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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.