An atom is made up of protons, neutrons, and electrons in which protons and neutrons are present in the nucleus and the nucleus is overall positively charged because protons are positive and neutrons are neutral.
Electrons in the atom are negatively charged particles that revolve around the nucleus. Due to the attraction between the positive charge of the nucleus and negative charge of electrons the atoms remain together in a compound.
Electromagnetic force generates when any charged particles move in a path. So it has both electric and magnetic force and this electromagnetic force holds atoms together in a compound because moving of the electron generates electromagnetic force.
Earth's birds developed their diversity through natural selection by some birds need to have long beaks if they need to fish and some need webbed feet to swim. They have these traits through natural selection.
