Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
Answers to end-of-chapter questions
b distribution for one mark:
malaria occurs between the tropics / tropics
and sub-tropics / in equatorial regions / South
and Central America, Africa and S-E Asia;
explanation for four marks:
Anopheles / mosquito / vector, distributed
throughout tropical regions;
Plasmodium falciparum cannot complete its
life cycle within mosquitoes at temperatures
less than 20 °C;
Anopheles, needs high rainfall / high humidity
/ standing water;
Anopheles lays eggs in water;
no transmission at high altitude;
too cold for parasite to complete life cycle;
no transmission in deserts;
no breeding grounds for mosquitoes;[max. 5]
c Plasmodium is intracellular parasite;
inside, red blood cells / liver cells;
antigenic concealment;
antibodies are ineffective;
short stage in plasma when antibodies are
effective;
Plasmodium is eukaryotic;
has many, genes / antigens;
difficult to develop a vaccine;
resistance to drugs used, to treat malaria / as
prophylactics;
example of drug;
Anopheles / vector, breeds in small pools of
water;
difficult to control all breeding places;
mosquitoes come into contact with humans;
mosquitoes become resistant to insecticides;
[max. 6]
[Total: 14]
8 a bacteria pass out in faeces of infected
person;
carried in, water / food, consumed by
uninfected person;[2]
b i 2.22;[1]
ii treatment for cholera involves supply of
oral rehydration therapy;
and provision of safe drinking water;
better response to emergencies (in some
countries);
effectiveness of response may depend on
number of cases;
ref to very high number of cases in Haiti;
may depend on remoteness of regions
affected by cholera;
or ways in which, emergency supplies /
personnel, can reach affected areas;
ref to high case fatality rates in, Nigeria /
Cameroon;
use of data to compare case fatality rates
in individual country with global rate;
[max. 3]
iii cholera is a serious disease;
death can occur very quickly after infection;
spreads quickly in population (especially
after a disaster);
deaths are avoidable;
if ORT is available immediately;
data is useful to predict, situations /
places, where cholera may occur;
WHO can coordinate responses to
outbreaks; [max. 3]
c i infected person travelled from an area with
an outbreak of cholera;[1]
ii water supply is not contaminated with
(human), sewage / faeces;
piped water / water supply is treated to
kill bacteria;
V. cholera destroyed in sewage treatment;
[max. 2]
[Total: 12]
9 a i Mycobacterium tuberculosis; accept
Mycobacterium bovis[1]
ii infected person, coughs / sneezes / spits;
aerosol / droplets, containing bacteria,
breathed in by uninfected person;[2]
b i Sub-Saharan Africa;
South-East Asia;
countries of, old Soviet Union / Russian
Federation;
India / Pakistan / Afghanistan;
South America / Bolivia;
Papua New Guinea; [max. 3]
ii TB linked with HIV infection;
HIV weakens immune system;
TB is an opportunistic disease;
Cambridge International AS and A Level Biology © Cambridge University Press 2014