Life Definition and 1000 Threads

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.

View More On Wikipedia.org
  1. Wrichik Basu

    Studying How to prepare for a life in research?

    I am student who wants to do research in physics, and aims for a life in research. Being in the final year of high school, I do not get a lot of time to devote to my passion - physics and related experiments. About 30mins in a day can be spared for extra studies, and I utilise this time fully...
  2. S

    Pressure Half-Life: 2L vs. 5L Containers

    Homework Statement A two litre sealed container is filled with air at atmospheric pressure. It is connected to a vacuum pump which can pump air at a flow rate that is proportional to the difference in pressure within the container to the pressure outside. This tells us that the pressure drops...
  3. V

    Engineering Is a Career in Academia Worth the Sacrifices?

    I am about 30 years old and I have come to realize I do not really enjoy my work. Actually, it is more like I do not enjoy working life. But studying was something I did enjoy very much (not student life, but actual studying). I miss the mathematics that was so strongly present when studying. I...
  4. A

    Misc. Interference Between Two Speakers -- Real Life Version of a HW problem

    Hello, Many of you are familiar with the homework problem that goes like the below, and though straightforward to solve in most general physics homework sets, I need to help getting it to work, which is not so easy in real-life. Consider two speakers separated by 2.0 meters. Find the points...
  5. jedishrfu

    Could Quantum Artificial Life Unlock the Secrets of Evolution?

    For the first time, an international team of researchers has used a quantum computer to create artificial life—a simulation of living organisms that scientists can use to understand life at the level of whole populations all the way down to cellular interactions. With the quantum computer...
  6. Hercuflea

    Half life from two identical radioactive sources cpm

    Homework Statement " Independent measurements are taken on two identical radioactive samples. On the first radioactive sample, a radiation detection system measures N decays on a radioactive sample during a total period of T. On the second radioactive sample, a radiation detection system...
  7. José Ricardo

    Other hypothetical types of life

    is there any sci-fi that would rerate a life based on ammonia or silicon or any other type of life?
  8. U

    Thoughts on magnetic fields and life on planets.

    After reading about Jupiter's magnetic field on ScienceAlert, I remembered another article about tree bark and magnetic anomalies (links below). I also remembered an article on birds being able to see magnetic fields as well. It got me thinking of how and if life is possible on anything other...
  9. Marco DF

    B What is the Role of Sub-Particles in the Existence of Matter?

    Hi everyone! Here the question(s). In the vacuum, the sub particles pop up and down (annihilation). If this is right, we can tell that the all matter is the attempt of sub particles to remain alive? so, is my glass of wine a desperate attempt of electrons, quarks, and all the other particles...
  10. D

    B The Mystery of Life: Exploring the Origins of Existence

    By latest estimate... how many billions of years after the Big Bang before life became possible? 2 billion yrs? 5 billion yrs? 7? And why?
  11. A

    Asteroid Impacts and Life on Earth

    Scientists say when asteroids showered on Earth they were the ones who brought water to Earth which started life. But how did few molecules of water started life on earth?
  12. T

    570 million year old animal life form

    Seems that us animals got an even earlier start than we thought. Short popular version: https://www.livescience.com/63289-ediacaran-leaf-fossil-is-animal.html Longer version: http://www.dailymail.co.uk/sciencetech/article-6043177/Animal-kingdom-OLDER-previously-thought-scientists-reveal.html...
  13. W

    How is physics knowledge used in everyday life?

    We all know the question: why do I need to know this? I have been thinking recently about how to add relevance to my curriculum. What I am struggling to come to grips with is how knowing physics, the topics typically taught in a high school intro course, can be useful in everyday life. I am not...
  14. N

    Which ideas do you think are intriguing?

    Looking in the mirror I just got a glimpse at the definition of a limit(Calculus) plus the beginning of calculus (Derivates & Integrals) then comes the usual goosebumps followed by a smile.And you? Which ideas are interesting for you to share?
  15. Krushnaraj Pandya

    Real life problem about angular momentum conservation

    Homework Statement suppose you're sitting on a rotating stool holding a 2kg mass in each outstretched hand, if you suddenly drop the masses, will your angular velocity increase, decrease or remain the same? Homework Equations dL/dt=net torque when net torque is 0, L=constant=Iw therefore...
  16. F

    I Real life example of the energy contained at E=γmc^2

    We've just begun studying about relativity, and I find it amazing that bodies have the energy of E=γmc^2. Even at rest they have E=mc^2. But where exactly is this energy present in real life? For example the keyboard I am currently typing this post with has a huge amount of energy, according to...
  17. avischiffman

    B Real-Life Demonstrations of Black Holes for Video

    Hi, I am working on a video, and I was wondering if any of you knew of some real-life demonstrations I can do about black holes? So far I have the gravity well, and the balloon covered by foil that you crush to show same mass but denser. My video is about the anatomy of a black hole, so I cover...
  18. N

    I What Happens When a Black Hole Reaches the End of Its Life?

