1Diversity and Universality of Organisms

It is hard to give a concise definition of exactly what life is. One might define it as the dynamic equilibrium of “living” itself, while others might say it consists of entities with the hierarchy of substances, cells, tissues and individuals. Some may even identify it as a machine coded by DNA or a vague existence with the soul. To allow the simplest possible expression of the basics of life science, this chapter deals with the following topics: what organisms are; how they came into existence and evolved into their current diversity of biotic groups; the principles common to all organisms; and the constituents and functions of cells, which represent the smallest unit of an organism (in other words, the substances that constitute cells and what their functions are). The account places particular focus on the diversity, uniformity and hierarchy of organisms.

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