Main Difference – Heredity vs Variation

Heredity and variation are two processes involved in the inheritance of characters from parents to the offspring during sexual reproduction. An offspring produced by sexual reproduction does not completely resemble the parents. But a number of characteristics which are unique to a particular species may be observed in the offspring of that particular species. The main difference between heredity and variation is that heredity is the mechanism which transmits characters, resemblance as well as the differences to the offspring from the parents whereas variation represents the visible differences shown by individuals within offspring and species. Genetics is the study of heredity and variations along with the environmental factors responsible for the variation.

Key Areas Covered

1. What is Heredity
      – Definition, Characteristics, Examples
2. What is Variation
      – Definition, Types, Characteristics
3. What are the similarities between Heredity and Variation
      – Outline of Common Features
4. What is the difference between Heredity and Variation
      – Comparison of Key Differences

Key Terms: Continuous Variations, Discontinuous Variations, Environmental Variations, Genetics, Germinal Variations, Hereditary Variations, Heredity, Inheritance, Offspring, Sexual Reproduction, Somatic Variations, Species, Variations

What is Heredity

Heredity is the transmission of traits from parents to the offspring. Heredity literally refers to the concept of ‘like beget like’. That means all living organisms tend to produce an offspring that resemble themselves. On that account, heredity causes all the similarities among generations of a particular species. The transmission of similar characters to an offspring from their parents is achieved by the transfer of genetic material by sexual reproduction. The transferable characters among offspring are identified as hereditary characters. Identical twins get the same hereditary characters. However, the phenotypic characters can vary under the influence of environmental factors. A father and son with jug ears are shown in figure 1. Their crowns also appear the same.

Figure 1: Heredity of jug ears

What is Variation

Though most of the phenotypic characters appear similar in parents and their offspring, some amount of phenotypic characters are not exactly alike. The different phenotypic characters occurring among individuals within the offspring and species are referred to as variations.

Types of Variation

• Hereditary variations and environmental variations are the two types of variations occurring among individuals in a particular species.

Hereditary Variations

Hereditary variations are caused by the changes in the structure and function of a gene, which is inherited from one generation to the other.

Environmental Variations

Environmental factors like food, temperature, humidity, light, and other external factors may influence a particular genotype, producing two different phenotypes. Two different phenotypic variations that arose from the same genotype are referred to as environmental variations.

• Based on the type of cells from which the variation occurs, two types of variations can be identified as somatic variations and germinal variations.

Somatic Variations

Somatic variations occur in somatic cells. The influence of the somatic variations is insignificant since they are not inherited to the offspring. Somatic variations are acquired during the lifetime of an individual and they are also referred to as acquired variations.

Germinal Variations

The variations occurring in the reproductive cells in the body are referred to as germinal variations. Germinal variations are inheritable to the offspring and provide the raw materials for the evolution.

• Based on the degree of difference, two types of variations can be identified as continuous variations and discontinuous variations.

Continuous Variations

Continuous variations are small and indistinct variations, which fluctuate with environmental factors. These variations are non-heritable; hence, they have no influence on evolution. Continuous variations are the most common type of variations among individuals in a population.

Discontinuous Variations

Discontinuous variations are large, distinct, sudden variations, which are less affected by environmental factors. These variations are heritable; hence, they are responsible for evolution through natural selection. 

Figure 2: Diverse coloration and patterning of coquina shells of Donax variabilis

Similarities Between Heredity and Variation

• Both heredity and variation are two components of genetics.
• Both heredity and variation are responsible for the genotype as well as the phenotype of individuals.
• Both heredity and variation are influenced by the environmental factors which deal with the individuals.
• Both heredity and variation are transmitted by genes.

Difference Between Heredity and Variation

Definition

Heredity:  Heredity is the mechanism which transmits characters, resemblances as well as the differences to the offspring from the parents.

Variation: Variation represents the visible differences shown by individuals within the offspring and species.

Diversity of Population

Heredity: Heredity is not responsible for the diversity within the population.

Variation: Variation is responsible for the diversity within the population.

Evolution

Heredity: Heredity has no influence on evolution.

Variation: Variation leads to evolution by introducing new phenotypic characters to the species.

Examples

Heredity: Flat feet vs arches, attached vs free earlobes,  flower color, seed type, and genetic diseases are examples of heredity.

Variation: Eye color, skin color, hair color, dimples, and freckles are examples of variation. 

Conclusion

Hereditary and variation are two effects of sexual reproduction of organisms. Heredity is the transmission of a unique set of characters from parents to their offspring. Variation is the observation of different characters among individuals in a particular species. Characters are inherited among generations of a particular species by genetic factors. Many of the variations promote evolution under the influence of natural selection. This is the main difference between heredity and variation.

Reference:

1. Dobzhansky, Theodosius, and Arthur Robinson. “Heredity.” Encyclopædia Britannica. Encyclopædia Britannica, inc., 08 Nov. 2016. Web. Available here. 25 June 2017.
2. Supamoo. “What is HEREDITY and VARIATION?” Biology. N.p., 11 Mar. 2011. Web. Available here. 25 June 2017. 

Image Courtesy:

1. “Jug Ear Heredity” By Xubor – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Coquina variation3” By Debivort – Own work by Author (CC BY-SA 3.0) via Commons Wikimedia

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