BIOL 1020U Chapter Notes - Chapter 23, 44: Tiktaalik, Diploblasty, Weight-Bearing
Document Summary
Background: morphological and molecular phyyylogenes indicate that fish are he closest relatives to four-legged land vertebrates. Hypothesis: land vertebrates evolved from fish by modifications of the skeleton and internal organs which made it possible to live on land. Tiktaalik a remarkable fossil found in 2004 that has fins, scales, gills like fish but wrist bones fingers, an amphibian like skull and a true neck which fish lack. Fossils confirm phylogenetic prediction that tetrapod vertebrates evolved from fish by th developmental modification of limbs, skulls, and other features. Resear shows that limbs of fish and amphibians are shaped by similar patterns of gene expression-further supporting phylogenetic connection. Canadian artic- perfect age and area to preserve rock from that age. Fossils and phylogeny show that animal forms were initially simple but rapidly evolved complexity. Macroscopic organisms thought to be animals first appeared in rock deposits from 575 million years ago, called ediacaran fossils from where they were discovered.
