Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased (they have died), or because they never had such functions and are classified as inanimate. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. Biology is the science that studies life.

There is currently no consensus regarding the definition of life. One popular definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve. Other definitions sometimes include non-cellular life forms such as viruses and viroids.
Abiogenesis is the natural process of life arising from non-living matter, such as simple organic compounds. The prevailing scientific hypothesis is that the transition from non-living to living entities was not a single event, but a gradual process of increasing complexity. Life on Earth first appeared as early as 4.28 billion years ago, soon after ocean formation 4.41 billion years ago, and not long after the formation of the Earth 4.54 billion years ago. The earliest known life forms are microfossils of bacteria. Life on Earth is probably descended from an RNA world, although RNA-based life may not have been the first life to have existed. The classic 1952 Miller–Urey experiment and similar research demonstrated that most amino acids, the chemical constituents of the proteins used in all living organisms, can be synthesized from inorganic compounds under conditions intended to replicate those of the early Earth. Complex organic molecules occur in the Solar System and in interstellar space, and these molecules may have provided starting material for the development of life on Earth.Since its primordial beginnings, life on Earth has changed its environment on a geologic time scale, but it has also adapted to survive in most ecosystems and conditions. Some microorganisms, called extremophiles, thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth. The cell is considered the structural and functional unit of life. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells.
In the past, there have been many attempts to define what is meant by "life" through obsolete concepts such as odic force, hylomorphism, spontaneous generation and vitalism, that have now been disproved by biological discoveries. Aristotle is considered to be the first person to classify organisms. Later, Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. Eventually new groups and categories of life were discovered, such as cells and microorganisms, forcing dramatic revisions of the structure of relationships between living organisms. Though currently only known on Earth, life need not be restricted to it, and many scientists speculate in the existence of extraterrestrial life. Artificial life is a computer simulation or human-made reconstruction of any aspect of life, which is often used to examine systems related to natural life.
Death is the permanent termination of all biological processes which sustain an organism, and as such, is the end of its life. Extinction is the term describing the dying out of a group or taxon, usually a species. Fossils are the preserved remains or traces of organisms.

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  1. EHJ

    If you catch a tire slasher they will probably have a knife in hand and try to threaten your life with it for interfering...
  2. Yarome

    Owner of Diversified Machines took his life one day prior to sentencing?

    Damn! I'm seeing this being passed around but no solid verification. Has anyone seen anything that backs this up? Supposedly took a car exhaust nap yesterday just prior to sentencing.
  3. redstar

    Milsurps for life

    Been on the forum for a while but never wrote an intro. Collect milsurp rifles and bayonets mainly. Forums like this are the lifeblood of collecting. Live in the south sound.


    Would like to know what kind of battery life are you getting on your carry pistol. My ROMEOZERO-ELITE On my Glock 43x, Carried all day long gets about 2-2 1/2 months of battery life, only carried during the day. Is this normal, What do you get? THANKS IN ADVANCE.
  5. sagia308

    Three pistols in the mountains couple life primer strikes using that Turkish 9mm

    Feg did good this time
  6. Knobgoblin

    New goal in life

    Having purposely NOT created an intro post, I am deeply and truly inspired by recent events. The exceedingly popular and hotly debated introduction thread of "Smashley the Stripper " actually got the lock . I have to ask. What are the odds? Literally , how many intros are on the books? And how...
  7. Yarome

    Body armor shelf life question

    Just curious. Say, for ceramic type IV body armor, what is it that gives them a limited shelf life? Is there any data on effectiveness rates over time? Are their storage methods (ie., dark and limited airflow) that will effectively prolong the life of body armor or is it a chemical breakdown...
  8. arakboss

    Whey Protein Powder Shelf Life.

    I have a large container of Whey Protein Powder that has a March 2022 expiration date but has been open for over a year. How long will whey protein powder typically last once the seal is broken? Edit: I just mixed up a spoon full in some water and it still taste as nasty as when I first opened...
  9. ilikegunspdx

    Kate Brown releases man convicted of killing teenage girl. He was sentenced to life in prison with no parole
  10. Cavedweller

    Three Sisters coming to life?

    Underground movement has been recorded lately in the vicinity of The Three Sisters. This may be nothing, but in this time of increased volcanic activity around the globe may bear watching.
  11. Lennie

    Life must be returning to normal.
  12. NckChppr

    Ammunition Shelf Life

    Hi all! My grandfather recently passed away and I inherited what can only be described as antique ammunition (some 22lr, 25acp, .38 "wadcutters", - all appear to be from the 70's and a myriad of shotgun ammunition that looks to be from the mid 90's). My guess is that I don't need to worry...
  13. Lennie

    Highway robbery in Nevada, cops use seizure laws to steal a veteran's life savings
  14. G

    Modern Smokeless powder manufactured to have shortened shelf life?

    A friend recently mentioned that during the Obama regime smokeless powder was required to be manufactured with a shortened or set shelf life. That new powder does not last long periods of time. Can anyone shed light or (hopefully) debunk this rumor.
  15. L84Cabo

    John Wayne: 5 Rules of Life

    I mean, the interwebz says that these are his rules so it MUST be true! I believe #4 is my favorite...but #5 is a close second. :) 1. Money cannot buy happiness but its more comfortable to cry in a Mercedes...
  16. Bam

    I opened carried for the first time in my life

    I spent the last two weeks in the free states of Idaho, Montana, and Wyoming. Instead of my normal compact concealed carry piece, I opted for my P229 in a OWB holster, and in some places my 460 magnum in a shoulder holster, grizzly country after all. For the most part, not a single care was...
  17. chukar

    Poor choices in life

    Why anyone would think that taking your summer vacation to Afghanistan this year is beyond me...
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