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.
- Anatomy: the detailed body structure determined by dissection.
- 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 capitol letter) and species (starting with a lower case letter), written in italics when printed (therefore underlined when written). e.g. Homo sapiens.
- 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).