Paul Davies : What is life ?

What is life ?

https://reasonandscience.catsboard.com/t1435-paul-davies-what-is-life

All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing. When viewed together, these characteristics serve to define life.
https://courses.lumenlearning.com/wm-biology2/chapter/properties-of-life/

Paul Davies & Jeremy England • The Origins of Life: Do we need a new theory for how life began?
Paul Davies at 15:30 Life = Chemistry + information
https://www.youtube.com/watch?v=R9IU2ZWrkhg

Norbert Weiner - MIT Mathematician - Father of Cybernetics
"Information is information, not matter or energy. No materialism which does not admit this can survive at the present day."


NASA’s current working definition of life
is “a self-sustaining chemical system capable of Darwinian evolution.”

Szent-Györgyi, who was awarded the 1937 Nobel Prize in Physiology or Medicine for his discovery of the action of ascorbic acid:
“In my hunt for the secret of life, I started research in histology. Unsatisfied by the information that cellular morphology could give me about life, I turned to physiology. Finding physiology too complex I took up pharmacology. Still finding the situation too complicated I turned to bacteriology. But bacteria were even too complex, so I descended to the molecular level, studying chemistry and physical chemistry. After twenty years' work, I was led to conclude that to understand life we have to descend to the electronic level, and to the world of wave mechanics. But electrons are just electrons, and have no life at all. Evidently, on the way I lost life; it had run out between my fingers.”

Paul Davies:
http://www.nytimes.com/books/first/d/davies-miracle.html

Reproduction.
Metabolism. 
Homeostasis
Nutrition.
Complexity.
Organization. 
Growth and development.
Information content. 
Hardware/software entanglement. 
Permanence and change. 

Daniel E. Koshland Jr. (University of California at Berkeley) formulated the “Seven Pillars of Life”. They are as follows:
1. A program
2. Improvisation
3. Compartmentalisation
4. Energy
5. Regeneration
6. Adaptability
7. Seclusion

Autonomy is one important characteristic of life. But there are many others, including the following:

Reproduction. A living organism should be able to reproduce. However, some nonliving things, like crystals and bush fires, can reproduce, whereas viruses, which many people would regard as living, are unable to multiply on their own. Mules are certainly living, even though, being sterile, they cannot reproduce. A successful offspring is more than a mere facsimile of the original; it also includes a copy of the replication apparatus. To propagate their genes beyond the next generation, organisms must replicate the means of replication, as well as replicating the genes themselves.

Metabolism. To be considered as properly alive, an organism has to do something. Every organism processes chemicals through complicated sequences of reactions, and as a result garners energy to enable it to carry out tasks, such as movement and reproduction. This chemical processing and energy liberation is called metabolism. However, metabolism cannot be equated with life. Some micro-organisms can become completely dormant for long periods of time, with their vital functions shut down. We would be reluctant to pronounce them dead if it is possible for them to be revived.

Nutrition. This is closely related to metabolism. Seal up a living organism in a box for long enough and in due course it will cease to function and eventually die. Crucial to life is a continual throughput of matter and energy. For example, animals eat, plants photosynthesize. But a flow of matter and energy alone fails to capture the real business of life. The Great Red Spot of Jupiter is a fluid vortex sustained by a flow of matter and energy. Nobody suggests it is alive. In addition, it is not energy as such that life needs, but something like useful, or free, energy. More on this later.

Complexity. All known forms of life are amazingly complex. Even single-celled organisms such as bacteria are veritable beehives of activity involving millions of components. In part, it is this complexity that guarantees the unpredictability of organisms. On the other hand, a hurricane and a galaxy are also very complex. Hurricanes are notoriously unpredictable. Many nonliving physical systems are what scientists call chaotic -- their behavior is too complicated to predict, and may even be random.

Organization. Maybe it is not complexity per se that is significant, but organized complexity. The components of an organism must cooperate with each other or the organism will cease to function as a coherent unity. For example, a set of arteries and veins are not much use without a heart to pump blood through them. A pair of legs will offer little locomotive advantage if each leg moves on its own, without reference to the other. Even within individual cells the degree of cooperation is astonishing. Molecules don't simply career about haphazardly, but show all the hallmarks of a factory assembly line, with a high degree of specialization, a division of labor, and a command-and-control structure.

