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Chapter 4: Classification and Biodiversity

4.1: Classification of Marine Organisms

Learning Outcomes

  • Candidates should be able to:

    • 4.1.1 Describe the classification of species into the taxonomic hierarchy:

      • Domain

      • Kingdom

      • Phylum

      • Class

      • Order

      • Family

      • Genus

      • Species

    • 4.1.2 Understand and use the binomial system of species nomenclature.

    • 4.1.3 Construct and use simple dichotomous keys based on easily identifiable features.

    • 4.1.4 (PA) Make observations and drawings from unfamiliar structures or specimens from key groups in the following topics:

      • Topic 4.2

      • Cnidaria in topic 5.2

Taxonomic Hierarchy (4.1.1)

  • Classification system organizes species into a hierarchy:

    • Domain

    • Kingdom

    • Phylum

    • Class

    • Order

    • Family

    • Genus

    • Species

  • Each group is called a taxon (plural: taxa).

  • The species is the fundamental taxon, allowing for breeding and producing fertile offspring.

Changes in Classification Systems

  • Historical Classification: Initially, organisms categorized as either plants or animals.

    • Linnaeus's System: Divided all living things into two kingdoms:

      • Kingdom Plantae (plants)

      • Kingdom Animalia (animals)

  • Later modifications included:

    • Identification of fungi and algae as distinct from plants due to advances in microscopy.

    • Expansion to five kingdoms by the 1960s:

      • Monera (bacteria)

      • Protista (protozoa and algae)

      • Fungi (mushrooms, yeasts, molds)

      • Plantae (plants)

      • Animalia (animals)

  • Current System (1990s): Six kingdoms after Carl Woese's findings:

    • Bacteria and Archaea (split from Monera)

  • Domains: Living organisms classified into three domains based on evolutionary lineage:

    • Eukarya

    • Bacteria

    • Archaea

Traditional vs. Modern Classification

  • Traditional Classification guidelines rely on morphological characteristics without genetic considerations.

  • Modern Classification integrates molecular and genetic data to inform taxonomic relationships.

Key Terms (Page 9)

  • Species: Group of similar organisms that interbreed to produce fertile offspring.

  • Binomial Nomenclature: System for classifying species developed by Carolus Linnaeus.

  • Taxonomic Hierarchy: Classification levels of organisms.

  • Dichotomous Key: Tool for identifying organisms based on observable traits.

Binomial System of Nomenclature (4.1.2)

  • Developed by Carolus Linnaeus in 1735.

  • Allows consistent naming of species, avoiding confusion.

  • Format: Genus species (e.g., Erithacus rubecula - European robin).

  • Highlights evolutionary relationships and facilitates scientific communication.

Use of a Dichotomous Key (4.1.3)

  • Functions as an identification tool based on observations.

  • Composed of a series of questions leading to identification stages.

  • Facilitates the classification of unknown organisms through observable features.

Assignments and Homework

  • Create Your Own Dichotomous Key: Project instructions available on Schoology.

    • Gain a practical understanding of classifying organisms.

    • Key project worth 50 points, graded by rubric.