Difference Between Continuous And Discontinuous Variations With Examples

Variations, the small differences that exist between individuals can be described as being either discontinuous or continuous.

What Is Continuous Variations?

In continuous variation, there is a complete range of measurements from one extreme to the other. Human height is an example of continuous variation. It ranges from that of the shortest person to the tallest person in the world. Any height is possible between these values. Individual can have a complete range of heights, for example 1.6, 1.61, 1.63 meters etc. This is what is referred to as continuous variation.

Continuous variation is the combined effect of many genes (known as polygenic inheritance) and is often significantly affected by environmental influences. Milk yield in cows, for example is determined by not only by their genetic make-up but also significantly affected by environmental factors such as pasture quality, weather and the comfort of their surroundings.

For any species a characteristic that changes gradually over a range of values show continuous variation. Examples of such characteristics are:

• Weight
•  Heart rate
• Finger length
•  Leaf length etc.

What You Need To know About Continuous Variations

• Continuous variation refers to the type of genetic variation, which shows an unbroken range of phenotype of a particular character in the population. 
• Continuous variations can increase adaptability of the race but cannot form new species. 
• Examples of continuous variation include height, weight, heart rate, finger length, leaf length etc.
• Continuous variations are formed due to crossing over, independent assortment and random fusion of gametes during fertilization.   
• The continuous variations are also referred to as fluctuations.
• Phenotypes of continuous variations have a continuous range and they are difficult to classify into specific categories.
• Presence of many genes for the determination of a particular trait causes continuous variation.
• There is no one-to-one correspondence of genotype and phenotype in continuous various.
•  When represented graphically, continuous variations give a smooth bell shaped curve.
• Continuous variations do not interfere the genetic system of the organism.
• Continuous variations are common type of genetic variations in a population. 

What Is Discontinuous Variations?

A characteristic of any species with only a limited number of possible values shows discontinuous variation.  Human blood group is an example of discontinuous variation. In the ABO blood group system, only four blood groups are possible (A, B, AB or O). There are no values in between, you either have a characteristic or you don’t. This is what is referred to as discontinuous variation.

Discontinuous variation is controlled by alleles of a single gene or a small number of genes. The environment has little effect on this type of variation.

Other examples include:

• Blood group
• Sex (male or female)
• Eye color

What You Need To know About Discontinuous Variations

• Discontinuous variation refers to the type of genetic variation, which shows two or more separate forms of a character in the population.
• Discontinuous variations are the main factor in developing continuous variations as well as in the process of evolution.
• Examples of discontinuous variations include tongue rolling, finger prints, eye color and blood groups.
• Discontinuous variations are formed due to changes in the genome.
• Discontinuous variations are also referred to as mutations or sports.
• Phenotypes of discontinuous variation have a discontinuous variation have a discontinuous range and they can be categorized easily.
• Presence of one or few genes for determination of a particular trait causes discontinuous variations.
• There is a predictable one-to-one relation between genotype and phenotype in discontinuous variation.
• A curve is not produced when discontinuous variations are represented graphically.
• The genetic system of an organism is influenced by discontinuous variations.
• Discontinuous variations develop periodically.

Also Read: Difference Between Genotype And Phenotype

Difference Between Continuous And Discontinuous Variations In Tabular Form

Similarities Between Continuous And Discontinuous Variation 

• Both variations occur due to the difference in DNA in different genomes caused by mutations and genetic recombination.
• Both cause phenotypic variation in different aspects including physical appearance, fertility, mode of reproduction, learning and mental ability, behavior etc.

Also Read: Difference Between Autosomes And Sex Chromosomes