Sunday, 29 December 2013
Sunday, 22 December 2013
Saturday, 14 December 2013
Important terms of heredity and evolution
Heredity: The transmission of characters (traits) from the parents to their off springs is called Heredity.
Variation: The differences in the character among the individuals of a species is called variation is necessity for organic evolution.
Both Heredity & variation are fundamental factors in the process of Evolution of an organism.
Genetics: The branch of biology which studies heredity & variation is called genetic.
Terms gene was coined by scientist – Johanssen in 1909.
Chromosomes: Chromosomes are thread like structures present in the nucleus of a cell which contain hereditary information of the cell. They are made up of DNA & proteins.
Gene: Gene is the unit of inheritance. Various genes are located in the chromosomes at fixed position genes are responsible for our characteristic features.
Chemically gene is a segment of a large polynucleotide molecule called de oxyribonucleic acid
DNA: Dexyribo nucleic acid DNA was first isolated by Frederick meisher from the nucleus of the pus cells.It is acidic in nature so the name is nucleic acid. DNA is a macromolecule/polymer which is made up of a large no. of smaller units called Nucleotide. So DNA is a polynucleotide.
Nucleotide is the basic structure unit of DNA.
Sex Determination: The process by which the sex of a per is determined is called sex determination.
The Chromosomes which determine the sex of a person called sex chromosomes which areof 2 types X & Y.
XX combination is always found in females
XY combination is always found in males.
ORGANIC EVOLUTION
Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of yrs. In which non species are provided.
DARWINISM / Theory of Natural Selection (by charles robert darwin)
(a) All the species produce a large no of offsprings but population remains fairly constant due to struggle bt the members of same species & different species for food, space & mate
(b) This struggle eliminates the unfit individuals. (Survival of the fittest)
(c) This gives orgin to variations which pass into progeny & over a long period of time, leads to origin of new species.
Limitations: It could not explain how the variations arise.
Variation: The differences in the character among the individuals of a species is called variation is necessity for organic evolution.
Both Heredity & variation are fundamental factors in the process of Evolution of an organism.
Genetics: The branch of biology which studies heredity & variation is called genetic.
Terms gene was coined by scientist – Johanssen in 1909.
Chromosomes: Chromosomes are thread like structures present in the nucleus of a cell which contain hereditary information of the cell. They are made up of DNA & proteins.
Gene: Gene is the unit of inheritance. Various genes are located in the chromosomes at fixed position genes are responsible for our characteristic features.
Chemically gene is a segment of a large polynucleotide molecule called de oxyribonucleic acid
DNA: Dexyribo nucleic acid DNA was first isolated by Frederick meisher from the nucleus of the pus cells.It is acidic in nature so the name is nucleic acid. DNA is a macromolecule/polymer which is made up of a large no. of smaller units called Nucleotide. So DNA is a polynucleotide.
Nucleotide is the basic structure unit of DNA.
Sex Determination: The process by which the sex of a per is determined is called sex determination.
The Chromosomes which determine the sex of a person called sex chromosomes which areof 2 types X & Y.
XX combination is always found in females
XY combination is always found in males.
ORGANIC EVOLUTION
Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of yrs. In which non species are provided.
DARWINISM / Theory of Natural Selection (by charles robert darwin)
(a) All the species produce a large no of offsprings but population remains fairly constant due to struggle bt the members of same species & different species for food, space & mate
(b) This struggle eliminates the unfit individuals. (Survival of the fittest)
(c) This gives orgin to variations which pass into progeny & over a long period of time, leads to origin of new species.
Limitations: It could not explain how the variations arise.
Saturday, 7 December 2013
evolution .....(introduction)
Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.
All life on Earth is descended from a last universal ancestor that lived approximately 3.8 billion years ago. Repeated speciation and the divergence of life can be inferred from shared sets of biochemical and morphological traits, or by shared DNA sequences. These homologous traits and sequences are more similar among species that share a more recent common ancestor, and can be used to reconstruct evolutionary histories, using both existing species and the fossil record. Existing patterns of biodiversity have been shaped both by speciation and by extinction.
All life on Earth is descended from a last universal ancestor that lived approximately 3.8 billion years ago. Repeated speciation and the divergence of life can be inferred from shared sets of biochemical and morphological traits, or by shared DNA sequences. These homologous traits and sequences are more similar among species that share a more recent common ancestor, and can be used to reconstruct evolutionary histories, using both existing species and the fossil record. Existing patterns of biodiversity have been shaped both by speciation and by extinction.
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