A2 Biology Edexcel Textbook answers to questions

Stretch _{and challenge quesrions are}

indicared throughour the Studencs Book with the following icon _{@.These questions are aimcd to}

r,.-.,.h and challenge all srudents by using diilcrent assessment suaregies including: a varicty

"r;r;;,;;;;;;;:;;:;;;;;:_1.rr.o

rvriring opportuniries _{and diffcrcnt question nro",}

,o enabre studenrs to deverop and use a 'varicry ofskills.All srudcnts shourd bc abre to give _{anslvers ro frcse quesrions}

and a basic ansrver 'is oudined belor.v for each of them, However it is _{expected rhat candidates working} at higher grades

wi'givc

a grcarcr _{dcpr'ofanswcr bri'ging in}

cxrcndcti _{knowleclge and} undersranding _{from a variety of}

sourccs, pages 1G-11

I

Marks arvarded for: Most imporrrnt rc:ic,ion _{because armost r,' lire on earrh dcpenc:} on it' only Iarge scare rvay _{in which new organic morecu-les}

arc synrhesised _{in living} organisms and the oniy rvay in rvhich a ncw supply of ATp can bc builr up. any

oL..

vaiid point.

Marks not awarded ror: without respiradon, celrs dic _{so phorosynthesis can,t take place.} wirhout _{slnthesis of proteins,}

tl-rcrc is no AT'pase, so no ATp cycle. _{Almost impossible to} rank reacdons _{in terms of importancc. Any}

orher valid point.

2 a

Releases energy rvhen AT? broken down to ADp in a form available to alr ce, enzymes. ADP and inorganic phosphatc _{can be rcrorrned inro A}

r-p by AT1)ase usirg energy iiom

universal reacdons, suclL as _{rcdox reactions, rri'Jrin rhc cer1.}

A^ny orher valid poinrs.

b

Evidcnce to incrudc: prescncc in'a, ccr-l rlpcs _{invcsrigatcd, prcscncc in every} species invesrigated, _{impacr on ceus if}

_,{fp

_synthcsis

o. br.r-k,ro*r-, in}ribited. Any other valid point. pages 1 2-1 3

l'l a

Bccause not

a'

rhc cclrs carry out phorosynt'esis

_-

_{any parrs or.rhc prant} which are

_-... not direcdy exposed to light wil) nor conrain chlorophyll.

'b..lFolded _{membranes givc Iarge surface area.}

Enzymes on mcmbrancS rnd in sUoma Lo crrr), out rcactions. Pr6sence of severar _{photosynrhetic pigments to absorb}

difrcrcnt waverengths _{of light,} Any other valid point.

2

Noneofthepigmcnrsabsorbwcti'thcgrccn/yclrorvrrcirsofthcspcc*um,AsrJrisright is not absorbed, it is _{reflectcd rvhich is,,vhy plants}

appcar green_

I

pages _14-17

Cyclic photophosphorylation _Non-cyclic

photophosphorylation involves PSI and p5ll

electrons _{ccfie froffi and retuin to} chlorophyLl in p5l

NADP _{recuced to reduced NAD during the} process

etectrons lost on excitation from the chlorophylt _{molecutes in}

PSli are _{replaced by electrons from the cx riation of}

*.t..-

'

no reduced N,.,D produced as

electrons return to chtorophyll

ATB reduced NAD and orygen formed

Edexccl A2 B'olo8y Implcmcnradon and Asscssmcnt Guide rorTeichcrs _{and'r'echnicirns gpcarson Educarion} Limircd 2oo9

arcasl

6

refcrencc to moniloring ovcr time; rcicrcncc [o non-functioning of s}'napscs / cq; conuol of {moror functions / motor ncurone lunction}; reicrcncc to {cercbcllunr f nlotor cortcx / parictal lobc};

rcference to substantia nigra / basai ganglion / mid

brain);

(2) dopamine cannot cnter rhc brain / L-dopa can be convcrted ro dopamine/

L-dopa is {casicr / cheapcr} to make /

conversel

(1)

1

tNtRI /

FMRI)

scan

/

{C'f

/ CAT} scan / thermal imaging /X-ravs / PET;

2

rcfcrcncc to 3-D imagc; _[only apphcs to

Ml{I'

I;MI{i'

CAT scan and P}iT']

3

{shrpe / sizc / colour} Jiflcrcncc;

4

densitY of ussuc;

5

comparison to image of a normal brain / mcthod of identification of damaged (3)

lTotat 6 Qarks]

3

ln a biochcmical process that depends on or is alfectcd by a number of factors' the process rvill bc }imitccl by tlrc factor that is ncarcst to its minimum value'

Thc amounr of light availablc alfccrs dlc amount of chiorophyll drat can be excitcd and drereforcthcamountofrcducedNADandADPproducedinthelight-dependentstage.

If*rcrersaiorvlcvcloflighttlrcninsufficicntrcduccc]NAl)andATPwillbeproducedto

allorv the reacdons of rJ-rc light-indcpcnccnt stagc to progrcss at thek maximum rate , so light is the lirnitir-rg factor.

Low levels of carbon dioxidc available for fixing in rhe Calvin cycle means that the rcacrions.rnnnt

prn.."d

irI drc miximu.r ratc]Whcn this is thc casc) carbon dioxidc is

rhe limrting factor. In rhe natural sirualion of plants it is mosr often carbon dioxide that is the hmiting factor'

All of rhc calvin cyclc rceirior.ls and many of thc light-dcpcndcnt rcacdons of

phoLosynthcsis arc controllccl by cnzyncs anrl ate drcrcforc scnsitive to tcmpelature.This mcans rhat. cvcn whcn t1-rc light and clrbon dioxidc lcvcls arc suitablc for a very high rate

of phorosynthesis, if the lcmperaturc is low, thc plant will be unable to take advantage of thc condirions.

'/

fhc _{habirar is the ,addres} ttrortr[s _shou]d

ot

"tt''o"t^ol

l'c

organjsm

_-

_{it dcscribc} Thc nichc _<iescribes

_*"

'o'."'n "'-top;"l

';;;;':];:'

tt'hcrc it livcs' suirable _examples of

.

rnhabit rhe same _{nro,,r, l,l]..} o[ an rnimrr

.'r,u'',,;;;;,'""tt

a lu; (mrnv _{oLhcr possibi.rires).} Ln u'oodrand: _,op

_{p..6.,"b-titt'pv}

uiff.."n,';,.,*l'olt" -

so sevcral organisms may squrrrer,

_crc.

rr fox, primarv

,

..;;;;;.;;r;::t:,n

_"riuq,/rcr _raDDltr ir' For cxrmplc, rood njchcs

hrEe rree_dweJjlng herbivore

-2'

Full dera:ls _shoLrld

bc _{givcn of u,h;.,L^.._ ,} .

Iink hcru.ccn

_,,lro;;;^":"

of.whichcvcr biomes choscn. _{A crcar}

_{undersr,.r;*^}

s and

_ric

'""0';;;,

;;;ii^'"li

^'''"1'understanding ortire

pages

2o-23

ur ulc llsbltal shc'rrld bc shown,

pages _{1B_i 9} pH of _{the soil}

J

Thc proccss _by rvh.ic are rcplaced _b,

",n..l:Tuniljcs

c'rf rnjrnals _arr.

*r...T.-#J"ffi

"#:f;.;;n1;,."jff

f$ilti:::*il:f

:ff;#::'-.

r"2

A communiry reached

_.,

_,t "

".u

";" "..-""":-ly

tre scme urrir _{condirions change} again. consisr _{of t,],re}

_,r,n.

a",1-ul thc, _{en'l of}

_r

serics of sr

communiries.

planrandr",",r,.f....r.;.r:rilil::il::H:"::,;;,"

Ld

Irrimary _succe:sjon

I

coloniscd _by

_1;;;::l

brre rock or sanJ dune

:) _

,

rings bur

rnor.i.,,.J.*

""''t'secotrdarl'succcssion on land tirar rvas r_1,

_{{.) tS+Cl}

The _{answcrs shoulcl}

jncjudc

somc or all of

"

t'l:i'

sreadv _growrh

'" ""

;;';;:j^:::t't'

rolJowing'

odrer points may be varid. soil devetoped.

