ORIGIN AND EVOLUTION OF LIFE Flashcards
means the appearance of
simplest primordial life from non-living
matter.
origin of life
means the gradual
formation of complex organisms from
simpler ones.
evolution of life
It states that life migth have first originated
on earth through a series of combinations of
chemical substances in the distant past and
it all happened in water.
Chemosynthetic Theory of Origin of Life
Chemosynthetic Theory of Origin of Life was proposed by
Alexander Ivanovich Oparin
the source of energy - ultraviolet rays or
electric discharge (lightening) or heat or a
combination of these caused reactions that
produced complex organic compounds
first stage
simple organic molecules combined to form large molecules which included peptides (leading to the formation of proteins), sugars, starches and fat molecules.
second stage
the large molecules of different kinds combined together to form multi-molecular heaps and complexes.
third stage
It is also believed that RNA molecules might have shown
enzymatic activity in the “primordial soup” of chemical
compounds. Such molecules have been termed ________
ribozymes
some sort of nucleoproteins or nucleic acids may have evolved by random
combinations which have provided two or more properties to coacervate like
bodies.
fourth stage
The formation of complex organisms through ‘change’ from simple ancestral types over the course of geological time.
evolution
The various present day organisms were not
created in the same form in which they exist today, but have gradually evolved from much simple ancestral forms of a common ancestor.
Theory of Organic Evolution
Though organisms of different species and
groups are quite different from each other
still they retain certain common features.
evidences from morphology
are the organs which are similar in structure and origin but may look very different and perform different functions.
homologous organs
The structure which are functionally similar but
structurally different are called _________
analogous organs
is any small degenerate
or imperfectly developed
(non-functional) organ or part which may have been complete and functional in
some ancestor.
vestigial organs
The animals or plants which possess characters of two different groups of
organisms are knowns as
connecting links
is the study of development
of an orgnanism
embryology
the embryos of all vertebrates are similar in shape and structure in their
early stages.
evidences from embryology
is the study of fossils.
paleontology
The fossils discovered provide the ancestral history of individual. Animals like horse, camel etc. are direct proofs of organic evolution. This can be very well illustrated by the past history of horse.
evidences from paleontology
All organisms have cell as the basic unit of life. The cell is made of biomolecules.
molecular evidence of evolution
still holds ground
but was modified with progress in genetics and
developed into the Modern synthetic theory which is
regarded as the most valid theory of evolution.
Darwin’s Theory of Natural Selection
which is a sudden genetic change.
mutation
which occurs in sexually reproducing organisms at every reproduction. The chromosomes and thus
genes of the parents mix at random during zygote formation.
genetic recombination
