There are animals, plants, birds, etc on our planet which we can see. It may be that life exists elsewhere in other planets, in some remote nebulae, we do not know. All that we know about life, we know from observation round about us on the earth or very near to the surface of the earth.
What is life?
The question of the life is a big one. The chemist, the physicists, the biologists and the psychologists each tells us very shortly what he thinks of life. The chemist tells us that all living creatures are built up of the same kind of stuff, which is called protoplasm, defined by Huxley as the physical basis of life.
A chemical similarity makes the whole world akin. He is greatly struck by the orderliness of the living laboratory by the way in which processing of the building up make good all the breaking down and by the quickness and quietness of it all.
The physicist who is chiefly concerned with energy (the power of doing work) and its changes would tell us first that we must suppose that living creatures creates any energy. Like engines which changes fuel into work, so organisms change the chemical energy of food into locomotion and work, sometimes into light, often into heat and also into stores, specially in the plant world.
But all living creatures are like engines in being transformers of one kind of energy into another. He tells us that he admires living creatures more than his own engines, because they get comparatively more energy out of their food than his engines gets of their fuel. A fish has more efficient engine than a battleship, and a fire-fly is a more economical light producer than an arc lamp.
The biologist is an expert on life the characteristic activities of plants and animals seem to him very different from those of the non living world.
Thus, life is the condition and state of being alive; the state in which animals and plants exist, as differentiated from in organic or dead organic matter. Life is understood through observation of the composition and activities of living things. The fundamental substance of life is protoplasm, which contains those chemical and structural combinations upon which the functions of life depend.
What causes life?
Life is said to be due to the presence of protoplasm. All living beings must possess protoplasm. Protoplasm (Gr. Protos, first, plasma: from-plassein: to form) means living matter, a homogenous, structure less substance, forming the physical basis of life, endowed with contractility.
It is a semi-solid complex mass made up of carbon, hydrogen, oxygen, nitrogen, etc. along with a large proportion of water. It is contained in small compartments called cells. On the other hand cells form a minute part of an organism and, on the other hand, they exist as a separate living unit.es of which protoplasm is composed but rather in the organization
Living and the non living
The primary distinction between the living and the non living is in point of chemical constitution, and cell structure. It is a fact that all the chemical elements which are found in living protoplasm occur, likewise, in non living materials or soil, rock, air and water. There is no single chemical which is peculiar to living matter.
The secret of life lies not in the ultimate substance of these chemical elements in to a living system. This is just like a broken watch which does not function, but when repaired it functions because it comes to possess an organization. The material in both cases is the same.
The bodies of plants and animals are composed of microscopic structures called cells, each of which consist of a tiny bit of living substance, or protoplasm, and an enclosing wall or membrane. The cellular plan of organization is an exclusive property of plant and animal bodies.
The living things assimilate
There exists in living matter the inherent capacity of modifying alien substances and transforming them into the very living substances which bring about the alteration. Man transforms the food, he ingests into blood, muscles, bones, hairs, etc. Plants synthesize sugar from carbon dioxide and water and subsequently transform some of these sugars and other substances into the proteinaceous living substance. Assimilation is the fundamental feature of growth.
The living things reproduce
A little amount of living matter in suitable environment will quickly increase. A pair of hen and peacock would multiply into so many of them. The reproduction is almost of similar kinds. Men generate human beings, cows generate cows, and dogs generate dogs, and so on.
It appears that the ovum and in the sperm there are certain fairly small members of “genes” (the unit responsible for the development of the inherited characteristics of individuals) which carry the hereditary characteristics. Generally, the genes carry the parental character: but sometimes there are spores or “mutants” which differs considerably from their parents. They occur naturally in a small proportion of cases. It is these spores that give the best opportunity for evolution, i.e. for the developments of new kinds of animals or plants from descent from old kinds.
A living thing moves about
Life may moves as swiftly as a flying bird, or as slowly as the expanding turnip, but it move. It may not be in movement continuously, for many seeds lie immobile for long periods, but sooner or later they burst and stir. The driving force of moment comes from within. All the same it is not necessary that everything that moves is alive. A projectile that moves through a long distance is not alive.
A living matter is not chemically static
Living thing is not chemically static but it undergoes continual chemical change. Our blood, for instance, undergoes one kind of change when it circulates round the body and an opposite change on coming into contact with air in the lungs.
