When writing scientific names using binomial nomenclature, we always only look at the genus and the species. In this case, the genus is <em>panthera</em> and the species is <em>leo</em>.
One of the requirements of writing scientific names is that the genus comes before the species and only the genus and capitalized; everything else is lower case. Also, everything is italicized. So the answer is <em>Panthera leo</em>.
