Notes for 11th Science Biology

11th Science. Subject- Biology

Chapter 1.Living World.

1.1 Basic principles of life.

A. The living being once produced / born has c to survive. For survival, it needs energy and many chemical molecules. For energy, it has to perform metabolism.

 Metabolism is breaking of molecules  called catabolism .

For example respiration.

While making of new molecules is called  anabolism .

For the example photosynthesis.

B. From birth onwards, organisms show tendency of growth and development. This growth is a well-orchestrated process. 

C. Growth and development are not the processes which have unlimited time span. At certain point of time, the molecules, organs, systems begin to loose their effective working and become old. This is ageing process of the body.

D. Life has to continue hence the organism tries to produce a young one like itself. It is possible due to reproduction (asexual or sexual). This ensures continuity of race. Mules, sterile worker bees do not reproduce; yet are living. Reproduction as is important characteristic of living organisms.

E. As the body looses it's capacity to perform metabolism, the organism dies. Death is also important characteristic of living organisms.

F. Any living being responds to thermal, chemical or or biological changes in the surrounding. Responsiveness / irritability is unique property of living beings.