It is true that natural selection & speciation leads to evolution.

i. The origin of species from pre-existing one leads to speciation of species

ii. Some individuals will be better adapted to the environment than others and will therefore be more likely to breed and pass on their alleles to the next generation, which is called as variation.

iii. This means that each population will begin to evolve different adaptations to suit their environment

iv. With time, this genetic drift, will accumulate different genetic variations leading to evolution of species.