“The fundamental laws governing living matter are, in all likelihood, the very same that govern the behavior of the hydrogen atom, namely the laws of quantum mechanics”.
Living things are sensitive
All living things are sensitive to a wide variety of external features on their environment, to light, variation of temperature, moisture and drought,; mechanical stimuli, such as pressure, tension, chemicals, gravity etc. The non living things do not possess the power of sensibility.
Origin of life
The problem of the manner in which life operated on the earth has been puzzling the man. Perhaps for all times, the problem of life beginning on our planet will remain insoluble, a philosophical question rather than a subject capable of experimental investigation and solution.
All that we know is that living protoplasm (livening matter), a homogeneous, structure less substance forming the physical basis of life, endowed with contractibility, with a chemical composition allied to that of albumen, existed on the earth aeons ago, that is probably originated in the oceans which covered most of the earth’s surface, and that it was extremely simple structurally, possibly very similar in its minuteness and organic form to some of the organisms which are dwelling upon the earth today. We do not know by what action or series of actions the first bit of protoplasm were formed.
With the passage of centuries, causeless changes occurred in the topography (Gr. Topos, a place, graphein, to describe: topograph, description of physical features or configuration of the specified area, usually indicated by a map detailing natural features on a given scale, as well as cities, roads, bridges), the climate and the plan of earth’s surface and the descendents of the first bits of life, whatever their origin, gradually becomes transformed into different types of organisms.
Possibly, this difference in types of organisms took place, in part, as adoption to changing environmental conditions, partly in response to internal genetic factors. In other words, the processes of evolution have been at work and are still at work mounding, eliminating, changing, and adding to the various forms of life which live on the earth’s surface.
Theories about the beginning of life
Several theories have attempted to account for the life’s beginning.
Theory of spontaneous generation
Spontaneous generation theory (L. spontaneous-sponte, of one’s own accord) holds that living organism develops directly from non living matter.
The contention of the biologists who subscribes to this theory was based upon such evidence as the appearance of bacteria extremely, small, single or grouped, reproducing rapidly by cross division or by formation of spores, almost always associated with the decomposition of albuminoidal substances, (and regarded as the germs or active cause of many diseases) in broth or in decomposing meat.
But the idea is not accepted by most biologists the work of many biologists, including Pasteur, proved definitely that the living protoplasm, which the upholders of spontaneous generation studied, developed from pre-existing protoplasm.
Pasteur and others showed that if broth and meat were heated for a time and protected from air currents, no bacteria would develop. Germs are present in the air and when they fall into such organic materials as these, they grow and reproduce.
Upheld theory of life’s beginning
Helmholtz, Lord Kelvin and others, state that life on our planet came to us from some other world, possibly from one of the other members of our system. They held that life may have been transplanted to our planet in narrow openings or meteorites and cosmic dust falling on the earth. There is nothing of impossibility in this transference of life from some other heavenly body.
Plant seeds have been found to preserve this latent life even after prolonged exposures to intense cold. Bacteria have been known to withstand appreciably high temperatures.
In fact the life property in seed and bacteria lie dormant when the conditions are inhospitable, and it bursts out with full activity when environments are favorable. This idea at times had a considerable following among scientists. In the absence of credible evidence in its support, it has but few adherents at the present time.
The theory does not also serve the purpose. It only provides us an answer to the origin of life on our planet, but does not solve the mystery of the origin of life.
The theory of Divine Creation
This theory holds that the Divine Being created living organism from non living matter. The view has been held since ancient time, entirely as a matter of faith. According to this theory, the dust of the earth may have been infused with life through some agency beyond the material conception of scientists who are inclined to assume that some time in the dim past, presence of favorable temperature, moisture, etc produced living protoplasm.
Evolution of life
Literally, the word ‘evolution’ means the act of unrolling or unfolding; a process of orderly change; gradual working out of development; a series of things unfolded; the doctrine according to which high forms of the life have gradually arisen out of lower forms of life.
To many people the word ‘evolution’ is connected vaguely to Darwin and monkey, with no relation to the evolution that had produced the monkey in the first place. A study of evolution attempts to trace the changes to their origin and to account for their occurrence.
