Feathers are modified as scales. According to the history, birds which have feathers are the descendants of the dinosaurs which have scales.
That's why feathers are categorized as scales in the present record according to studies. <span />
The gradual abundance of oxygen (by product of photosynthesis) made it possible for aerobic organisms to grow more and evolve.
Hope that helps!
Mass number = protons + neutrons
If you have the # of protons and the mass #, subtract the number of protons from the mass number to get the number of neutrons.
If you have the number of neutrons and the mass number, subtract the number of neutrons from the mass number to get the number of protons.