Growth and development. Individual organisms grow and ecosystems tend to spread (if conditions are right). But many nonliving things grow too (crystals, rust, clouds). A subtler yet altogether more significant property of living things, treated as a class, is development. The remarkable story of life on Earth is one of gradual evolutionary adaptation, as a result of variety and novelty. Variation is the key. It is replication combined with variation that leads to Darwinian evolution. We might consider turning the problem upside down and say: if it evolves in the way Darwin described, it lives.

Information content. In recent years scientists have stressed the analogy between living organisms and computers. Crucially, the information needed to replicate an organism is passed on in the genes from parent to offspring. So life is information technology writ small. But, again, information as such is not enough. Though there is information aplenty in the positions of the fallen leaves in a forest, it doesn't mean anything. To qualify for the description of living, information must be meaningful to the system that receives it: there must be a "context." In other words, the information must be specified. But where does this context itself come from, and how does a meaningful specification arise spontaneously in nature?

Hardware/software entanglement. As we shall see, all life of the sort found on Earth stems from a deal struck between two very different classes of molecules: nucleic acids and proteins. These groups complement each other in terms of their chemical properties, but the contract goes much deeper than that, to the very heart of what is meant by life. Nucleic acids store life's software; the proteins are the real workers and constitute the hardware. The two chemical realms can support each other only because there is a highly specific and refined communication channel between them mediated by a code, the so-called genetic code. This code, and the communication channel -- both advanced products of evolution -- have the effect of entangling the hardware and software aspects of life in a baffling and almost paradoxical manner.

Permanence and change. A further paradox of life concerns the strange conjunction of permanence and change. This ancient puzzle is sometimes referred to by philosophers as the problem of being versus becoming. The job of genes is to replicate, to conserve the genetic message. But without variation, adaptation is impossible and the genes will eventually get snuffed out: adapt or die is the Darwinian imperative. How do conservation and change coexist in one system? This contradiction lies at the heart of biology. Life flourishes on Earth because of the creative tension that exists between these conflicting demands; we still do not fully understand how the game is played out.

The cell's self-generated “electrome”: The biophysical essence of the immaterial dimension of Life?
Over 100 different definitions of “Life” have been published in the past.5 To my knowledge, none takes all presently known dimensions and types of organization of living systems into account in an unambiguous and holistic way as in the definition that I logically deduced.5,6 It meets all criteria a good definition of Life should meet according the philosophers of science Schetjer and Agassi.10 In this deduction opposing the situations “still alive” vs. “just not alive any longer,” instead of by following the classical procedure of comparing the properties of living- versus non-living matter, yielded the view that communication activity is what “Life” is all about. What we call “Life” is nothing other than the total sum of all acts of communication exerted by a given sender-receiver compartment at moment t, at all levels of its compartmental organization (cell organelle, cell, tissue,…, whole organism,…, population, community, Gaia level).

Any biological compartment, whatever its degree of complexity dies at the very moment that it irreversibly (to exclude regeneration) loses its ability to communicate at its highest level of compartmental organization. It can be shown by electrophysiological methods that a cell is dead from the moment that its voltage gradient over its plasma membrane is irreversibly lost. “Death” refers to a particular level of compartmental organization, namely the highest one. In the case of e.g. a vertebrate, the brain is the highest (coordinating) level of communication. A brain-dead person is no longer a person, but a corpse which is an aggregate of cells and tissues.  The transition from “still alive” to “no longer alive” involves a drastic change, namely a total and irreversible collapse of the communication activity (= handling of information) at the highest level of compartmental/communicational organization of the dying entity under consideration.



https://sci-hub.yncjkj.com/10.1038/nrmicro2108




https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5100658/

The 7 Characteristics of Life:

1. Living Things are Composed of Cells:

Single-cell organisms have everything they need to be self-sufficient.
In multicellular organisms, specialization increases until some cells do only certain things.
2. Living Things Have Different

levels of cellular organization
Levels of Organization:
Both molecular and cellular organization.
Living things must be able to organize simple substances into complex ones.
Living things organize cells at several levels:
Tissue - a group of cells that perform a common function.
Organ - a group of tissues that perform a common function.
Organ system - a group of organs that perform a common function.
Organism - any complete living thing.
3. Living Things Use Energy: Earth's energy source is the Sun

Living things take in energy and use it for maintenance and growth.
4. Living Things Respond To Their Environment:

Living things will make changes in response to a stimulus in their environment.
A behavior is a complex set of responses.
 5. Living Things Grow:

Cell division - the orderly formation of new cells.
Cell enlargement - the increase in size of a cell. Cells grow to a certain size and then divide.
An organism gets larger as the number of its cells increases.
6. Living Things Reproduce: reproduction

Reproduction is not essential for the survival of individual organisms, but must occur for a species to survive.
All living things reproduce in one of the following ways:
Asexual repoduction - Producing offspring without the use of gametes.
Sexual reproduction - Producing offspring by the joining of sex cells.
7. Living Things Adapt To Their Environment:

Adaptations are traits giving an organism an advantage in a certain environment.
Variation of individuals is important for a healthy species.


