Life and Living Organisms

 

As mentioned in previous article, we came to know about biology, i.e. the study of living organism. Before knowing about the living organism lets us know the life. Do you know, What is life?

In this article we are going to read about life, living organism and their characteristics and how they differ from the non living ones.

What is life?

On earth, Life is an open system of linked organic reactions catalyzed at low temperature by specific enzymes, which are themselves products of steady system.

        Being a kind of energy, life can neither be seen or touched. Hence, it eludes a direct and precise definition, just like love, hate, cleverness, happiness, intelligence, honesty, dishonesty, goodness and similar abstraction .It is simply the livingness or capacity of “continuous energy recoupment” of an ever active, changing ,and highly organized matter (protoplasm). 

Thus, Life can be defined as “The ever active a changeable state of organized matter.

 In molecular biology, ”Life is unique”, complicated cellular organization of biomolecules and cells themselves that shows different biochemical reactions which results in occurrence of vital activities like growth, reproduction, development, metabolism, responsiveness, and adaptations.

 Living organism and Characteristic of living organism

All living things share certain key characteristics which separate them from non living things.

Characteristics of Living Beings:

1. Form, Size and Individuality: Organisms are of definite forms and sizes which differ from species to species .Further, slight variations in forms and sizes distinguish members of the same species imparting individuality to them. Nonliving objects from sand particles to great mountains and a drop of water to large oceans are, on the other hand, of indefinite and bizarre forms and sizes.

2. Protoplasm (Protos= first; plasma form): The real living matter in living beings is protoplasm which is the physical basis of life. All vital activities (All physical and chemical changes taking place inside the protoplasm and any exchange of materials between the protoplasm and its environment) take place in the protoplasm. Proteins and several other chemical substances in a definite ratio and proportion constitute the protoplasm. Life depends upon the stepwise reactions taking place between these chemicals in a definite sequence.

3. Chemical Organization: Living and nonliving objects differ, not in their component units of matter at subatomic, atomic or molecular levels, but only in chemical organization of atoms and molecules. The molecular organization is, thus, , "the logic of life".                                                                             

                                                              The protoplasm is a complex chemical system of basically similar   organization in all organisms. Its main constituents are large and complex organic molecules (macromolecules) of high molecular weights. The nonliving objects are, on the other hand, merely unorganized mixtures of small and simple molecules (micromolecules) which are never more than 2000 in molecular weights.

4. Cellular Organization: Protoplasm does not occur on earth as unprotected, exposed matter. It is found only in the form of minute (microscopic) and well-organized membrane-bound masses of atoms and molecules called cells. Thus, cells are the structural and functional units of body in all organisms. In unicellular organisms, the body consists of a single cell. In multicellular organisms, the body consists of many to numerous cells. In most multicellular organisms, the cells are further organized into definite tissues, organs and organ systems.

5. Metabolism: Look at a stone; it is lifeless and, hence, has the same distribution of atoms and molecules as last year or year before, or even earlier. Now, think of an organism, say a dog; it is always doing something or the other eating, breathing, defecating, urinating, barking, running, fighting. Copulating, and so on. It is taking matter from the environment in the form of food and returning it back to the environment in the form of faeces. Obviously, matter is being continuously transformed within its body cells: molecules are synthesized, stored and broken down. That is why, cells have been regarded "miniature chemical factories.

                                      All physico-chemical changes, continuously taking place in the "matter" in living cells, are collectively called as the metabolism of the cells.

The metabolism is further divided into two categories (i) Anabolism and (ii) Catabolism

1.     Anabolism: The biochemical reactions concerned with the 'synthesis' or 'building up of complex substances from simple ones are called Anabolic reactions (Anabolism). During this process, the free energy is stored in the form of potential energy. Synthesis of carbohydrates from CO₂ and presence of light and chlorophyll during photosynthesis is an example of anabolism.

       6CO₂ + 12H₂O ---------------> C₆H₁₂O₆ + _6O2 + 6H₂O ( IN PRESENCE OF SUNLIGHT AND CHLOROPHYLL)

2.        Catabolism: These are the biochemical reactions concerned with the breakdown of organic nutrient molecules into simple substances. During this process the potential energy is converted energy. Oxidative break down of glucose during respiration is an example of catabolism.

              C₆H₁₂O₆   + 6O2 -------------------> 6CO₂ + 6H₂O + Energy (in presence of enzymes)

6. Movements and Locomotion: The dog under your observation moves about and can also move its limbs, ears, tail, head, etc. Thus, spontaneous movements, basically for food and protection, by means of energy produced within their body cells, is an essential characteristic of organisms. Machines, though lifeless, also move, but only by means of external forces and under external commands and controls, never spontaneously, i.e. by themselves.

In an organism, movement implies motion of parts of while locomotion implies movement of the whole body from place to place.

