I think the answer is trees
The answer to your question is Fulgeration
The atmosphere is a mixture because it contain many types of gases , liquids and solids.
The answer is; cell surface receptors that are recognized as antigens by the recipient's immune system.
Therefore the organ is attacked as a foreign substance . This is why organ transplants are given by the closest family member to reduce the antigen variability that causes transplant rejection. Tissue typing is done to ensure that the organ or tissue is as similar as possible to the tissues of the recipient.
Answer:
incoming Paleoindians, the first Americans, who allegedly hunted them to extinction.