Classification and taxonomy

1. Classification and taxonomy

2. Starter: Group the TV Shows Sponge Bob Squarepants Star Trek ER Friends Heroes Neighbours Big Brother X factor Doctor Who House Lost The Simpsons Desperate Housewives Eastenders Futurama

3. Learning objective • To understand how and why we classify organisms Success criteria • Define the terms classification, phylogeny and taxonomy • Discuss the changes to classification systems over time • Describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species • Compare and contrast the five kingdom and three domain classification systems • Explain the relationship between classification and phylogeny

4. Key Terms • Taxonomy • The study of the principles behind classification • Classification • The process of organising of living organisms into groups. • Natural classification – grouping according to how closely organisms are related and reflects evolutionary relationships • Phylogeny • The study of evolutionary relationships between organisms

5. Classification and Phylogeny • Classification of organisms depends their evolutionary relationships • Phylogeny is the study of the evolutionary relationships between organisms

7. Phylogeny Questions • Turn to page 200 and look at Fig 1 • Which two are closer related? • Gorilla, Thrush, Snake • Man, Gorilla, Snake • Snake, Frog, Trout

8. Phylogeny Answers • Gorilla, Thrush, Snake • Thrush and Snake, share a more recent common ancestor • Man, Gorilla, Snake • Man and Gorilla, share a more recent common ancestor • Snake, Frog, Trout • All same relation, have the same common ancestor (this is known as monophyletic: all evolved from same species)

9. Taxonomic Hierarchy: Domain

10. Evolution of classification systems • Carl Linnaeus started it all off 250 years ago using visible features of organisms - limited • C17th microscopes allowed us to look at cells, later electron microscopes allowed us to look inside cells • Physiology • How living organisms work • Biochemistry • Comparison of biological molecules eg. Cytochromec (protein used in respiration: almost all species have it, but it is not identical in all, the more similar the amino acid sequence the more closely related the organisms) • DNA • Comparison of DNA sequences – probably most accurate

11. K P Crisps Only Fry Good Spuds Kingdom Phylum Class Order Family Genus Species Classification systems (from GCSE) Levels of Classification Organisms can only belong to one group in the taxonomic hierarchy. As you rise through the ranks of classification (taxa) the individuals grouped together show more and more diversity

12. Activity • Come up with a mneumonic to remember the taxa of classification • D K P C O F G S

13. Taxonomic Hierarchy

14. The 5 kingdoms (We’ll come back to this next lesson in more detail) PROKARYOTES Prokaryotes

15. Kingdom vs Domain • In 1990 Carl Woese suggested 3 Domain classification system based on fundamental differences in RNA • He divided the prokaryotes into • Bacteria (Eubacteria) • Archaea (Archaebacteria) • This is now widely accepted

16. Taxonomic Hierarchy: Domain

17. What is a species? The hierarchy ends with species. A group that can contain only one organism. A species is a group of similar organisms able to reproduce and produce fertile offspring. Scientists constantly update the classification systems because of discoveries about new species and new evidence about known organisms.

18. Exam question June 2010 Q.2 ACCEPT ‘grouping living things’ Look for the idea of similar organisms being placed in the same group or different organisms being placed in different groups 1 CREDIT cell features e.g. nucleus / membrane- bound organelles / cell wall / prokaryotic-eukaryotic features / unicellular 2 CREDIT component of cell wall 3 IGNORE chromosomes 4 ACCEPT ‘how they feed’ / nutrition / ‘how they reproduce’ 5 ACCEPT ‘how closely related’ IGNORE refs to interbreeding / fertile offspring a) placing, living things / organisms / named organisms, into, groups / categories / taxa / named taxonomic groups ; based on / AW, similarity / difference ; b) • morphology / anatomy / (observable / physical) features / appearance / AW ; • biochemistry / cytochrome C ; • genes / DNA / genetics / RNA ; • behaviour / physiology / embryology ; • idea of shared, evolutionary past / phylogeny ;

19. Exam question June 2010 Q.2 Mark the order of letters (ignoring the dotted lines) All 6 in correct order = 3 marks If any incorrect, then credit T S in order at beginning = 1 mark U Q in order at end = 1 mark R before W anywhere in the sequence = 1 mark ACCEPT phonetic spellings ACCEPT alternative terms for names of kingdoms and domains throughout (e.g. plants / plantae) 2 ACCEPT ‘eukaryota’ 3 DO NOT CREDIT protists / protozoa 6 IGNORE RNA unqualified DO NOT CREDIT other forms of RNA ACCEPT any detail of protein synthesis b ii) T S R W U Q ; ; ; c) • 3 domains AND 5 kingdoms ; • domains are, bacteria / eubacteria, AND, archaea / archaebacteria, AND, eukarya / eukaryotes ; • kingdoms are prokaryotes AND protoctists AND fungi AND plants AND animals ; • eukaryotes split into different kingdoms / all eukaryotes are in the same domain ; • all prokaryotes are in the same kingdom / prokaryotes split into different domains ; • domain classification based on, rRNA / ribosomes / RNA polymerase / protein synthesis / enzymes / flagella / membrane structure ;

20. Plenary • Why do we study how closely related we are to other species? • To help us understand our own evolution. By studying the organisms that are closely related to us can help us to understand our own biology and behaviour.

21. Homework • Find 3 closely related organisms (same from the Domain to the Genus taxa) • Find 3 organisms that are not closely related (different at the Domain taxa) • Write out their full classification: domain to species taxa