What is LIFE?
Life is an exclusive property of the different types of Living organisms in the world. Life on earth originated about 3.5 million years ago. Biology is the science which deals with the study of living organisms.
Most of the living organisms show wide diversity and fundamental similarity. All the living organisms must possess protoplasm with the genetic substance.
Fundamental properties of Living organisms
1. Cellular organization and Highly ordered structure
Living organism’s body is made up of one cell to many cells. Cell is a structural and functional unit of the body. Each cell is covered and isolated from the surroundings by a limiting membrane. The limiting membrane called as plasma membrane which is responsible for control the exchange of various substances across it. There are Two major types of cells occur in the world, one is Prokaryotic cells and another one is Eukaryotic cell.
Prokaryotic cell doesn’t have nuclear membrane or nucleoli. Eukaryotic cell has True nucleus, consisting of nuclear membrane or nucleoli.
2. Complexity of organization:
Generally Living organisms show hierarchical organization from cellular level to organ system level. Several organ systems make up an organism. The ordered complexity is not seen in the non-living things.
ATOMS – MOLECULES- CELL – TISSUE – ORGAN – ORGAN SYSTEM – ORGANISM- POPULATION- COMMUNITY- ECOSYSTEM – BIOSPHERE.
Living Things ⇔ Non-living Things
3. Sensitivity/ Response to Environment:
Sensitivity is the property of showing response to external or internal stimuli (physical, chemical or biological). The ability to show response is called Irritability. Generally living organisms show response to external or internal stimuli.
Example: Plants show sensitivity to environment such as light, water and temperature.
Growth is the fundamental character of living organisms but Growth cannot be taken as a defining property of living organisms because Growth in living organisms is grow from inside and Non-living things is by accumulation of material on the surface.
5. Energy utilization/ Energy processing/ Metabolism
The chief source of energy for living organisms is Sun light. The chief energy carrier for various reaction is living organisms is ATP(Adenosine Tri phosphate). ATP is ‘cellular energy carrier’.
The sum total of all the chemical reactions occurring in the bodies of organisms constitute Metabolism. The process of building up complex substances from simpler substances is called Anabolism or Anabolic process. Example: Building up cells and cellular components.
The process of breaking down complex substances into simpler substances to release energy is called as Catabolism or Catabolic process. Examples: Cellular respiration, Digestion.
Reproduction is the process of producing new organisms of the Parent’s type. Reproduction occurs by vegetative, asexual and sexual methods. Sexual reproduction involves fusion of gametes forming a zygote which develops into a young organism.
Asexual reproduction can be done by the Binary fission, Budding, Fragmentation.
Examples: Protozoans by Binary fission
Sponge, Hydra by Budding
Planarians by Fragmentation
Homeostasis is the dynamic constancy of the Internal environment of an organism within a range that cells can tolerate. Homeostasis is the maintenance of steady sate or relatively constant internal conditions different from the surrounding environment. Most of the living organisms maintain ‘constant internal environment’ by various physiological adaptations.
Example: The maintenance of healthy blood pressure in the body
The maintenance of Proper calcium level in the body
The maintenance of Body temperature and blood volume
Life is constantly changes from simple to more complex forms. Variations in organisms arise through ‘mutations’ or gene re combinations.
According to Charles Darwin’s natural selection theory states that living beings accumulate their beneficial variations over a period of time and tend to evolve gradually into new types of organisms after surviving the struggle for existence.