By: Jose Damian Sotomayor Casale
Specie variation by definition is explained as any difference or diversity within a species characteristics. To explain this better we are going to use the Axolotl specie as an example. The characteristics that varies in the specie is their color. Due to certain factors a Axolotl's pigment varies from a mosaic, albino, or copper. This is a signal of evolution happening in a physical characteristic of this specie. Without this changes some of the Axolotls would have been unable to survive due to their unfitting color, this way their population can strive.
Knowing this happens to each species in a moment of their life they will pass this characteristics to their offspring. In the case of the Axolotl the color would be passed down through DNA helping spread and increase the number of this characteristic in the specie. This way they can ensure this characteristic survives out in the wild, spreading and combining with other physical and chemical qualities.
Knowing some of the environmental factors wont favor all the offspring it is destined (most of the time) only the most fitting to this place would survive. For example one Axolotl could have been born with a lower level immune system resulting in death. Although it is something sad we now know this problem of a weaker immune system wont affect other future Axolotls since it did not have the chance to reproduce. The fact that something can reproduce and survive are directly linked, it is for the own good of the specie.
Extinction is what comes after survival. Those who do not suit their environment will most likely end in extinction. For example if some place were to change to be dryer for some external factor a certain animal can have a harder time coping with higher temperatures, affecting its body system resulting in a body system failure and then death. The number of such specie would decrease in such matter making finding a partner harder thus diminishing the number further, until there is no individual left.