Table of Contents
VARIATION IN POPULATION
Population is a group of organisms of the same specie living in a specified area within a given period of time. Variation refers to the differences which exist between individuals of the same species
Types of variations
- Morphological variation
- Physiological variation.
Morphological variation is the noticeable physical appearance of individuals of the same species. This physical appearances change gradually within a population. The feature observed shows a gradual transition between two extreme forms (continuous variation) e.g. size (height or weight), colour and finger prints.
Physiological variation is the difference in the ways individuals of the same species behave or react to conditions in their environment. It is not visibly apparent like morphological variation. It relates to the functioning of the body. In physiological variation, organisms can be grouped into two or more classes within a population without any graduation or intermediate between or among them (discontinuous variation). Examples of such variation are behaviour which can be temperamental, accommodating, excited or calm, blood groups, ability to roll the tongue, ability to taste phenylthiocarbamide etc.
CAUSES OF VARIATION
There are two causes. They include:
- Genetic differences
- Environmental influence.
A sudden change in a gene called mutation can be inherited when sex linked. This then brings about variation e.g. a gene responsible for green fruits in plants may be altered to produce a yellow fruit in the same plant
Environment include housing, food, healthcare, educational facilities, parental care etc. e.g. an intelligent person exposed to an unfavourable environment becomes dull.
APPLICATIONS OF VARIATION
- Crime detection: Use of finger prints which can be arch, loop, whorl or compound.
- Determination of paternity using blood group
- Development of hybrids of desired traits in agriculture
- Classification of human race based on skin colour, shape of nose, texture of the hair into Caucasoid (European), Negroid (Black African) Mongoloid (Chinese and Japanese), Australoid (Australian)
- Blood transfusion: The blood group of the donor must be compatible with that of the recipient. If not, the donor’s RBC will clump in the recipient’s blood vessels causing serious harm to the recipient. Each blood group is characterized by specific proteins in the blood which are antigens in the RBC and antibodies in the blood plasma. The table below shows antigen-antibody reactions between donor and recipient bloods.
(Antigen a + b)
|A (Antibody b)||+||–||–||+|
|B (Antibody a||–||+||–||+|
|O (Antibody a + b)||–||–||–||+|
+ means positive reaction (no clumping)
- means negative reaction (clumping)
Note: O is a universal donor while AB is a universal recipient
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