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BAcHTLLERATo \Q_7 TNTERNAcToNAL

BIOLOGY

Higher Level

Friday 8 May 1998 (morning)

Paper 3 I hour 15 minutes

A
Candidate name: Candidate category & numbcr:

The maximum mark for this papcr is 40. :-

INSTRUCTIONS TO CA§ÍDIDATES

Write your candidate name and number in thc boxes above.

'Do NOT opcn this examination papcr until instructcd to do so.

Answer ALL of the qucstions from TWo of thc opüonc in the spaces providcd.

At the end of the examination, completc box B below wiü dctails of the Options answcrcd.

B c D
OPTIONS ANSWERED EXAMINER MODERATOR IBCA

/20 t20 t20

/20 t20 t20

TOTAL TOTAL TOTAL
t0 t§ IQ

EXAMINATION MATERIALS
Required:
Calculator
Allowed:
A simple translating dictionary for candidates not working in thcir own language
2?*tü2 16 pages
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Option D-Evolutioo

Dl. The scattergram below shows the relationship between brain size and total body
mass in species of mammal. Primate species are shown as solid circles and other
species of mammal as open circles.
[Source: CUP, Encyclopedia of Human Evolution.]

o
Humans
oo
\ oo
o
o' o
o o.oo
brain a
size o
(log
p;
scale)

t
;#á-óo o
o

o Primates
6O
o Other mammals
o
o

body mass (log scde)

(a) Using the data in thc scattcrgram,

(i) statc the relationship bctwecn body mass and brain sizc in mammals I I markl

(ii) compore thc brah sizc in rclation to body mass of primatcs with that
of oihst marn¡nals [2 nurk]
:.................

(This question controltlr,s on tlw follow@ pasel

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(Question D I continuedl

(iii) exptain briefly how thc scattergf,am can be interpreted to show that
human brains are largcr than thosc of other primates. [2 marksJ

(b) Increascs in brain sizc in relation to body mass could be due either to
increasesin brain size or docrcascs in body mass. suggcst ooc advantage to
primates of reduccd body mass. I mark]
I

D2. (a) Outline the main stagss in fossili¡ation. [3 marksJ

(b) §tate or mcthod th¡t can bc usd to date fossils. I I markJ

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D3. (a) Discuss how isolation can lead to speciation.

[7 marksJ

(b) Dcacfibc oE cramph of a ring species.

[3 marksJ

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Option E-Neurobiolog¡r end Beheviour

El. (a) Describe the social organisation of honey bee colonies. [6 marksJ

(b)
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{2 marksl
,d q
^oÍc

(b) Suggest one example of the survival chances of an animal being increased
by innate behaviour. I I markJ

E3. The crested newt, (friü¿rus carndex\, has a courtship consisting of the following
stages: l. malc approachcs fcmale and sniffs her head
2. male waves his tail towards the fernale's head
3. male hits femalc on het head with his tail
4. male deposits sperm next to the fcrnalc
5. female picks up sperm.
A receptive female responds to thc courtship by remaining motionless until
picking up the sperm. The male or fcrnale can stop the courtship at any stage by
moving away.

(a) Using only the information given above, suggest otre way in which:

(i) the male can find out if the fernale is of the correct species; fi markJ

(ii) the fcmalc can dccide whcther or not to sclect the malc for mating. I I markJ

(This question contin ¿es on the following page)

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(Question E3 continued)

Nitric oxide (NO) regulates sexual behaviour in some animals. Newt brains
contain nitric oxide synthase, which catalyses the formation of nitric oxi¿e.
amount of this enzyme was measured in the brains of male newts at uurlou,
iir"
stages as shown below.
[Source: Narure vol 382, p 31. Zerani and Gobetti]

'ot
40
Brain nitric
oxide synthase
activity/arbitrary
units

. Before After
courtship -- -- waving Hitting
sniffing Tail hcad sperm compreting
deposition courtship
Stages of courtship

Q normalcourtship
! immediately after a female has stopped a courtship during one of its stages
NI tS minutes after a female has stopped a courtship during one of its stages

(b) Outline the changes in the amount of nitric oxidc synthase in the brain of a
male during the stages of normal courtship and afttr completing it.- - marksJ
t2

(c) using thc data in thc qucstion, deduce thc effects of the female newt on
nitric oxide levels in the brains of male newts. marksJ
[3

::8. I El
Turn over
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Option F-Applied plant and animal science

Fl. Crops of cassava in parts of Benin in West Africa are sometimes attacked by a
grasshoppgr, Zonocerus variegatus. A ñeld trial was carried out to investigaté a
method of biological control-of the grasshoppers. Four l00m x l00m plots
were sprayed with spores of a fungus, Metarhi:ium favoviride. Four óther
similar plots were left untreated. The density of grasshoppers in the plots was
measured before and after spraying. The time of spraying (s) and ihe mean
results are shown below.

ñrJ

o,

o
C)

o
o
0
't,

o
>,4
.á
(u.
r,\ J

Time after spraying / days

(a) Compare the results for the sprayd plots with thosc for the control plots,
during thc period from before the spraying until eight days after spraying. [2 marksJ

(This qwstion continues on the following page)

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( Question Fl continued )

(b) Explain the evidence from the trial that the

biological control method was
effective.
[2 marksJ

(c) studics showed that thcre was_signiñcant movement

and out of the spral$ prots. usiñt ir,iá"ü¡i of grasshoppers into
grasshoppers migrating- into the piots
,nJirün!, deduce whether
the spores of thcfungüs tt. rr'¡s'¡ué
after D"v ,pri¡íüLre infectcd by
[2 marksJ

(d)

p markJ

F2. (a) State on r¡se of domaticatcd animals.

