Because an antibody is "made" relative to the antigen, but kept at low levels when you are exposed the first time ("primary immune response"). The second time you're exposed to the same antigen, memory cells recognize it and the body produces a high level of antibodies, and the level of antibodies usually remains higher for a longer time ("secondary immune response"). This is your basic immune response (primary and secondary).
This explains exactly why vaccines are effective to extremely effective.
Cancer cells reproduce the same way the other cells reproduce. The difference between cancer cells and others is that their reproduction is uncontrollable. They constantly go through the cell cycle and they reproduce. Two ways cell reproductions are meiosis and mitosis. DNA duplicates itself. Cancer is incessantly receiving messages.
Answer:
Habitat Isolation
Explanation:
Ecological, or habitat, isolation occurs when two species that could interbreed do not because the species live in different areas.
