It is very difficult to define life and living beings, Life is a self regulated complex system of molecules where chemical reactions are going on all the time that lead to its maintenance, growth and reproduction. Living beings are organised self regulated discrete entities which exhibit the various characteristics of life like movements, growth, responsiveness and reproduction. Such self sustained movements are major criteria which distinguishes living beings from the non-living ones. MOVEMENTS
Changes in position are called movements. Living beings show both visible and invisible movements. 1. Visible movements are those which can be detected by human eyes. Example- running of dog, flying of a bird etc.
Plants do not show locomotion. They are fixed. Visible movements are slow with the exception of plants like Mimosa pudica (sensitive plant, Touch me not) which show folding of leaves on being touched. Breathing movements are absent in plants. 2. Invisible movements are those changes in position which cannot be observed by human senses because they occur at the molecular level. Example- entry of nutrients into cells or release of waste from them. Viruses are also made of molecules. However, they show molecular movements only inside their host cells.
Life processes are those basic functions of living beings which are essential for their survival. They are the same in all types of living forms whether unicellular or multi-cellular, plants or animals.
1. Maintenance of protoplasmic structures- All living beings are made up of protoplasmic structures. They have to be kept in functional state whether an organism is active or inactive.
2. Metabolism- It is the sum total of all chemical reactions which occur in a living being due to interaction amongst its molecules. All functions of organisms are due to metabolism. Metabolism has two components i.e. Anabolism and Catabolism.
* Anabolism- It...