Evolutionary Biology is the study of history of life forms on earth. The origin of life is considered a unique event in the history of universe. The Big Bang theory attempts to explain to us the origin of universe. Louis Pasteur by careful experimentation demonstrated that life on earth comes only from pre-existing life.
Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc). It was then preceded by chemical evolution, i.e., formation of diverse organic molecules from inorganic constituents.
The subsequent events to show first form of life are a conjectured story based on Darwinian ideas of organic evolution by natural selection. The conventional religious literature shows the theory of special creation.
A study of fossils in different sedimentary layers indicates the geological period in which they existed. The study showed that life-forms varied over time and certain life forms are restricted to certain geological time spans.
The Comparative study of anatomy and morphology among organisms of today and those that existed years ago shows similarities and differences. The homologous structures are the result of divergent evolution while the analogous structures are the result of the convergent evolution.
The process of evolution of different species in a given geographical area starting from a point and radiating to other habitats is called adaptive radiation
According to Hugo deVries it is mutation which causes evolution. Mutations are random and directionless.
According to Hardy Weinberg principle allele frequencies in a population are stable and are constant from generation to generation. The total genes and their alleles in a population remains a constant. This is called genetic equilibrium.
Sometime the change in allele frequency is so different in the new sample of population that they become a different species. This original drifted population becomes founders and the effect is called founder effect
The Study of comparative anatomy of different organisms, fossils and comparative biochemistry provides evidence for evolution. The story of evolution of modern man is complex and interesting. The evolution of man appears to parallel evolution of human brain and language.