JAMB Biology Past Questions & Answers - Page 319

1,591.

In organism where the 2nd number of chromosomes is 16, the number of chromosomes in each gamete will be

A.

32

B.

16

C.

8

D.

 4

Correct answer is C

A gamete is a haploid sex cell of an organism which is reproduced sexually. They contain half the number of chromosomes in an organism.

no of chromosomes = 16, hence, no of chromosomes in the gamete = \(\frac{1}{2}\) of 16 = 8

1,592.


What will be the result of the first filial generation (F1) and the second filial generation (F2) of a mono-hybrid cross between pure line normal-winged Drosophilia flies and pure line short-winged flies, if the gene for the normal wing is dominant?

A.

F1 flies all short-winged and F2 flies all normal-winged

B.

F1 flies all normal and F2 flies all short-winged

C.

F1 flies all short-winged and three-quarters of F2 flies are short-winged

D.

F1 flies all normal-winged and three-quarters of F2 flies are normal-winged

Correct answer is D

No explanation has been provided for this answer.

1,593.

Dead plants and animals are decomposed by bacteria and fungi into

A.

nitrate

B.

nitrites

C.

amino acids

D.

ammonium

Correct answer is D

When a plant or animal dies or an animal expels waste, the initial form of nitrogen is organic. Bacteria or fungi convert the organic nitrogen within the remains back into ammonium \(NH^{+}_{4}\), a process called ammonification.

1,594.

The part of the brain that controls heart beat and breathing is the

A.

olfactory lobe

B.

cerebellum

C.

cerebral hemisphere

D.

medulla oblongata

Correct answer is D

No explanation has been provided for this answer.

1,595.

When a short-sighted person views a distant object without spectacles, the image is formed

A.

on the retina

B.

in front of the retina

C.

behind the retina

D.

on the blind spot

Correct answer is B

The light rays focus just in front of the retina, resulting in distant objects appearing blurred.