IGCSE Biology Paper-1: Specimen Questions with Answers 188 - 189 of 208

Question 188

Question

MCQ▾

The diagram shows part of a genetic diagram for the inheritance of sex in humans.

XY and XX System

What are the sex chromosomes in different gametes?

Choices

Choice (4)

a.

P-X, Q-Y, R-X, S- X

b.

P-X, Q-Y, R-X, S-Y

c.

P-Y, Q-Y, R-X, S-X

d.

P-X, Q-X, R-X, S- Y

Answer

a.

Explanation

XY and XX System

XY and XX system – e. g. Most of the fishes, Amphibians, Reptiles and Mammals.

  • In such cases the Y-chromosome is male determining, and the absence of Y-chromosome determines the femaleness. Moreover, the male sex is heterogametic (producing two types of sperms – X-containing and Y-containing) while female is homogametic (producing one type of eggs/ova – all X-containing) . The X-containing sperm and Y-containing sperms can also be called as Gymnosperm and endosperm, respectively.
  • In human also, it is the genetic make -up of sperms that determines the sex of the child and it is very unfortunate that women are blamed for producing female children (daughters) and even ill-treated for this false notion.

Question 189

Question

MCQ▾

The diagram shows a single cotyledon.

Structure X, Y and Z

What is the structures X, Y and Z?

What Are the Structures X, Y and Z?
XYZ
Aplumuleradiclecotyledon
Bcotyledonradicleplumule
Ccotyledonplumuleradicle
Dplumulecotyledonradicle

Choices

Choice (4)

a.

A

b.

C

c.

D

d.

B

Answer

a.

Explanation

A Seed Have One or Two Coverings Seed
  • A seed may have one or two coverings called seed coats develops from integuments of oracle. The outer seed coat is called testa, while the inner one is named as tegmen.
  • The surface of the seed possesses a fi ne pore at one end is called micropyle.
  • The testa ensures survival of seeds. The micropyle of ovule permits the entry of water needed at the time of germination.
  • Just behind the micropyle hilum is present. It is a scar left on the seed coat when it is detached from the fruit wall.
  • Within the seed coat there is the embryo, consisting of an embryonal axis and two cotyledons. The cotyledons are often fleshy and full of reserve food materials.
  • At the micropylar end of the embryonal axis, bears the radicle and the other end contains plumule are present.