8 14 Cell reproduction and the cell cycle 14.1 Cell reproduction Countless divisions of a single-celled zygote produce an organism of astonishing cellular complexity and organiza- tion. Any individual cell is bound to die, because cells are subject to wear and tear as well as to accidents. 25 million cells are undergoing division each second in an adult human and blood cells renewed at the rate of about 100 million per minute. If an organism is to continue to live, it must create new cells at rate as fast as that at which its cells die and for some cells, cell division is a special active process that is responsive for a special physiological activity, for example, the reproduction of gonial cells and apical meristem cells of plants as well as the selective proliferation of lymphocytes in immuno-response§ 14 Cell reproduction and the cell cycle 14.1 Cell reproduction Countless divisions of a single-celled zygote produce an organism of astonishing cellular complexity and organiza￾tion. Any individual cell is bound to die, because cells are subject to wear and tear as well as to accidents. 25 million cells are undergoing division each second in an adult human and blood cells renewed at the rate of about 100 million per minute. If an organism is to continue to live, it must create new cells at rate as fast as that at which its cells die and for some cells, cell division is a special active process that is responsive for a special physiological activity, for example, the reproduction of gonial cells and apical meristem cells of plants as well as the selective proliferation of lymphocytes in immuno- response