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Learning objective 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 Success criteria To understand how and why we classify organisms

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

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

Phylogeny Questions Turn to page 200 and look at Fig 1 Which two are closer related? 1. Gorilla, Thrush, Snake 2. Man, Gorilla, Snake 3. Snake, Frog, Trout

Phylogeny Answers 1. Gorilla, Thrush, Snake 1. Thrush and Snake, share a more recent common ancestor 2. Man, Gorilla, Snake 1. Man and Gorilla, share a more recent common ancestor 3. Snake, Frog, Trout 1. All same relation, have the same common ancestor (this is known as monophyletic: all evolved from same species)

Taxonomic Hierarchy: Domain

Evolution of classification systems Carl Linnaeus started it all off 250 years ago using visible features of organisms - limited C17 th 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. Cytochrome c (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

Levels of Classification K P Crisps Only Fry Good Spuds Kingdom Phylum Class Order Family Genus Species 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 Classification systems (from GCSE)

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

Taxonomic Hierarchy HumansChimpanzee DomainEukaryote KingdomAnimalia PhylumVertebrate ClassMammal OrderPrimate FamilyHominid GenusHomoPan Speciessapienstroglodites

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

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

Taxonomic Hierarchy: Domain

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.

Exam question June 2010 Q.2 a)placing, living things / organisms / named organisms, into, groups / categories / taxa / named taxonomic groups ; based on / AW, similarity / difference ; b) 1. morphology / anatomy / (observable / physical) features / appearance / AW ; 2. biochemistry / cytochrome C ; 3. genes / DNA / genetics / RNA ; 4. behaviour / physiology / embryology ; 5. idea of shared, evolutionary past / phylogeny ; 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

b ii)T S R W U Q ; ; ; c) 1. 3 domains AND 5 kingdoms ; 2. domains are, bacteria / eubacteria, AND, archaea / archaebacteria, AND, eukarya / eukaryotes ; 3. kingdoms are prokaryotes AND protoctists AND fungi AND plants AND animals ; 4. eukaryotes split into different kingdoms / all eukaryotes are in the same domain ; 5. all prokaryotes are in the same kingdom / prokaryotes split into different domains ; 6. domain classification based on, rRNA / ribosomes / RNA polymerase / protein synthesis / enzymes / flagella / membrane structure ; 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

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.

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