Heridity and Variation
The offspring’s of all the organisms (plants and animals) resemble their parents in several aspects. This is only due to the phenomenon of heredity. Hereditary literally means “tendency of like begets like” i.e. all living organisms tend to produce offspring’s like themselves. Hereditary may be defined as the transmission of characters from one generation to successive generations or from parents to their offspring’s. Thus, heredity is the cause of similarities between the offspring’s, so that the individuals of the same parents resemble each other in many aspects. Heredity involves the transfer of genetic characters from parents to the offspring’s via the egg and sperm. These transferable characters are called “hereditary characters”.
Though offspring’s receive all the characters from their parents, they are not exactly alike. Differences are found even between the offspring’s of the same parents. It is difficult to find out the identical individuals. The progeny differs not only in itself but also with the parents. These differences are called variations. Thus, variations may be defined as the visible differences between the parents and the offspring’s or between the offspring’s of the same parents.
Types of Variation:
There are two types of variation: Hereditary variation and Environmental variation
Hereditary variation: The variations which arise as a result of any change in the structure and function of the gene and are inherited from one generation to another are called hereditary variation.
Environmental Variations: Two individuals with the same genotype may become different in phenotype when they come in contact with different conditions of food, temperature, light, humidity and other external factors. Such differences among organisms of similar heredity are known as environmental variation. These are not heritable.