UNDERSTANDING LIFE -

1. Presence of protoplasm is the important feature of life which acts the site of metabolism.
2. Maintenance of life by protoplasm requires continuous energy conversion and using energy for performance of certain vital activities.
3. Protoplasm is made up of inorganic (81% - water 80% + minerals & gases 1%) & organic matter (19% - protein 14% + lipid 3% + carbohydrate 1% + regulatory substances as enzymes, hormones, vitamins & nucleic acid 1%)
4. Inorganics are always micro biomolecules.
5. Organics may be micro or macro biomolecules.
6. C, H, O, N, P, S form about 98% of body weight of organism.
7. O element is maximum i.e. 62%.
8. Thus life can be defined as "the ever active and changeable state of organized matter".
9. A living being act as an organisation so they are called organism.
10. Living organism are morphous.

These are main characters of living beings -

1.      ORGANISATION -

(i) Protoplasmic level - e.g. Protozoa

(ii) Cellular level - e.g. Porifera

(iii) Tissue level - e.g. Coelenterata, Ctenophora

(iv) Organ system level - e.g. Platyhelminthes to Mammals

• These levels beyond the individual organism are -

(i) Population level - All individuals of a species in a particular area.

(ii) Community level - Population of different species as plants or animals present in a particular area.

(iii) Ecosystem - Living beings inter act with non-living components.

(iv) Biosphere lelvel - Different ecosystem of all the geographical regions of the world form the biosphere.

• Factor regulating the organisation -

(i) Aggregation - It involves grouping of smaller units to form large units.

(ii) Interaction - It involves interrelationship between different components of an aggregate.

(iii) Equilibrium - Tendency to keep a balance or stability e.g. to maintain ecological balance in nature.

(iv) Change - It is ability to show variation as different atoms as C, H, O, N, combine in different ways to form different chemical in body.