Year : 
2021
Title : 
Biology
Exam : 
JAMB Exam

Paper 1 | Objectives

21 - 30 of 40 Questions

# Question Ans
21.

The correct sequence for the perception of smell in mammals is?

A. chemicals --> olfactory nerve endings --> brain

B. dissolved chemicals --> nasal sensory cells --> brain

C. chemicals --> mucus membrane sensory cells --> brain

D. dissolved chemicals --> sensory cells --> olfactory nerve --> brain

Detailed Solution

In mammals(humans), the process of olfaction begins when volatile molecules enter the nasal cavity and activate receptors in the olfactory epithelium (OE). The olfactory receptor (OR) proteins are located in hair-like projections of the olfactory sensory neurons (OSNs).
There is an explanation video available below.
22.

I. High birth rate and high immigration rateII. Low birth rate and high immigration rateIII. Low mortality rate and low emigration rateIV. High mortality rate and high emigration rate.Which combination of the above can cause rapid over-crowding in climax biotic communities and human settlements?

A. II and III

B. I and III

C. I and IV

D. I and II

Detailed Solution

Low mortality rate, high birth rate, high immigration rate and low emigration rate are causes for rapid over-crowding.
There is an explanation video available below.
23.

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?

A. 35%

B. 16%

C. 46%

D. 23%

Detailed Solution

No of Imperata spp = 23
Total plant species = 50

Percentage of imperata spp = \(\frac{23}{50} * 100℅\)
= 46℅
There is an explanation video available below.
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?

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

Detailed Solution

Saltwater fish can't survive in freshwater because their bodies are highly concentrated of salt solution (too much for freshwater). The water would flow into their body until all their cells accumulate so much water that they bloat and die eventually.
There is an explanation video available below.
25.

If a DNA strand has a base sequence TCA, its complementary strand must be?

A. ATG

B. TAG

C. GAT

D. AGT

Detailed Solution

The complementary strand for TCA is AGT

There is an explanation video available below.
26.

The two key cations involved in the action potential of nervous transmissions are?

A. Na+ and Fe2+

B. Mg2+ and K+

C. Na+ and K+

D. Fe2+ and Mg2+

Detailed Solution

The Na⁺ / K⁺ - helps maintain resting potential, affects transport, and regulates cellular volume.
There is an explanation video available below.
27.

I. Rattus rattus. Il. Agama agama III. Bufo regularis IV. Tilapia zillii
The order of evolutionary advancement of the above vertebrates is?

A. I, II, III, IV

B. I, IV, III, II

C. II, III, IV, I

D. IV, III, II, I

Detailed Solution

Evolutionary sequence in vertebrates: Fishes → Amphibians → Reptiles → Birds → Mammals.
IV → III → II → I
There is an explanation video available below.
28.

Which of the following produces both hormones and enzymes?

A. Ileum

B. Pancreas

C. Gall bladder

D. Kidney

Detailed Solution

The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar.
There is an explanation video available below.
29.

The correct sequence of the movement of urea during urine formation is?

A. glomerulus ---> Bowman's capsule -> convoluted tubule ---> Henle's loop -> collecting- tubule

B. glomerulus -> Bowman's capsule -> convoluted tubule -> Henle's loop -> convoluted tubule -> collecting tubule

C. convoluted tubule -> glomerulus --> Nettle's loop -> Bowman's capsule->collecting tubule

D. convoluted tubule -> Bowman's capsule -> Henle's loop -7> glomerulus -> collecting tubule

Detailed Solution

The kidneys filter unwanted substances from the blood and produce urine to excrete them.
There are three main steps of urine formation: glomerular filtration, reabsorption, and tubular secretion.
These processes ensure that only waste and excess water are removed from the body.
There is an explanation video available below.
30.

The order of passage of food in the digestive system is

A. ileum --> caecum ->large intestine -> rectum

B. ileum --> colon --> caecum -> rectum

C. large intestine --> ileum -> caecum -> rectum

D. colon -> caecum -> ileum -> rectum

Detailed Solution

There is an explanation video available below.
21.