_{Tr"i :tj:}

num-ber of spccics r

d*'siepg6

_,r

_r..

r,fl

a period

"tr'r*"*i*'i"as

condidons changcd and nrore

rrrey broughr

".*

;l:::.:'o

*i'n"",;;;;;,ii

10""'

t nt4-e0 as drc isrrnd _had droppings _n"O

,o

.j_tlltt

on lheir

b",ii;r';;;;,"'

tcrultrv' Oncc bircls colonissd j51sn.s

b

some

_{rp..r.,,rt.h,il^'lo"}

"to'';;';;;ril*"'ed

rerriJicv _of

_rle

soil with _rheir r brceding

_{poprrrri^i:t:.tlc}

isl:rnd

'nd

,,rr,

,o;tttut"o

again reladvely _rapidly'

r-hc _island.,

oin

r.l,l,oiplanrs

So

.;;';;.::"*t:"

but crnnot _{survivc to} establish cumuJaLive

_ro..,"r,"

rimcs than

_"t"

";;r;i;;;:

or _{l.isnrs lta'c}

bccn obscrvcd _on courd drop

_{.",.,0.,i1,1.t}

n'

'""',,.;;;;;'J;::::il:i,ilj;::.#i:r'.*j',",,,

c

If rJrc prcdrcrrc_rrrs

by s .

drop as

row,,

_{, o,}

_{*,Tl'li;:;l:Jil:i;:,1,1"-,::::l}

::

::J

s; , ii, s _{couJcr evenruarJy}

mOrenCwspcCiCSbecc_ ---'!

rut.u wlll rcma

pases

24-22

:me cstabrishccr

_{o"r;;;v:i,ffi::';J::::or1'rcn}

so up

ir

1a

-lhe

non_livjng _elemenrs of r

ll"^'; :l..

_"

i;;

:il?J,*

;::;:::

:,::l

ln,.n

.

pop u, a d on or organi living. _Dxrmprc,

-

.;':::i.T:

environnrcnr iu which a p

nu

otrr'.

_roir.

"-

:o

rncludc unv

or,.lo,.l;.,,::l;T:::j.ililj:::Ti;

*

.

1

_^,

.

,-,Lr

lsrcvant _{pOtntS sUcl} I

_y

nolottc _factors dctcrmir

-

_ctc.rhis

'";;";..r;::,1,;]l','1""'t

orrbe soir, rhc which _pranrs

_*',,

o.li,'"',].i:l]"'"1"i"

rvatcr avaitalririry

crc.Thjs _{in rurn}

decides

_{*i,,:.'j,,,,,,,}

ot rhe soil, rhc lcnli

:i1:.5;;'#.T#l:1il:H;l'ff

j:i;';Jii::.::J"i:::'""1:':l'11.,

in,rurn _affecrs

_*.

"*..

*ur"'r

ptants _rvill be able to erorv

".d

*.t".,.

#Xi.'ltJril,,

:oronisers

"r,",.;';;;,,:J|j:::,'",T:.::.bc

abre ro surv,ve. rn rerms

_ortr.

_r.,i]

col oni s ers of _{a n}

a re a, r

r,;;;

_;;.;":r'

An1' 5ri1r61. cxamplcj sucir as in a wind1, en'ironmcnt watcr will evaporate from the ground morc rapidll, 5e rvill bc lcss availabic ibr living organisms, high light lcvcls but low oiygen levcls meitn many orgarrisms cannot grow rvcll and rcproduce etc.

Any suitablc examples dcmonsuadng an _{understanding of how the animal/plant is} adapted to the panicular abioric factor sclecrcd.

pages 28-29

I

Is+c]

'lhe

answcrs should includc somc or all _{olr]rc following. other} points may be valid.

Any rhrce suitable cxamplcs, including one bird anri onc mammal, with clear explanation ofhorv tcrritorics arc markcd and defcndcd, e.g. scinr marking, physical displav/dance, fighring.

y

\vith

liule biodiversity, if onc organism is alfccted by discasc it will have a major in"rpac. on the small numbcr of otl.rer organisms in the ccosystcm

_-

rhcy won,t gct eaten or

tleir

prey numbers will fall subsranrjaliy.\Xuirl lrttlc biodiveLsiLy rJrere will bc fcw other available food resourccs. Also discasc is ntore likr:ly to sprcad benvccn inciividuals where there are fcrv bulfer spccies. In a more di'crsc communiry, changcs ciue to disease are lilely ro havc lcss of an cilccr as rhcrc is much more varicry of food choice and more buffcring organisms to prcvcnt sprcad o[ discasc.

pages 30-33

1

inrraspccific

_-

bctwccn mcmbcrs of the samc spc:ics, c.g. for territory, mares, food. I^raspccilrc compcritior tc'cls to affcct drc rb'.<rrncc of

r

particular spccics of organism

_-

lorv rcsources, rnuch compcutron, less reproduction and more mortaliry

-numbe r dccrease. Plenty of resourccs

-

littlc coinpctirion, Iors of breeding, Iorv mortality, numbers increase.

interspccific

_-

bctwccn mcrnbcrs ol diflcrcnt spccics, c.g. for space, food.

Interspecific

_-

this lcnds to affcct the diitriburion of spccics in a habitat and also the abundancc of spccics

_-

thc biodivcrsity. If onc spccics comperes very successfully against othcrs, it wi'll tcnd to drive thcm to extinction in thc arca.

2 [s+c]

Thc ansrvcrs shourd rncludc somc or an of thc foilowing. orher poinrs may be vrlid.

a

Adding food

_-

hare dcnsiry more dran rriplcd. Excluding predarors

_-

hare _{dcnsity more rhan doublcd.} Ferrilising d.ie grass had no major effcct.

Adding food anri rcmoving prcdarors

_-

harc clcr.rsir,v wcnl up by a facror of abour i5.

b

_{Ifaddfood,haresbrce,rmorcsucccs:fulry,burmoreuiil arsohetakcnbypredarors}

which will also breed succcssfully. So rhc impacr _{olrhc lood on rhe hare popularion is} not luliy illustratcd in thc population numbers.

Jlt;:*

hare

popurarion

-**'se4eu****;"''**

_#J

other _racrors

0.r,"

_,.'*,1

_{l::l:::":.0."}

a resurt _{or L}

;*:::,:4

o',..,"#*,ii',

l"*.-

iTl,.

*.'-,1,i'i'"1;#,;ffiTiffnipuiadon,

ffi

lTj

_T;:;;

",,n::

j:

:,il:ff

fi

,l.,ilili

*

:

*

:

*o,

i" u

*, .,

,"JJ,i:;:i*lfii:TFl.ili?lllT;;T,".J*ji::,;:,::.fi

:::::ff

_:a;,

:::;:

_i'Jili;:;"T

i:

:

il

ff

j:::'"il,3;::

:

::l

a;;.'

;;il"';i

"1

?.

_""I

;:::

:mltri;IT

ii

I ri

t,tr

r;H

_H

I

x

i

jl

jrirfi

i

ll

;::T*

:* i

l;

"".

".,"-

*:rr-,:rr.'n

I)ensiry_indcpen denr

_f

.,"-R..,

r,,.

il;

;;..Jil:::::i,f

1",'hl,

rlc

disrribu r io,: of _{r n^^;^}

,^ffi

_tr

_*,iriilH?t

_x,

_{:,r":,i, #*.:?Im}

;

r

.Densiry-dcpend.",;;;:-:"

oecorncs _{densiry-depcnd.;}

;;;::'

no\v mush lishr, warer erc. is

;ili:::

*

;

.

;;;

_;

;

: J

:.i,il.:lTff ,,l..:.ilffi

il::

l::T

:

::::

:,

: s o rvii

]

cn d Pages

34-37

- _"*r vrvc rn a parLictrlar

I a

Algac and coral rcr

b

opcn

".;;;

;;;:,11100r",-,u-

proclucd

c

.r

rioush

_*.,

n.

"."

11..' p'od _u'rion

;;,;"

_J;#

j

1:,'1,::'-

t

s urface ;,

r,,,

_{, r,;s.,i.;;,}

,;:::

procjucdviry rrcrc _{is a}

2 a

proc,ucerJ,"

,;;;:t'ct

on total

_o."ur.ur',,

""

cnormous amount _{of opcn}

ocean so

'..m*",*iiffi:ffi::,,j:#

b

(r 6.7

_.

_..,

_;';,;rt

consuners; B.e%

' .

anr

r",*0,.**"".'

-.- 30 1/3

₌

_1o'o%

isn"'.

