List two causes of variation within a gene pool.

Describe how variation contributes to evolution by natural selection.

Outline what is required for speciation to occur.

a. sexual reproduction / random fertilization / meiosis

b. mutation

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

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”.

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