Dear scientists, can any one describe the scientific nature of living things-as to why there are human,cow,insects and other many variable living things?
The answer is not that simple as you need to go through a detailed investigation and study. However with recent advancement of science the answer is not far away. Molecular sciences can perhaps explain the molecular nature of living things,to complement the old Evolution theories that ever existed.
I think the best way to answer your question is to direct you to the theory of evolution; that is, that organisms change over time to better adapt to their environments. I strongly suggest you read a book on the topic, as no number of small descriptions will even come close to giving you a good picture of what evolution is all about. One of my favorite, and most recommended books, on the matter is the following: Endless Forms Most Beautiful, by Sean Carroll