1999 Biology Paper I Marking Scheme

i~-Marks

1+I

-/', ,~

(ii) Because the cytoplasm of cell 0 is Conned by repeated divisions of the cytoplasm of cell C I without cell enlargement ,

...I

+(iii) Sheep X I

Because the body characteristics of Dolly is determined by its genetic material, which is derived from and identical to that in the body cell of sheep X...

I

+(iv) No """""""""'"because dIe process does not involve dIe fertilization of gametes..

Total: 10 marks

1.(b) (i) During the fitness test, the heart beats rapidly to supply more bloodto the skeletal muscle 1

.This provides an.abundant supply of food and oxygen to the muscles 1so that a large amount of energy can be released in respiration '.". 1for the vigorous contraction of the skeletal muscles 1At the same time, more blood supply to the muscles also helps to remove rapidly

thecarlJondioxide/heat roducedb the muscles ; 1EffeClhie communication (C) 1

" ..-.. c.' ) P ' h 1-.11 eter s cart ;;; ;; Because the energy demand of Peter and David was the same for the fitness test 1

and Peter's heart could supply the same amount of blood/oxygen to the skeletalmuscle : 1

at a 10~j~~~.:.~.:..~~..~...~ ~!.~~:..:~...~..~.::: : I

'::1~

(iii) (1) 'glucOse ~ J la'Cticacid1

(2) To provide additional energy to the skeletal muscle cells 1so that the skeletal muscle can contract more vi2orousl): 1

Total: 12 + I"marks

.(c) (i) Gelatin in jelly solution B was digested / disappeared / lost its effectdue to the presence offresh pineapple juice I

(ii) Gelatin was present in solution C,butnot in solution B 1-This suggests that the pineapple juice contains protease

/ enzyme that digests protein or gelatin 1The enzyme is denatured / inactivated at high temperature 1

I Effective communication (C) 1 I

(accept alternative answers suggesting that pineapple juice contains a .'heat-sensitive substance that acts on gelatin)

--

(iii) Beefcontains protein which is digested by the protease in the pineapple juice Allowing the beef and pineapple mixture to stand for half an hour will give

enough time for the enzyme to work

Total: 8 + 1 marks

99-CE-BIO 1- 9.,,' :vr, -:J;?TT -?(j'-;:r-':;r""),\::4:'-i~ ::r ..~',,~_.~::-;.,:';.:~:::~:.~ ""..R"~IX'BU ~ OS '"\-PORA'IEACIIFRS" USE ONLY

1999 CE Biology Paper 1 Marking Scheme

1.(a) (i) Cell C contains a diploid set of chromosomes because its nucleus I chromnsnmcs comes from cell A which is a body I diploid cell :

Q1-f.'l

(2) mass decreases by 0.6 g"""~.'. "... I

(ii)...r1l...~I

To study. the e~ect ~f d~.ect illumination on ~e lo~er or upper epidenn!~ on the rate of transpiration of the leaf

ORTo compare the rate of transpiration of the leaf when the lower epidermis is illuminated by the spotlight with that when the

upper epidermis is illuminated --(iii) The decrease in mass in treatment I is greater than that in treatment II, thus indicating that the transpiration rate in treatment I is higher... Due to direct illumination by the spotlight,

the temperature of the lower epidermis in treatment I is higher than that in

treatment II This leads to faster evaporation of water '.. Water vapour diffilses out more rapidly through the stomata ,

Thus the transpiration rate is higher in treatment I.

anyoneset

ORDue to direct illumination by the spotlight,

stomata of the lower epidermis open more widely in treatment 1 than

in treatment 11 The surface area for the diffusion of water vapour is greater "."".".""""".'.

so that diffilsion of water vapour becomes faster Thus the transpiration rate is higher in treatment 1.11-.-

