One species does not “turn into” another or several other species — not in an instant, anyway. The evolutionary process of speciation is how one population of a species changes over time to the point where that population is distinct and can no longer interbreed with the “parent” population. In order for one population to diverge enough from another to become a new species, there needs to be something to keep the populations from mixing. Often a physical boundary divides the species into two (or more) populations and keeps them from interbreeding. If separated for long enough and presented with sufficiently varied environmental conditions, each population takes its own distinct evolutionary path. Sometimes the division between the populations is never breached, and reproductive isolation remains intact purely for geographical reasons. It is possible, though, if the populations have been separate for long enough, that even if brought back together and given the opportunity to interbreed they won’t, or they won’t be successful if they try.
2. How can evolution produce complex organs like the eye?
In the process of natural selection, individuals in a population who are well-adapted to a particular set of environmental conditions have an advantage over those who are not so well adapted. These individuals pass their genes and advantageous traits to their offspring, giving the offspring the same advantages. Generation after generation, natural selection acts upon each structure within an organ like the eye, producing incremental improvements in the process. Each tiny change in a structure is dependent upon changes in all the other structures. In this way, individual parts of a system evolve in unison to be both structurally and functionally compatible. Eventually, over thousands and sometimes millions of years, the small improvements add up — the simple, systematic process has produced an almost unfathomably complex organ. Recently, scientists have found clues to the evolutionary pasts of some of the most complex organs, helping to clarify how this process works.
3. Does evolution stop once a species has become a species?
Evolution does not stop once a species becomes a species. Every population of living organisms is undergoing some sort of evolution, though the degree and speed of the process varies greatly from one group to another. Populations that experience a major change in environmental conditions, whether that change comes in the form of a new predator or a new island to disperse to, evolve much more quickly than do populations in a more stable set of conditions. This is because evolution is driven by natural selection, and because when the environment changes, selective pressures change, favoring one portion of the population more heavily than it was favored before the change.
4. Is evolution happening now?
Evolution is always happening, though often at rates far too slow to be observed in a matter of days, weeks, or even years. The effects of evolution can be felt in almost every aspect of our daily lives, though, from medical and agricultural dilemmas to the process of choosing a good mate. In medicine, there’s the question of how long the antibiotics we take now will remain effective, given the relatively fast rate at which bacteria can evolve resistance to drugs. In agriculture, the need to protect this year’s crops is pitted against the concern that doing so will set the stage for insects to evolve pesticide resistance. For all of us, there is the issue of decreasing biodiversity, as most scientists believe that life on Earth is currently undergoing a mass extinction in which 50 percent or more of species will die out. These are just a few examples of ways in which evolutionary processes affect our daily lives.