Invertebrates ©Peter_Allsop peterallsop.com

Invertebrates There are about 35 different phyla of animals. You should remember nine of them

Invertebrates There are about 35 different phyla of animals. You should remember nine of them. Eight of the nine are invertebrates

Invertebrates There are about 35 different phyla of animals. You should remember nine of them. Eight of the nine are invertebrates. As we examine each one, you should learn the evolutionary adaptations of that phylum.

Phyla Porifera Cnidarians Platyhelminthes Mollusca Annelida Nematoda Arthropoda Echinoermata Chordata.

Porifera sponges No symmetry Sessile (do not move) Filter feeders Only two cell layers: ecto- & endoderm No true tissues or organs Evolved from colonial organisms Reproduce asexually & sexually; hermaphroditic.

Cnidarians hydra and jellyfish Radial symmetry Stinging cells—cnidocytes Gastrovascular cavity—no transport system Digestion both extracellular and intracellular Two cell layers: ectoderm and endoderm May have a free-swimming larval stage Polyps reproduce asexually and medusas reproduce sexually (life stages).

Platyhelminthes flatworms (incl. tapeworms) Bilateral symmetry Three cell layers Cephalization True tissues & organs Digestive cavity with one opening Acoelomate Flat body for absorption of O 2 by all cells.

Mollusca cephalopods, gastropods, bivalves Protostome coelomates Soft body, often protected by hard shell Bilateral symmetry 3 body zones: foot, visceral mass, mantle Radula—like a tongue, but with teeth Open circulatory system—hemocoels Gills and nephridia.

Annelida segmented worms Protostome coelomates Bilateral symmetry Digestive system = tube within a tube Closed circulatory system Blood contains hemoglobin Diffusion of O 2 & CO 2 through moist skin Hermaphroditic but not self-fertilizing.

Nematoda roundworms Unsegmented Bilateral symmetry Protostome pseudocoelomate No circulatory system Many are parasitic (trichinosis).

Arthropoda insects, crustaceans, arachnids Protostome coelomates Jointed exoskeleton Segmentation: head, thorax, abdomen More sensory apparatus Open circulatory system—hemocoels Malpighian tubules for removing waste Trachea—air ducts Some have book lungs or book gills.

Free Response Question Describe the differences between the terms in each of the following pairs. Give examples for each from the major phyla we have studied. a.Acoelomate—Coelomate b.Protostome—Deuterostome c.Radial Symmetry—Bilateral Symmetry

Echinoermata sea stars and sea urchins Deuterostome coelomates Most are sessile or slow moving Bilateral symmetry as embryo; radial as adult Water vascular system = modified coelom Tube feet Sexual reproduction with external fertilization Can also reproduce by fragmentation & regeneration Endoskeleton of calcium plates.

Chordata fish, amphibians, reptiles, birds, mammals Deuterostome coelomates Notocord serves as axis of body Dorsal, hollow nerve cord Tails. Human coccyx is vestigial tail. Birds & mammals = hemotherms (constant body temperature) All others are poikilotherms (cold-blooded) though some reptiles are endothermic.

Mammals class Nurse their young with milk Have hair or fur made of keratin Homeotherms Placental = develops in womb Marsupial = born early, develops in pouch Monotreme = egg-laying (duck-billed platypus and spiny anteater).

Primates order Hands with opposable thumbs Claws have become nails Eyes are in front and close together for binocular vision Nurture their young for a long time.