GENERAL PRINCIPLES OF CLASSIFICATION
Classification is the science that puts organisms into distinct groups to make their study easy and systematic. Modern scientific classification is based on structure and functions. Organisms with similar anatomical and morphological characteristics are placed in one group while those with different structures are grouped separately.
Modern studies in genetics and cell biochemistry are used to give additional help in classifying organisms. There are seven major taxonomic groups. The kingdom is the largest group. Others are phylum (division for plants) class, order, family, genus and species, the smallest.
- Living organisms are named using Latin or Latinised names.
- Every organism has two names.
- This double naming is called binomial nomenclature.
- This system of naming was devised by Carolus Linnaeus in the 18th Century.
- The first name is the generic name – the name of the genus.
- The second name is the name of the species.
- The generic name starts with a capital letter while that of the species starts with a small letter.
- The names are written in italics or are underlined in manuscripts.
Bean =Phaseolus vulgaris.
- Phaseolus is the generic name,
- Vulgaris is specific name. Dog = Canis familiaris.
- Canis is the generic name, familiaris the specific name.
General Characteristics of Kingdoms Organisms are classified into five kingdoms.
Viruses do not fit neatly into any of the above kingdoms.
- They are simple and not cellular.
- They are metabolically inactive outside the host cell.
- Most of them can be crystallised like chemical molecules.
- Therefore they do not exhibit the characteristics of living organisms.