10 questions from the JAMB 2021 Biology paper, with answers and explanations. Tap "Show answer" under each one when you are ready.
JAMB 2021Question 1 · Animal Biology and Comparative Physiology
When a marine fish was taken from the ocean and put in a tank of fresh water, it died after a short period because?
A.the tank was too small compared to the large-ocean
B.the body cells of the fish swelled and burst as a result of the hypotonic fresh water
C.the body cells of the fish shrank as their sap was hypertonic to the freshwater
D.there was no food in the tank, so the fish starved
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Answer: B. the body cells of the fish swelled and burst as a result of the hypotonic fresh water
A marine fish's body cells are hypertonic relative to freshwater; when placed in freshwater, water rushes into the cells by osmosis causing them to swell and burst.
JAMB 2021Question 2 · Cell Biology and Biochemistry
When a Spirogyra cell is immersed in a salt solution more concentrated than its cell sap, it?
A.remains unchanged
B.takes tip water and burst
C.absorbs a little water
D.loses water and shrivels
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Answer: D. loses water and shrivels
In a salt solution more concentrated than its cell sap (hypertonic), the Spirogyra cell loses water by osmosis and shrivels (plasmolysis).
JAMB 2021Question 3 · Classification
The most abundant group of organisms in the animal kingdom?
A.Mammalia
B.Aves
C.Insecta
D.Annelida
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Answer: C. Insecta
Insecta (insects) is the most abundant and diverse group of organisms in the animal kingdom.
JAMB 2021Question 4 · Ecology and Environment
When the original king and queen of termites die, they are replaced by
A.the king and queen of another colony
B.some adult reproductives from the same colony
C.some adult workers which are specially fed to breed
D.developing nymphs nurtured as secondary reproductives
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Answer: D. developing nymphs nurtured as secondary reproductives
When the original king and queen die, developing nymphs are nurtured and become secondary (replacement) reproductives in the termite colony.
JAMB 2021Question 5 · Genetics and Evolution
If a DNA strand has a base sequence TCA, its complementary strand must be?
A.ATG
B.TAG
C.GAT
D.AGT
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Answer: D. AGT
Base pairing rules (A-T, G-C) applied to TCA give a complementary sequence of AGT.
JAMB 2021Question 6 · Mammalian Physiology and Anatomy
In the mammalian respiratory system. exchange of gases occurs in the?
A.lungs
B.bronchi
C.bronchioles
D.alveoli
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Answer: D. alveoli
Gaseous exchange in the mammalian respiratory system occurs in the alveoli.
JAMB 2021Question 7 · Mammalian Physiology and Anatomy
The appendicular skeleton is composed of the pectoral girdle?
A.pelvic girdle, fore and hind limbs
B.pelvic girdle and fore limbs
C.lumbar vertebrae and pelvic girdle
D.lumbar vertebrae, fore and hind limbs
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Answer: A. pelvic girdle, fore and hind limbs
The appendicular skeleton is composed of the pectoral girdle, pelvic girdle, and the fore and hind limbs.
JAMB 2021Question 8 · Mammalian Physiology and Anatomy
The correct sequence of the movement of urea during urine formation is?