What is evolution and origin of life

Definition of Evolution

 The term ‘Evolution’ was coined by “Herbert Spencer”.(also “survival of the fittest”)

 The term ‘organic evolution’ was coined by Charles Darwin, but ‘theory of first organic evolution’ was given by Lamarck.

 Evolution is defined as history and development of race With variations.

 “Descent with modification” is the central theme of Evolution.

 The term ‘Evolution’ in biology means gradual changes.

 Evolution is generally progressive, and for evolution the most Important requirement is variation.

 Concept of evolution was given by Empedocles and a Buffoon.

 Empedocles is the founder of the concept of evolution, but The father of evolutionary concept is a Buffoon.

 Trend of evolution was first explained by Lamarck.

 The ultimate source of organic variation is mutation.

 One of the most Important factors for the development of a New species is the geographical isolation.

Types of organic evolution

Progressive evolution: Formation of more complex, elaborate and specialized structures from simpler ones.
Retrogressive evolution: Development of simple and less elaborate forms from complex ones.
Microevolution: Development of minute changes due to gene mutations and recombination’s. These changes occur below species level.
Parallel evolution: Independent formation of similar traits by related groups of organisms.
Convergent evolution: formation of similar traits by unrelated groups of organism, as wings in insects, birds and bats.
Divergent evolution (Adaptive radiation): Formation of different structures from a common ancestral form. EG: Fore limbs in horse, bat and human beings.
Macroevolution: Development of large changes like formation of new species and genera due to mutation causing large scale changes in chromosomes.
Mega evolution: large change giving rise to new families, orders, classes, etc.
Coevolution: Evolutionary changes in one or more species in response to change in other species of the same community.

Origin and Evolution of life

The study of origin of life is ‘ Evolutionary Biology’ or ‘Bio evolution’.

The terms ‘Bio evolution’ or ‘Evolutionary Biology’ were suggested by Meyer.

There are six theories of origin of life:

Theory of special Creation

 Oldest view, proposed by Hebrew et al.

 Life was created by some supernatural power (god)

 According to Bible and Hindu philosophy, god created all organisms.

 The Spanish priest Father Suarez was the greatest supporter of this theory.

 Christian mythology: Adam and Eve were the first Man and woman on earth.

 Hindu mythology: Brahma is the creator who created first Man and woman on Earth.

Theory of spontaneous generation (a biogenesis or auto genesis)

 Organisms form automatically from non-living matter By a process of spontaneous generation.

 Greek philosophers of pre-Christian period Thales, Ana Ximenes, Anaximander, Empedocles, Aristotle, etc. are the followers of this theory.

 Ana Ximenes proposed the air as sole cause of life.

 The Belgian plant nutritionist Jean Baptize Van Helmont stated that young mice could arise from wheat grains, when these were put in the dark along With a moist, dirty shirt.

 Discarded by Louis Pasteur, Francesco Redis.

Theory of Biogenesis

 Theory of spontaneous origin of life was not accepted by Italian biologist and physician Francisco Redis (1668), Italian investigator Spallanzani and French scientist Louis Pasteur.

 All these scientists supported ‘biogenesis’ and proved that new organisms can form only from pre-Existing ones.

 The idea of spontaneous generation was first refuted By Francesco Redis. Spontaneous generation of flies from rooting meat, disproved by Francesco Redis.

 The theory of biogenesis is however not applicable to origin of life because it doesn’t explain the origin of Life.

Cosmogenic theory

 Cosmogenic theory was proposed by Richer and Supported by Arrhenius.

 Life comes from outer space in the form of spores.

Theory of catastrophism

 Sudden creation of life from inorganic materials was supported by Georges Cuvier, ‘the father of modern Paleontology’.

Operon - Haldane Theory /biochemical origin of life

 Alexander I. Operon was a Russian biochemist.

 He hypothesized that conditions favoring abiotic formation of organic monomers existed in the primitive Atmosphere.

 Hydrogen atoms were most numerous and most Reactive in primitive atmosphere. Hydrogen combined With all available oxygen atoms and formed water.

 Thus, water and ammonia were probably the first compound molecules of the primitive earth.

 The atmosphere of Earth at the time of origin of life was Without the free oxygen atoms.

Note: The ‘origin of species’ book was written by Charles Darwin.

 The Operon - Haldane theory suggests that complex organic molecules formed through a series of chemical reactions in the Earth’s ‘primordial soup’.

 Most widely accepted theory of origin of life.