Chapter 33 ~ Chapter 33 ~ Invertebrates

Parazoa Invertebrates: animals without backbones Closest lineage to protists Loose federation of cells (unspecialized); no tissues Phylum.: (only one) Porifera (sponges)

Phylum: Porifera (“pore bearer”) no distinct tissues or organs do have specialized cells no symmetry sessile (as adults)

Eumetazoa: Animals with true body tissue The Radiata, I Diploblastic Radial symmetry Phylum: Cnidaria (hydra, jellies, sea anemones, corals) tissues, but no organs two cell layers predators tentacles surround gut opening extracellular digestion release enzymes into gut cavity absorption by cells lining gut

Stinging cells of Cnidarians hydra stinging cell with nematocyst trigger discharged nematocyst undischarged tentacles mouth sensory cell

The Radiata, II Phylum: Ctenophora (comb jellies) 8 rows of comblike plates of fused cilia (largest animals that use cilia for locomotion) Tentacles with colloblasts (adhesive structures that capture prey)

Eumetazoa: The Acoelomates Phy: Platyhelminthes (flatworms, flukes, tapeworms) Bilateral; no body cavity Predators, scavengers, parasites Some cephalization~ development of brain concentration of sense organs in head ectoderm mesoderm endoderm acoelomate

Eumetazoa: Pseudocoelomates, I Body cavity partially derived from mesodermally derived tissue Phylum: Rotifera 1st with a complete digestive tract Hydrostatic skeleton Parthenogenesis: type of reproduction in which females produce offspring from unfertilized eggs

Eumetazoa: Pseudocoelomates, II C. elegans Phylum: Nematoda (roundworms) Very widespread group of animals (900,000 sp. ?) Cuticle (tough exoskeleton) Decomposition and nutrient cycling Complete digestive track; no circulatory system many are parasitic hookworm Trichinella spiralis

The Coelomates: Protostomes, I Phylogenetics debated…. Phy: Nemertea (proboscis and ribbon worms) Complete digestion and closed circulatory system (blood) Phy: the lophophorates (sea mats, tube worms, lamp shells) Lophophore: Circular shaped body fold with ciliated tentacles around the mouth

The Coelomates: Protostomes, II Phylum: Mollusca (snails, slugs, squid, octopus, clams, oysters, chiton) Soft body most protected by a hard shell of calcium carbonate Foot (movement), visceral mass (internal organs); mantle (secretes shell); radula (rasp-like scraping organ) true coelem increases complexity & specialization of internal organs

The Coelomates: Protostomes, III Phylum: Annelida (earthworms, leeches, marine worms) True body segmentation (specialization of body regions) Closed circulatory system Metanephridia: excretory tubes “Brainlike” cerebral ganglia Hermaphrodites, but cross- fertilize leech fan worm

The Coelomates: Protostomes, IV Phy: Arthropoda trilobites (extinct); crustaceans (crabs, lobsters, shrimps); spiders, scorpions, ticks (arachnids); insects (entomology) 2 out of every 3 organisms (most successful of all phyla) Segmentation, hard exoskeleton (cuticle)~ molting, jointed appendages; open circulatory system (hemolymph); extensive cephalization

Arthropod groups arachnids crustaceans insects 8 legs, 2 body parts spiders, ticks, scorpions crustaceans gills, 2 pairs antennae crab, lobster, barnacles, shrmp insects 6 legs, 3 body parts

The Coelomates: Deuterostomes, I Phylum: Echinodermata (sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, sea daisies) Spiny skin; sessile or slow moving Often pentaradial

Invertebrate quick check… Invertebrates: Porifera, Cnidaria, Ctenophora,Platyhelminthes, Rotifera,Nemertea,Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata Which group includes snails, clams, and squid? Which group is the sponges? Which are the flatworms? …segmented worms? …roundworms? Which group has jointed appendages & an exoskeleton? Which groups have radial symmetry? What is the adaptive advantage of bilateral symmetry? Which group has no symmetry? Which group includes snails, clams, and squid? Mollusks Which group is the sponges? Porifera Which are the flatworms? Platyhelminthes …segmented worms? Annelids …roundworms? Nematodes Which group has jointed appendages & an exoskeleton? Arthropods Which two groups have radial symmetry? Cnidaria, Echinoderm What is the adaptive advantage of bilateral symmetry? cephalization Which group has no symmetry? Profiera