Quiz 1: Life: Biological Principles and the Science of Zoology

It is difficult to define life as there are no defining properties for life. The properties exhibited in the beginning are different from the properties we see today. This is because evolution has taken place. In the same way, unexpected properties have emerged and are seen in different combinations today. So it is difficult to set down standard properties for "life". Hence scientists have taken a few characteristics seen in almost all organisms and given them as the properties of "life".

The basic chemical differences that differentiate between living and non living systems are: • Living systems are made up of chemical molecules like carbohydrates, proteins, nucleic acids and lipids. • A hierarchical system of organization of matter exists in living systems • A genetic program is present in the nucleic acids of living systems • Living systems take required nutrients from their surroundings for their growth and development. These nutrients are used in the process of metabolism.

Living things are highly organized in a "hierarchical" manner: lower levels of organization are progressively integrated to make up higher levels. The building blocks of matter, called atoms, lie at the base of life's organizational structure. This hierarchical organization leads to the emergence of new properties at different levels of biological complexity. The emergence of new properties at a particular level is influenced and restricted by the properties of the components of the lower levels. An animal which cannot hear cannot develop speech and language. It is also dependent on the interaction of the different components to give rise to novel combinations.