Each cell is alive even if it is part of a multi celled body, and all living organisms consist of one or more cells. Also, cells reproduce by dividing so it follows that all existing cells must have arisen by division of other cells. As a cell divides it passes it hereditary material- its DNA- to offspring.
Flowering plants produce male and female cells. The male cells are called pollen and the female cells are called ova. When a flowering plant is fertilized, it produces offspring in the form of seeds. However, not all plants reproduce flowers. Simpler plants, like mosses, lack these specialized structures.
Stem cells are very controversial for several reasons. Mainly, because stem cells need to be harvested from Embryos, which raises a huge ethical debate as to weather the (scientifically speaking, alive) embryo harvesting is not cruel and twisted, as these are human beings that are being used. Another ethical issue is that it is related to human cloning, and often times stem cells are mislabeled. Not to mention that there is an argument for the idea of cloning humans to be used for limb replacement, throwing everybody in a tizzy. Overall, one of the greatest medical acheivements of recent years has lots of issues that haunt it.
The human respiratory system<span> is a series of organs </span>responsible<span> for taking in oxygen and expelling carbon dioxide. The primary organs of the </span>respiratory system<span> are lungs, which carry out this exchange of gases as we breathe.</span>
