Organism

An organism is a living being that arose through a process of natural evolution by natural selection and is composed of organic materials, or which may have originated through other means but bears anatomical and histological similarities to such naturally evolved beings. The common flora and fauna of most terrestrial worlds consist entirely of organisms; many intelligent races are also organisms, including humans.

The study of organisms is called biology. Sometimes "biology" is used to refer to the study of life in general (more usually called etory), and the study of organisms in particular is called "eubiology", but this usage, already in the minority, has been declining.

Classification

All organisms belong to the universe of Asceuastoe (pronounced /æsˈkjuːəsti/), and accordingly are sometimes called Asceuastans (pronounced /æsˈkjuːəstən/)—though quite rarely, and generally only when the intent is to make it perfectly explicit that only true organisms are under discussion (as, particularly on worlds where other forms of life are nonexistent or unrecognized, the word "organism" is sometimes used more broadly to also refer to other life forms, if only hypothetically). Within that universe are different alliances based mostly on chemical composition and in particular on the nature of the genetic code. Humans, for instance, along with all other Terran organisms, belong to the alliance of Spirileges. The alliances are further subdivided into empires according to independent developments of life; usually this means one empire per mound, though it's possible for life to spread from one world to another leading to the same empire being represented on both, or (rarely) life may arise twice independently on the same world. Sometimes Asceuastoe is classed with the (dubious) universe of Hathroa (perhaps along with other universes even more dubious) into the superuniverse of Autoctista.

Anatomy

Though there is much variation in the anatomy of organisms, there are some common threads. Most macroscopic organisms are characterized by a division into cells—essentially smaller organisms that have formed colonies that compose the whole organism. (Microscopic organisms consisting of independent single cells also exist in all known empires of Asceuastoe.) The makeup of cells varies between empires (and to a lesser degree within an empire), but most consist of some sort of protoplasm held within some kind of shell or membrane, and containing various smaller structures called organelles, as well as the cell's genetic code (which may or may not be sequestered within a nucleus.)

Above the level of cells, similar cells are organized into suites called tissues, which often occur in sheets. Several tissues may compose an organ, a more or less discrete part of the organism which performs a particular function, such as the heart or the brain. Finally, the organism itself comprises a number of organs—although the philosophy of hathroics holds that this is not in fact the top level, but that organisms themselves can in turn be components of living structures called hathra.

Life cycle and reproduction

Most organisms reproduce through either binary fission or sexual procreation. The former is more typical of small, single-celled organisms and the latter of the more complex organisms, though this distinction certainly is not universal. Other forms of reproduction such as parthenogenesis do exist, though usually as secondary abilities of organisms that also reproduce sexually. It is not uncommon for an organism's offspring to be very different from its parent, but to in turn give rise to an organism similar to the parent it disresembles, a phenomenon known as alternation of generations.

In any case, except in the case of the reproduction by replication of multicellular organisms, most organisms begin as a single cell, which then gradually divides and differentiates as the organism ages. Many organisms at one or more points in their life cycles undergo a dramatic change in form, a process called metamorphosis.

With the exception of some simple organisms that, roughly speaking, have few parts to wear out, most organisms eventually pass their physical peak and degenerate, a condition often called "old age" but more technically known as senescence. This may occur due to a variety of processes, most involving either depletion of necessary parts or substances, or overaccumulation of substances harmful in excessive quantities. While senescence may not be a direct cause of death, it may weaken an organism enough to leave it vulnerable to other conditions that would be easily withstood by a younger, healthier body. Although senescence can be arrested or even reversed by advanced magical or medical means, it is not trivial to do so, and on the majority of worlds most or all organisms are doomed to "die of old age".

See also

• Organism on Wikipedia