The green lizards that can eat more ants live longer and are able to reproduce passing on their traits.
Change starts to happen
The lizards in this forest mainly eat ants. There is variety in this population of lizards. Some have a better shaped mouth to be able to dig into the ground to get the ants. The lizards with the spots have a broader mouth and are not able to get ants as well.
The yellow spotted lizards can't get food so they start to die off and they can't stay alive long enough to reproduce.
In this generation the yellow spotted lizards become less adapted in the population.
Eventually, the trait that allows the lizards to eat ants becomes more common. The yellow spotted lizards are almost gone form the species because they can't get enough ants to live and reproduce.
Because the green lizards are more successful they become more numerous in the population.The green lizards are the only lizards in the population now because of their advantage in getting ants and passing it through the generations.