There are two major factors which may cause variation in living organism s. The factors are genetic differences and influence of the environment.
Genetic differences are concerned with those traits that are inherited from a parent. When the parent bears children, each child inherits some characteristics of the father and some of the mother. It should be noted that no two children inherit exactly the same combination of characters from father and mother.
There are also in some case when genes factors that are responsible for inherited are altered or changed. such a sudden change in a gene is called a mutation. A mutation can be inherited and brings about a variation. For example, a gene responsible for a green fruit may be altered to produce a yellow fruit from the same plant.
INFLUENCE OF THE ENVIRONMENT
The environment plays an important role in the variation that may occur in human beings. The environment includes housing, food, health care, education facilities, parental care e.t.c A person who is intelligent which is derived from his parent may become dull if he is exposed to unfavourable environment e.g absence of schools, good, food, inadequate medical attention e.t.c
On the other hand, a person has borne into a good environment such as good medical care, good parental care, good feeding e.t.c even through may be deficient genetically can improve in the physical and mental build-up, hence the changes resulting in variation.
APPLICATION OF VARIATION
Variation has wide application in human life. These applications include:-
CRIME DETECTION:- Morphological features which are peculiar to an individual can be used by police and other detectives to trace criminals. Examples of such features include height, the colour of the skin, the colour of hair, the colour of the eyes and fingerprint. Physiological features such as rolling of tongue and difference in blood group are also used.
Every human being human belongs to one of the four major categories of the fingerprint which are aches, loops, compound and whorls.
BLOOD TRANSFUSION:- There are four main blood groups. These are A, B, AB and O. Blood groups are characterised by specific proteins in the blood and these and these are antigens in the red blood cells and antibodies in the blood plasma. Antigens are subtances which will stimulate an animals to form protein compound called antibodies. When a victim of an accident loses large quantity of blood or a woman at birth loses large quantity of blood or a woman at birth loses too much blood, it can be replaced with blood obtained from another person called the donor.