जैव विविधता का कौन सा स्तर विशेष रूप से एक ही प्रजाति के जीवों के भीतर जीनों की भिन्नता और अंतर द्वारा अभिलक्षित होता है?

Out of the estimated millions of species on Earth, approximately how many species have been scientifically identified and described to date?

In the context of factors contributing to higher biodiversity in tropical regions, what is the specific role played by higher levels of insolation?