query: SELECT DISTINCT ?personLabel ?twitterName ?pic WHERE {
    ?person wdt:P2002 ?twitterName ;
    wdt:P106 ?occupation .
    OPTIONAL { ?person wdt:P18 ?pic . }
    ?occupation wdt:P279* wd:Q864503 . # all subclasses of biologists
     SERVICE wikibase:label {
       bd:serviceParam wikibase:language "en" .
     }
  }
  