S.5 And S.6 Biology Classification Of Organisms Caltec S.5

A-LVEL BIOLOGY (2012) NAKAPANKA JUDE MAYANJA 0774649208/070471664 Page 1 of 27 CLASSIFICATION OF ORGANISMS Classification is defined as the grouping of organisms together basing on the features they have in common. Taxonomy is defined as the science of classification. Braches of taxonomy Nomenclature is the giving of names to organi sms. Systematics is the placing of organisms into groups basing on their similarities and differences. Binomial nomenclature is the assigning of two Latin names to each organism. The first name/word is the generic name and the second name/word is the specific name. In binomial nomenclature, the following rules are observed; i. The generic name starts with the upper case (capital letter) while the species name starts with a lower case (small letter) . ii. Unless written in italics, the two words must be underlin ed separately e.g. Homo sapiens / Homo sapiens. THE TAXONOMIC HIERARCHY This is the descending order in size of the taxonomic group is Kingdom, Phylum (division in plants), Class, Order, Family, Genus and Species. Each taxonomic group is called a taxon or taxa (plural). Each taxon posses a diagnostic feature i.e. features which are unique (peculiar) to that group e.g. presence of vertebral column is a diagnostic feature for phylum Chordata. Fur is a diagnostic featu re for class mammalia and feathers are peculiar to birds. What is a species ? This is a group of organisms having many common physical and other features and if sexually reproducing, they can breed to produce fertile offsprings. WAYS OF CLASSIFYING ORGANISMS Artificial classificati on: this is based on one or a few easily observable characteristics for simplicity and convenience. Natural classification: this considers natural relationships between organisms e.g. internal and external features. The features considered include;  Embryol ogy  Physiology  Biochemistry  Cell structure  Behavior …