Heredity and Evolution revision notes

 Heredity and Evolution Revision notes

 

 

l    Heredity and hereditary changes

-          Heredity is the transfer of biological characters from one generation to another with the help of genes.

-          Johann Gregor Mendel is pioneer of modern genetics.

-          In 1901, mutational theory was given by Hugo de Vries.

-          In 1902, paired chromosomes in the cells of grasshopper were observed by Walter Sutton.'

-          In 1944, all living organisms   except   viruses   have   DNA   as   genetic   material   was   proved by trio of scientists Ostwald Avery, Maclyn McCarthy and Colin MacLeod.

-          In 1961, a model was proposed for process of protein synthesis with the help of DNA by Francois Jacob and Jack Monad.

-          Science of heredity is useful for diagnosis, treatment and prevention of heredity disorders, production of hybrid varieties of animals and plants and in industrial processes in which microbes are used.

l    Transcription, Translation and Translocation

-          Information about protein synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is necessary for body. These proteins are synthesized by DNA through RNA. This is called as 'Central Dogma'.

-          Process of RNA synthesis is called as 'Transcription'.

-          The code for each amino acid consists of three nucleotides. It is called as 'Triplet codon'.

-          Dr. Har Govind Khorana, made an important contribution in discovery of triplet codons for 20 amino acids.

-          As per the message on mRNA, amino acids are supplied by the tRNA. For this purpose,

                       tRNA has 'anticodon' having complementary sequence to the codon on mRNA. This is calle‘Translation.’

-          The ribosome keeps on moving from one end of mRNA to other end by the distance of one tripletcodon.

This is called 'Translocation' such many chains come together to form complex proteins.

-          These proteins control various functions in the body of living organisms and their appearance too.

-          Sometimes any nucleotide of the gene changes its position, that causes a minor change which is nothing but the mutation.

l    Evolution

-          Formation of new species due to changes in specific characters of several generations of living organ isms as a response to natural selection is called as evolution.

-          3.5 billion years ago, life had been non-existent on the earth.

First primitive type of cells may have been formed from the mixture of different types of organic and

inorganic compounds.

-          There may have been some differences among those cells and according to the principle of natural selection, some may have shown good growth and some may have perished which could not adjust with the surrounding.

l    Evidences of evolution :

-          Morphological evidences : Various similarities like structure of mouth in animals and leaf  shape in plants indicate that there are some similarities in those groups and hence, it proves that their origin must be same and must have common ancestors.

-          Anatomical evidences : There is similarity in structure of bones and bony joints in organs of each of human, cat, bat and whale. This similarity indicates that those animals may have common ancestors.

-          Vestigial organs: Degenerated or underdeveloped useless organs of organisms are called as vestigial organs. Various vestigial organs like tail bone (coccyx), wisdom teeth and body hair are present in human beings.

-          Paleontological evidences: Remnants and impressions of organisms remain preserved underground. These are called as fossils.The time passed since the death of a plant or animal can be calculated by measuring the radioactivity of C-14 and ratio of C-14 to C-12 present in their body. This is called ' carbondating'. It is used in paleontology and anthropology for determining the age of human fossils and manuscripts.

-          Embryological evidences: Comparative study of embryonic developmental stages of various vertebrates shows that all embryos show similarity during initial stages and those similarities decrease gradually.

l    Darwin’s theory of natural selection.

-          Charles Darwin published the theory of natural selection which preaches the survival of the fittest.

-          Darwin had published a book titled 'Origin of Species'.

l    Lamarckism

-          Jean-Baptiste Lamarck proposed that morphological changes occurring in living organisms are responsible for evolution and the reason behind those morphological changes is activities or laziness of that organism.

-          Development of organs due to specific activities or their degeneration due to no use at all was widely accepted but transfer of those characters from generation to generation was rejected. Because it had been verified many times that modifications brought in us are not transferred to next generation and thereby, Lamarck's theory was disproved.

l    Speciation

-          Formation of new species of plants and animals is the effect of evolution.

-          Geographical or reproductive isolation also leads to speciation.

l    Human evolution

-          Humans are said to have evolved from ancient animals like lemur approximately 7 crore years ago.

-          There has been consistent evolution in man since then.

-          Apes which started to live on land as forest declined showed gradual developement.

-          Their lumbar bones developed, their posture changed and they started using hands.

-          These apes then grew up in size and became more intelligent.

-          The first human like animal recorded was “Ramapithecus”ape from East Africa.

-          Development of apes continued with development of their brains and discovery of fire.

-          These developed apes were called as Homo sapiens.

-          Neanderthal man was the first Homo sapiens.

-          Since then the evolution has been faster.

 

Scientist and Year		Discovery / Contribution
1	Gregor Johann Mendel, 1886	Series of experiments on pea plant to explain inheritance of characters.
2	Hugo de Vries, 1901	Reasons behind sudden changes.
3	Walter and Sutton, 1902	Paired chromosomes in grasshopper cells.
4	Ostwald Avery, Maclyn, McCarthy and Colin Macleod (1944)	All living organisms have genetic material in the form of DNA. (except viruses)
5	Francois Jacob and Jack Monad, 1961	A model process of protein synthesis with the help of DNA in bacterial cells.
6	Dr. Har Govind Khorana, 1968	Discovering of triplet codons.
7	Willard Libby, 1960	Developed carbon dating method.
8	Charles Robert Darwin, (1809 - 1882)	Proposed the theory of evolution.
9	Jean - Baptiste Lamarck, (1744 - 1829)	Activities of the organisms are responsible for their evolution.