The 4 factors affect evolution, according to Darwin’s Origin of Species are;
Variation
Heritability
Competition
Differential survival
Variation ensures that there is variability of population traits on which selection pressures will apply.
Heritability means that the traits must be able to be passed down to offsprings through gametes.
Competition occurs when the individuals in the population compete for limited resources
Differential survival occurs due to competition for resources and other selection pressures. This result to the survival of the strongest and weeding out of the weak from the population.