    When a black hole is mostly evaporated and it starts to evaporate faster and faster, what will this look like? How big when they start to emit visible light and how long from then until finally gone? Will these be like cosmic level bursts or quiet fizzle?
  19. M. M. Fahad Joy

    Other What Should I choose for my career, as my aim in life?

    To become successful in life, I must choose a definite aim of my life. But what proffession should I choose?
  20. S

    I Did astronomers just lengthen the expected life of the Sun by 5 Gy?

    I had always thought that the Sun was about midway through its regular lifetime (i.e., before it becomes a red giant), but this article seems to say that instead of having another 5 Gy until then, it will be another 10 Gy. https://www.yahoo.com/news/scientists-sun-apos-death-even-164400014.html...
  21. Stephenk53

    What was your biggest regret in life

    What was your biggest regret in life that you are okay sharing. Mine was not taking almost any AP or honors courses in high school. I would likely have more scholarship money if I did take more and I would know more. Also if you do not want to say your biggest regret but want to say something...
  22. ISamson

    Do animals have life goals or wishes?

    Hello. I know that many humans have lifelong goals, like becoming an engineer, winning the Nobel Prize or something. But do animals have the same? I understand that the goal of all living things is to give a successful and prospering offspring, but do animals and living things other than us have...
  23. jim mcnamara

    Psychology: How will we react to discovery of alien life

    Jung Yul Kwon et al, How Will We React to the Discovery of Extraterrestrial Life?, Frontiers in Psychology (2018). DOI: 10.3389/fpsyg.2017.02308 https://phys.org/news/2018-02-humans-react-pretty-news-alien.html#jCp Answer: probably well (this is a limited pilot study) The pilot study analyzed...
  24. Space_Girl

    B Life Outside Our Planet Without Oxygen and Water

    Hello everyone :) I have a question.Is it possible for life to exist in other planets without oxygen and water? I mean just because we need it to survive here on Earth.It doesn’t mean all planets need it to support life as well.
  25. JonMoulton

    New Life History Simulation Modeling Platform

    mod: approved HexSim Life History Simulation Modeling Platform - free to download. Landscape ecology, anyone? After >10 years of development, the HexSim life history simulator is ready for use by students and researchers.HexSim is a free, versatile, multi-species, life history simulator ideal...
  26. G

    Could 'aliens' already know there's life on Earth?

    We can indirectly measure the atmospheric composition of worlds outside our solar system. Suppose there are aliens out there. On their world, they use the same technique we use to measure the atmospheric composition of worlds. Suppose they turn their telescope on Earth. Is it possible they...
  27. AbstractlyAlgebraic

    Programs I need some life advice about possibly changing my major.

    Ok, so I'm a third year math student, and... I don't like it. It's just really not for me. I took Real Analysis and hated it. I took Abstract Algebra and hated it. I took Complex Analysis and hated it. I know it's supposed to be beautiful or whatever, but I just don't care at all, and I am...
  28. R

    Should We Develop a Unique Terminology for Alien Lifeforms?

    https://phys.org/news/2017-12-genes-space-successfully-unknown-microbes.html While debating the issue of clickbait headlines, I remembered that recently the Russians had embarrassed themselves with such a leap of flying unicorns...
  29. jedishrfu

    Frank Abagnale Talks about his Life

    Frank Abgnale of the Catch Me IF You Can movie fame talks about his real life for Google: He's worked for the FBI for 40+ years as a specialist in cyber crime. Its a very interesting talk. Here's a biography.com profile on his life too. https://www.biography.com/people/frank-abagnale-20657335
  30. BillTre

    Evidence for Early Origin of Life on Earth

    Science news reports: (original report abstract here) Eleven micro-fossils though to be the remains of bacteria (some dispute this) from Australia dated to 3.5 billion years ago have been analyzed with secondary ion mass spectrometry (SIMS). This has revealed different ratios of different...
  31. TheQuestionGuy14

    Could Time Travel In Fiction be applied to real life?

    I've watched a lot of time travel movies, most are just pure sci-fi. Bht some movies use parallel universes to explain the time travel in the plot. Here's where my question comes in: Say if time travel ever was invented, but it created parallel universes when people went back. Would this mean...
  32. wolram

    B Life is less likely on exoplanets

    https://www.sciencedaily.com/releases/2017/11/171130180031.htm However, the question of habitability is highly complex. Researchers led by space physicist Chuanfei Dong of the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University have recently...
  33. L

    B Life on a planet near a black hole

    Suppose life would evolve on a planet near a black hole, like the water planet on Interstellar. And just like on Earth, they eventually discover a theory of relativity and also how to send a rocket away from planet/black hole and back. Could they take advantage of the huge time dilation between...
  34. N

    What is the Mass of a Sample Given its Half-Life?

