In-Depth Notes on Phylogeny and Systematics

Phylogeny Overview

• Definition: Phylogeny refers to the evolutionary history of a species or group of species, based on common ancestry inferred through homologous traits.

Systematics

• Concept: Systematics is the discipline that biologists use to classify organisms and determine their evolutionary relationships.

• Methods: Utilizes information from fossils and DNA, primarily focusing on morphology, to infer these evolutionary relationships.

Binomial Nomenclature

• Definition: A scientific naming system founded by Carolus Linnaeus.

• Examples:

  • Alces alces: Moose (North America) or Eurasian elk (Europe)

  • Cervus canadensis: Wapiti/Elk

  • Cervus elaphus: European Red Deer

• Note: Common names often do not accurately reflect the organism's nature.

Linnaean Classification Hierarchy

• Species: Panthera pardus (Leopard)

• Genus: Panthera

• Family: Felidae

• Order: Carnivora

• Class: Mammalia

• Phylum: Chordata

• Domains:

  • Bacteria

  • Archaea

  • Eukarya

• Related Species: Panthera onca (Jaguar), Panthera leo (Lion), Panthera uncia (Snow Leopard), Panthera tigris (Tiger)

Phylogenetic Tree Interpretation

• Branch Point: Represents a divergence of lineages indicating a common ancestor.

• Terms:

  • Sister Taxa: Two lineages that are more closely related to each other than to others.

  • Basal Taxon: Diverges early in the history of a group.

  • Polytomy: Unresolved pattern of divergence indicating multiple lineages diverged simultaneously.

Case Study: Whale Meat Analysis

• Context: Questions surrounding the legality of whale meat sold in Japanese markets.

• Methodology: Comparison of mitochondrial DNA from whale meat samples to known species.

Homologies vs Analogies

• Homologies: Phenotypic and genetic similarities due to shared ancestry.

• Analogies: Similar traits resulting from convergent evolution, where unrelated species adapt to similar environments, potentially causing confusion in phylogenetic development.

Examples of Homologies and Analogies

• Homologies:

  • Dolphin flippers vs Human arms vs Bird wings vs Bat wings

• Analogies:

  • Bird wings vs Insect wings; examples of convergent evolution in flying and burrowing organisms (e.g. Notoryctes typhlops and Scalopus aquaticus).

Conclusion: Understanding phylogeny is essential for categorizing life forms and tracing their evolutionary pathways, and it is influenced by both shared traits and adaptations to environments.