4.0: evolution

Question 1

how does variation occur

Answer 1

1. spontaneous mutation (formation of new alleles)
2. meiosis (recombination of existing alleles)
3. random fertilisation (zygote formation, recombination of existing alleles)

Question 2

smallest unit of evolution

Answer 2

population

• forces of natural selection act on individuals
• individual organisms CANNOT exhibit genetic variation and cannot evolve
• allele freq changes over successive generations

Question 3

types of natural selection: directional

Answer 3

NS acts against 1 extreme that is disadvantageous

• gradual shift in average

Question 4

types of natural selection: stabilising

Answer 4

NS act against 2 extremes
intermediate phenotype favoured

• reduced variation in trait
• more uniform population