Biological Classification and Cladograms

Taxonomic Hierarchy:

• Domains: Three main domains of life.
• Levels of Classification:
• Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• As you move down the ladder:
  • Decrease in the number of organisms
  • Increase in similarity among organisms.

Common Ancestor:

• Bottom of the classification tree represents the most basic organisms.
• Organisms develop further characteristics as we move up the classification system.
• Example Traits:
• Insects at the bottom (do not have vertebrae)
• Vertebrates and tetrapods higher up (have these traits).

Derived Characteristics:

• Characteristics that appear in more recent generations but not in older ones.
• Used in cladograms to show evolutionary changes.
• Each line in a cladogram represents a derived characteristic.

Cladogram Interpretation:

• Read from bottom to top; recent descendants at the top of the tree.
• Lines indicate the number of derived characteristics.
• Organisms are always at the top, with derived characters below.
• Pay attention to how the cladogram is structured; follow the order from basic to more complex organisms.

Key Points for Exam Preparation:

• Recognize how to identify traits in a cladogram.
• Understand the significance of each derived characteristic and what they indicate about the organisms' evolution.
• Review examples of common ancestors and recent descendants.
• Practice reading and interpreting cladograms accurately.