What is Genetic Recombination and Evolution ?
Variation among the offspring of living organisms results from genetic recombination through sexual reproduction and mutation. Variation among offspring is important because variation is the driving force of evolution. In other words, if generations of offspring were exact "clones," or replicas of their parents in every way, over long periods of time these successive generations, which remained unchanged, would have exactly the same tolerances or abilities as the original parents.
We know that environmental conditions on Earth change over long periods of time. For instance, over the course of the Earth's life, temperature ranges can get lower or higher. Food resources can become scarcer, and predators or diseases can become more efficient. So if all the offspring were the same, generation after generation, they would have exactly the same tolerances to lower or higher temperatures in terms of reproductive ability. Then, if the Earth's temperatures gradually became too cold or too hot for them to reproduce effectively, the population might decrease: all of the individuals would be equally susceptible to higher or lower temperatures, and be unable to reproduce healthy offspring, if at all.
The same phenomenon can easily apply to other factors. For instance, if there were no individuals among the offspring that could eat a different food source and survive, the population would dwindle when their primary resource gradually got used up. Or if none of the individuals among the offspring were able to run a little faster to escape predators, they would all eventually fall prey to the predators. And if some of the population did not have higher resistance to diseases, the entire population would be equally vulnerable, succumb to sickness, and not be around to reproduce after a while!
However, if genetic recombination resulted in offspring that included several individuals different (adapted) enough to survive the changed environment over the course of many generations, they might survive the changed conditions and live to reproduce. In this way, each successive generation that produces varied offspring is able to change over time, carrying on the species.