Repeated in history, nations have evolve progressively until, after reaching the zenith of their fame and power, their evolution has proceeded at a more or less rapid decline, resulting in some cases in their obliteration. The evolution may be both progressive and retrogressive. This disappearance of species, genera and even of families of plants and animals has taken place while new species and genera have arisen.
The evolution of organism proceeded at first from relatively simple to more complex forms. While the socialist is concerned with the evolution of society, the historian with the evolution of nations, their rise and fall, the scientists is concerned with the evolution of his particular science.
Dr. Austin H. Clark offered a theory in 1937 which he termed ‘exogenesis’. According to this theory, life at the beginning was balanced, and embraced all general forms. This theory denies that vertebrates sprang from something lower, doubts existence of missing links and questions Darwin evolution.
Plants and animals life
Biologists say that at sometime in the course of evolution the differentiation of organisms into plants and animals occurred. Such modification probably did not occur at a single instance in evolutionary history but very likely arose here and there under different conditions at different periods.
They can not logically say that the plant kingdom originated from the animal or the animal kingdom from the plant. It seems that here and there, in the course of evolution, some organism assumed plant like features in varying degrees, others become animal like. The changes occurred at different time; some persisted and the differences which they produced became intensified, others weakened and died out.
Biologists regard plants and animals as two main branches of the family tree, the branches springing from a common ancestral trunk. They are creatures intermediately between plants and animals which are called ‘plantimals’ by biologists.
a) Now the chief differences between plants and animals are:
b) Most plants are stationary. On the other hand, most animals have ability to move from place to place.
c) Animals have a limited scheme of growth, whereas plants have unlimited one.
d) Most plants have a structural framework composed chiefly of cellulose, a substance absent from the bodies of most animals.
e) Animals are unable to manufacture foods and other complex substances from raw material of air and soil, whereas plants can manufacture foods and other complex substances from them.
Is man getting clever?
The human brain may be developing itself to stage which will make the man of the future look back on the 20th century as an age of mental weakling, says G. N. Ridley, a British scientist, in his book, “your brain and you”.
Ridley says that man’s intellectual advantage over animals is due to the fact that he has three layers to his brain while they have only two. A fourth may now be evolving which will lead to a corresponding higher degree of intelligence.
Dealing with the relations of mind and body, Ridley claims that high blood pressure, permanently grey hair, bad teeth and constant colds can all spring from mental stain.
On the other hand, children whose body lacks necessary calcium may become bad tempered and emotional. Other facts about the brain are that it is made up of 77 percent water and the energy from half a peanut is sufficient for an hour’s concentrated thinking.
The struggle for existence of life
It is a phrase coined by Darwin; although on every one’s lips, it is not yet always clearly understood. As Darwin says the phrase is to be used in a “large metaphorical sense” including endeavors to secure the welfare of the offspring as well as life and death competition at the margin of substance.
There is over production both among plants and animals. A single orchid flower may produce over one million seeds, a single plant of pig-weed may form 20, 00, 00,000 seeds, one mushroom may scatter into breeze as many as 20.00,00,000 necessary for growth of spores.
Obviously neither the room nor the food materials necessary for the growth of these enormous numbers or reproductive structures is available. That is, too many offspring are produced to survive.
Competition for life
Because of the limitation of space and foods all these myriads of offspring can not survive, and they compete with each other for sufficient space in which to grow. The struggle may be for food, for foothold, for shelter, for mates, for satisfaction of appetite, and so on.
It includes all the activities of living creatures when they have to face difficulties and limitation in their environments, and for sufficient food materials for their nutrition. Thus there develops a struggle for existence not only among organisms of different species but also among individuals of the same species.
Only a small percentage of offspring is able to win in this struggle and to achieve growth and maturity, the great majority of individuals suffering defeat and death in this competition.
The balance of life is maintained by complex relations among many kinds of living things. A grasshopper lays its eggs, which grow into insects and begin at once to eat the tender leaves of grass and other vegetation.
In case the grasshoppers are allowed to grow unchecked, there is a danger of destruction of the kinds of vegetation that are used as food. But birds feed upon grasshoppers, a single bird often eating in one day as many as the entire brood of one mother insect.
The insects that survive are those which while getting their own food escape the birds and also the diseases and climate changes that surround them. The birds that devour the insects are themselves the food for other animals. This process results in equilibrium among the species growing in a particular region, so long as factors tending to disturb this equilibrium do not arise.