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.
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 – 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.
What is the structures X, Y and Z?
X | Y | Z | |
A | plumule | radicle | cotyledon |
B | cotyledon | radicle | plumule |
C | cotyledon | plumule | radicle |
D | plumule | cotyledon | radicle |
Choices
Choice (4) | |
---|---|
a. | A |
b. | C |
c. | D |
d. | B |
Answer
a.Explanation
- 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.