Larus argentatus vs sea gull

Larus argentatus and sea gull both are nouns.

Word	Noun	Adjective	Verb	Adverb
Larus argentatus	Yes	No	No	No
sea gull	Yes	No	No	No

As nouns, sea gull is a hypernym of Larus argentatus; that is, sea gull is a word with a broader meaning than Larus argentatus:

Larus argentatus: large gull of the Northern Hemisphere
sea gull: mostly white aquatic bird having long pointed wings and short legs

Other hypernyms of Larus argentatus include gull, seagull.

Larus argentatus (noun)	sea gull (noun)
large gull of the Northern Hemisphere	mostly white aquatic bird having long pointed wings and short legs