What is variation? Give an account of different kinds of variations and its importance in organic evolution. (UPSC 2024, 15 Marks, )

विविधता क्या है? विभिन्न प्रकार की विविधताओं और जैविक विकास में उनके महत्व का वर्णन करें। (What is variation? Give an account of different kinds of variations and its importance in organic evolution.)