<span>The embryonic period is the most important phase of development for organ formation. The embryonic period in humans begins at the moment of fertilization and continues until the end of the tenth week of gestation. Rapid growth and differentiation occurs during this period, which produces varied cell types.</span>
<span>Two seafloor plates and a seafloor plate and continental plate.</span>
A physical change could be the plantet and biosphere have a lot more O2 in the air so more organisms can survive and evolve