<span>Picture below shows that the most comprehensive barrier is the waterproof layer of skin that covers the body’s surface. If human skin is intact, it keeps the body out of the reach of infections. The picture summarizes physical and chemical barriers against infection. </span>
Since cell division occurs twice during meiosis, one starting cell can produce four gametes (eggs or sperm). In each round of division, cells go through four stages: prophase, metaphase, anaphase, and telophase