_{,r.r.,in;*":::l}

_:'

would _be

roo compric

.

vu,er

ccosysrcm,*o,jil

rvirhin a

"*,,1.1"*,,"r;:,':::::],""

as a food wcb, can

b

Any _rcasonable

assLrm

wirrrin _biomass

"r,;;i,i.ll]:,:^.Juding

using

,".,,r.';.:'j":'-o'*

*'*

stucJics

_of

species _which

".. ".i"

".i^",i..

spccics, qsLirnr,.,

","

u"o"iru,l11lll*i:iJii::::*

transfer in,o u

,p..;.,

_*".i.

il:;:f.l

in nurnber, ma.ng _csrimrres

Pages 38-39

1

[s+c]

The ansrvers should include some or all of the follorving. orher points may be valid.

The link shouid bc made bctwecn releasing carbon from sinks more rapidly than normal and morc rapidly $an photosynthcsis ctc' can removc it'

i'Z\

Ar-osohcre: increasing intjusUiaiisarion, clccUicity gencralion, cars and othcr road

'J

_,.hi.l*,

acroplanes, ali producrng carbon dioxide cmissions affect amount of carbon dioxide in the armosPhere.

Soil organic mattcr: tcmpcrature (rate ol acriviry any scnsiblc altcrnativc.

Occan: tcmperature) any sensiblc alternative'

o[ brcrkdorvn) dcath rate of organisms,

Nlarinescdimcrlts:c!osion)acidiryofrvater,acidrainctc.)anyscnsiblea.ltcrnadve. Terresuiaiplants:seasonofthcycarintcmpcratcareashasabigefiectong}oba.l photosynthcsis lcvcls, dcforcstation' crop growrh and harvcsting'

Pages 40-41

i'il

p.opt" _{could stop eating} becf and using tlairy producls, bccausc millions of people around

V

,r.," *orro reiy on mcat and miLk fiom ruminanrs as a major part of rheir dict and big farmingintercs$havealotofeconomicc}outand*'ouldobjcct.Anyothervaiidpoint.

2[S+C]-l.ircanslvctsshouit]irrcludcson]eolallofl}rcfollolving'othcrporntsmaybe

valid.

Thegreenhouseeffecrisvitaltomaintaintl]cSuIl.i]CeofthcEarthatatcmperatule suitable for life. It is thc enhanccd grcenhousc cffccr, clue ro increasing levels of greenhouse gases, that is potentially a problcm'

pages 42-45

t

20.81%; allow i9-21%

@

Carried out ovcr iong period of timc, r,ery large numbcr of rcadings, sanic or sinrilar measuringequipmcnlusedlhroughout,areaoflolvairpollurionetc.ADyotherrelevant Point'

y':', _clives a much longcr timc pcrspccrivc (rcadings going back over a thousand years),

V

.ho*,. narural falls and riscs in carbon dioxide concentrarion and events of last coupie ofhundrcdycars.Anyclt-lrcrvaiidpoints.i{clirrbiliLy0.2ppnr.Corrciadonwilhother cvidencc.

€) ffr.

data shorv rhar armosphcric carbon tlioxidc icvcls hlvc increEed.They do noi show the sourcc of the carbon dioxidc'

A .i^--.^,:.r.,..^t

\) a

Jtuocnl s}rou}d questior-i validiry of c1ata, Staustical ncdrods used, inciusion of

uce-ring data in original'

b

200svcrsioncontainsalargcrnloulrtofcxtlrdttalronrhundrcdsofstudics,nvo diflerent starisrical methods used, figures calculated both wiih and rvithout uee ring

data. AnY othcr valid Point'

tt.t pages _{46_47}

86'7%,70.7%-

carbon dioxide

frn*

r^.-ir r..

,

,

--."^

-":"t"

lrr tc^perature?

a

E'idenco _^F

_^^-^..

from _{lossil fuels}

has incrr:ased mote _{than other sources.}

a

_{E'idence ofcarerur}

research rn.r

.L:r:---.

' --u!q rl'1u1c _{uran otner} sources. tcrms

orclrriry

_{oridcas,::HlJ:i:l:::.::^'tn}

up rlrc _{rrrcnsrrrs and *cakncsscs}

in terms of clarity of idcas, rcliability _{of tlara ctc.}

l^:"0

a.

closeness of dara, rvhich comes

::::"

*:

c",*;;;,

ffi

;ffi:::ll

T*:

:: ::^?.1tf

,,"10..^,ure

or possib,e valid points. validity and re _{Iiability of dam,}

Any other

1

Graph _{A shows glaciatior}

;,'.'.'T.f

_tr;:*:J?:ffi

ff

:ffi,ill,,;i;lTililTJf

_ffill[

jff

:

Graph B _{shows close correle} e'ets. _{which comcs}

firsr

*

.r#::

j::t"'.'*llru...:

,.-ogruture and carbon dioxide lcvcls.which .on-..,

nrra--.il"ri

1lt _{Parlern beLwcen}

lemperature and carbon dioxi

36.70/^

tn

zot

langc in carbon dioxic.lc or change in rcnperature?

pages

_4&51

I

Any va)id poinrs _sucF

don'r know

_t;;;;i

as; rmpossible to predicr ne

ci r i ve ro r e d u c e "., o

";

ijj;;",';

;;

_ffi

_;'

_;

":'#::-i::;*:"TJililii

_".

2 a

43y0,2.7yo

b

t5Omm

c

_{Increasing carbon}

enhanced

_{,...*o,1lo*t*}

levels thought to cau on mounrains, _,.r,

ur"

_{.T.,, ,"..".ri;;;;;;.use}

.rise in global temperatures due ro poies. _This

_.rur",

.l"1o.I ltrrl"g

c"

"

?iffiututt'

causing _{melring of}

snow cover -lse _ln

average sea

levels.

nperatures and mehing of snow at

i3)

Parricul:rrlV affccts disr

"'

_::TR:,T,1;

j*i

##{r

i:;::

l:::.:*J:i:d,

o c,im a rc c,ranse

_-

_ri

sins carbon

arc a s wh e r e

*

",

;."

;

;

:li*;;

:T:,H

_i

:

i[,:.,

J,

#il

;;

:il:,""#

l"

4

_{Look for claricyof}

thought _and

understanding of rh, pages

_52-53

--.'"lrurrrg

or ure _{possible sequcnces} ofevcnrs,

I

Any _{valid poinrs} here. h

ln*:T";*

jt

_fli;;t

_if

:]:

T:;T

"

;l"tl

I_,*,

I

a,

_{n. .n1b.dy}

_can though lhar invorves n","i^d,

ot]'utn*

" *"

1""*tJl'on'nt

counries _cannot strive to be unpopura. ", "

n"r,lll

in"'"""

'"

';;;:;;.i

morc dcvclopcd _counrics

*'cn

rnevitably unpopuJar

",

,::.1t,::o

'"0

t";,;;:;xrde

emissions' politicians don't rvant

2

IS+cr

The answers

_,n,n"

*0"'

"" '"0'"li"'i.i:i.:':J::"::'-",'":icirv/peror

etc are

valid.

-- - -"ourd includc _{some or}

ail of the fo.llowing. _other

points may be Answer should _{cover rhc}

ansrver, _and

",,;.;;;#J;1,1,]tii;illJr',ll;.1i:*,,thar

,nereis no comprete

Edercel _{A2 Biology Implementation}

rnc

#e forTcachcrs and _{rechniqiaos opearson}

Arges

54-55

(

1)

I'rorcomicsistJrcstu.ll oIali rhcdiffcrcntJrrorcinsrharcanbcmadeasaresultof *ie genomc throughout thc lifc olan individual, at all

tie

diflcrcnt stages of developmcnt as

,

a rcsult of differenriai gene expression. Should note that there are far more proteins than gcnes. Genomics is the srudy of thc DNA, thc se qucnce of drc gcnes and the specific alleies in place in an individual.

y

(.1) Diif.t.n,

allelcs arisc as a rcsult oi'mutaiion

_-

changcs in rhc scquence of DNA bases.

''

_{Chunges in allcle frcqucncy in a populadon usually occur in rcsponse to enviror,,mental}

changcs.

lf

a particuiar allclc or combination ol'rllclcs produccs a survival or rcproductivc advantage for

tle

organisms rvhich havc thcm so thcir oflspring are more likely to survive and brced again, the frequcncy of rhe allcle will increase (e.g. Malpeque oysters from AS levei). Alternarively, if a particular ailele becomes disadvantageous, the frequency wiil dccrease (c.g. Biston bcuilaria from AS lcvel).

pages

56-57

$/

In ordcr to plant the apple orchards huge areasrof natural bushes would have been ploughcd up.-lhis wouid have dcsrroycd many harvLhorns, tre natual habirat of the flies, rvhich in turn would havc lcd to some fcmalcs bcing lcft rvith no alternative but the apple uccs on rvhich to iay drcir cggs.Thcn some of tJrcsc flics would have had aileles which hclpcd thcm rccognisc thc sccnL of thc appics, or digcsr applcs cffecuvely, or lay eggs ar times that fit the pattern of apple uee llor,vering and fruiting ratler than hasthorns.These flies would be most likely'to survivc and pass on rheir alleles, thus changing the allele

lrcquency in rhe popularion and moving towards speciation.

