Variations

VARIATION

· Individuals of a species having similar characteristics but rarely identical are said to variants of the same species and the differences between them are called VARIATIONS.

· In biology, any difference between cells, individual organisms, or groups of organisms of any species caused by either genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials (phenotypic variation).

· Variation may be shown in physical appearance, metabolism, fertility, mode of reproduction, behaviour, learning and mental ability, and other obvious or measurable characters.

· Genetic variation is a result of subtle differences in our DNA

· Genetic variation is a term used to describe the variation in the DNA sequence in each of our genomes.

· Genetic variation is what makes us all unique, whether in terms of hair colour, skin colour or even the shape of our faces.

· Genetic variation refers to diversity in gene frequencies.

· Genetic variation can refer to differences between individuals or to differences between populations.

· Mutation is the ultimate source of genetic variation, but mechanisms such as sexual reproduction and genetic drift contribute to it as well.

Types of Variation

The types of Variations are:

· Morphological variation: These are variations in the physical appearance of individuals such as size, height, weight, length, colour and proportion of body parts.

· Physiological variation: These are differences in the way member of the same species behave or react to things or conditions in their environment such as ability to roll the tongue; ability to taste certain chemicals; ability to lay many eggs; ability to produce more seeds.

· Continuous variation: These are changes among members of a species that can be graduated from one end of the scale (low) to the other end of the scale (high). Examples are height and weight of organisms such as plants and humans. Morphological variations are usually continuous.

· Discontinuous variation: These are differences expressed with no intermediate forms, that is, it is either present or absent. Examples include, ability to smell; ability to taste substances even at low concentration; number of castes of a polymorphic species such as termites; ability to roll tongue; blood group; finger print; colours of flowers; shape and colours of seeds in plants of the same species. Mostly, physiological variations are discontinuous.

Application of Variations

Blood Groups

· Blood group is used in blood transfusion.

· Before this can be done, it is checked that both donor’s blood and recipient’s blood have compatible antigens.

· Incompatible blood types lead to AGGLUTINATION, a situation that leads to the clumping of the blood of the recipient that can lead to death.

Uses of Variation.

Ø Crime detection: No two people have the same fingerprints. Also identification of the blood group of blood stains found at the crime scene

Ø Anthropology and Evolution: Evolutionary evidence can be found in some the blood groups, for instance the Rhesus factor (Rh) found in humans has been identified in apes.

Ø Skin colour: Variations in skin colours has been used to classify humans into three main races:

o Caucasians – light skinned with different eye and hair colour – these are Europeans or people of European origin.

o Mongoloid – yellowish or brownish-yellow skinned people with dark eyes – Chinese and Japanese

o Negroid – dark skinned people with dark eyes – black Africans and people of African origin.