Chapter 33 ~ n Chapter 33 ~ Invertebrates

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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