(iv) Peel off the upper and lower epidennis """'" rtl

LJ anyOR one

=:~:::: ~e::~:~~~:~~; ~~.~~i~~~d.&~~d;.;i~~~~id';;';;i;;';;i;':::::::.'m set

Total: II marks

2.(b) (i) Bile produced in the liver cannot be stored in A IWhen food enters the duodenum, insufficient amount of bile is released .'."'..'..'."'.' 1for emulsif}'ing fats in the food IThus the surface area for the action of Ii ase decreases '.' 1Effective communication (C) 1

When pan of structure D is removed, digestion and absorption of food is reduced 1Energy intake becomes less than the energy expenditure in the body 1This may lead to the use / mobilization of fat / food reserves stored in the body... 1

(ii)

(iii) (I) *insulin

...1

...I,.. I

(2) It cannot regulate the blood glucose level as blood glucose would not be converted into glycogen in the cells orB ..

Total: 10 + 1 marks

99-CE-BIO 1 -10

1999 CE Biology Paper 1 Marking Scheme ';'\';'f'::~ ;";.,j', :i '.. .,'~; :'.. 'Marks

2.(a) (i) (I) mass decreases by 2.4 g..,.

anyone

set

Total: 9 + 1 marks

;!':::d

I

".~"I;';~:!.

T'Z"

(I ~ P-T

,,1999 CE Biology Paper 1 Marking Scheme .;".I...~ :';' -!', ;" ,;,;.",.;1 ~ Marks

2.(c) (i) On Day I, the air temperature was higher than the body temperature , 1Heat from the body could not be lost to the environment by conduction, convection -

.and radiation ; , , '..:; i...; ~~ IHOwc-ver:he -could loselieatihrough the'iv.aPorado~~fswea-t-.-::~ 1

-_.whichabsorbsheatfromthebod surface;-;-;-:.,.-;;-; ,-;;.;,;;-.-;-..; ;, 1Effective communication (C) 1

(ii) Vigorous exercise would lead to the generation of large amount of heat in the body 1As sweat could not evaporate efficiently at the higher relative humidity on Day 2, ., Iless heat was lost from the body through sweating , IAs a result, the body temperature would rise steadily 1and this would lead to the breaking down of normal metabolism / enzymatic action I

--.

~y 91 -f. f"'-.' -, ",:..1 !~) ,--,'!

Marks

(ii) The dry mass of the algae at hour 24 was greater than that at hour 0 '.." 1because the algae have carried out photosynthesis in the 24 hours... ,.. 1to make carbohydrates / organic compounds ..,.,."".,., ,., 1And the rate of hotos nthesis is reater than the rate of res iration of the al ae 1Effective communication (C) I

(iii) (1) The algae grow faster when they are supplied with exhaust gas 1

(2) 1The exhaust gas is rich in carbon dioxide ".", so that the algae can carry out photosynthesis at a higher rate..,

(iv) The carbon dioxide output to air is reduced 1leading to a decrease in the greenhouse effect which is caused by carbon dioxide 1Thus it helps to slow down I prevent global warming ".'.'.. 1

Total: II + I marks

3.Cb) (i) 12 .o..o o.o.: ~ ~ ~ '.' ":: '.'.."'...'. I

c..) (I) 10-s 10~ 10-) .' , III ppm, ppm, ppm .,.- ..',~ (2) _10o2ppm; I()o. ppm :"."...i ; , ;.;.;;..~ :;~.._;..:,_.,;' I

_Deduct 1. mark once ifno unit is given-

(iii) (I)' Because cells in-region A are capable of rapid growth while cells inregion B are not : :::

anyoneset

(2) Mark the whole length of the root with lines at reg~ inte~als After a few days, compare the distance between the markings ..:.. ~ Th.emarkingsonregionAwouldbefurthera~.: ~.:!~ I

OR- :: .

Repeat the experiment .usingsect!ons from region B '.~.: ' ' ~'.

These sections would show little elonga.~on ~ ~.~~~.