2

Any suitable cxamples.

arges 58-59

* (!)

tn ordcr to mcasurc gcncdc divcrsity, to idcnrify relationships berween d.rfferenr species, ro uack the process ofcvolution, ro idenrify lraud in foodsruffs such as caviar, to idendfy ways of conuolling discasc. Any orlicr suirable cxamplcs.

2

Ilecause thcy are prescnt in a rvidc rangc of different organisms, and so rhey can be

comparcd.The gcnes mutate a[ a measurable and suitabie rate, which al]ows the time sincc cven rclatively closcly rclatcd organisms shlrcd thc srmc gcncs to be calculated. pages 60-61

f}) a

_V

Fossil evidcnce is limircd: only relarivcly small numbcrs of organisms are fossilised, small nutnbcrs oIfossils arc found, fossils c,ltcn nor intrct.Thcre may also be

similaritics in anatomy duc to convcrgcnt cvolution. Any valid other point.

(9

ONa

starls to dcgradc immcdiatcly aftcr dcadr so iimircd application. Mutarion rares of diffcrent genes varies considerably so timing can be very diflerenr depending on which gene used.

c

Evidence from any one source has limitadons and potcntial inaccuracies which reduce its validity. If evidence from different sources gives similar results, the more valid are any conclusions drawn. Similarly, using diflcrcnt sourccs can show up discrcpancies and prcven! time and money being wasted on erroncous data. Any other valid point.

@

t

t

n a

i

The r ns rvcr s r.

--.***sa-msmrrtu'Liui.;;o#"***;gggi*

valid.

,. " "hould includc somc _{or all of}

drc loilorving. _Orher

points may be Helps to _{validate nerv}

rr sevcral _reams

,r"0"..'ullilt-t

bv presenting ir to pe rs confirmed. _Anor",

n.,:l,u::

':'utt'

in

'.t.i*r;J:""

t?' _{conslrucdve criticism'} when cooperadvc _rcsearch

u.;1'ot"

to bc aired

^t;^;;;;i"n'tle'aliditv

of all _{their findings}

c x ch a n g c

",

o, r*

*

_",,

_" ]I"l'o'"'

"

o ;

;

;; i,'

JJil::"'-;t';

li

ii1

_iiii'

_ln

"'ill'

l)isadven12gs5.

prcssurc _{to nrrht;.r, .,,..r ..} ,lrive _{peoprJ ro}

;il;"rJ:tlish

attd rppcar at co'fcr, runding

sroups can

.ourrh.l"

r}cv

_{have;"*r;;;;';:t"t"'can}

skcw rescarch and

-

ca'y rnor;ring

_,.,n.r,

_{o..,lll:pul"'}

p'p"... T,ilin-''rdara'

Vcsrcd interesrs and Jarqe rhe accepred _view

can o.

u.l.t'l:tt

qer Bood

.r;';;:;;

,'a'cr

car) _{minimise audicnce} moders. peopre

need ro be

"o1tjl n

""*ti,"-.*

**rtr'\cw

tccas _{rvhich go agairrst} mi ri ga r es

.*,,",,,.""i,

_*

_;

n:I;l;l;

;;#JJ.'.:,:':'J.:::

:::

::*il,

_ff

-Edexcel _{A2 BioloEy}

Inplemenurr'on _{and Asscssment}

Guide for Teachers _and -llchnicians

(,p€a.50n

pages

66-67

1 a

'lhc

_{hcat of}

the body is producerl as a resuh oi the mctabolic reactions taking place, parricularly respiradon in active tissucs such as Lhc _{muscles and rhe brain.After death} thesc rcactions slow down antl str

rime he a t energy is i o. t uy,o ai"ulp,.,

;:"::;:::*:';::l?

_::ff

:1111;ll ?J,i

$.

evaporadon so &e body cools down.

b

rhemctabolicreactionsdonotailstopimmcdiatclyaftcrdeath-manycellsconrinue to respirc, conuact' rnd so on, unrir arl rhe availabjc oxygcn and ATp is used up. so heat continues to bc gcncrarcd in the first hours aftcr j.",t-r,

"trr,ougl-, at a slo*,er rare, so body tcmpcrarure drcips but rclarively slowly.

c

'lhc

_{tcmpcralurc glallie}

rll bclrvccn rhc boely and lhc cnvironmenl wili affect ratc of cooling, for exalnplc if somconc dics insidc a warm _{housc the body rvill cool down} more siowly than

ilit

is on a cold rvindy hilisidc, so rhe cxternal temperarure and. wea*ter condirions have to be takcn into considerarion. A naked body rvill cool much fastcr by convection than a ciothed body, and a _{body *,rapped in blankets or a duvet}

will cool down cvcn morc slorvly due to _{insulatron..t.u"ttody will cool laster than} a dry body as a rcsult of l.rcat lost as drc rvatir _{cvaporxrcs, and dearh in a warm bath} or

leside some lorm oiheating will also change rhe raie of cooling. Even the body posirion _{ar{ects rhc rltc of cooling}

-

a srretchccr our body has a much bigger exposed surlacc arca 10 volulne ratjo

fiao

a curlcd up onc ar.id so wrjl cool dorvn faster. All

of

thcsc diflcrcnt factors huvc to bc takc' ir-rto _{considcr:rLion rvhcn using tcmperarurc}

as a

guidc to tirc tintc rrf dcarlr.

2

vcry littlc differcncc as rhcy arc poikilothermic and so _{their body temperature is normally} vcry similar to rhe ambrent tcmperarure.

3

Llmitcd valuc bccause, although thcre is a _{gcncra)iscd parrern ofrigor, there are} large 'ariarions rrom one individual to anothcr dcpcndi'g on factors such as:

'

amount of ATP storcd i;.1

tic

_{muscles ar rhc rirnc of'dcarl.r which}

depcnds genctic tendency and lcvcis of fttncss

'

Icvcr _{oI acrivity bcrorc dcirrh}

_-

_{rr'rv nruch dr-r)}

hus bcc' uscd

.

tempcrarure _{oi the} individual ar

frc

point oi deadr

.

_{teinpcraturc of rhe surroundings}

'

spccd ar rvhich rigor passcs ulso cjcpcnds

_o'

J vf,ricty of frcrors sucjr as cxr.crnal tcmpcrarurcJ acdvity of cnzymcs.

Other _{examples may be valid.} pages 68_71

t

ll:,lt:"

srallc is causcd by r'hc coroniscrs

-

rnacrobic bacLcria. _{EqTymes rrom lysosomcs} orcak down _{cells releastug cell conrcnts on rvhich anacrobic}

bacteria grow. As more cells are broken _{dorvn, the bactcria sprcad.}

'

The bactcria are rollorvcd by a numbcr of species of flies, c.g. browflies, rvhich lay eggs'The larvac _{(maggots) leed on the rissucs,}

bre aking their down further.

.

As rhe body liqucfics, adulr ilics can lccd on ir too.

'

Bccdcs arrivc whosc iarvac lccd on maggots. Parasitic rvasps lay their eggs in thc larvae.

Ede\ccl A2 _{tsiology lrnplementarion anrl Asscssincnr}

.

_When

*;"""'move

in.

""*

s'rqrsn[

spccics such'as _t.l-,e

Ehcete fiies

,n".,",

_*,,i'li]::"f

*.

body _{arc roo}

h i, r"

r,..,r.i.t'

*one .h.,uin J

;

Jj

;::XT:l: T:::

ll_,,.*:

any more, bcede

, ;r"^jr::,;:;:::::

morh iarvae

_reed

. -.b ldrrass _bcedes,

ham beetres _and

notj'ihsr'de

".;f,l:::.:'ll:'"'

"'.

,",;o:.;

on the _{hair unril}

onlv drv bones _arelert. ''ct"a,. ."icntn,lutside)' bui

t"t

"*"t

t'iio'turc

tnd JcvcJ

'r

cxpusur"'r

r cnr pera ure

.iil,f

T:::*,

sh ourd bc

_r,".

]'-':','"u'o';;;;

1l,

"i

n:ilH:i:;

rarc

and,"*".