    Homework Statement http://d2vlcm61l7u1fs.cloudfront.net/media%2Ff62%2Ff62b6919-e60f-405b-81fb-2323ceeb03ee%2FphpsL4bVl.png Homework Equations So I need that in micrograms tho. So 4402*10^-18/1000=4.4*10^-18kg. or 4.4*10^-12 micrograms that stills say it's wrong tho.
  35. ISamson

    Is water really necessary for life?

    You know how they always say that without water there would not be life, right? Astronomers also look for life on planets with hints of water in their spectrum. But is water really necessary for life? Some ET life could not be a tiny bit similar to ours and might not even need water or water...
  36. F

    Phase diagram of water in real life

    Hello, All substances that are either in the liquid or solid state have a small vapor pressure which implies that they are always slowly (solids especially) evaporating and turning into a gas (vapor). The phase diagrams of water and carbon dioxide indicate only states (P , V) of pressure and...
  37. ISamson

    Do you think ET life exists elsewhere?

    Hello. Recently looking through the numerous articles on space.com I came across the interesting news that a few months ago a team has sent a 'message' to the GJ 273 system 12 light years away. What do you think? Can we expect an answer in 25 years? Thanks. P.S. Please take time to read the...
  38. Grands

    Schools How to achieve the best results in life

    Hi guys. I opened this thread to ask opinion about people that have more experience them me about his argument. I'm 19, last year of high school. I was always a person that study a lot, and I dedicate all myself to the school. I always tried to do my best in every subject I had to study at...
  39. P

    Protein melt temp/half life relation?

    Is anyone familiar with a way to determine the half-life of a protein from its melt temperature (Tm)? It seems like there ought to be some sort of correlation, be it theoretical or empirical.
  40. S

    B Should we search for non-biological "life"?

    I am very interested in Astrobiology and just came across this 7-year old abstract by Seth Shostak (of SETI): http://www.sciencedirect.com/science/article/pii/S0094576510002195 There is a lot of emphasis on searching for biological life outside of our solar system, especially with the...
  41. Greg Bernhardt

    Proofs and facts in science, math and life

    Warning! Laymen reasoning ahead :) I've long heard that in science nothing is proven. That proof is a mathematical term. So what exactly do you call a certifiably known fact? An example is that the Earth is round or at least that the Earth is not flat. What do you call that? Can we not say it's...
  42. C

    I Real life application of Euler's method/numerical method

    Hi! For my math investigation project, I was trying to predict the trajectory of an object in a projectile motion with significant air resistance by using the Euler's Method. But it seems like the differential equation involved there can easily be separated into different variables, and so it...
  43. Z

    Studying Is it possible to understand quantum mechanics in student life?

    QM is gradually conquering my mind day by day. i can't think anything expect it. i always thinking while eating,before sleeping,in classroom,while outside. my college performence is badly affecting as QM is not in my course. i just want to understand anyhow_could anybody guides me to understand it.
  44. S

    What drives a polymath's insatiable curiosity and love for scientific method?

    I am a total geek, that is to say I am totally and obsessively interested in absolutely everything that might submit to scientific method, and a few wild cards (penny shares?), that I keep an eye on. And always have been, for sixty years now. Not being an idiot two things excite me most, 1) a...
  45. R

    Intelligent life other than on Earth

    What do you think?
  46. S

    Physics Find Your Path in Physics: 3 Ideas for a PhD

    Hello! I apologize if my question is not really related to the topic of this page, but I would really appreciate your advices. So I want to do theoretical physics for my phD (mainly BSM physics) and I need to present to a non-science public, for a scholarship, 3 ways in which I want to...
  47. A

    Job Skills What Masters Degree Should I Pursue as a Biology Major to Advance My Career?

    hello! So i have been working in manufacturing (aseptic processing) big pharma for more than a year now. I have a biology degree. I am 26 to 27 next month. I do not like it at all, since I feel like I am in some ways at the bottom of the food chain. Least payed, little advancement and...
  48. R

    Does thermodynamics tell us that life will eventually end?

    Hi. I apologize if this question has already been made. Unfortunately it's also difficult for me to formulate, especially in english. If you consider the Sun and Earth as an isolated system, where the Sun is able to produce energy indefinitely (it's not going to become a red giant), will life...
  49. F

    Life on other planets, are we looking at the wrong planets?

    Scientists are looking for Earth like planets/bodies to find life on other planets/bodies, somewhere that is warm enough that liquid water can exist, and somewhere with basic organic molecules. Here's where I have a concern, in the 4 billion years of Earth's life, to our knowledge life had only...
  50. I

    Different amino acids in different life forms?

    Hello, Are the 20 amino acids that are usually referenced when building genetically coded proteins in all of life, and no other amino acids or are these only in humans and animals? I found the sentence below on this website and I wasn't sure what to make of it, is it true that there are...
Back
Top