 + 23 = 50 plants. Imperata accounts for 23 of them, so its percentage of the total is 23 ÷ 50 × 100 = 46%.
AI-reviewed · calculation checkedThe habitat of an epiphyte growing on a tree is best described as
A: arboreal
A plant growing on a tree as an epiphyte occupies an arboreal habitat. The tree provides support; an epiphyte does not necessarily draw its food from the host.
AI-reviewed · source checkedIn a grazing food chain, the greatest amount of energy available for transfer occurs at the level of the
C: producers
Producers introduce energy into a grazing food chain by fixing it into organic matter. Only a fraction passes to each higher trophic level, so the energy available is greatest at the producer level.
AI-reviewed · source checkedThe hygrometer is used for measuring
A: relative humidity
A hygrometer measures humidity. Relative humidity expresses the water-vapour condition as a percentage relative to saturation at the same temperature.
AI-reviewed · source checkedWhich option most precisely describes the positions of a dominant allele and its recessive alternative in a heterozygous diploid cell?
B: at corresponding loci on a homologous chromosome pair
Alternative alleles of the same gene occupy corresponding loci on a homologous chromosome pair. In a heterozygote, one copy may be dominant and the other recessive.
AI-reviewed · source checkedIn the usual human XX–XY chromosome model, whether fertilization produces XX or XY depends on the X or Y chromosome carried by the
A: father’s sex cell
In the usual XX–XY inheritance pattern, the egg contributes an X chromosome. The fertilising sperm contributes either X or Y, producing an XX or XY chromosome complement respectively.
AI-reviewed · source checkedConsidering ABO compatibility alone for red-cell transfusion, which statement is correct?
C: Group AB is the universal recipient
In the ABO model for red cells, group AB lacks anti-A and anti-B antibodies and can receive cells from any ABO group. Rh type, other antibodies and compatibility testing also matter in real transfusions.
AI-reviewed · source checkedDarwin used natural selection to explain
D: organic evolution
Darwin explained organic evolution through natural selection acting on inherited variation. Alfred Russel Wallace independently developed natural selection, so this historical contribution was not Darwin’s alone.
AI-reviewed · source checkedThe role of the male adult honey bee is to
C: mate with the queen
The male honey bee, or drone, has a reproductive role: mating with a queen. Workers perform most hive maintenance, ventilation and brood care.
AI-reviewed · source checkedAn inherited feature that helps an organism survive and reproduce in its environment is called an
D: adaptation
An adaptation is a feature or inherited characteristic that improves an organism’s fit to its environment. Such traits can increase survival or reproductive success under particular conditions.
AI-reviewed · source checked