_llll

t'he ratc of

clrcmt*,l."lt

of rl-re cllect on dccn-^-^: '

avairabiriry

"r

rllTililll'l ;*,.l#::]'vmic

rcrcLicns

-

"'*;'t"j:"n'

For _exampre'

3

succession

_foir,

Y to insccc

t;t"-^,:,:.

tl.re lcvel

"tt-ttrr.. ,fri,i;?::ff;tt"t

,long *in'o]..jotvs-a regular patrern _sor bv e.

ort'irol'rruion

th"

condiio,,;;;;:?;.':'*ining

fie

srs.c _{ors,,"^- ..}

ts+cJ

₄

_a

_Exposcd

ooo

n"'"'t'.*,.

"ri",",jl'"[,t^""t1]:1:,0"'"

^;r,;,;;.:ff:on

in a bodv'

;:TffTffi

_il:li:ii:

1,1"

H'ruiii:::

:;x

;:;-.r

c s c

cn

s s ca n

;:'.'";ffi::l;r:^tdm,*i{[$:":,1""i',#l',n:J;:::"?.t:

.h"ng"",

_,,

_.,

_{,I_tl-oeraturc}

_{shorvs less} r

a c ri vi r y or

th c

jll'j:'1,'.

il;;::;iff:::

::

":,

"

r;

;;:

;'r[.

"..

b

AdvangSgg5,''

lssomposing

organisms.

-"

'-rirpcraturc are _{duc ro}

variadons _in the wrth obtaining '' fcwcr cr'hical issucs'

'"'"

^

Disadvanl2ggs.

_{l::::'.,'';;":;ll}

_;:].,j,:u"'

orpis carcasses,

rewer probrems organisms,

_a;rr.flgt

arc not pcople, so r,hcrc

ff

'ffi

_{iltit:f;:t'-$;',;.:;:li:.:[::'i;']Ji"t""it'_1,ii."",,,"}

c

Advantages: Lhe r Discdvanragcs:

",:::]::

"'

d jrccdv _rcrcvanr ro nurnan

_{bodics,,,;li:1^,::::'"lJ*r,-.,iri.:..}

,::::'tisation

of hurnan bodies A ny o rher,.,.

_;r;;

;:;,

r

n cre h um 3 n rc m e i n s

;;";:

_ffi

l'ffi

:XT.H:

_:ri:l:,',

pages _72*77

il;*

=:r1;av,

it drres

",""o

*ffi;;;

I

rr

^^--::.,:,,,1r,

rnore informar.

;Ji

:::

i::

_TH#:;T

TiH[:1

fi

_3j

x:*

n r s,,w. _or,h

e *u ee

i:;:{''i","..

i:*;J}iil:":x,ffi

_I*"^f

:T,Hlt,fr

_r..,,.,

,o::::'"

't

"..i'"-""'il,.j ;:'^:::T'*""

*r*

*i""L"

l^i"

*:

or rhe _three

H'

i,:ffi

_i;t

"

t**i

:id;l

:

::l it

_;

_H

":j::il

:

::1,r,:

ff

::,;T:

.*.

I?J.

_{i,:ffii;1":,Y::-:}

$ffi:::::l;H"n;;:^"

1"'"''" '1's

is imp'r'[an'l

il:

;;::il"I.,].ll

_ii,i

_;

_:::unna

n,

rc rc',

c,

n,

cd''

Jff;;:.*.;

_::

_;ffi::

;t;

_*m#:friifr

ilr

i;:I

_T:

_J':..l.ffi

i,"..,..m

="

.

ff

*iJ":,?#;:*ff

i'i,rffi

_{Ili,lliHli-..,.,..il::iii}

ffi.:,":,?il:,,.";;;;il:'";ilil:iil*.:j;:.J*j::i',,T;l;;,:

j:;

,u acld ln a _{specific place} in an am.ino _{ac.id cha.in.}

Edexcel A2 Biology _{ImpJcmcnradon}

and Assessmcnt

Guidc forTcrcllcrs _andTccl

-

uicianscPors"n'

-2 [s+cl

-fhe ansrvers should includc some oI all of the following. other points may be valid' .iianscriprion:ArcgionofDNAunravcls.onlyrhc5'primeDNAsuand(thetemplate or anlisense suand) is uanicribcd to give a singlc suand oi rnl{NA''l'he uanscription is

broughtaboutbyanenzymecalledDNA-directedRNApolymerase(RNApolymerase). Evcry rr.iplcr

"oJ" on the DNA givcs

risc to a complcmcntary codon (uiplet of bases) on tire mRNA. Every rhyminc in tl-re

DNA

rempiate is replaced rvith uracil in RNA' Apart

fromthischange,tlrenewlySynlhesisedl{NAsuandhasthesamesequenceasthenon-template, coding or sensc slrand of the

DNA'

Translation: mRNA molccules pass thIough the pores in the nuclear membrane and movetothesurfaceofrheribosomes,transporlingtheinstructionsfromthegenestothe sirco[proteinsynthesis.Eachtl{NAmoleculehasaunitofdrreebasesaroneendofthe molecuiek,'o'"n",thcanticodon.EachIRNAmolcculcalsobindstoaspecilicamino acid cJcpcnding on thc cotlc of thc anticodon'

.fhcribosonrcsarctlaclculrol.alargcatlr]astlrrllsuburrir.-llreyarc5O%llNA.Thcy surroundthosepartsoithemRNArvhic}-risbeingaclivc}yfanslated,andthenmove alongrodrcncxrbit..fircirjobistoholdtogcthcrrhcnrllNA,IRNAandcnzymes controlling thc proccss of prorein synthesis in tl-'c corrcct posiuons'

ThcribosomcstartsrcaelingtlrenrRNAataSl'artcodon(AUG).Thiscodesforlhe amino acid methioninc. Molecu'ics of transfcr RNA carry individual amino acids to the surface of lhe ribosome. Each

tl{NA

lines up its anticodon alongside a complementary codoninrhemRNAandisboundinplacetotheribosonerr,hileenzymeslurkrheamino acidtothcprcviousoncitrtl.tcaminoacic-ieiluirrbypcpuclcbonrjs.oncciisjobisdonc, theIRNAreturnstothecl'roplasrntopickupanotheraminoacid.Theribosornemoves alongt}rcmolccu.leolml{NArcvcalingonccodonafteranothcrunulthcendisreached at a slop codon (UA.A^, UAC or UGA)' producing a complered polypeptide chain'

.3 ts+c]

Theansrvcrssho\rldinciudesomeorallof thefollowing.ot]rerpoinrsmaybevalid' TheyusedthemouldNeurosporacrassawhichhasashorrlifccycle,iseasilygrownand

murarcs easily.-I1e original srrain of rhc mouid could grow on minimal medium (with few nuuicnrs) as it could synthcsise all amino acids and sugars it ncctled. Moulds were exposed toXraystocauscmutadon.N4utadonsinthcchcmicalpathlvaystharaffectedtheability to synrhcsisc particular amino acids would show up casrly bccause mutated slrains needed one or more nuuients added to the growth medium othenvise they rvould die. Crosses of differenr sfains rvere carried out, to show drat dre ability to synthesise all amino acids cou]d return and be passed on. From thc evidcncc of many experiments came the hypothesis that a single missing cnzymc was rhc rcsuit of tl-ic mutadon of one gene'

4

Scicnrisrs recognised that rhc cnd result of a gene was not always an enzyrne) for example that it could be a structural prorcin or some othcr rypc of protcin and so the definition became broader, As rhe suucture of complcx proteins like hacmoglobin wele unraveued) scienrisrs rcaliscd thar sc.rmc prorcins wcre made up ol scvcral po$pepride stlands).and

thlt

ciilicrcnt rnrriarions changcrl diffcrcrrt polypcptidc strands which shcwed the gcncs rvcrc cociing ibr indivrdual polypepticlcs, not ahvays thc samc thing as the final protcin'

5

.iye _{now know rhat} diffcrcnt proteins can bc manufacrurcd from the same gene, from *te evidcnce that.all r|rosc protcins arc alTcctcd by murarion in tl.rat gcne.We also understand thar pos!-ranscripdonal changes may occur in mRNA, lrom observations of the action of spliceosomcs. OtJrcr poinis may bc valid'

irli:rj i!; ::rt.lt,

Pages 78_81

I *

is the _{producrion of an anarysis}

of rhe DNA of an individual _{based on mini- or} microsatetite groupings _{from a limired}

""*b;;;;;;"ns

which can be compared with similar profiles from ou\er individuals.

