Cladism is a method of classification based on the evolutionary history of organisms, dividing organisms into meaningful groups and subgroups. It was developed by Willi Hennig, an entomologist, in 1950, but was not really accepted until the 1980s. Clades can be represented in terms of a cladogram . A cladogram is a branching diagram that depicts species divergence from common ancestors. They show the distribution and origins of shared characteristics.
Evolution results in modifications of characteristics over time.
Cladistic Phylogenetic Systematics acknowledges only Monophyletic groupings as valid. Problems with the Cladistic position Cladistics would seem at first to be more objective then the linnean and linnean-based systems, simply because in getting rid of higher taxa it also does away of the arbitrariness of whether a higher taxon is, say an order or a class . Cladists believe that cladograms are testable hypotheses of phylogenetic relationships. To give an example. When cladistics first came out there was a huge reaction against palaeontology .