Biology 2021 Jamb Examination
Biology 2021 Jamb Examination
Question 21
The correct sequence for the perception of smell in mammals is?
In mammals, smell perception begins when dissolved chemicals interact with sensory cells in the nasal cavity. The sensory cells transmit impulses via the olfactory nerve to the brain, where odors are interpreted.
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Question 22
The number of plant species obtained from a population study of a garden is as follows:
Guinea grass (15), Ipomoea spp (5), Sida spp (7) and Imperata spp (23)
What is the percentage of occurrence of Imperata spp?
Guinea grass (15), Ipomoea spp (5), Sida spp (7) and Imperata spp (23)
What is the percentage of occurrence of Imperata spp?
The total number of plants = 15 + 5 + 7 + 23 = 50.
Percentage occurrence of Imperata spp = (23/50)*100 = 46%, indicating it is the dominant species in this study.
Percentage occurrence of Imperata spp = (23/50)*100 = 46%, indicating it is the dominant species in this study.
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Question 23
I. High birth rate and high immigration rate
II. Low birth rate and high immigration rate
III. Low mortality rate and low emigration rate
IV. High mortality rate and high emigration rate
Which combination of the above can cause rapid over-crowding in climax biotic communities and human settlements?
II. Low birth rate and high immigration rate
III. Low mortality rate and low emigration rate
IV. High mortality rate and high emigration rate
Which combination of the above can cause rapid over-crowding in climax biotic communities and human settlements?
Rapid over-crowding occurs when populations experience high birth rates and low mortality rates, as well as high immigration and low emigration.
Hence, combinations I and III promote population expansion.
Hence, combinations I and III promote population expansion.
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Question 24
When a marine fish was taken from the ocean and put in a tank of fresh water, it died after a short period because?
Marine fish cells are adapted to saltwater; placing them in hypotonic freshwater causes water to enter cells by osmosis, leading to swelling and bursting (lysis), which results in death.
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Question 25
If a DNA strand has a base sequence TCA, its complementary strand must be?
DNA complementary base pairing rules: Adenine (A) pairs with Thymine (T) and Cytosine (C) pairs with Guanine (G).
For TCA, the complementary sequence is AGT.
For TCA, the complementary sequence is AGT.
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Question 26
The two key cations involved in the action potential of nervous transmissions are?
Action potentials depend on the movement of $\text{Na}^+$ ions into the neuron and $\text{K}^+$ ions out.
These ion exchanges create the depolarization and repolarization necessary for nerve impulse propagation.
These ion exchanges create the depolarization and repolarization necessary for nerve impulse propagation.
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Question 27
I. Rattus rattus
II. Agama agama
III. Bufo regularis
IV. Tilapia zillii
The order of evolutionary advancement of the above vertebrates is?
II. Agama agama
III. Bufo regularis
IV. Tilapia zillii
The order of evolutionary advancement of the above vertebrates is?
Tilapia (IV) is the least advanced fish, Bufo (III) amphibian, Agama (II) reptile, and Rattus (I) mammal, showing progressive evolutionary complexity from aquatic to more advanced terrestrial vertebrates.
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Question 28
Which of the following produces both hormones and enzymes?
The pancreas has dual functions: endocrine (produces hormones like insulin and glucagon) and exocrine (produces digestive enzymes such as amylase and lipase) aiding both metabolism and digestion.
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Question 29
The correct sequence of the movement of urea during urine formation is?
Urea is filtered from blood at the glomerulus, collected in Bowman's capsule, passes through the proximal convoluted tubule, descends Henle's loop, and finally enters the collecting tubule for excretion.
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Question 30
The order of passage of food in the digestive system is
Food moves from the ileum into the caecum, then to the large intestine where water is absorbed, and finally passes to the rectum for excretion.
This sequence ensures efficient digestion and absorption.
This sequence ensures efficient digestion and absorption.
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