Changes in Classification

Outcomes:

Identify an example where classification has changed as a result of new evidence

In 1758, Carolus Linnaeus drew up rules and developed workable keys for classifying and naming plants and animals. As science knowledge about living things has increased, it has been necessary for the two kingdom classification system (plants and animals) proposed by Linnaeus, to be continuously changed to incorporate this new knowledge.

The invention of the microscope led to the discovery of microscopic forms of life. These organisms didn’t fit into the classification system of the time. The system had to be changed to incorporate this new group or organisms.

Further advances in technology and scientific knowledge saw a four kingdom classification system developed and then a five kingdom system. More recent discoveries and developments have resulted in a six kingdom classification system. There has been plenty of scientific debate in the process.

A disadvantage of natural classifications is that because they predict evolutionary relationships, they change with new information

Taxonomists will reclassify groups of species when new evidence arises to compromise the traditional classification scheme

Groups of species may be separated into different genera if new evidence suggests they evolved from different ancestral species

Species originally classified as figworts have been reclassified into different genera based on DNA sequence comparisons

Alternatively, different species may be grouped into a shared taxon if new evidence suggests more recent common ancestry

The Homininae sub-family was created to include gorillas and chimpanzees when it was deduced that they share more common ancestry with humans than with other great apes (e.g. orang-utan)

Reclassification of Hominids

Activity:

Take a look at ‘The Six Kingdoms’, Rhode Island College website http://www.ric.edu/faculty/ptiskus/six_kingdoms/ for more information. Also https://methanogen.weebly.com/impact-of-technological-advances-on-classification-systems.html

Changes to the classification system have meant that the classification of some species of organisms has changed too. It is possible, for example, that caecilians could once have been classified as snakes.

1. Construct a representation that shows the:

Kingdom, Phylum and Class that caecilians belong to
Kingdom, Phylum and Class that snakes belong to
physical characteristics which reptiles and caecilians have in common,

2. a) At what classification level are caecilians and snakes separated into different groups?

b) What characteristics distinguish them?

Here are some useful websites to begin your research:

‘Amphibian – Caecilians’, San Diego Zoo website http://www.sandiegozoo.org/animalbytes/t-caecilian.html

‘Flesh-eating amphibians filmed’, BBC News, http://news.bbc.co.uk/2/hi/science/nature/7235205.stm

‘Snakes’, SeaWorld, Busch Gardens website http://www.seaworld.org/animal-info/animal-bytes/animalia/eumetazoa/coelomates/deuterostomes/chordata/craniata/reptilia/squamata/snakes.htm

Google Sites

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