The correct sequence for the perception of smell in mammals is?

A. chemicals --> olfactory nerve endings --> brain

B. dissolved chemicals --> nasal sensory cells --> brain

C. chemicals --> mucus membrane sensory cells --> brain

D. dissolved chemicals --> sensory cells --> olfactory nerve --> brain

Detailed Solution

In mammals(humans), the process of olfaction begins when volatile molecules enter the nasal cavity and activate receptors in the olfactory epithelium (OE). The olfactory receptor (OR) proteins are located in hair-like projections of the olfactory sensory neurons (OSNs).
There is an explanation video available below.
22.

I. High birth rate and high immigration rateII. Low birth rate and high immigration rateIII. Low mortality rate and low emigration rateIV. High mortality rate and high emigration rate.Which combination of the above can cause rapid over-crowding in climax biotic communities and human settlements?

A. II and III

B. I and III

C. I and IV

D. I and II

Detailed Solution

Low mortality rate, high birth rate, high immigration rate and low emigration rate are causes for rapid over-crowding.
There is an explanation video available below.
23.

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?

A. 35%

B. 16%

C. 46%

D. 23%

Detailed Solution

No of Imperata spp = 23
Total plant species = 50

Percentage of imperata spp = \(\frac{23}{50} * 100℅\)
= 46℅
There is an explanation video available below.
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?

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

Detailed Solution

Saltwater fish can't survive in freshwater because their bodies are highly concentrated of salt solution (too much for freshwater). The water would flow into their body until all their cells accumulate so much water that they bloat and die eventually.
There is an explanation video available below.
25.

If a DNA strand has a base sequence TCA, its complementary strand must be?

A. ATG

B. TAG

C. GAT

D. AGT

Detailed Solution

The complementary strand for TCA is AGT

There is an explanation video available below.
26.

The two key cations involved in the action potential of nervous transmissions are?

A. Na+ and Fe2+

B. Mg2+ and K+

C. Na+ and K+

D. Fe2+ and Mg2+

Detailed Solution

The Na⁺ / K⁺ - helps maintain resting potential, affects transport, and regulates cellular volume.
There is an explanation video available below.
27.

I. Rattus rattus. Il. Agama agama III. Bufo regularis IV. Tilapia zillii
The order of evolutionary advancement of the above vertebrates is?

A. I, II, III, IV

B. I, IV, III, II

C. II, III, IV, I

D. IV, III, II, I

Detailed Solution

Evolutionary sequence in vertebrates: Fishes → Amphibians → Reptiles → Birds → Mammals.
IV → III → II → I
There is an explanation video available below.
28.

Which of the following produces both hormones and enzymes?

A. Ileum

B. Pancreas

C. Gall bladder

D. Kidney

Detailed Solution

The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar.
There is an explanation video available below.
29.

The correct sequence of the movement of urea during urine formation is?

A. glomerulus ---> Bowman's capsule -> convoluted tubule ---> Henle's loop -> collecting- tubule

B. glomerulus -> Bowman's capsule -> convoluted tubule -> Henle's loop -> convoluted tubule -> collecting tubule

C. convoluted tubule -> glomerulus --> Nettle's loop -> Bowman's capsule->collecting tubule

D. convoluted tubule -> Bowman's capsule -> Henle's loop -7> glomerulus -> collecting tubule

Detailed Solution

The kidneys filter unwanted substances from the blood and produce urine to excrete them.
There are three main steps of urine formation: glomerular filtration, reabsorption, and tubular secretion.
These processes ensure that only waste and excess water are removed from the body.
There is an explanation video available below.
30.

The order of passage of food in the digestive system is

A. ileum --> caecum ->large intestine -> rectum

B. ileum --> colon --> caecum -> rectum

C. large intestine --> ileum -> caecum -> rectum

D. colon -> caecum -> ileum -> rectum

Detailed Solution

There is an explanation video available below.