the answer is chemical reaction
Organisms<span> regulate complex systems through chemical interactions through feedback mechanisms. The feedback mechanism can respond to perturbation either as positive feedback (the same direction) or a negative feedback (opposite direction). The contractions in childbirth is an example of positive feedback. The hormone oxytocin is released in the body when contraction begins to further aid the contractions. An example of negative feedback is the regulation of blood glucose level. The continuous rise of blood glucose level may lead to diabetes.</span>
The condensation of water vapor formed the early oceans. It is an important part of the water cycle. It is easy to eliminate the other answers in this question. It can't be meteorites, living organisms, or nitrogen.
All cells have cell membranes, and the membranes are flexible. So animal cells can have various shapes, but plant cells only have the shapes of their cell walls. That's nice for plants, because it gives them the ability to grow up and out, where they can get lots of sunlight for making their food.
A version of a trait that requires a homozygous genotype for expression is called a recessive allele.