Random mutation's role in the length of a giraffes neck and other animal traits?

Question

Let say 5 million years ago the giraffes ancestor's neck was 2 inches long, then a random mutation occured that made one giraffes ancestor's neck a couple inches longer and then that individual could eat leaves higher in the branches and survive and pass on the genes. Today the giraffes neck is like 60 inches or longer, so does this mean that an additional random mutation needed to occure for each incremental increase in the giraffes neck. For example the neck was 2 inches, then 4, then 6..... and so on, with an individual random mutation responsible for each increase. Or was it just ONE initial random mutation that occured 5 million years ago and the rest of the length increase in the neck occured because of other reasons.

Answer 1

No, no, no. You're missing the basic point of how natural selection works.

You start with VARIATION. In all the world's population of giraffes, there are a range of neck lengths, some short, some long, most at some range in between. This does not have to be the result of mutations ... just basic variation that we see in all attributes (some of us are taller, some shorter).

If more giraffes are born than can survive, and eat the right kind of vegetation, then the taller ones may live a little longer and/or produce more offspring. This could be because a long-necked giraffe can eat from both tall and short branches, while short-necked giraffes can only eat from short branches ... so the long-necks can survive a drought better. Or it could be that female giraffes develop a preference for mates with longer necks (this is called sexual selection). Whatever the reason, those giraffes at the taller end of the range consistently do better than those at the shorter end ... so after millions of years, you have *very* tall individuals.

Answer 2

It really comes down to the "survival of the fittest" in all circumstances. Giraffes would have had necks of all different lengths, but the only ones to survive would have been the ones with the neck long enough to reach the branches for food and long enough to reach the ground for water (due to the size of their legs). The other types would have eventually died out.

Answer 3

Giraffes didn't have to stretch their necks to get food on trees but as time went with scarcity of food they began to stretch their necks.This best explained by Darwin's theory in Variation.When body parts are not used for a long time,they go away but body are used,they are maintained but in a different shape or length.I hope i didn't miss.It's been a long time since i got that.

Answer 4

Any and all changes in an organism are caused by random mutations or other genetic "mistakes". So to answer your question, the initial lengthening as well as any successive lengthenings were each caused by a separate mutation.