Nnormal exhalation, the diaphragm and intercostal muscles relax to contract the chest, which creates a positive pressure. this is what type of process?

This is the passive type of process.

As the diaphragm relaxes, the pleural cavity contracts, which exerts pressure on the lungs. As a consequence, the volume of the lungs reduces and the air is passively pushed out of the lungs. Exhalation is passive, thanks to the elastic properties of the lungs.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).