Evolution (Part-I)

Introduction: In the previous lecture, we discussed the chemical theory to explain the origin of life. Life is originated as primitive cell with ability to replicate, absorb nutrition and repair the damage. These single cells are the starting material to form multicellular system and eventually the development of organisms with tissue and organ system. In addition, individual organisms also acquire features over time to adopt better towards changed environment. The progressive advancement of organism is by the process known as evolution. Aristotle has considered evolution as “Ladder of chain” or “Scala naturae” involving hierarchical linking of series of forms.

    
Chemical Evolution: The term evolution refers to change from one form to another. Change in living organism with time is known as organic or biological evolution. The process of evolution can be understood from the fact that unicellular organism appear first, simple multicellular and later development of complex multicellular organisms such as seed plants and vertebrate animals. The fishes were the initial early vertebrate and it gradually change to form amphibians. These amphibians has produced reptiles and that has evolved further to give birds and mammals. These hierarchical linking of different species is considered by ladder of chain by Aristotle as given in Figure 5.1. In the same series, mammals have evolved to human involving ape-like primates by acquiring changes over the course of time (These changes and different intermediate forms are discussed in a later lecture).