6.4.2

Classification of Living Organisms 2

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The Three-Domain System

The ‘three-domain system’ was proposed by Carl Woese and classifies organisms based on chemical analysis:

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Archaea

  • Primitive bacteria, many of which are extremophiles (i.e. live in extreme environments).
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Bacteria

  • True bacteria.
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Eukaryota

  • Organisms that possess complex subcellular structures (e.g. protists, fungi, plants and animals).

Evolutionary Trees

Evolutionary trees are used to show how scientists believe organisms are related.

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Evolution

  • The start of the tree is a common ancestor and the branches show the species that have evolved from the common ancestor.
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Classification

  • Current classification data is used for living organisms and fossil data is used for extinct organisms.

Jump to other topics

1Cell Biology

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

6Inheritance, Variation & Evolution

7Ecology

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