All 20 questions from the Post-UTME Screening (Post-UTME) Biology 2015 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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Severe deficiency of thyroxine in man causes
In adults, severe long-term thyroxine deficiency causes myxedema (cretinism is the equivalent condition when deficiency occurs in infancy/childhood).
The closing up of the lid of a pitcher plant on the entry of an insect is referred to as
This rapid, non-directional response to a stimulus (touch) is a nastic movement, not oriented relative to the direction of the stimulus.
Dormancy in seeds may be caused by
Seed dormancy can result from the embryo being immature/underdeveloped at the time of seed dispersal, delaying germination until development is complete.
Which of the following is found in the retina?
The retina contains photoreceptor cells - rods and cone-shaped cells - which detect light and colour respectively.
Insulin and glucagon are hormones produced by the
Both insulin and glucagon are produced by the islets of Langerhans in the pancreas.
The correct order of the ecological sequence in nature is
The natural hierarchy builds from species, to a population of that species, to a community of populations, up to the ecosystem level.
An ecological factor which applies to all types of habitat is
Temperature is a universal abiotic factor affecting all habitats, whereas turbidity and salinity mainly apply to aquatic habitats and pH varies more specifically.
When two or more species in a community feed on the same kind of food, they belong to the same
Organisms that feed on the same type of food occupy the same trophic (feeding) level in a food chain/web, regardless of species.
The fixation of free nitrogen in the soil is carried out by
Azotobacter is a free-living, nitrogen-fixing bacterium in the soil that converts atmospheric nitrogen into usable forms.
The major outcome of competition among organisms is
Competition drives natural selection, as better-adapted individuals are more likely to survive and reproduce.
Production of the viviparous seedling is an adaptive feature of
Mangrove plants (like Rhizophora) produce viviparous seedlings that germinate while still attached to the parent plant, an adaptation to their unstable, saline, waterlogged habitat.
In which of the following zones of the marine habitat is the intensity of light at its minimum?
The benthic zone, at the sea floor, receives the least light of the listed zones, as it is furthest from the surface.
An ample of aquatic plants which live completely submerged in water is the
Ceratophyllum (hornwort) is a fully submerged aquatic plant, unlike Pistia and Salvinia (floating) or Typha (emergent).
Which of the following plants is most adapted to the grassland ecosystem?
The baobab tree is characteristically adapted to savanna/grassland ecosystems, with features suited to seasonal drought.
In a normal succession, species diversity
As ecological succession proceeds towards a climax community, species diversity generally increases.
In an experiment, the following results were obtained: I. Original weight of soil = x g, II. Weight of oven dried soil = y g, III. Weight of humus in soil = z g. The percentage of water in the soil is therefore given by the expression
The water lost on oven-drying is (x-y). Expressed as a percentage of the original soil weight (x), the percentage of water = (x-y)/x x 100.
The best method of preventing leaching is
Planting cover crops helps bind the soil and reduce the movement of water through it, minimising the leaching of nutrients.
In Nigeria, the organization responsible for the control of all aspects of population is the
Population-related health matters in Nigeria fall under the purview of the Federal Ministry of Health.
In the human body, blood fluke inhabits the
Schistosoma haematobium, the urinary blood fluke, inhabits the veins around the bladder, causing urinary schistosomiasis.
The clearing away of plants from water banks and draining off water collections are control measures targeted towards the eradication of
Clearing vegetation from water banks and draining stagnant water removes the habitat of the snail intermediate host of Schistosoma, helping control schistosomiasis.
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