4.5.3 Hierarchy of the Taxa

Hierarchy of Taxonomic Groups

Organisms are classified into a hierarchical structure, with each level becoming more specific:

1. Domain

• The highest taxonomic rank.
• Three domains: Bacteria, Archaea, and Eukaryota.

2. Kingdom

• The second broadest group.
• Example: Animalia (animals), Plantae (plants), Fungi, Prokaryotae (bacteria), and Protoctista.

3. Phylum

• Groups organisms based on their basic body plan.
• Example: Chordata (animals with a backbone).

4. Class

• Further divides organisms within a phylum.
• Example: Mammalia (mammals) within Chordata.

5. Order

• Groups organisms within a class.
• Example: Carnivora (meat-eating mammals).

6. Family

• Groups related genera within an order.
• Example: Felidae (cat family).

7. Genus

• A group of closely related species.
• Example: Panthera (big cats such as lions and tigers).

8. Species

• The most specific group.
• Defines organisms that can breed together to produce fertile offspring.
• Example: Panthera leo (lion).

Binomial Naming System

• Each species is given a scientific name composed of:
  • Genus (capitalised)
  • Species (lowercase)
• Example: Homo sapiens (humans).
• This system provides universal identification to avoid confusion caused by common names.

Features of the Hierarchy

1. Non-overlapping groups – Each organism fits into only one group at each level.
2. Ordered from broad to specific – From domain down to species.