Time and Displacement

New Senior Secondary Mastering Biology

Chapter 13Suggested answers to Exercise and Reading to learn

p.4/4

Ch 13

Reproduction in humans

Multiple-choice questions (p. 13-38)1D2A3B

4C5B6D

7A8C9A

10A11B12D

13A14D15D

Short questions (p. 13-40)16a

Part Number

Contains smooth muscle to move sperm4

Adds a liquid secretion to sperm before they are released3

1m x 2

bA scrotum

It keeps testes cooler / at 35C so sperm can be made / sperm live longer.1m

C erectile tissue

It can be filled with blood.1m

B penis

It becomes erect / stiff / rigid so it can reach high in vagina / the top of vagina / the entrance of uterus.

Effective communication1m

17aiAcrosome releases enzymes / proteases which digest the protective layer of the

ovum.2m

iiThe protective layer thickens / hardens / changes in structure.2m

bSperms are produced by meiotic cell division which involves independent assortment of chromosomes.

Homologous / pairs of chromosomes separate independent of each other.2m

18aiumbilical cord1m

iicarbon dioxide1m

biuterine1m

iiabdominal1m

cimammary glands1m

iiantibodies1m

Structured questions (p. 13-41)19a25.7 / 25.5026.00 m1m

bThese enzymes can break down protective layer and1m

allow the entry of sperm nucleus / DNA into the ovum.1m

cMitochondria provide ATP / release energy / carry out respiration1m

for the movement of sperm.1m

dThis increases the chance of reaching the ovum / egg / fertilization1m

because sperms have to travel long distance / not all sperm viable / many sperm do not survive.1m

20HKCEE Biology 1995 I Q1c

1.(c)(i)(1)diameter = 53 (50 to 55) ( 0.03 mm 1

= 0.159 mm (0.150 mm to 0.165 mm)

(no unit, no mark) 1

(2)because cell A contains food store 1

(ii)(1)* ovary 1

(2)* testis1

(iii)(1)fertilization1

(2)It forms a zygote)

which will develop into a new individual )

OR

It combines the genes from both parents )

to result in genetic variation in the offspring )any TWO point 1+1

OR

It restores the diploid chromosome number )

which has been reduced to half by meiosis during

gamete formation / so as to maintain the chromosome

number of the species constant )

(iv)The penis becomes erect 1

and it is inserted into the vagina 1

Semen is then ejaculated 1

Total : 11 marks

1.(c)(i)(1)The performance on this question was good, although some candidates did not show their calculation.

(2)A considerable number of candidates wrongly wrote that cell A is large so as to provide a large area for meeting cell B. Some candidates did not seem to understand the word account and attempted to calculate the size of cell A.

(ii)Some candidates did not read the question carefully. They gave the names of the cells instead of the organs that produce them.

(iv)A number of candidates misinterpreted the question. They elaborated on how semen is produced and failed to describe the process of semen transfer.

21HKCEE Biology 2006 I Q7

7.

(a)4th to 8th March / (4th 7th March

There is a great drop in the thickness of the uterine lining in this period

(b)15th to 20th March (any range within these days and cover day 17 + 18)

Around day 17, ovulation occurs

The chance of fertilization is high as sperms and the egg can survive for a couple of days in the female reproductive tract

Also, the uterine lining is thickened and ready for the implantation of the embryo

If sexual intercourse occurs in this period, there is a high chance of pregnancy

(c)This method only allows her to detect ovulation when thereis a rise in the body temperature

But it fails to predict the fertile period before ovulation

23HKCEE Biology 2002 I Q2a2.(a)(i)It forms a physical barrier1

to prevent sperms from meeting the ovum1

(ii)AIDS / hepatitis B, C or E / gonorrhea / syphilis (accept other correct answers)1

(iii)Menstruation will still occur1

because the operation does not affect the production of the female sex hormone by the ovary1and the transport of the hormone by blood1

Under the influence of the female sex hormone, the uterine lining will get thicker1

and shed off later

Effective communication (C)1

(iv)Title (T) 1/2

Drawing including cell outline (D) 1/2

Two chromosomes shown i.e. haploid, chromosomes as single thread1+1

The ovumEssay (p. 13-43)24aAny four from:1m x 4

Midpiece of sperm contains mitochondria

which supply ATP

to the tail for motility.

Acrosome contains digestive enzymes

released when membrane rupture

which digest the protective layer of the ovum.

Haploid nucleus of sperm can enter the ovum and fuse with nucleus.

bBreakdown of membranes1m

decreases the diffusion distance.1m

Presence of villi1m

provides large surface area for exchange.1m

Slow movement of blood at exchange surfaces1m

allows more time for exchange of materials.1m

Transport proteins present1m

for active transport of ions1m

Blood circulating in placenta1m

maintains the concentration gradient.1m

(3m for features, 3m for reasons)Reading to learn (p. 13-44)1Condoms and vasectomy1m x 2

2Both vasectomy and IVD prevent the transfer of sperm to the female body.1m

However, contraception achieved by IVD is reversible while vasectomy is permanent.

1m

3Testes

1m

Testes are the organs which produce male sex hormone.1m

Menstrual cycles may be irregular and hence cannot predict the exact date of ovulation.

Effective Communication (C) 1

Marks

1

1

1

1

1

1

1

1

Total: 8 marks

( Oxford University Press 2009