Heredity vs Variation
Heredity and variation are two closely related terms in genetics though, there is a subtle difference between heredity and variation, which has to be understood carefully. Heredity is the passing of characters of parents to their offspring. A progeny can inherit characters either by sexual or asexual reproduction. On the other hand, variation is the process of the changes occurring, or the differences of the inherited characteristics. These variations can be the results of genetic variation or environmental variation.
What is Heredity?
Every individual organism is a result of the reproduction of its parent organism either by sexual or asexual reproduction. In asexual reproduction, individuals obtain exactly similar genetic composition from their parents. Whereas, in sexual reproduction, half of the genes are from the mother and the other half is from the father. Thus, progeny is more like their parents than other non-related individuals. This phenomenon of offspring inheriting their genes from parents is known as heredity.
However, progeny phenotype or external appearance of an individual is determined by its genetic composition (genotype; G) and environment (E) in which they live (P = G + E). E.g. Some tall plants become stunted when they are in harsh environments that may lack water and other nutrients.
The above described inherited characters are called hereditary characters.
Heredity is offspring inheriting their genes from parents
What is Variation?
Variation can be identified as the differences in characteristics of individuals in a population. Discrete variations and continuous variations are two types of variations.
Discrete variations – discrete variations can be demarcated by their distinct nature. These types of traits are governed by one or a few genes, and the impact of environment on gene expression is very less.
E.g. The trait eye colour has discrete variations such as brown, blue.
Ear lobe of a person can be attached or free.
Continuous variations – these types of variations show continuously changing values or data for the selected character. Therefore, these types of traits are governed by multiple genes or polygenes. Thus, it is also known as polygenic character. The environment is highly influenced by the character expression.
E.g. Height of a person or a plant.
Continuous characters can be represented using frequency distribution curves.
Phenotypic variations of an individual are the result of genetic and environmental variations. Genetic variations in a population can be occurred due to mutation, recombination, and gene flow. Mutation is the permanent change of a nucleotide sequence of an organism. If this change occurs in a coding region, products of the gene become different (e.g. DDT resistance mosquitos resulted due to mutation). Recombination is the process of exchanging genetic material between non-sister chromatids. As a result, gametes produced by single cell division cycle become unique to one another. Gene flow occurs when an individual organism moves into a new population. It increases the variation in alleles in the population.
Adult Osteocephalus cannatellai showing variation in dorsal coloration
What are the similarities and differences between Heredity and Variation?
• Definition of Heredity and Variation:
• Heredity is the passing of characters from one generation to another.
• Variation is the differences present in characters exhibited organisms.
• Phenotypic Characters:
• Both heredity and variation include the phenotypic characters of an organism.
• Environment and Genotype Influence:
• Both heredity and variation are influenced by the genotype of an organism and the environment in which the organism lives.
• Importance in Evolution:
• Both heredity and variation are important in evolution; for natural selection.
Images Courtesy:
- Father and son by “Mike” Michael L. Baird (CC BY 2.0)
- Adult Osteocephalus cannatellai showing variation in dorsal coloration by Daniel Mietchen (CC BY 3.0)
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