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Chapter 8

Chapter 8. Classification. Learning Outcomes. By the end of this week, you should: recognise the value of identification and scientific naming (nomenclature). develop knowledge of the principles of classification. recognise that biological classification contains a hierarchy of levels.

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Chapter 8

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  1. Chapter 8 Classification

  2. Learning Outcomes By the end of this week, you should: • recognise the value of identification and scientific naming (nomenclature). • develop knowledge of the principles of classification. • recognise that biological classification contains a hierarchy of levels. • become aware that taxonomic systems are subject to change. • recognise features typically used in constructing major taxonomic groups.

  3. Why is identification important? • Endemic animals • Deadly and harmless snakes • Personal safety • Knowing the difference between poisonous and harmless plants. • Early settlers and stock • Quarantine • Medicine • Conservation • Forensics • Palynology • Agriculture and horticulture • Pests and control measures

  4. What do scientists use to classify organisms? • Whole specimens • Actual, image or verbal description • Bits and pieces • Microscopic – plant cell walls, leaf vein patterns, pollen grains, seed shape • Macroscopic – feathers, hair, teeth, shells, fruits • Molecular – genetic material • Indirect evidence • Track, burrows, nests, scratchings, scats, calls/songs • Reference collections – herbaria, museums • Keys

  5. Keys • Dichotomous key – choosing between two alternatives Complete the key activities.

  6. Scientific naming • Based on Latin or Greek words – pages 227, 228 • Two part names (binomial) – international • Linnaeus’ binomial naming system • 1758 • Systematic • First part = generic (which genus it belongs to), always begins with a capital letter • Second part = specific name (which species it belongs to), lower case • Informative about how closely related organisms are

  7. Why is scientific naming important? • Universal, no matter what language • Common names can be reused for different species • An indication of relatedness • Common names may be misleading – suggesting relationships that are not valid Complete the quick-check questions on pages 224 and 229

  8. What is classification? • Naming and describing. • Organising closely related species into groups. • Combining these groups to form larger, more inclusive groups.

  9. What is a species? • Pages 230-231 • Use of structural similarities? • The ability to interbreed? • The use of chromosomes and DNA?

  10. Principles of classification • Separating into groups • Based on the presence of absence of various features • Uses a series of decisions in a dichotomous key

  11. Features of classification • Classification schemes can vary depending n their function. • Usefulness of the scheme depends on the criteria selected: • Objective (not subjective) – the same meaning for different people = reproducible and predictable results • Meaningful (not arbitrary) – conveys useful information • Schemes are not fixed, but can change when new information becomes available. • Schemes can be single or multi-level (hierarchical).

  12. Benefits of classification • Easier to deal with smaller numbers of groups than very large number of separate items. • Provides information about relationships between organisms. • New items can be added in a predictable way. • Information can be easily retrieved. • Predictions can be made about an item based on its classification.

  13. Hierarchical System • Levels of classification are called taxa (sing. taxon) • The closer the evolutionary relationship between two organisms, the more similar their classification. • The hierarchical system of classification: • Kingdom • Phylum • Class • Order • Family • Genus • Species • Come up with a pneumonic to help you remember! Look at pages 240-242. Complete the quick-check questions on page 242.

  14. Domains • Bacteria - prokaryotes • Archaea – extremophiles • Eukarya - eukaryotes Watch the Clickview video and answer the questions on classification.

  15. Cladistics • Identifying the relationships between various organisms and deciding which organisms should be included in particular groups. • “How many derived features do they share?” • Primitive characters – features that were present in a common ancestor, and so appear in all members of the group. • Derived characters – advanced or modified features that evolved later and appear in some members of the group.

  16. Cladograms • Shows the evolutionary relationship between particular organisms based on the derived characters they share. • A fork/branching point appears whenever a derived feature appears in some members of the group.

  17. Classifications can change • Based on further study. • DNA and protein sequencing can show differences.

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