We have learned that world can be divided into living and non living. And the branch of Science that deals with the study of living organisms is called as Biology. But do you know what makes you and me alive? What makes the spider, lizard, dog and tree etc alive? Or what makes table, rock, snow, bulb and mobile or laptop as non living thing? Have you ever observed that the branch of the tree becomes dead or act as non living thing when it get detached from the tree. How will you define life? What makes the living world different from non-living?
The most common opinion would be, that the living organism increases in mass or increases in number or population or ability to move. But if we see, the rocks, mountains and glaciers also grow in size (They grow in size because of the accumulation of particles from outside of its surface). Glaciers can move too, but we cannot call them living organism. Whereas, infertile human couple, mules, zorse, Liger, working bees and ants cannot reproduce and it would be incorrect to consider them as non living. So question arises, how can we define the living organism.
The living thing follow following characteristics –
- It grows in body mass (size).
- Ability to reproduce.
- It is locomotory.
- It caries metabolic reactions.
- They are made of cell/s.
- Maintenance of Homeostasis
- They have ability to sense the surrounding.
Let us discuss the characteristics in more detail –
- Increase in body mass – Increase in body mass is bit different in single and multicellular organism. In single cell organism, the cell increase in size and biomass because of accumulation of nutrients, synthesis of DNA, proteins and other vital biomolecules. In multicellular organism, its size increases because of increase in the number of cells. In plants and animals, the biomass increases because of cell division. Plant cell being totipotent, they can multiply through out their life span. Whereas, in animals cells called as stem cells have the ability to multiply and replace the dead cells. Such characteristic is not found in animal cell.
- Ability to reproduce – Reproduction means ability to form progeny or offspring with parental characteristics. Reproduction can be sexual or asexual. Sexual reproduction means involvement of two parents (different sexes). The progeny is formed from the combination of genetic information from both the parent. The sexual mode of reproduction is observed in plants and animals. There are different modes of asexual mode of reproduction like binary fission, budding, fragmentation. The asexual mode of reproduction produces copies of parent.
- Locomotion – They move from one place to another for food and shelter. The unicellular organism move with the help of flagella (bacteria), pseudopodia (amoeba) or cillia (paramecium). The multicellular animal move with the help of legs. The plants do not move and but get bends towards the sunlight.
- Metabolism – The living cells are made of different types of biomolecules. To keep the cell alive, thousands of metabolic reactions occurs simultaneously. Some of them are anabolic, where they synthesizes complex biomolecules or metabolites from simple one; some of them are catabolic, where the complex molecules are broken down in to simple one. The sum of anabolism and catabolism is called as metabolism. No non living organism exhibit the metabolic reactions.
- They are made up of cells – The living organisms are made up of fundamental unit of life i.e. Cells. The cells of unicellular organisms are simple than multicellular form. The cells are made up of different organelles which works in coordinated form. In multicellular living organism, the cells of similar type collaborated to form tissue; the tissue forms different organs. The organs are perform specialized function. The different organs altogether forms a body.
- Homeostasis – The living organisms maintains the pH and temperature inside the cell (in case of unicellular) or body (in case of multicellular). The optimum pH and temperature is needed to be maintained for carrying out different molecular and metabolic. The change of pH and temperature of the environment does not affect the internal environment.
- Ability to sense – They responds to the stimuli received from an environment in the form of chemical, physical or biological. The bacteria can sense the environment (nutrients or toxic chemical) with the help of surface receptors and move accordingly. We, humans can sense our surrounding with the help of sensors. The plant can sense light, water and temperature and shows the growth accordingly.
Difference between Living and Non Living Organism –
|Living thing (organism)||Non Living thing|
|They are alive (possess life)||They are non alive (do not posses life)|
|They shows growth and development||The living organism do not shows growth and development|
|They are able to reproduce and make their offsprings||They do not reproduce|
|They are made up of cells||They are not made up of cells. They are made of elements or compounds|
|They need nutrients for survival and growth||The non living organism do not need nutrients|
|They can sense environment and respond||They cannot sense environment|
|They respire and carry out metabolic reactions||They do not respire and No metabolic reactions occur in non living organism|
|They have limited life span (they are mortal)||They have unlimited life span (they are immortal)|
|They have locomotary organ and they can move by themselves||They cannot move by their own|
look at your surrounding and enlist at least 10 living and non living things.