Evolution

• evolution is the sequence of gradual changes from simple life to complex life forms
• The study of history of life forms on earth is called evolutionary biology
• as the universe expanded the temperature lowered and the gases like hydrogen and helium were formed later
• theory os special creation - Father Suarez
• theory of panspermia - Richter
• theory of spontaneous generation - van Helmont
• theory of chemical evolution - Oparin and Haldane
• theory of special creation


  God has created life by the divine act of creation
• Theory of panspermia


  The life on earth arose from the spores or panspermia which came from outer space and developed into living forms.
• Theory of spontaneous generation


  Life originated from non-living matter automatically
• palaeontology is the study of fossils
• the organs which have the same fundamental structures but are different in functions are called homologous organs
• homology in organs indicates common ancestry. It is based on divergent evolution which leads to the formation of homologous organs
• The relationship between the structures of different groups of animals due to their similar functions is called analogy or convergent evolution
• the organs which are rudimentary or poorly developed and are non-functional in the processor but were functional in the ancestor or in related forms are called vestigial organs
• Theory of recapitulation or biogenetic law


  Ontogeny recapitulates phylogeny
• biogeography is the study of distribution of animals and plants on earth
• Adaptive radiation is the process of evolution of different species starting from a point in a geographical area and finally radiating to other areas of geography
• Chemical resistance is another example of natural selection. The excess use of herbicides and pesticides leads to the selection of resistant varieties of microbes in very less time
• Homology indicate common ancestry

  based on divergent evolution
• homologous organs have same structural design and origin but perform different functions
• divergent evolution is the same structure is developed along different directions due to adaptations to different needs
• analogy does not indicate common ancestry

  result of convergent evolution
• analogous organs are anatomically different but functionally similar
• convergent evolution are the different structures that evolve to perform same function and hence have similarity