In ecological competition, two members of the same of different species compete for the same resource. In this example, a falcon and an eagle compete. Other resources beside food are water, shelter, sunlight, etc. depending on the biome. Whichever species or organisms can better suit to the environment and use its adaptations survive, and they are the ones who pass on their genes to the next generation. Whoever do not, their genes fade away. Over time, this gradual change causes impacts on the gene pool.
Here, we have reproductive isolation. Although there is a cool combination, the new Donkog cannot reproduce. This is because a dog has 39 chromosomes. With this variance, it becomes impossible for it to reproduce due to problems in even tetrad splitting. In addition, other Donkogs don't have homologous chromosomes to the Donkog in this picture.
Behavioral isolation also occurs. The male tries to attract the female with a song. However, the female does not respond to that song. These two then do not mate, mate another bird, and then forms different adaptations and evolutions. This is due to a difference in their breeding rituals.
Here is geographic isolation. In this instance, the allopatric barrier(road) prevents these two organisms to mate. They find other mates, food sources, ways of life, no natural selection, etc. After a long period of time, these two organisms become two species.
If you really loved me, you would cross over this road...
With temporal isolation, the example here is of two different toads, each of which mate in different seasons. This is a form of isolation through timing of breeding. Due to this, these two animals/species never breed and become more and more different over time or develop two new species if the original two were part of the same species.
Maybe next summer.....
Mutations, usually one slight change in an allele or gene can cause a mutation. When that organism reproduces, it creates more offspring with those genes. This cause adaptations and evolution in the end.