(iv) The root would bend towards the side with auxins .: :..: ;' ~::.~: 1

This is because the auxin concentration on this side is about 10.~ ppm

whereas on the other side is about 0 ppm I

I ~~s $e growth of.ro~.t on,~!s side is inhibited while the other side is not I

I Effective communIcation (C) 1 I

Total: 10 + 1 marks

3.(c) (i) The muscular wall of the uterus contracts Irhythmically and powerfully ~ , 1to push ~he baby out of the uterus : : : : 1

(ii) Perio~ X : IOvulation occurred around period X Ithus fertilization might occur after sexual intercourse ::... ..:,'.. .:., 1

Besides, around this period, the uterine lining is ready for the implantationoftheem~ryo:.~..: ~~ ~ ' ~:,: ~ ~.: ~.. I

(iii) The day of ovulation may vary from cycle to cycle 1

The duration of the menstrual cycle ora wom~...;-;:-.:'~~;:-:::":-:;-:::-~~;;;)ll \~ " heL'Ii.Ji;" ...,..., .Ki,'~,~.\"~-'- ...l>, .I

_I k;\ (J"8 Pu L' Tota.1 .9 marlGs, (.; lell n. ..'. ...\ to ~e- '-';:1 -:!t- fie. I

1999 CE Biology Paper 1 Marking Scheme

3.(a) (i) Dry mass of the algae is the mass of the algae in which all the water has beenremoved :.: :

a,1-fr

(ii) On reaching the 50th floor, the air pressure on the two sides of the eardrumbecame unequal : : I

The eardrum was pressed outwards IThus it could not vibrate freely in response to sound vibrations I

I

I

(iii) Pathogens / genns in the throat have spread along the Eustachian tube to the middle ear ,

Total: 10 marks

4.(b) (i) The mealworn1S take in oxygen during respiration 1Any carbon dioxide produced by the mealwonns is absorbed

by the soda lime IThis lcads to a drop in air pressure inside the syringe ".,. ., , )

and the water droplet will be drawn downwardsThus the rate of movement of the water dro let indicates the rate of res iration I

." --Effectivecommunlcatlon (C) 1

,,- (ii) (1) The rate ofrespiration9fmeaJworms increases with an increasc.in temperature ...1

from 20°C to 50°C ~ )

(2) With an increase in the external temperature,the body tempciraturc ofmcalworn1S rises ; ~:.; I

Thus the enzymatic activity of the wonns increases ...: ;.: 1-" This lcads to an increase in the metabolic rate/body activities/energy demand )

thus the respiration rate of the mealwonns rises

(iii) To allow time for the air temperature inside the syringe to become equal to the--temperature of the water bath Iand the respiratory rate of the mealworms to become adjusted to the new temperature ..1

Total: 11 +1 marks

4.(c) (i) During the daytime, the rate of photosynthesis of the algae exceeds that of respiration ..1Thus the fish can have sufficient oxygen for respiration IAt night, the large population of algae undergo respiration only IThe dissolved oxygen content in seawater is greatly reduced IThus the fish die of suffocation , 1

Effective communication (C) 1

(ii) A large marine fish eats ~ small fish, which in turn eat a 13[2e Quantitv ofmicroscopic algae 1

Since the toxins cannot be broken down or excreted by the fish 1the toxins of the microscopic algae are passed along the food chain to the large fISh 1and accumulate to a higher concentration in the tissue of large fish 1 .

Total: 9 +1 marks

99oCE-BIO 1 -13

1999 CE Biology Paper 1 Marking Scheme Marks',:: ,.."; '. :I;j .,:;:; .;,. '."';1 ,~: .

4.(a) (i) (I) A and B """""""""""""" '."...' ".'.:'..~:~:; ~ I orO

(2) A is the .semi-circular canals I

It serves to detect the direction of head movement IB is the .cochlea I

It serves to detect sound vibrations I