The Mechanism of Life by Stéphane Leduc

INTRODUCTION  2
Life was formerly regarded as a phenomenon entirely separated from the other phenomena of Nature, and even up to the present time Science has proved wholly unable to give a definition of Life; evolution, nutrition, sensibility, growth, organization, none of these, not even the faculty of reproduction, is the exclusive appanage of life.
Living things are made of the same chemical elements as minerals; a living being is the arena of the same physical forces as those which affect the inorganic world.
Life is difficult to define because it differs from one living being to another; the life of a man is not that of a polyp or of a plant, and if we find it impossible to discover the line which separates life from the other phenomena of Nature, it is in fact because no such line of demarcation exists—the passage from animate to inanimate is gradual and insensible. The step between a stalagmite and a polyp is less than that between a polyp and a man, and even the trained biologist is often at a loss to determine whether a given borderland form is the result of life, or of the inanimate forces of the mineral world.
A living being is a transformer of matter and energy—both matter and energy being uncreatable and indestructible, i.e. invariable in quantity. A living being is only a current of matter and of energy, both of which change from moment to moment while passing through the organism.
That which constitutes a living being is its form; for a living thing is born, develops, and dies with the form and structure of its organism. This ephemeral nature of the living being, which perishes with the destruction of its form, is in marked contrast to the perennial character of the matter and the energy which circulate within it.
The elementary phenomenon of life is the contact between an alimentary liquid and a cell. For the essential phenomenon of life is nutrition, and in order to be assimilated all the elements of an organism must be brought into a state of solution. Hence the study of life may be best begun by the study of those Physico-chemical phenomena which result from the contact of two different liquids. Biology is thus but a branch of the physico-chemistry of liquids; it includes the study of electrolytic and colloidal solutions, and of the molecular forces brought into play by solution, osmosis, diffusion, cohesion, and crystallization.
In this volume I have endeavored to give as much of the science of energetics as can be treated without the use of mathematical formulæ; the conception of entropy and Carnot's law of thermodynamics are also discussed.
The phenomena of catalysis and of diastatic fermentation have for the first time been brought under the general laws of energetics. This I have done by showing that catalysis is only one instance of the general law of the transformation of potential into kinetic energy, viz. by the intervention of a foreign exciting and stimulating energy which may be infinitely smaller than the energy it transforms. This conception brings life into line with other catalytic actions and shows us a living being as a store of potential energy, to be set free by an external stimulus which may also excite sensation.
In a subsequent chapter I have dealt with the rise of Synthetic Biology, whose history and methods I have described. It is only of late that the progress of physico-chemical science has enabled us to enter into this field of research, the final one in the evolution of biological science.
The present work contains some of the earliest results of this synthetic biology. We shall see how it is possible by the mere diffusion of liquids to obtain forms which imitate with the greatest accuracy not only the ordinary cellular tissues but the more complicated striated structures, such as muscle and mother-of-pearl. We shall also see how it is
{xv}
possible by simple liquid diffusion to reproduce in ordered and regular succession complicated movements like those observed in the karyokinesis of the living cell.
The essential character of the living being is its Form. This is the only characteristic which it retains during the whole of its existence, with which it is born, which causes its development, and disappears with its death. The task of synthetic biology is the recognition of those Physico-chemical forces and conditions which can produce forms and structures analogous to those of living beings. This is the subject of the chapter on Morphogenesis.
The last chapter deals with the doctrine of Evolution. The chain of life is of necessity a continuous one, from the mineral at one end to the most complicated organism at the other. We cannot allow that it is broken at any point, or that there is a link missing between animate and inanimate nature. Hence the theory of evolution necessarily admits the physico-chemical nature of life and the fact of spontaneous generation. Only thus can the evolutionary theory become a rational one, a stimulating and fertile inspirer of research. We seek for the physico-chemical forces which produce forms and structures analogous to those of living beings, and phenomena analogous to those of life. We study the alterations in environment which modify these forms, and we seek in the past history of our planet for those natural phenomena which have brought these physico-chemical forces into play. In this way we may find the road which will, we hope, lead some day to the discovery of the origin and the evolution of life upon the earth.



