New Section

Introduction to the course on biological diversity and phylogeny, focusing on exploring the diversity of life forms on Earth through the metaphor of a tree representing relationships between living beings.

Course Objectives and Focus

• The course aims to analyze the diversity of life forms on Earth using a tree metaphor to explore relationships between different organisms.

• Focus will be on exploring diversity within Bacteria, Archaea, and Eukaryotes to establish evolutionary relationships.

• Discussion will include viruses, an area still controversial in the tree of life representation.

Historical Perspective on Biological Classification

Examining the historical development of biological classification methods and their impact on phylogeny studies.

Importance of Historical Review

• Understanding past classification strategies helps comprehend present and prepare for future developments in biology.

• Exploring reasons behind classification needs and strategies for organizing diverse life forms.

Evolution of Classification Methods

Tracing the evolution of classification methods from Aristotle's dichotomy to Linnaeus' hierarchical system.

Evolutionary Milestones

• Aristotle's early dichotomy between plants and animals based on observable characteristics.

• Transition from fixed species concept to dynamic evolution understanding with advancements like microscopes.

Linnaeus' Contributions and Modern Influences

Discussing Linnaeus' contributions to hierarchical classification systems and their enduring impact.

Linnaean System Legacy

Evolution of Classification Systems

This section delves into the evolution of classification systems for living organisms, highlighting key shifts in paradigms and the impact of evolutionary theories on taxonomy.

Paradigm Shift to Evolutionary Focus

• The discussion begins with a shift towards understanding evolution, challenging the static view of the world. Lamarck and Wallace's evolutionary theories marked a paradigm change where continuous change and movement were recognized.

Impact of Evolution on Classification

• Living beings are products of an evolutionary process, altering how classification is perceived. Darwin's publication in 1859 on the origin of species was a significant milestone in this regard.

Evolutionary Perspective in Taxonomy

• The discussion transitions to classifying organisms from an evolutionary standpoint. Traditionally, plants and animals were treated as two distinct kingdoms, reflecting a long-standing dichotomy.

Challenges in Classification

• Early classifications placed bacteria as plants due to certain cellular features. Fungi were also categorized as plants based on cell wall characteristics, showcasing the complexities in traditional classification systems.

Ambiguities in Organism Classification

• Organisms like amoebas and glenas posed challenges as they exhibited characteristics of both plants and animals, blurring the lines within the classic dichotomy.

Discussion on Biological Classification

In this section, the discussion revolves around the evolution of biological classification systems and the establishment of three domains in the tree of life.

The Work of Vez and Three Domains

• Vez, a molecular biologist from 1977, established a tree of life based on RNA and ribosomal molecules, identifying similarities among eukaryotes.

• Vez categorized prokaryotes into bacteria and archaea, noting that archaea are closer to eukaryotes evolutionarily than bacteria. This led to the acceptance of three domains in biological classification.

Evolution of Classification Systems

• A proposal from 2007 divides eukaryotes into various groups within the tree of life, reflecting an explosion of life with multiple branches.

• The progression from two kingdoms to three, four, five kingdoms (with variations), culminating in the acceptance of three domains by Vez. Fungi are grouped under opisthokonts while green and red algae are considered plants.

Changing Perspectives in Biological Classification

• The evolving knowledge and methodology have led to changes in the tree of life. Different characteristics analyzed have reshaped our understanding.