2018

Question 1

The teacher told the students they should not investigate the growth of bacteria at 35 °C.
Suggest why the teacher told them not to grow bacteria at 35 °C.

Answer 1

it could encourage the growth of human
pathogens

Question 2

The teacher also suggested that the students should have carried out the investigation
using three flasks at each temperature.
Explain how this suggestion would have improved the students’ investigation.

Answer 2

reduce impact of , anomalous / AW , results 
measure / increase / show / ensure , repeatability 
allow , calculation of standard deviation / (named) statistical
test 
(calculated) mean likely to be , more accurate / closer to true
value (than individual value) 

Question 3

A student looked at Fig. 20.1 and wrote:
“The longest male cheetah that was measured was 1.52 m long”.
Explain whether the information in Fig. 20.1 supports the student’s answer.
the figure shows the top of the sd bar at 1.52m

Answer 3

No, because…
idea that standard deviation is not the same as range 
SD does not include all
outliers / error bars don’t show range

Question 4

can anything be concluded about the significance of differences if theres no stats test

Answer 4

little / nothing (can be concluded) 
because no (named) statistical test done

Question 5

Explain why a genetic bottleneck can lead to low genetic diversity

Answer 5

(many) alleles lost (when population dropped)  ora
(modern population) descended from few survivors /

Question 6

Explain why genetic drift is likely to be of particular concern in the population of 100
cheetahs in Iran.

Answer 6

idea that one individual or allele has proportionally higher effect
on small population 
(more likely that) alleles will be lost from population 
(population) more vulnerable / likely to become extinct due , to
environmental change / AW 

Question 7

When the island of Madagascar became separated from the African continent, there
were no members of the cat family, Felidae, on the island.
Outline how a fossa could have evolved from a much smaller, mongoose-like ancestor

Answer 7

allopatric speciation 
different , selection pressure / environmental conditions (from
mainland) 
(random) mutation 
(fossa-like) individuals with , mutation / (new) feature ,
survive / reproduce  ora
beneficial / AW , alleles passed on 
directional selection 

Question 8

Islands, such as Madagascar, often have species that are different from those on the
nearest land mass because they are reproductively isolated.
State three other conditions that must be present in order for speciation to occur.

Answer 8

mutation / genetic diversity 
natural / directional , selection 
idea that environment / selection pressure , is different from the
‘other’ population 
time

Question 9

what are some bacterial growth requirements

Answer 9

bacteria need (named) elements other than C and H

example of other element linked to use in bacterium e.g nitrogen

absence of other elements is a limiting factor (for
bacterial growth)