The factors in the evolution of any organism are too numerous to list. After all, natural selection guided not just the evolution of the giraffe from its immediate precursors, but also the evolution of those precursors to their precursors, and so on. But if you're asking why the giraffe evolved such a long neck, then there are a number of hypotheses to consider. For instance, the giraffe's neck might have lengthened due to competition over foliage (food) with other grazers. Or it might have lengthened due to sexual selection - potential mates favouring those competitors who might win a headfight with a rival. Or it might have evolved due to the pressure of predation - those giraffes with a longer neck sooner being able to spot a predator. Any of these is possible - and it might be that the giraffe's neck evolved due to a combination of these.
It seems that giraffes have been naturally selected to have long necks.
natural selection
Adaptation is the result of natural selection.
by natural selection.
Yes, natural selection is always occurring.
Natural selection can only work on genetic variation that already exists. So mutation comes first, then natural selection.
Its NaTuRaL sElEcTiOn if you didn't know.
natural selection
Adaptation does not allow for natural selection: natural selection causes adaptation.
yes elephants have large ears to cool down.
Genetic variation in itself does not 'support' natural selection: it is what natural selection acts upon.
Natural selection is what causes adaptation.
No, natural selection is the mechanism that drivesevolution.
Adaptation is the result of natural selection.
Natural selection.
Natural Selection
That selection was natural.
Natural selection