7. Nutrition: You must have seen your dog eating. All organisms periodically obtain matter (food) from their environment and use it for growth, repair, storage, secretion, reproduction and production of energy for vital activities. This is called their nutrition. It includes feeding, digestion of nutrients, absorption of digested substances and their assimilation in the cells of body, and egestion or elimination of useless, undigested residues of the food.

8. Growth: Remember that if you own a dog which a pup once and now it turned into a big one, this is called as that your dog grown older.

Any permanent and irreversible increase in form and volume usually accompanied by increase in dry weight of any organism is called Growth. It is the final result of successful metabolism. In a successful metabolism, anabolic processes dominate over the catabolic processes. In plants growth continues indefinitely with the help of meristematic cells whereas in animals it stops after attainment of a definite age.  A dry piece of dead wood after absorbing water vapour from the humid air increases in size, volume and weight, but it cannot be called growth because the wood returns to its original form and weight when the water has evaporated. Sometimes crystals of a substance may grow but their growth is different from the growth of living organisms. The growth of crystals is due to external causes whereas the growth of living organisms occurs due to endogenous causes.

9. Respiration: In all living organisms respiration takes place continuously. In this process, organisms usually take up oxygen from the environment and usually release CO₂. Food materials like carbohydrates, fats and proteins are continuously oxidized in this process with consequent release of energy. All vital activities of the organisms are dependent upon this energy.

10. Excretion: Continuous degradation of nutrients in body cells for producing energy yields not only energy, but also CO₂, H₂O and nitrogenous and other waste products which are useless and harmful to the body. Hence, organisms discharge these waste products into the environment. Elimination of CO₂ is called carbonaceous excretion. It is a part of respiration. Elimination of other waste products especially of nitrogenous substances, such as ammonia, urea, uric acid, etc is called nitrogenous excretion.

11. Sensitivity and adaptability (Responsiveness): Living organisms wherever they live, are sensitive to changes in the environment (sensitivity) and have the power to adjust (in form and function) to the environment (adaptability).

12. Regeneration and Immunity: Organisms can regenerate injured tissues and, in some cases even lost parts. Larger organisms even possess a power to fight against antigens and pathogens. This capacity of defense is called immunity.

13. Reproduction and Life cycle: All living beings follow a definite life cycle, i.e., they are born, they grow, they develop, they reproduce, become senescent and then die, but life continues via reproduction and heredity. Thus they carry out different life activities in a definite sequence. By reproduction they give birth to the young one which are exact to copy of their mother.

14. Organic evolution: Although each organism produces its own kind, yet the process of sexual reproduction is such that variations amongst the resultant offspring are inevitable. Accumulating through innumerable generations, these variations ultimately lead to the origin of new kinds of organisms from older ones. This is called organic evolution. It implies that an organism is not only a producer of new organisms of its own kind, but also a creator of organisms of new kinds.

Through evolution, species acquire new ways to survive, to obtain and use energy, and to reproduce. One might sum all this up by saying that a living organism is a self-reproducing system capable of growing and of maintaining its integrity by the expenditure of energy. Life is the sum total of all these things. The principles of biology can be applied to world problems such as over-population, disease, environmental degradation, famine and drug addiction etc.

 

Differences between Living and Non-Living Things

The most significant differences between living and non-living things are discussed below:

1. The organisms that are alive and compose of tiny particles, i.e. cells are known as living things.

The things, which are once alive or are never alive, are known as non-living things.

2. Responsiveness is a trait in living things, through which they sense things and react to external stimulus.

 As against this, non-living things are insensitive to an external stimulus.

3. Processes like anabolism and catabolism occur, in living things only and no such reaction take place in non-living things.

4.      Living things can respire, excrete, reproduce, sense, feel and even response but non living things will never show any of these process.

 

5. Living things are very well organized in the sense that cells form tissues and organs are made up of various tissues, these organs when to work together as a system, it is called as the organ system where as non-living things do not have any such type of organization.

 

6. Growth is a basic trait of all living things, i.e. the living organism go through a regulated growth, due to the presence of cells in the body.

         Conversely, non-living things do not grow. They remain as such and no changes occur in them with the change of time.

7. Living things control their internal environment, so as to maintain the minimum conditions required for the cell to function.

 On the other side, non-living things do not have to control the same.

8. Living things are subject to evolve, i.e. the genetic makeup of the living organism change over time, so as to allow them to survive and reproduce, in the environment easily.

Non-living things do not experience evolution.

9. Food, air, water and light are basic needs of living things, i.e. they cannot survive without it. On the other hand, non-living things have no such requirement.
10. All living organism have a lifespan, and after which they die. On the contrary, non-living things do not have life, and so they can be recycled or reused even after they became obsolete.

11.  Healing and regenerations are the property of living organism while nonliving organism do not show any such phenomenon.

 

 Now after knowing about the living things and non living things and their characters lets us know about the diversity in living world. We will continue this in our next article.