Concept & Use of a Classification System

• Organisms can be classified into groups by the features that they share
• Classification systems aim to reflect evolutionary relationships (change of adaptive features of a population over time, as a result of natural selection)
• Species: organisms which can reproduce successfully
• Classification is traditionally based on studies of morphology and anatomy
• Morphology: the overall form and shape of their bodies e.g. wings or legs
• Binomial system: a system of naming species in which the scientific name of an organism is made up of two parts showing the genus (starting with a capital letter) and species (starting with a lower-case letter), written in italics when printed (therefore underlined when written)
• Kingdom --> Species = Similarity increases
• DNA is the chemical from which chromosomes are made
• Each DNA molecule is made up of strings of smaller molecules containing four bases
• Biologists compare the sequences of the bases in the DNA of organisms from two different species
• The more similar the base sequence, the more closely related the species are to one another
• Organisms which share a more recent ancestor have base sequences in DNA that are more similar than those that share only a distant ancestor
• The sequences of bases in DNA and of amino acids in proteins are used as a more accurate means of classification (cladistics)
• Anatomy: the detailed body structure determined by dissection