5.3 – Classification of Biodiversity

5.3 – Classification of Biodiversity 

Binomial Nomenclature:

  • The first name in the binomial naming system is called the genus and is always capitalized.
  • The second name starts with a small letter and is called the species.
  • The name must be written in italic. (in handwriting, underline the name), for example: Escherichia coli
  • Genus name abbreviation can be used if the full name is already used, for example E.coli
  • Species: is a group of organisms which can interbreed and produce fertile offspring.
  • Sub-species: species might potentially interbreed if a barrier (e.g. geographical) or other challenge was removed.


  • A taxon means a group of something
  • Scientists arrange or organize species in to a hierarchical set of groups in order to organize organisms into specific similar groups based on similar characteristics
  • As one goes higher up on a classification chart, the greater the number of species are included into the group

  • All organisms are classified into three domains: eukaryota, bacteria, archaea
  • The Archaea and Bacteria domains are prokaryotes. These are organisms that do not have a membrane bound nucleus and their DNA is not associated with proteins.
  • The Eukarya domain includes eukaryotes, or organisms that have a membrane bound nucleus.
  • Groups organisms primarily based on differences in ribosomal RNA structure. Ribosomal RNA is a molecular building block for ribosomes.

Identification of species:

  • Natural classification is very useful for research into biodiversity
  • Easier identification for new species that do not obviously fit into a specific
  • A dichotomous key could be used to put an organism into a classification that fits that organism the best
  • This would not work as well for artificial classification (e.g. Colour of flower petals)
  • Since organism evolved from a common ancestor, new species would share similar characteristics (likely internal), allowing for easier identification and classification. For example the pentadactyl limb, or mammary glands in mammals

Plantae Classification:

  • Bryophytes: no vascular tissue, very small, use spore to reproduce e.g. moss
  • Filicinophytes: has vascular tissue, use spore to reproduce e.g. fern
  • Coniferophytes: has vascular tissue, use naked seeds to reproduce, woody
  • Angiospermophytes: has vascular tissue, produce flowers

Animalia classification:

  • Porifera: sponges, no mouth or anus, filter food from current, attached to rocky surface
  • Cnidaria: jellies, radical symmetry, has mouth but no anus, many has stinging cells
  • Platyhelminthes: flatworms, bilaternal symmetry, mouth but no anus, no segmentation
  • Annelida: segmented worms, bilaternal symmetry, has mouth and anus
  • Mollusca: squid, bilaternal symmetry, has mouth and anus, usually has a shell
  • Arthropoda: inserts, bilaternal symmetry, has mouth and anus, jointed, has exoskeleton and joints

Classification of vertebrate class 

Dichotomous key:

  • A dichotomous key is a key constructed from a series of statements arranged into pairs.
  • The two descriptions should represent separate choices or characteristics that determine the difference between two organisms.
  • Both choices are read and compared with the organism to be identified.
  • If the first characteristic is present in the organism to be identified follow the instructions at the end of the statement. If the characteristic is not present go to the second statement as this should be true.
  • Once a choice is made, that selection directs you to another pair of descriptive statements.
  • One statement might identify the organism or lead you further on in the key.
  • This process is repeated until a successful identification is obtained.