User:Uthpala/Sandbox

VARIATIONS:

Variations are differences found in morphological, physiological, cytological and behaviouristic traits of individuals belonging to same species, race and family. Types of variations:

1. Somatic or somatogenic variations These variations affect the somatic cells of an organism. They are also called modifications or acquired characters because they are acquired by an individual during its lifetime. They are caused by three factors, which are given below

a)	Environmental factors: The environmental factors such as light, temperature, nutrition, wind and water supply etc., bring changes in the plants as well as animals.

b)	Use and disuse of organs: The continuous use of organs make them stronger and disuse make then weaker. For example, a player who exercises daily has a strong muscular body as compared to one who does not perform exercise.

c)	Conscious efforts: Modifications due to conscious efforts are observes only in those animals, which have intelligence. Receiving education, slim bodies, boring of pinna, small feet and bonsai, etc., are some examples of conscious efforts.

2. Germinal or blastogenic variations They are inheritable variations formed mostly in germinal cells which are either already present in the ancestors or develop as new due to mutations. These are of two types. i.	Continuous variations: They are fluctuating variations which oscillate due to race, variety and species. ii. Discontinuous variations: These are mutations which are suddenly, unpredictable, inheritable, not connected by any intermediate stages, these variations are the source of all germinal variations and most of the evolution.

Importance of variation:

•	Neutral variations are often pre adaptations to certain environmental changes like pesticide resistance, antibiotic resistance, cold resistance, etc. • They are essential on the struggle for existence. •	They provide individuality to an organism. •	Variations allow breeders to improve races of plants and animals. •	Discontinuous variations introduce new traits. •	These help in speciation.