Chapter 17 - Evolution of Animals - Echinoderms & Chordates.pdf

This preview shows page 1 - 4 out of 7 pages.

Chapter 17: Evolution of Animals II - Echinoderms & Chordates 17.1 - Introduction Our seas were filled with jawless vertebrates Lots of fauna came to an end due to a mass extinction Land got colonized by insects Vertebrates interested in what was going on on land due to the insects This encouraged the movement for some fish to “migrate” to land to get their food Humans would only be about 2 Myr on this scale, so not a very long time ago Oldest → Most recent 1
First animal fossil → First fossil of chordates & craniates → Colonization of land by animals ( Arthropods ) → First fossils of animals with jaws → First fossils of terrestrial vertebrate ( Amphibians ) → Origin of reptiles 17.2 - The Echinoderms Chordates and Echinoderms share characteristics of deuterostomes : Radial and indeterminate cleavage Development of the coelom from the archenteron Formation of the mouth at the opposite end of blastopore Good MC question! Marine animals that move slowly or are sessile Radial adult form, but the larvae shows a Bilateral Symmetry Notes: Echinoderms: Think of Starfish Adult form of living Echinoderm show a Radial Symmetry, but we know that it originates from a Bilateral Symmetry Sea Lily: Sessile Fossils more than 500 Myr are morphologically similar to existing species Urchins and sea cucumbers 17.3 - The Chordates The Chordates: 4 common derived characteristics Notes: Notochord: Primitive vertebral column, but this is a long bar of cartilage (connective tissue) that provides rigidness to tail Compare morphology of worm vs. chordate But in chordates there is a switch in body now What was dorsal is now ventral, what was ventral is now dorsal Now notochords are found as intervertebral discs (there is a jelly that allows flexibility) → jelly is a remnant of notochord Our post-anal tail reforms itself and is something different We had pharyngeal slits, but we lost them; but fish didn’t lose them as it is functional for them 2
Cephalochordates Morphology resembling a chordate in adulthood Spends most of their life in sediment with head facing out Cirri helps them catch food particles

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture