Cambridge O Level Biology · Syllabus 5090 · Classification
Binomial System
What is Binomial System?
The binomial system is the internationally agreed way of naming species using two words: the genus name first, beginning with a capital letter, followed by the species name in lower case. Both words are italicised when typed and underlined separately when handwritten, for example Homo sapiens.
This definition is part of the Classification chapter in Cambridge O Level Biology.
Binomial System in context
A species is a group of organisms that can reproduce with one another to produce fertile offspring. Every species is named using the binomial system: the genus name first, beginning with a capital letter, followed by the species name in lower case, for example Homo sapiens. Both words are italicised when typed and underlined separately when handwritten. Resemblance is not the test — a horse and a donkey produce a mule, which is not fertile, so they are two different species, while two dogs of different breeds belong to one species.
Questions students ask about Binomial System
How do you write a scientific name correctly?
Use the binomial system: the genus name first, beginning with a capital letter, then the species name in lower case, for example Homo sapiens. Both words are italicised when typed and underlined separately when handwritten. Writing Homo Sapiens or homo Sapiens loses the mark, because the capital belongs on the genus only and the species part always stays lower case.