noun (n)

• an advocate of the doctrine that the world can be understood in scientific terms(noun.person)

  source: wordnet30
• a biologist knowledgeable about natural history (especially botany and zoology)(noun.person)

  Synonym:
  natural scientist
  

  source: wordnet30
• One versed in natural science; a student of natural history, esp. of the natural history of animals.(noun)

  source: webster1913