Anytime you want to describe the selection pressure that would transform dinosaurs into birds, feel free to chime in. Oh, wait a minute, Kotatsu already answered that one. A dinosaur got chased into a tree and it was beneficial for the dinosaur to grow feathers and wings. Hey Kotatsu, was that a female or male dinosaur which got chased into the tree?
Neither. That happened when God was still creating all animals individually, making the necessary mutations by hand.
Is it due to ill will that you display this lack of understanding of simple concepts, or are you like this in real life as well?
Let me explain one more time, while trying to find out exactly what part of the scenario it is you cannot understand:
Over a prolonged period of time a group of small dinosaurs gradually became arboreal.
Do you agree with this?
These arboreal dinosaurs were faced with a dilemma their terrestrial relatives did not have. Their environment contained huge holes; the trees were not a continuous mass as the ground was.
Do you agree with this?
Therefore, to get from one tree to another --- to escape from predators, to get more food, or just to move around --- they basically had two choices. They could either go down from the tree they were in, walk over to the next one, and climb that one. Or they could jump from one tree to another without touching the ground in between.
Do you agree with this?
Conceivably, some choose the former; these are not interesting for us, as they did not provide the ancestors of modern birds. Those who chose the latter, however, are what interests us. They found that when jumping from one tree to another, some always misjudged the distance, was caught by the wind, or something, and fell to the ground. Often, these animals did not survive because of the fall.
Do you agree with this?
The individuals who didn't fall to their death survived. This is a very simple concept, but essential. Some of these surviving individuals reproduced after having moved from one tree to another.
Do you agree with this?
Conceivably, there was a reason why some individuals managed to jump from one tree to another while others fell to their deaths. This reason may have been partly or totally based on the differences in the genome of the individuals.
Do you agree with this?
Over time, a larger percentage of those individuals or lineages which were better at judging the distance, keeping in the air, or possessed other necessary characters for moving about between trees survived to reproduce, whereas those lineages whose judgement or skills were not as good survived to a lesser extent.
Do you agree with this?
The genomes of these lineages, whether they survived or not, changed over time due to mutations.
Do you agree with this?
Some of these mutations provided a change in a character which made it easier to get from one tree to another without falling to your death. For instance, as MrScott showed, a single point mutation in modern hens make their feet grow feathers. While we cannot know the corresponding sequences of these arboreal dinosaurs, we can at least draw the conclusion that changes of this magnitude need to be based on extensive genetic change.
Here, I suspect you will disagree, if you haven't already.
The lineages in which these fortuitous mutations occurred --- and please notice that this is not limited to random point mutations --- were incrementally better equipped to move about in the trees. Thus, over time, they grew more plentiful than those lineages without the fortuitous mutations.
Agree?
As several factors weigh in on the success of moving from one tree to another, mutations which made this process simpler are conceivably numerous. In some lineages, one fortuitous mutation occurred, in others other fortuitous mutations occurred.
Agree?
These lineages could often interbreed, thus "collecting" or exchanging fortuitous mutations by sexual selection (all birds are sexual, and I assume here that dinosaurs were, too). Sometimes, this meant that one or more fortuitous mutation in one lineage was replaced by non-fortuitous ones in the progeny. In other cases, non-fortuitous mutations were replaced with fortuitous ones.
Agree?
The progeny of these latter cases were better equipped for moving about between trees than those of the former cases. This interbreeding continues over and over again, with approximately the same distribution of results.
Agree?
Now for the punch line: In the present case, one or several of these fortuitous mutations caused the "carrying area" of the scales to increase. Again, this is not necessarily a great change, as we have seen. These lineages became the precursor to birds, because these enlarged scales were precursors of feathers. Once this process had started, it was just a matter of what I believe you have referred to as "microevolution": just as different dogs have changed quite rapidly, changes in length and shape of these scales were just minor adjustments, because a character to improve upon had already developed: the scales.
As I have mentioned repeatedly before, this was not necessarily the best way to achieve greater survival to reproduction among arboreal animals, nor is it the only one in evidence today. Several other mechanisms have evolved, and some of them have even evolved on other dinosaurs (see
Microraptor and its four wings, for example). However, that was the way it happened, and these changed scales have since been improved upon until they are well nigh unrecognisable as scales, and the birds well nigh unrecognisable as dinosaurs. But only "well nigh", because upon closer study --- and I am a birdwatcher with a great interest in dinosaurs, so I have taken time to study this closer --- the similarities are enormous. The gait, the stances, the general morphology --- in several different ways it is easy to come to the conclusion that dinosaurs are the ancestors of birds. And like a cherry on top, we also have an extensive fossil record describing exactly this change.