I I markJ

(b) *" effects of rearing domesticatcd animatq using intersive

i:tf;Sr.
[2 marksJ
I ...........:..
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F3. (a) the differences between wind-po[inated

OO".ff.rJrT and insect-pollinated
[7 marksJ

(b) Explain thc advantage

I of prwcnüng
flowe.rs. r--'----€ thc pollinaüon or fenilisaüon
srrl¡Isauon oI cut
of cut
I
j ma*sJ

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Option G-EcologY rnd Conssr¡tion

Gl. (a) Describe the role of CITES in the conscrvation of endangered spccies. [6 marks]

(b) Explain bricüy üe advanUgca of h 3¡t¡ of cndangcred spccies' [4 marksJ

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G2. Ecologists have recently completed a study

of nitrogen cycling in the Flooding
lTp" ecosyste.m.of Argentina. The study took piace áurin! spring.- F"n-"r
this ecosystem is.heavilygrazed by cattle. the resulti
of tnñ p".t ir.-rto*n
below' The numbers in tñe boxes show.mean nitrogen .ont.nü in millijiams
per square metre (mg m-r). The numbers beside the airows show the
mean-daily
flows of nitrogen per square metre (mg m : day-r).
[source: Chaneton Lemcoffand Lavadó. l. npinea Ecology 1996. JJ pp 291_302]

atmosphere

rnorganlc matter
in soil
4200

litter (fallcn dead

leaves and stems)
60

4.71

(a) (i) state the nitrogen-containing chemical absorbed by the plant roots
from the soil. I I markJ

(ii) Predi* the name of thc nitrogen<ontaining chemical rcleased into the
atmosphcre by thc cattle. t I markJ

(b) (i) Calculate thc daily change in mass of nitrogen in org"anic mattcr in soil. t mark]
I

Answer ...... mg
(This question continues on the following page)

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(Question G2 continued)

(ii) With reference to microbial activity in the soil, suggest a reason for the
change. I I markJ

Another part of the ecosystem from which cattle had been excluded for seven
years was investigated. Although there was some feeding by wild herbivores, the
amount of grazing was much lower. The amount of litte¡ was found to be
470 mg m-:. Nitrogen absorption by roots was found to be 37 ms r¡-2 day-,.

(c) Explain the differences betwcrn thc grazcd and the ungrazed areas in:

(i) amount of nitrogen in littcr fi markJ

(ii) rate of absorption of nitrogen by plant roots. [2 marksJ

G3. (a) State the difference between tropical forests and tanperate forests in:

(i) relaüvc biodivcrsity I I markJ

(ii) photosynthetic cfficiency. I I markJ

(b) Suggest ore reason for the differcncc in photosynthetic efñciency between
tropical forests and ternperate forests. I I markJ
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Option H-Further Human Physiology

Hl. Physiologists recently investigated glucose absorption in the ileum using the
following method- They placed two substances similar to D-glucose in tne lmalt
intestine of a living rat and took blood s_amples from the aort" und t"p"iic
portal vein during one minute afterwards. For each substance the alrtic
concentration was subtracted from the concentration in the hepatic portal vein
to obtain an esrimate of the amount absorbed.
[source: uhing and Kimura. J. clinical Investigation 1995, p 27901
(a) Explain the reason for subtracting the aortic concentration from the
concentration in the hepatic portal vein.
fi markl

The table below shows the mean results of the experiment.

Difference ¡n blood cooclntr¡ti<n betwce¡ rortr

Concentr¡tion pleced in and heprtic portd vein /nmol gr
the su¡ll intestine
/mmol dm-r L-glucosc 3-mcthyl glucosc

100 20 420

200 30 7ffi
400 50 930

(b) using-o-nly the data in the table, compare thc absorption of L-glucose with
that of 3-methyl glucosc. marksJ
[2

p-8lucosc, L'glucosc and 3-mcthyl glucose are absorbed passirdy in the small
intestine at thc same rate. Dglucosc and 3-methyl glucosc'can ahb be absorbed
by active transport, using thc same carriers.

(c) If the expcrimcnt wru¡ repeated using D-gtucosc, deduce whether more
would be absorbcd by passive or by active iransport, at a concentration in
the small intestine of 400 mmol dm:r of D-gtucosc. marksJ
[2

(This question continues on the following page\

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(Question Hl continued)

(d) using the data i1 th9 table, discr¡ss

of
-- gtucosc.concentrationo
c'rcosc concentration on
the proponion of active p"rsiuc seffecr
tr"nsport.
"ná ,, marksJ

H2' Li§t fucG factots wüiclt incrcasc

the risk of coronary heart
genetic factors. discase, other than
[3 marksJ

,-..-:.:...:..:..................¡¡.........¡
1

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H3. (al Outline the responses that occur in humans when the body
temperature
falls below normal.
[7 marks]

(b) which tyPc of fbedback mcchanism is involvcd in the responscs to

.Expl.ain
low body tcmpcatu¡o j marksJ
t

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