THE VARIETY OF LIVING ORGANISMS

Classification

Classification

On Earth there are over 1.5 million types of living organisms, from the simple to the more complex. Ever since humans began to observe the natural world they’ve attempted to give these species some form of order by looking at their similarities and differences.

The word taxonomy stems from the Ancient Greek word ‘taxis’ which means ‘arrangement’. In science this is the process by which species are identified, named and then classified. Taxonomy is important in a number of ways:

  • by keeping such a record it can help scientists understand more about a species
  • taxonomic nomenclature is universal so that information can easily be shared
  • it’s vital for keeping a check on biodiversity

Phylogenetics looks at how organisms are related through evolutionary relatedness. To discover this scientists need to look at molecular sequencing and morphological data. Phylogenetics is useful within taxonomy however the two are still very different, both in terms of logistics and the methods used. A problem faced by phyology is that its needs to use living organisms as fossil records contain little data. This means estimates of early evolutionary events have to be made

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Taxonomic Classification

The taxonomic classification system is divided into five kingdoms:

  • Prokaryotae
  • Protoctista
  • Fungi
  • Plantae
  • Animalia

Although today there is a new three domain system:

  • Domain Eukarya
    • Animalia
    • Pkantae
    • Fungi
    • Protista
  • Domain Archaea
  • Domain Bacteria

Each hierarchy can be up into the following:

Kingdom

?

Phylum

?

Class

?

Order

?

Family

?

Genus

?

Species

Each smaller group is contained within a larger composite group and there’s no overlap between groups.

It can be very difficult to define a species, especially to classify an organism as a whole new species. However there are a number of methods used:

  • biochemical: for example, using DNA
  • anatomical: they have a similar anatomic structure
  • embryological: the stages of develop are similar
  • reproduction: the ability to produce fertile offspring
  • immunological: how organisms react to the antigens of another organism
  • behavioural: similar behaviour, for example primates living in social groups