Speciation and classification
Classification is a means of organising the variety of life based on relationships between organisms and is built around the concept of species. Two organisms belong to the same species if they are able to produce fertile offspring. The fact that all organisms share a common ancestry allows them to be classified.
Originally classification systems were based only on observable features but more recent approaches draw on a wider range of evidence to clarify relationships between organisms. This has been helped by advances in genetic technology.
A phylogenetic classification system attempts to arrange species into groups based on their evolutionary origins and relationships. It uses a hierarchy in which smaller groups are placed within larger groups, with no overlap between groups. Each group is called a taxon (plural taxa). One hierarchy comprises the taxa: domain, kingdom, phylum, class, order, family, genus and species. Each species is universally identified by a binomial consisting of the name of its genus and species, eg Homo sapiens.
Transfer of genetic information from one generation to the next can either ensure continuity of the species or lead to variation within a species, which can ultimately lead to the formation of a new species.
Factors such as reproductive isolation can lead to accumulation of different genetic information in populations', potentially leading to the formation of new species.
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Links and Resources
This Catalyst article provides useful background/reading around the subject matter for A level biologists on the topic of speciation and classification. The theme that students should take from this article is that species investigation is not something that belongs in the past, speciation and classification is very much a part of modern biology.
Students could be given this article to read as a homework/directed study, as stimulus material for a lesson starter discussion on the subject of why is it important to maintain as many species as possible?
This Catalyst article is about the naming system used for biological species, devised by Linnaeus. The purpose of biological names is investigated and the article also explains how the naming system works. There is a good explanation of why classification can change when new evidence is presented.
This is a good article to introduce students to the topic of speciation and classification, it would be a useful reading/review/summary activity for students to complete as a homework/directed study before this topic is started in class.
This detailed booklet on animal taxonomy, written by the Institute of Biology, provides an extensive guide to the subject of classification. The booklet is really only suitable for teachers who want to refresh their knowledge about this topic before delivering to students.
It would be possible to use certain sections of the booklet with students--these just need to be selected carefully. For example on pages two and three of the booklet, there are two very good examples of why the identification of species is such an important activity. These paragraphs could be copied (possibly retyped) for students to read and review. They could then be asked to provide a summary response to the question why is the identification of species so important?
In this first activity, from the Linnean society, students consider classification and binomial nomenclature. The idea of hierarchy is illustrated, before explaining Linnaeus’s system of classification and the terms kingdom, phylum, class, order, family, genus and species. There is also a useful introduction to the use of Greek and Latin vocabulary in science.
This is a detailed and comprehensive resource that provides an eight page worksheet, with eleven questions suitable for A level. This resource could be used as it stands and would not require teachers to amend it in anyway.
There is a teacher guide containing all the answers. These could be used for students to peer assess completed worksheets.
In this second activity from the Linnean society students consider the principles and importance of classification and taxonomy, the importance of Linnaeus’ contribution to science, using and constructing keys and making valid and reliable observation.
The activity will require students to access the Linnaeus collection on-line.
The activity is estimated to take two hours. It would be suitable to start it in class and then for students to complete the remaining questions as homework/directed study.
There is a teacher guide containing all the answers included in this resource. These could be used for students to peer assess completed worksheets.
This third activity from the Linnean society is another detailed and comprehensive resource that provides an eight page worksheet, with a case study, and fifteen questions suitable for A level. This resource could be used as it stands and would not require teachers to amend it in anyway.
The activity looks at speciation, dimorphic and polymorphic species and Batesian mimicry. In Batesian mimicry a palatable species mimics an unpalatable one, thus protecting itself from predation. There are a number of questions related to identification of species and the challenge this presents. This activity is suitable for use under several topics: evolution, speciation, classification and populations.
This activity would be suitable to use in class, with remaining questions completed for homework/independent study.
This comprehensive booklet is split into three sections. In the first section titled systematics there is a good couple of introductory pages regarding classification and taxonomy. These would make for suitable homework reading for students. The text format may not be the best, but the reading level should not be a problem for A level students.
The remainder of this section of the booklet then provides a comprehensive history of taxonomy. This is a very interesting account, and may be good background reading for teachers, but is probably too detailed for students. As with the other sections of this booklet there are some particularly good diagrams and illustrations.
The remaining two sections of the booklet cover the five kingdoms. Again the level of detail included is comprehensive and more than any A level requirement; however as with the previous section they would make good reading for teachers wanting to refresh their knowledge about this topic. Also, as with previous section, there are some very good tables; illustrations and images used in both of the kingdom sections, and it would be worth considering how these could be incorporated into resources to use in lessons. Possibly projected onto the whiteboard or colour copied for students to classify.