BIO 3220 COMPARATIVE VERTEBRATE ANATOMY Thank you to McGraw-Hill and Dr. Anil Rao (MSCD) for use of PowerPoint illustrations

Basic Definitions Anatomy Morphology

Phylogeny – Evolutionary History Paleontology Functional Adaptation Comparative Morphology Embryology

Homology Shared common ancestry Same embryonic precursor

Analogy Shared function Insect wings & bird wings Gills & lungs

Homoplasy/Homoplastic Organs Shared anatomy Generally, not homologous E.g. Insect wings vs. leaf

Key Points Homology Analogy Homoplasy

Form vs. Function Function, then form – Darwin’s Theory of Natural Selection – Adaptation Form, then function – Preadaptation

Evolution Random chance mutations, coupled with geographic isolation leads to… Change in gene frequency in a population

Divergent Evolution Related Present species evolved from common ancestor

Convergent Evolution Not closely related Dissimilar features evolved to become similar features

Parallel Evolution Related & Isolated Corresponding features undergo equivalent changes in isolated environments

Organic Evolution Present day species are descendants of previous species Changes that have taken place in plants & animals over time

Vestigial Structures Phylogenetic remnant Better developed in ancestor E.g. pelvic girdle in python

Key Point Can you think of a vestigial structure in humans?

Rudimentary Structure More developed in descendant E.g. neck, ear

Ontogeny An individual’s life history Fertilization to death Influenced by environment as well as genetics Structures earliest to develop are likely the oldest phylogenetically

Heterochrony Paedogenesis – Gonads develop quicikly Paedomorphosis – Immature features of ancestor become features of future SPECIES Neoteny – Immature features are retained as an adult in the INDIVIDUAL

paedomorphosis