OCR AS Biology

Revision Notes

4.3.2 Binomial System

Binomial System

  • A species is a group of organisms that are able to reproduce to produce fertile offspring
  • Binomials are the scientific names given to individuals species
  • Binomials consist of the organism’s genus and species name in modern Latin
  • For example, the binomial for humans is Homo sapiens and the binomial for dogs is Canis familiaris
  • Binomials are extremely useful for scientists as they allow for species to be universally identified – the binomial for a species is the same across the entire globe

Naming species

  • Species are often given common names, but these common names are often differ between countries and do not always translate directly between different languages
  • In order to avoid confusion about what group of organisms scientists are talking about, all species are given a two-part scientific name using the binomial system
  • This naming convention was developed and established by the Swedish scientist Carl Linnaeus in the 18th Century
  • The binomial name is always italicized in writing (or underlined if it is not possible to italicise)
  • For example:
    • The most commonly known yeast is Saccharomyces cerevisiae
    • It is common to abbreviate the genus name (e.g. S. cerevisiae)
    • Saccharomyces paradoxus is another species of that is a member of the same genus as cerevisiae

Exam Tip

The binomial for a species is always typed in italics or underlined when handwritten. The genus name should have a capital letter but the species name should not.


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