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Date November 2016 Marks available 3 Reference code 16N.2.HL.TZ0.4
Level Higher level Paper Paper 2 Time zone TZ0 / no time zone
Command term Describe Question number 4 Adapted from N/A

Question

List two causes of variation within a gene pool.

[2]
a.

Describe how variation contributes to evolution by natural selection.

[3]
b.

Outline what is required for speciation to occur.

[3]
c.

Markscheme

a. sexual reproduction / random fertilization / meiosis

b. mutation

No mark for crossing over unqualified.
Reject natural selection/evolution as causes of variation.

a.

a. (variation is) different phenotypes/differences between individuals in a population/species

b. struggle/competition for survival

c. some individuals have advantageous characteristics/are better adapted/have greater chance of survival/reproduction (than others)

d. favourable alleles/genetic variations passed on/inherited by offspring/next generation

Reject “pass on phenotypes”.

b.

a. divided species/gene pool / part of species/gene pool becomes separated / species splits into separate populations

b. reproductive isolation / lack of interbreeding 

Mark point b refers to a lack of interbreeding between separated populations in a species, not the lack of interbreeding after speciation.

c. may be due temporal/behavioural/geographic isolation

d. different natural selection/different selective pressures

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 5: Evolution and biodiversity » 5.2 Natural selection
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