Lesson 4 - Morphological Concepts
Intro / Background
Homologous structures: features that share a common ancestry. May or may not be similar in function or appearance. Not all similar structures are homologous.
Example: Front legs of newts and pectoral find of lungfish are anterior appendages both arose from pectoral finds of a CA.
Therefore, newt front legs are homologous to lungfish pectoral fins.
Immediate Function: What it is doing plain and simple by itself (eyes: sensing light)
Biological Role: What it contributes to or allows the organism to do (eyes: vision, mating, hunting etc.)
Use anatomical, developmental, and/or phylogenetic evidence to predict whether structures in different vertebrate taxa are homologous
Evidence for Homology: Embryonic Origin!
If structure A and structure B have different embryonic origins, it is evidence that these structures did NOT arise from same structure in a CA. And vice versa.