But human has developed “robots” which can perform several of these tasks but still it does not considered as “living organism”. In addition, with the advancement in technology, the criteria for living organism is redefined. These re-defined criterias are as follows:

1. Complex organization-Composed of different types of cells
2. Metabolism- To produce energy and utilize preformed food material.
3. Responsiveness- To respond to the extreme environmental conditions. Such as Temp, wind, starvation. 
4. Growth- Endogenous Growth
5. Reproduction- ability to give off springs
6. Evolution- To better suits to the changed environment or metabolism.

Diversity and complexicity in biological system: Biological system has vast variety of organism.  A large number of species you can see around you, whether it is insects, butterflies, different types of birds and other pet animals. Different types of plant species available in north-eastern india is given in the Figure 1.1.

Figure 1.1 : Different types of plant species found in northeastern india.