The causes of variation within a species are:
-
Environment:
-
Various environmental factors like food, light, heat, etc. play an important role in somatogenic variations.
-
Changes in genetic pattern:
-
Changes in the genetic pattern due to any factor results in some minor or major changes in the organism inheritable in the next generation.
-
Crossing over:
-
Results in recombination of genetic pattern during meiosis.
-
Dual parentage:
-
An organism developed from the zygote is formed as a result of fusion of male and female gametes (50% each from father and mother).
-
Mother and father also have dual parentage.
-
Hence, a child has 50% characters from parents, 25% from their grandparents and 25% from their great grandparents.
-
Thus, dual percentage plays a key role in variations.
