Binomial System (OCR A Level Biology)

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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

Examiner 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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Alistair

Author: Alistair

Expertise: Biology & Environmental Systems and Societies

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.