1. http://infohost.nmt.edu/~klathrop/7characterisitcs_of_life.htm
2. http://www.gutenberg.org/ebooks/33862

Attempts to Define Life Do Not Help to Understand the Origin of Life

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208307/

Attempts to define life are irrelevant to scientific efforts to understand the origin of life. Why is this? Simply put, the study of the ‘origin of life’ is an effort to understand the transition from chemistry to biology. This fundamental transition was the result of a lengthy pathway consisting of many stages, each of which is the subject of numerous scientific questions. Simple chemistry in diverse environments on the early earth led to the emergence of ever more complex chemistry and ultimately to the synthesis of the critical biological building blocks. At some point, the assembly of these materials into primitive cells enabled the emergence of Darwinian evolutionary behavior, followed by the gradual evolution of more complex life forms leading to modern life. Somewhere in this grand process, this series of transitions from the clearly physical and chemical to the clearly biological, it is tempting to draw a line that divides the non-living from the living. But the location of any such dividing line is arbitrary, and there is no agreement on where it should be drawn. An inordinate amount of effort has been spent over the decades in futile attempts to define ‘life’ – often and indeed usually biased by the research focus of the person doing the defining. As a result, people who study different aspects of physics, chemistry and biology will draw the line between life and non-life at different positions. Some will say there is no life until a well defined set of metabolic reactions are in place. Others will focus on spatial compartmentalization, on the various requirements for Darwinian evolution, or on the specific molecules of inheritance. None of this matters, however, in terms of the fundamental scientific questions concerning the transitions leading from chemistry to biology - the true unknowns and subject of origin-of-life studies.

What is life ?

Reproduction.
Metabolism. 
Homeostasis
Nutrition.
Complexity.
Organization. 
Growth and development.
Information content. 
Hardware/software entanglement. 
Permanence and change. 

Daniel E. Koshland Jr. (University of California at Berkeley) formulated the “Seven Pillars of Life”. They are as follows:
1. A program
2. Improvisation
3. Compartmentalisation
4. Energy
5. Regeneration
6. Adaptability
7. Seclusion

Autonomy is one important characteristic of life. But there are many others, including the following:

Reproduction. A living organism should be able to reproduce. However, some nonliving things, like crystals and bush fires, can reproduce, whereas viruses, which many people would regard as living, are unable to multiply on their own. Mules are certainly living, even though, being sterile, they cannot reproduce. A successful offspring is more than a mere facsimile of the original; it also includes a copy of the replication apparatus. To propagate their genes beyond the next generation, organisms must replicate the means of replication, as well as replicating the genes themselves.

Metabolism. To be considered as properly alive, an organism has to do something. Every organism processes chemicals through complicated sequences of reactions, and as a result garners energy to enable it to carry out tasks, such as movement and reproduction. This chemical processing and energy liberation is called metabolism. However, metabolism cannot be equated with life. Some micro-organisms can become completely dormant for long periods of time, with their vital functions shut down. We would be reluctant to pronounce them dead if it is possible for them to be revived.

Nutrition. This is closely related to metabolism. Seal up a living organism in a box for long enough and in due course it will cease to function and eventually die. Crucial to life is a continual throughput of matter and energy. For example, animals eat, plants photosynthesize. But a flow of matter and energy alone fails to capture the real business of life. The Great Red Spot of Jupiter is a fluid vortex sustained by a flow of matter and energy. Nobody suggests it is alive. In addition, it is not energy as such that life needs, but something like useful, or free, energy. More on this later.

Complexity. All known forms of life are amazingly complex. Even single-celled organisms such as bacteria are veritable beehives of activity involving millions of components. In part, it is this complexity that guarantees the unpredictability of organisms. On the other hand, a hurricane and a galaxy are also very complex. Hurricanes are notoriously unpredictable. Many nonliving physical systems are what scientists call chaotic -- their behavior is too complicated to predict, and may even be random.

Organization. Maybe it is not complexity per se that is significant, but organized complexity. The components of an organism must cooperate with each other or the organism will cease to function as a coherent unity. For example, a set of arteries and veins are not much use without a heart to pump blood through them. A pair of legs will offer little locomotive advantage if each leg moves on its own, without reference to the other. Even within individual cells the degree of cooperation is astonishing. Molecules don't simply career about haphazardly, but show all the hallmarks of a factory assembly line, with a high degree of specialization, a division of labor, and a command-and-control structure.

