Topic Phylogeny: Explaining the history of diversity

Overview of Phylogeny

• Phylogeny is the hypothesized evolutionary history of a species or group of related species, often shown in a branching tree diagram.

Objectives

• To explain the phylogenetic approach to evolutionary history, differentiate homology and analogy, interpret primitive vs. derived character traits, and create/interpret cladograms and phylogenetic trees.

Key Concepts

Requirements and Assumptions of Phylogeny

1. All organisms have ancestors.

2. Organisms share heritable character traits.

1. Phylogenies Reveal Relationships

• Evolutionary change can lead related organisms to become more dissimilar over time.

Important Terms in Phylogenic Trees

• Root: Most recent common ancestor of all taxa.

• Node: A split point representing a common ancestor.

• Branch: Evolutionary path.

• Tip: Extant groups.

2. Homology

• Homology Defined: Similarity in character traits due to shared ancestry, independent of function.

• Examples: Bones in the forelimbs of whales, humans, lizards, and birds, deriving from a common ancestor.

3. Analogy

• Analogy Defined: Similar in function and appearance but differing in structure and origin, arising from convergent evolution due to similar environmental pressures.

• Example: Cacti and spurges showing similar succulent forms due to adaptation to arid environments.

Summary

• Understanding phylogeny is crucial for interpreting evolutionary history and relationships, with the distinction between homologous and analogous traits being key to assessing origins.