Living and Non-living –
If something is living, it will carry out all the seven functions which are movement, reproduction, sensitivity, nutrition, excretion, respiration and growth. Some non living things may show one or two of the seven characteristics of living things but not all of them.
For ex.-car moves, crystals grow in size during crystallization process.
Why are molecular movements needed for life?
Living organisms are well organized structures i.e. organs made up of tissues; tissues are made up of cells; cells have smaller components in them and so on (made up of molecules). Such organized systems must keep repairing and maintaining their structures. Since all structures are made up of molecules , there must be molecular movements around all the time.
Viruses are right on the border between living and non-living as they lead “ a kind of borrowed life”.
For a virus then to be classified as alive it must – reproduce, obtain and use energy, grow, develop and die and respond to the environment. Viruses have genetic material i.e. DNA or RNA. They evolve through time and thus can adopt to their environment, classify them as alive. But, they need a living cell in order to function and reproduce otherwise they play as dead or non-living. Moreover, viruses do not show any molecular movements in them until they are in some living cell.
What are life processes?
Life processes are the processes taking place inside a living organism. e.g. nutrition, respiration, transportation, excretion etc.
They work in coordination to grow by providing energy and maintain the living beings. The living organisms need energy to grow, develop, synthesize protein and other substances and even to maintain a state of order in our body when we are not doing anything. This energy comes from outside sources called food.
For a single celled organisms there is no need of specific organs for taking food, exchanges of gases, transportation of food and oxygen and other gases or removal of waste etc., because the entire surface of the cell is in contact with the environment. Thus simple diffusion may meet the requirements of the single celled organism.
In contrast , in the multi cellular organisms all the cells may not be in direct contact with the surrounding environment and simple diffusion can not meet the requirements of all the cells. Further, such organisms need specific organ / systems i.e. for taking food (digestive system), for exchanging gases (respiratory system), for transportation of food and gases (O2 and CO2) (transportation system), for removal of waste (excretory system).
Ten well developed Organ System of the Human Body
- The digestive system
- The respiratory system
- The circulatory system
- The excretory system
- The reproductive system
- The skeletal system
- The muscular system
- The nervous system
- The integumentary system
- The endocrine system