can anyone?

Question

explain the concept of evolution by natural selection
thx

Answer 1

Put in simplest terms, naturally occuring genetic variation gives some species, and some members of species a competitive advantage over others. Call these variations ADAPTATIONS, and environmental factors NATURALLY SELECT for organisms that have these adaptations, and select AGAINST organisms that do not have these adaptations. Thus, those that survive (the fittest) pass these adaptations on to their offspring, and those that do not have the adaptations, die off. Keep in mind this selection takes many many many years.

The nature of sexual reproduction is to create variation, and variation will be in either "direction of a phenotype" (a person who is 6'0 will have children who are 5'10, 6'0, and 6'2 for example). This is the nature of inheritance.

Now, lets hypothetically say that we were all at one time "species X". The average member of species X can run 6mph. Well, some members can run 9mph, and some can only run 3mph, again by nature of inheritance. Well, if food were running short lets say, or any situation that "selected" for faster species members, everyone who ran LESS THAN 7mph would die, and those who ran GREATER than 7 MPH would survive.

So now when this population of faster runners reproduces (7mph,8 mph, 9 mph), their offspring will run, again by nature of inheritance, maybe between 6mph - 12mph (as opposed to 3mph - 7mph). Lets call this group now SPECIES Y.

Suddenly, perhaps more food is available, and speed is no longer a selective advantage. Well, variation will continue to occur, but this time, slower members will not be selected against. So, some will continue to be slower, and some will get faster. The ones who get faster, are Species Z. The ones who didnt get faster, remain Species Y. But both have survived because nothing has selected against them!!!

So looking at humans and their "evolutionary predecessors", remember that humans have slowly been removing themselves from any competition with apes. Only this time don't look at speed, look at many many traits (intellience, walking on 2 legs, opposable thumbs, etc.) We have been able to find our own food, and are involved in littlle competition with them for quite some time now.

When thinking about evolution, you must think BIG PICTURE. That's how I always saw it. You must think who is gaining SELECTIVE ADVANTAGES because of ADAPTATIONS FOR SURVIVAL, and who is going to be at SELECTIVE DISADVANTAGE based on COMPETITION AND LACK OF SURVIVAL.