Growth and development. Individual organisms grow and ecosystems tend to spread (if conditions are right). But many nonliving things grow too (crystals, rust, clouds). A subtler yet altogether more significant property of living things, treated as a class, is development. The remarkable story of life on Earth is one of gradual evolutionary adaptation, as a result of variety and novelty. Variation is the key. It is replication combined with variation that leads to Darwinian evolution. We might consider turning the problem upside down and say: if it evolves in the way Darwin described, it lives.

Information content. In recent years scientists have stressed the analogy between living organisms and computers. Crucially, the information needed to replicate an organism is passed on in the genes from parent to offspring. So life is information technology writ small. But, again, information as such is not enough. Though there is information aplenty in the positions of the fallen leaves in a forest, it doesn't mean anything. To qualify for the description of living, information must be meaningful to the system that receives it: there must be a "context." In other words, the information must be specified. But where does this context itself come from, and how does a meaningful specification arise spontaneously in nature?

Hardware/software entanglement. As we shall see, all life of the sort found on Earth stems from a deal struck between two very different classes of molecules: nucleic acids and proteins. These groups complement each other in terms of their chemical properties, but the contract goes much deeper than that, to the very heart of what is meant by life. Nucleic acids store life's software; the proteins are the real workers and constitute the hardware. The two chemical realms can support each other only because there is a highly specific and refined communication channel between them mediated by a code, the so-called genetic code. This code, and the communication channel -- both advanced products of evolution -- have the effect of entangling the hardware and software aspects of life in a baffling and almost paradoxical manner.

Permanence and change. A further paradox of life concerns the strange conjunction of permanence and change. This ancient puzzle is sometimes referred to by philosophers as the problem of being versus becoming. The job of genes is to replicate, to conserve the genetic message. But without variation, adaptation is impossible and the genes will eventually get snuffed out: adapt or die is the Darwinian imperative. How do conservation and change coexist in one system? This contradiction lies at the heart of biology. Life flourishes on Earth because of the creative tension that exists between these conflicting demands; we still do not fully understand how the game is played out.

Organization

Organization. Maybe it is not complexity per se that is significant, but organized complexity. The components of an organism must cooperate with each other or the organism will cease to function as a coherent unity. For example, a set of arteries and veins are not much use without a heart to pump blood through them. A pair of legs will offer little locomotive advantage if each leg moves on its own, without reference to the other. Even within individual cells the degree of cooperation is astonishing. Molecules don't simply career about haphazardly, but show all the hallmarks of a factory assembly line, with a high degree of specialization, a division of labor, and a command-and-control structure.

Organization defines how tasks are divided, resources are deployed, and departments are coordinated.
https://en.wikipedia.org/wiki/Organizing_(management)#Structure

Comment: Dividing, deploying, coordinating, assigning, managing & controlling are all tasks assigned to organizing principles, and are always the product of intelligent action.

Organization and variation constitute overarching hypotheses that frame the intelligibility of the objects within the biological domain. Organization frames the intelligibility of biological objects. What makes biological systems specific with respect to other natural systems is ultimately the fact that they arebe the result of the expression of genetic information. Organisms are governed by two theoretical principles: organization and variation. All biological organisms, in all their diversity and richness of forms and kinds, meet two general principles without exceptions: they are organized, and their organization undergoes variation.  The principle of organization focuses on the specific complexity of biological systems. Organization refers to the differentiation of functional roles (i.e. division of labor) among the parts of a system and, at the same time, to their integration and coordination as a whole. The realization of organization involves the conservation of relevant biological aspects, which in turn are associated with the maintenance or reestablishment of local and global biological symmetries. Biological organization tends to maintain itself and, thereby, to counter and remove potentially deleterious variations, while preserving useful variations. The principle of organization grounds functionality within biological systems. 

1. https://www.sciencedirect.com/science/article/abs/pii/S007961071630089X?via%3Dihub

Steven A. Benner Defining Life 2010 Dec 10

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005285/

Libretext definition:

Evolution: long term adaptation/speciation
Cell-based: Cells are the fundamental unit of life
Complexity: allows physical/biochemical changes (dynamic order)
Homeostasis: maintains balance between change and order
Requires Energy: needed to do work (cellular functions)
Irritability: immediate sensitivity and response to stimuli
Reproduction: the ability to propogate life
Development: programmed change, most obvious in multicellular organisms