Taxonomy
Today, there are many changes in the classification of living things. This turmoil in taxonomy has led to many alternative classifications. It is caused partly from the move from Linnaean to cladistic principles, and partly by the use of DNA sequence data in taxonomy. An example is: the way derived groups like birds should not be classified at the same level as the group they evolved from. Yet birds have traditionally been a class under the Linnaean system.