2

Used to produce a DNA profilc.

.

'lhe _{srands of} DNA

I

cndonucleases

_*t

_i.h

_,.o*

a sample are _{chopped into liagmenrs}

using resrriction Dirrerent _resrricr""

.il:::iliffi

:::Hl

J,",ff

,l,fi

:::T

_;::,*T:.

sequences knorvn as recognition _{sitcs rvhich are}

found ar cirrrer side of mini and micro-satellite _{rrnits. leaving repeatr:d}

."r.,,r.,,..r',n,r.r.

.

_{The fragments of} diffe f

ragmcnts"..pr,..ai.'TJ,I:T1T".J,:.;:::oJo:if

i:T;:i,:ff

_Tl::J.:

mainrain a consrant pH).

'

The ger contains a dyc rvhich bincrs to rhc DNA _{fragmcnrs..I.hc dyc wilr} fluoresce when p)ace _{d under LJV light,}

rv'ich

_rt",

,1."'ON^ _{bands visible rvhen rhe} electrophoresis is complete.

_Ti"

_{n-lor, .o*rno,r,r'ur.O ay.}

is EtBr (ethidium

'

bromide). _{A different}

dye is also

_{.aa.a ,"}

_{,fr. ONa}

the sample s

..

uh.y

_-ou.

*uough thc

gel.

' samplcs to shorv the posirion of

*"::""i:"J:;:JJ::"',:"9

through the appararus and rhc

nNA

fragmenrs move

rherragmenrs_"".;.,"i;i.0.:.;X."J"ffiH:':;::f

;,n**l?:,i*:X

DNA fragmenrs are usually placed in a

.;r;;i;;

.

.

When elecrophoresis _is

complete, the plate is placed _{under UV lighr.}

The

DNA

fragments _{fluoresce and shorv}

up

_{.i.u.ly," il;;;}

_{be identificd.} I'his is the original _mcthod:f

p""

fingerprinting, _{rvhich needs a}

relarively large sample of

_{DNA ITslrowsuplargcDNarrrgmJnrs.r",rt,"r,mjninrunrol50basepairs,i.e.}

minisatetites _{However smalrer regions}

"f

DNA i;i;:sutcrJitcs)

and specific genes can no\v be idcndficd _{using cxtcnsions}

o[ this t".t_ln;qu".

a

The _{porymcrase chain reaction}

rcpcats dre _{normar rcp)ication orDNA} using the enz),me _{DNA polymerase. The}

reacranrs _ _{,fr" OI,IA} polymerase, primers _{lsmatt sequences}

of DNA ,,uhi.,

t"-0,"

to be amplified, _DNA

th'

,"p"."t.i

DNA

_,;;

_{;J::":::::-:1\^}

lvhr:h. mu:t join to thc beginning or

n u cl e o d d e b a s e s _ a r e

{::J:jn:",:

f

:'r:

I

Tf,'

:l

;;ffi

:,e:*;,;h:

The reacdon mixrure is first heatcd ,o

_{so-g5t i*.00r,30}

seconds which causes the DNA suands ro scparare _{as rJ-e}

hyilrogcn bonds hoiding _{drcm togerher break} down. The mixture is then coo.led _{do*n to 55_60}

"C anneal) to rhe singre _{DNA suands. r.rnuuv}

rh.

ilJH"T:::T:.r,"li:11."..,

ar leasr a minute,This _{is thc optimum}

_,.;;;;;;

w_hich builds

ro

_{.o,norn..n,a ry s rands}

or D NA I

o";

::

:

X

::'#..,.fr

:,:IiJ.

'llhese

three basic steps are re _{rcated around 30 rimes}

of rhe original

_DNA,

druuro JU trmes to

giit

:round 1 billion copies

Edexcel A2 Biology lmplementation and Assessmenr _{Guidc for'ftachcrs}

4 a

Traces of biological matcrial are uscd as a source of DNA rvhich is amplified using

pcR

and then used ro produce a profile. Because the chances of

wo

individuals having the same DNA profile are extremely low, when the DNA proflle of a

suspect matchcs DNA tiom thc crime scene rhis is takcn as sfong evidence of rheir involvcmcnt in somc rvaY'

boniyidcnricallwinslrrr,cjdcnricalDNAprofilcs,lrcrlvcvcrfamilymemberdshorv many morc similaritics than non-rclated people"so, if rhe DNA of a suspect of one ctime is checked, if DNA from anothcr family mcmber is on the database, it will come up as a close march. This can lcad policc to thc rigirt suspect) eve n if rheir DNA is not on drc databasc.

Pages 8z_83 2..\

X UJ

'

Extemely small so can casily ger jnro rhe body.

+

Sirnple s,'ucrurc of prorcin coar and gcnetic _{matcrial mcans rhe}

virus can wilhstand harsh condidons _{and rerain infecriviti}

::i:."tr"r

a.achnrcnr poinrs (VAps) ro cnablc thc'irus ro :rrr:rcir ro spccific _{tvpes of}

.

_{Some have}

specific mechanisms lor injecdng _{rheir DNA inro} cclls.

'

Virar geneLic _{matcriar is adaprcd}

ro take over hosr cclr

_-..n"r;r;;.

_For example,

:::::Ti:::,

direcdy as a temprare for borh neiv viral

_{oNa ,.a i,,rre}

_mRNAs rranscrip rase

#.il::::J,:'3"i:K:'

_"irr

I RNA

u""'

o'i,",r.*",',

or rcvcrsc is then used

_{,, ;;:;::::}

_:'^::i","^^

corrcsponding to the viral genome which

gcnomc.

a template lor new viral proterns and ultimately a nerv viral RNA Orher _{points may be valid.}

ts

p

tS+C1

'l}e

answers _{should include} somc or i

valid.

irrsluse somc or all of the _{ibllowing. Other poinrs mav} be

a

Like living organisms, _{they reproduce,} con

obligate

_lnr...uurr.

_{orrrlr"""r'""l"ll;.illtarn}

genetic material' undergo evolurion, _are other living

";l:n:;*"'es

(can onlv exist and reproduce

_.r'o^..rti,

in rhe celis

of

tr

Unlike living _{organisms, drey don,c fecd, respire,}

excritc, movc, or shorv any sensidvity _{The onJy characterisdc}

ofriving *rings shorvn is reproducdon. pages B4_85

L!

tS+C1 The ansrvers _{should include}

some or a.

. valid.

,rLrucre some or ail of the foilowing. Other points _{may be}

Lyric:virll

_{gcne.c mrtcriar}

is _{rcplicarcd indcpcndcntly of}

r_hc host DNA straight _afrer glterir.rg th,e host celr. Marure

ri^r..

_u..

-i'.

uy host ccll, which evcnruauy

_biiris

_ana releases rarge _{numb.rs ofnew virus}

ou.,i.i.r.rnar.

go on _{to invadc other hosr ceus.The} virus _{is said to}

be virulent

_{Cir.r,._.;;;;;;.}

'

Lysogenic: _Viruses

r

DNA inro ,n.

h.,;i;lT:;:::'::;;::L':::.:':t

gcr inro rhc rr.sr

cc'

1hcy _{inscrr their}

is produced

_t

_o-

_th"

"i.-l

DN;

b;:";.". .7.3:

*,t

hosr ccll divides.No

'RNA

of a repressor _{prorein which}

-"u;ii;|;rr;o:::"-u''"',4'n"s

causcs thc producrion

ffi

::t""3;::::,1:*"'"'ao'-,o".vi'I,,"'il:il::il.lilx'*il:t;::'"'

r^

Jiuons'

'

l*]j a

Reroviruses _{have RNA}

as _{genedc mareriar iniread} of DNA.

b

They have more comnlpw

tir^^..^r^-by reverse

",,.J;;::T'["j:fi:L::RNA

nrst has to bc rransrared inro DNA

il:Ht,*:::erted

into ,r,.

r,,.,

o*a. v,;li

3",ifi:'#:?:l:.,i::::

,:,i1"

proreins

^"0

_"*.i,

.ilff

ll,T

ii}iliiivira

I

m^NA

a c

Lr;'

;,"*;::

l*,'"*,,i,"r

Edexcer 42 Biorog-y _{Impremcnrarion and Assessmcnt}

cuide fofTcrchers and _{rcchnicians opcorson}

d!,'rnx!,nF{i$rr7f+f,.ttF!{@rtsjftlqiir:i:J@&ratrs,$t!LrKd6lfd&-8rs&1x\*F!}*F$r:!:titjwRl:rani*{}'Jst'It :'::il,tii rr'rii..,Ji i;il'';llfj pages

86-87

,i"r tf

'r

pages BB-89

li) a

Rapid, reiiable

-

can occur cvery 20 minutcs in idcrl condidons

.

