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Comparing Invertebrates

Comparing Invertebrates. The First Multicellular Animals. Fossils evidence from Ediacara Hills, Australia show some of the earliest and most primitive animals (575-543 mya). Altough these animals were bilateral and segmented, they were probably simple and with little internal specialization.

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Comparing Invertebrates

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  1. Comparing Invertebrates

  2. The First Multicellular Animals • Fossils evidence from Ediacara Hills, Australia show some of the earliest and most primitive animals (575-543 mya). Altough these animals were bilateral and segmented, they were probably simple and with little internal specialization.

  3. Beginnings of Invertebrate Diversity (The Cambrian Explosion) Burgess Shale fossil evidence shows that animals became more diverse after the Cambrian period (544 mya). Some animals had evolved shells, skeletons, and other hard body parts - which were preserved as fossils. The Cambrian Explosion Video Clip: http://www.pbs.org/wgbh/evolution/library/03/4/l_034_02.html

  4. Invertebrate Phylogeny Invertebrate Cladogram Chordates Cladogram (shows evolutionary relationships) Echinoderms Arthropods Annelids Mollusks RadialSymmetry Roundworms Flatworms Pseudocoelom Deuterostome Development Cnidarians Radial Symmetry Coelom Protostome Development Three Germ Layers;Bilateral Symmetry Sponges Tissues Multicellularity Single-celled ancestor

  5. Evolutionary Trends • Specialized Cells, Tissues, & Organs simple --> complex • Body Symmetry asymmetrical --> radial --> bilateral • Cephalization no head --> head • Segmentation no body segments --> specialized body segments • Coelom Formation (body cavity) acoelomate --> pseudocoelomate --> true coelom • Embryological Development protostome --> deuterostome

  6. Comparing Invertebrates Major Characteristics Germ Layers BodySymmetry Cephalization Coelom Early Development Sponges Absent Absent Absent Absent — Cnidarians Two Radial Absent Absent — Flatworms Three Bilateral Present Absent Protostome Roundworms Three Bilateral Present Pseudocoelom Protostome Comparing Invertebrates Chart Section 29-1 Major Characteristics Germ Layers BodySymmetry Cephalization Coelom Early Development Annelids Three Bilateral Present True coelom Protostome Mollusks Three Bilateral Present True coelom Protostome Arthropods Three Bilateral Present True coelom Protostome Echinoderms Three Radial (adults) Absent (adults) True coelom Deuterostome

  7. Invertebrate Digestive Systemssimplest animals: intracellullar digestion (inside cells)complex animals: extracellular digestion (digestive tract) Intestine Gizzard Crop Mouth/anus Pharynx Mouth Gastrovascularcavity Anus Gastrovascularcavity Annelid Cnidarian Crop Pharynx Anus Pharynx Mouth Rectum Mouth/anus Stomachanddigestive glands Intestine Flatworm Arthropod

  8. Invertebrate Respiratory SystemsAquatic invertebrates: diffusion and/or gillsTerrestrial invertebrates: book lungs, tracheal tubes, etc. Trachealtubes Gill Siphons Movement of water Spiracles Insect Mollusk Airflow Booklung Spider

  9. Invertebrate Circulatory Systemssimplest animals: diffusion through body surfacecomplex animals: heart(s) to pump blood in a circulatory system Heartlike structure Hearts Small vessels in tissues Heart Bloodvessels Sinusesand organs Bloodvessels Heartlikestructures InsectOpen Circulatory System Blood is partially contained. Blood is pumped into sinuses. Blood comes in direct contact with tissues AnnelidClosed Circulatory System Blood is contained in vessels. More efficient (active animals)

  10. Invertebrate Excretory SystemsAquatic invertebrates: diffusion through body tissues.Terrestrial invertebrates: nephridia, malpighian tubules, etc. Flame cells Flatworm Excretorytubules Nephrostome Excretory pore Flame cell Excretory tubule Nephridia Digestive tract Annelid Malpighian tubules Arthropod

  11. Invertebrate Nervous Systems (Response)Centralization: nerve cells are more concentrated. Cephalization: ganglia are organized into a brain (controls body)Specialization: special sense organs to detect light, sound, movement, etc. Arthropod Brain Ganglia Ganglia Brain Nerve Cells Flatworm Cnidarian Mollusk

  12. Movement and SupportHydrostatic skeleton: fluid filled body cavity that supports muscles.Exoskeleton: hard outer skeleton made of chitinEndoskeleton: internal structural support Type of Skeleton Hydrostatic Exoskeleton Endoskeleton Sponges Simple (spicules or spongin) Cnidarians X Flatworms X Roundworms X Type of Skeleton Hydrostatic Exoskeleton Endoskeleton Annelids X Mollusks Some Some(shells) Arthropods X Echinoderms X

  13. ReproductionAsexual: reproduce rapidly in favorable conditions (genetically identical)Sexual: creates genetic diversity with a combination of sperm and egg Porifera Reproduce asexually (budding) or sexually by releasing sperm which fertilizes and egg. (external fertilization) Arthropoda Reproduce sexually when male deposits sperm inside the female to fertilize eggs. (internal fertilization)

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