Lecture on Diversity of Life

Introduction

• Trees used in the lecture are a combination of the "Tree of Life" web project and a 2001 paper in Science on mammal phylogeny.
• Phylogenies are continuously refined and debated among researchers; details may vary across different courses.

Phylogenetic Trees

• Ribosomal RNA sequencing across 600 species shows three main groups: Bacteria, Archaebacteria, and Eukaryotes.
• Initial surprise: Archaebacteria, initially expected to group with Bacteria, are distinct.
• Three possible tree structures due to unknown root:
  • Bacteria as outgroup
  • Archaebacteria as outgroup
  • Eukaryotes as outgroup
• Using duplicated genes, Bacteria identified as outgroup for Archaebacteria and Eukaryotes.

Tree Diagrams

• Circular diagrams can represent phylogenies, showing equal time existence across species.
• Linear phylogenies, as provided, are useful for educational purposes and exams.

Details on Major Groups

Bacteria and Archaebacteria

• Eubacteria (True Bacteria):
  • Have cell walls, lack nuclei.
  • Mitochondria and chloroplasts are descendants of Eubacteria.
• Archaebacteria:
  • Resemble Eubacteria but biochemically and genetically more similar to Eukaryotes.
  • Found in extreme environments (e.g., geothermal springs).

Eukaryotes

• Have nucleated cells, true multicellularity.
• Three major groups:
  • Green Plants (outgroup)
  • Fungi and Animals (monophyletic clade)
    • Surprising phylogenetic relationship: fungi closer to animals than plants.

Green Plants

• Include algae, mosses, ferns, gymnosperms, and angiosperms.

Fungi

• Include mushrooms, yeasts.
• Yeast often used in research due to close genetic relation to humans.

Animals

• Not detailed extensively in this lecture, but similar phylogenetic trees can be created for animal diversity.

Conclusion

• The lecture underscores the complexity and beauty of life's diversity.
• Encourages students to appreciate and learn the phylogenetic tree as it represents evolutionary history.