_b

Brings ab<;ur gcnctic variation rvhich can cnablc bactcria to survive unfavourable conditions.

(2';

_z

_h shows that genclic material can be taken up by bactcria in sflficient quantity to

\-/

bring about a changc in chrracrcr of the organism. and in this casc make it infecrivc.

b

Whcn rhc dead bactcri'a wcrc attackcd by cnzymcs t]-lat dcsrroyed cerbohyd-ratcs and proteins it had no clfect on t]re ability ofthc transforming factor to changc the R bacteria into S bactcria.This shows t-hat the uansforming factor is neither carbohydrate nor prol.ein. However, rvhen the DNA is destroyed, the uanslormadon does nol rake placc, providing strong evidencc for DNA as the transforming factor.

v

X^

/

R iS+Cl

Thc ansu'ers shouhi includc sonre or all of thc following. Other compararive

'

\)-

_-

_{points may bc vaiid.}

5tructurai features Animal cells

Bacteria

lMruses

Average size (mm) '10-i00 0.5-10 0.02-0-3

Cenetic materiat DNA DNA DNA or RNA

Outer tayers lipoprotein cell surf ace

membrane

cel[ surface membrane and bacteriat cell wall made of

peptidoglycan with olher compounds such as teichoic acid,

lr po polysaccha ri d es

may have slime

capsule or lrytr

may have an outer lipid enveioPe

protein coat ot caPsid

made up of rePeating

ca psome re5

Main inclusions nucleus

conta'nirB I

cytoplasm generic n

ater.al

_I

geret;c ma:e:'al

(DNA)

_|

{or'r.n)

ribosomes

l'PLasnids

mitochond.ia

_l'mesosomes Colgr

body

I

tysosomes

I

vesicles

I

cytoplasm

I

cenrriotes

I

c)'tosLeleton

I

vacuoles

I

endoplasnric

I

reticulum (RER

and

I

sER)

I

genetic material

Movement varie5

-

may not

move, may be

amoeboid, may use

cilia, fiaBelia, etc.

may have

i,agellae

I

.

:il'.

movement

*{ses

90-91

-**''"*w>Ejoeicirii*;[;i;aiH

1L/ts+c]

Thc answers qhn,rr.r

i-^r..:

*

_'

Ill":,,

.,,,.

o,,.j,lni).|ff::::"tr;:,]:'|."'forlowing

other points mav be varid

nelv viruses.The _{host ceil" ..a,,^!_^,1}

_,

olism of the cell and causing it rn

*-r.^

F

J;:;:'fi

I

lil.T'i:::'

;""

il:;":ffi

;i

IT:

::: .ffJ5i:

ji

_I1-'

,Tm

I

;r,,,:

3li;,

=;ff

;

T:

*:

::

:

il;lil

_;

_;:

m

_;*".r*;l

;:

fi

::::,

Bactcria: _{Cause diseasc}

rhrn,,-h ,u^ -nndc,rox,ns

"..

,,ooo","r*il::f:

#::l;l::u.,,,

rhey grou, and reproduce.

I hev ofien cause fevcr,

_{ut"..n..ll,,l}

_.;:"t

_:::*

laycr of Gram-n.guriu. u.",.riu.

il::::'fili:i:,,"Jj:ff

_{"T::';;;;;,;;:;;.l'lTfi}

,::;::,iili:'i:llr:::

c

o,

i:.,-

;;;.:";H,:ff

.:.,

;I

*

*'

o''"'*'

_{*;::::iT;::?:,.,}

-

carbon compounds

or

_water.

in decomposers, carbon

.o;uuotuttt

stages: _{dead orgaoic} matter rpounds _{in decomposers}

+

CO2 in air pages _{92_95}

$ ts*c]

The ans,,vcrs

varid. Sujrabic _.rbr"

_,,:::r11

incrudc sornc or uil c

'

vecrors:,."rn.*j,

_{ii"li*,:.";;;l}

_{':; ::t''"}

ftrrrorving' _otr:cr

points mav bc

.

fomires: narural skin ffora and sebum

.

_{direct contact:}

skin

.

inhaladon:

_-"",;

;;:;;.:,Til",#,,tt"

ingesdon: _saliva,

mucus, stomach _acid

.

_{inoculadon: clotring}

'$

Lrrorr*.s

are enzymes _rhlr

_.,.

_{,_.r^",-^_. r} mucus _rhat

_{line' ott ..'111t-tan}

clesrroy bactcrial <

acr to desLroy

_bn.,".ir,

]:i'j:o" """-'

_'n"

*;";,';;"t'

rvalls L)'sozvmcs _{are prescnt} in the are also

present,r.r,.r.,"o,"1"

patricularly

tilil:

ur:nary _{and reproduclivc}

tracts'They

.:-\

and dcstov

_il;';;,

_.:.'gt'tlt

Gram-positive bacteria.They

lj)

Phvrl.rl

barriers:

ural cnler and might infect the eyes.

.

_{Skin is a}

tough _watet

parhogcns

_{,."", ,.,",llollcuter}

layer impregnared wirh kerarin

rhat prevents ceris and

"",u;;:;*',:*;::?j:j::""t,

brood-rich rjssrrcs rvrrcre ,r,{,

"oura i,,u,a.

.

_{Mucus forms}

a sLiclc

,,

o.n,

_{o,*".";,;::,:1::}

*n'ch

acrs as a physic

.

resp ira ror

_v,,,.,

" " o

lTiJ"'''';

;

;",."n'#

_il'J

_J:lTl

: :

_"ff

:;TfJ

ilr ogen s Chem.ical _barriers:

.

Sebum _{is a laycr}

_oioi

grorvth of

pathor.ni.'ot

top of the skin that con: skin b a cteri

a.

_o_.

_{_,}

_1,,.

_t..i,

b",

;;;

_il;

"",1,;:'

::il

Tj.ilT..:,,ffi

,X:;

.

_{Acid in} rhe _{stomach h} desrroyed

',

*", ,.";T.1T

pH and _{acts as a barrier}

ro mosr _{pathogens rvhich} are

Edexcel 42 Biology Implementation

and Assessmenl _{Cuidc forTLachers}

and Technjcians ,Opcarson

iii::::'til ''i::'._..J.:: i -itt:i: i: l1:iiiiiiii'in: S.1t3.*;r!rr:':' Biological barriers:

.

Skin and gut flora

-

thcse arc tire hcalrhy bactcria grorving on the surface and lining thetubesolrl-rebody.'I.hcyoutcompetcpathogcnsandprcventthemgainingcntlyto rhe body.

Lysozymcsarecnzymcsfoundinn'rucusatrdrearsthatbreakdownbacrerialcellwalls and kill ihcm bcforc thcy can infect the tissues'

Thevomitingreflexejectsbactcriaandvirusesfromthebodybeforeaninfectioncan sPread far.

AnY other valid Points' oaPes

96-99

o

Masr ceus and damagcd whltc biood ceils rclease chemicals

known as hisramines

:'rvlriclrcuusct]lcblorlJr'csselsitttiteutelt,llrrtieulrril,())eilltcriulcs,ttlclilutccrusirrg

s4'\

wlocalheatandledncss.Hcatreducestheefficicncyofreproductionofpathogens.

.

Histamines aiso makc *rc rvalls of rhc capiilaries lcak-v so fluid, incluciing plasma, white biootl cels and anribodies ars forced our of rhc capillarics causing swelling (oedema) and often Pain.

..$Thiteb}oodce.Ilscngulfpa*rogcnsbyphagocyrosis,anlibodicsinactivatepathogens, pain makes you takc care of iniured sirc'

2l]ccauscthcysimplyrcacttonol]-Sclf-tilcrcsporrscisnotspccifictoaparticular pat)rogcn.

3 a

A raiscd lcmpcraturc can hclp rhc body combat infection by lowering the

'-^""1"'1ion

ratc of rhc pathogcus' Also thc imtrunc systcm works bcttcr at highcr

rLPr uuuLuvrr

temperalures and so rvili be more succcssful at combaring thc infection'

blfbodytemperarurerisesabove4O.C,thedcnarurationoisomeenzymesmayoccul causlngp.,*un".,,tissuedamage.Ifrlreremperatureisnotloweredfairlyquickly death maY result'

pages 100*.103

Q

rrr"

imrnunc _{sysrem re}

:l

*:

o"o,

n*. ."ir;::

T::

;.T#"#il:: i'

surracc or p arhosens.

rhe

ceus anack

_thcm.

-'!

urrlrrurrs system recognises as selfand so does not

@

B cells:These _{have rece}

invading

_{t;;;.;r:ilttor}

proteins which recognise the anrigens _{on rhe surface} r.rf

pathogen.

- '-eY Sive rise to cloncs of cclrs

.halrilriuc9

a'ribodies to u

,p".in"

T _{cells:These come in t}

production of

anribodie

types

'f

helper celis produce chcmicals that stimuiare the

r\

s. T killcr _{cells produce}

chen

(+)

Non-sp.crnc _{responses rccognise}

,n.

_{;".J;." ;";:''^t'}

*:tdcstrov

_parhogens.

gcncral reacdons _{against anything}

thar is non-se'.

_o.ll"n

ttttont'

_non-sclfand

iniriate response _invoiving

rhe _{masr ceils and ,h.}

_{hir,r;;;;:1:;j::}

:l.?;,::1,-_".,

The specific _{responscs o}

Ve ry specific _andgens

""lt:-1--'""^system

rccognisc _nor just _non-scll but also

p a,h o g c n s,,'. o

;".

;;,;

"

;,:

i

*fi

"':

fi

:

il;T

#

TJJ

t*

*Tji1*.11:.,,..

Edexcel ,A-2 Biology Implemenration _{and Assessmenr}

Guidc for Tlrchers rnd Tec)nicians _{6person pducarion}

fages

104-105

C '

Disinfectants kiil bacteria lrom the area, lrom insrruments etc.This ieducei the

*:-

Iikelihood of bacteria bcing uansfcrrccl from cnvironrnenr to the patient/wound.

'

Antiseptics are applied to skin and to wounds.They kill bacteria and so reduce rhe likelihood of wounds becoming infecte d, bacteria getting inro blood etc.

'

Anribiotics desroy bactcria rvithin a parienl and so rcducc rhe likelihood olinfecrion passing from one person to anodrer through cither dircct or indirect contacr.

@ a

lndrcl80Os'3{J0rvot.ttcnrlicclperl0OOOObabicsborn(600-900womeninfectcdpcr

o

100 000 babics born). lh thc carly 20OOs cicar-hs terc 0.85 \romen pcr l0O 000 babies

-

DOrn

G fft"i.

_\-/

work was important bccause it shorvcd clcar cvidence for rhe eflectivencss of antibiotic drugs in trcating a bacterial infection which killed many young women each year.

It feU short of modcrn erhics and standards because rhcrc rvere no lab trials on dssues and cells, no conuol patients rvho did not receivc the drug or who received a placebo, no doublc-blind trinl, probably no

plticnt

pcrmission for rhc trcatmcnt sought, and no ethics committee decision on rvhether thc uial should go ahead. Other points may be valid.

pages 106-107

(! fi."

_\r

following describcs the basic inlormarion. Orher dcrails may be found from research.

'

Ronald Hare, one of Fleming's young assistants, found that penicillin mould grows best at quite iow temperatures.

'

Dr

Cecil Paine, ano*rcr onc of Alcxander Fleming's pupils, was rhe fust person to try peniciilin our on peoplc. A local nriner got a stone in his eye and had a massive infection rvhich was making him blind. Painc washcd rhc eye with his penicillin cxullct, and thc cyc rccovcrcd. Painc also usccl his pcnicrllin wash to trcxt a tiny baby which had pickcd up an c1'c infecdon as it was born.The baby was curcd and irs sight was saved' Painc nevcr publishcd what hc had donc, bur he taLked to Howard Florey, a new professor at the uruversiry, who wcnt on to follow up the work.

'

Norman Hcatlcy rvas a kcy man in drc Oxford team. Hc worked out a way of making enough pcnicillin to text it and _{carricd oul thc following cxpcrimcnr. Eight mice rvere} infected with bacteria which _{would kill} them in 24 hours. Four were given penicillin. The four treated mice stayed hcalthy

_-

but rhe orhcr four died.

In

1940-41 Heatley dcvclopcd special pot vcsscis so hc coulcl grow morc mould and so collect more pcnicillin. In just a fcrv wccks hc had madc cnough pcnicillin for Florcy to uy ir out on

.

a lully grorvn man.

'

Mary I-lunt brought a mouldy mclon into t}rc jab tirat shc had found on a market stall. The mould was a new sort of PerLtcillilnz which produced much more penicillin than *re originai srain.Thc ncrv mould rvould also grow in big fermentation tanks ivhich was the break*rrough which cnablcd industrial producdon to go ahead. Ms Hunt got rhc nickname'Mouldy Mary'.

l^

t2/ u

Ant

rrvo examples of rhe aclion of bacter ia _{clearly explaincd.} means it kills _{bacteria. Bactcriosradc}

means ir stops _{bacteria grorving/}

b

Bacteriocidal reproducing,

"

_{,arH::lTi::i_}

some andbiorics are bacteriosraric.ar.rerari'e)y

low concenradons, infecdons,

"

G.;

;x:::;Tffj::::1J,":

rlrc

inlccrion,;;;,";;

_;;;","""."

pages _{108_1 1} 1

1

Mutation _{causes a change}

that _{arfects the way the antibiotic}

gers into _{or affects the bacreria.} The antibiotic _{is a selecdon facror}

by Liirirg.u

_u*.lia

thar arc sensidvc ro it.Thererore rhere is rapici evolution so that rhe _{rcsist*, orn.}

_i..""r"s

lre mosr

.orr*o,,

iorrr,.

t

_"

f,l:,

The answer should include some or ali of tire _{following. Orher points mav} be Keep antibiotic prescripdon to a minimuml _ensur

of treatmcnt with anubiotics; _{be espccially}

_careful

fJlat padcnts complete the course anribiorics _{in *re case of}

C.

dilficite.

with the use of broad-specrum

b

Minimise _{exposure to reduce}

rhe _{lik€lihood of rcs.}

Make sure that rhe whorc course _{or.anribio,,., ,, .r,rur,} mutation being selected for. srighrly increased resistance are definiteiy

"u.o

".:::;l;;racrcria

rvith onry a

3 a

_{Broad-specuum andbiolics wipe}

out large _{numbers of the}

normal gut flora so c. dfficib can get established, produce

_{,"*ii; ;;;:;}

. b

Narrow-specrum _andbiotics

are urscred

",

*".:^:::::,:Ttt"*''

spccific _{infcction. so they}

arc lcss lik"cly

_{; ,;;;;:l-tms}

rvhich are causing a minimise _{opporruniries}

for

c.

dfficite;"

il";.::,ff,lt.:::

r,,tora

ancr so

4

_{}ixamplcs of good practicc}

inclrrcic:

.

Docrors, _{nurses and.}

other health carc prolcssionalr

arcc':hoi based gers between seeing parients

,..""J;;t[* jTiil:';'.",':"t

reciuccs chances of passing ti.,..n

_{*. So";*-;;;;}

arcohor gers ,o

,h.rJ;.

_{orrimited u,.}

_i.

_{o",i,"iil,*Tff;:h,"1"J,":}

,r

""

.

_{Avoid clothing which}

might carry bacrer.ia _{from pat} .

rvarches _{and rong_srceved shirLs}

ir-he.,*

.;;'";:;r.;;:::,ll:.',,e,g.

rong rjes, wrisc HeaJrh professionals _w

lrom the

_outside.

,ear

steriliscd scrubs ail drc time to avoid bringin$in pathogens

'

Monitoring _{parienrs lor inlecrin^}

_{r_t--}

-r_:-_. avoids spread

"ro.*.;j:l:t'ion

rvhen _{admitdng and}

rreaung and nursing _{in isoladon}

'

Encourage visitors ro u

inlection _{into hospital}

_{i:':ffiT il:}

use alcohol gels to minimise risk of _bringing

'

'fhorough _cicaning

oi _{hospirai.war<isr roilcis, bcd pans}

ctc, prcvcnrs _{and conr:ols} the spread of disease 'i,v _removing

br.r..i.,

_fr..;i;:

:-,

",".

.

_Using

chlorine_bascci _disinlecrant

to be sure C. dirlic;lcis _destroyed. Any _{otlrer valid points.}

ljdcrccl n 2 Djolo!,y _{lmplcmcntarioI}

3nd Asscssnrcrl _{6uidc for-ltrchcrs !nil.Ji.clttic;rD3}