Ch. 33: Invertebrates (Animals without a backbone)

1.Phylum Porifera: Sponges -Sessile (attached to bottom) -Spongocoel (central cavity) -Osculum (large opening) -Choanocytes (flagellated collar cells) -Hermaphroditic (produce both sperm and eggs)

2.Phylum Cnidaria: hydras, jellyfish, sea anemones, and coral animals. -Diploblastic -Radial symmetry -Gastrovascular cavity (sac with a central digestive cavity) -Nerve net -Hydrostatic skeleton (fluid held under pressure) -Polyps and medusa -Cnidocytes (cells used for defense and prey capture) -Nematocysts (stinging capsule)

NOT the same as alternation of generations that occurs in plants as both polyp and medusa are diploid organisms.

3.Phylum Ctenophores: 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)

4.Phylum Platyhelminthes: Flatworms -Reproduce asexually via regeneration -Reproduce sexually; hermaphorditic cross-fertilization

-Bilateral; no body cavity -Predators, scavengers, parasites -Triplobastic; mesoderm but, GVC with only one opening – pharynx -Some cephalization – ganglia, eyespots -Many pathogens (Schistosoma, Cestodidias)

The blood fluke Schistosoma infects 200 million people, leading to body pains, anemia, and dysentery.

-Tapeworm (Cestodidias) absorb food particles from their host. -Tapeworm eggs are released in feces. -Contaminated food and water can infect host. -Tapeworm larvae encyst into muscles of host.

5.Phylum Rotifera: are pseudocoelomates with jaws, crowns of cilia, and complete digestive tracts. -1,800 species, are tiny animals (0.05 to 2 mm), most of which live in freshwater. -Internal organs in the pseudo- coelomates. -Pseudocoelomate acts as a hydro- static skeleton. -Pseudocoelomate also acts as a circulatory system.

-Some rotifers only exist as females, reproducing more females from unfertilized eggs (parthogenesis). -One type of rotifer produce 2 types of eggs: 1. Eggs that produce females 2. Eggs that produce degenerate males that live just long enough to fertilize eggs.

6.Phylum Lophophorate: Bryozoans, Phoronids, and Brachipods. -Molecular data shows that lophophorates are protostomes. -Named Lophophores as they all have a common physical feature: the lophophore.  The lophophore is a horse-shoe-shaped or circular fold of the body wall bearing ciliated tentacles that surround the mouth.

-They also have a U-shaped digestive tract and the absence of a head. -True coeloms completely lined with mesoderm. -Bryozoans are colonial organisms: -Colony is usually encased in a hard exoskeleton. -Mostly marine -Sessile, coral reef builders

-Phoronids are tube-dwelling marine worms, 1mm to 50 cm long in length. -Some live buried in sand, within chitinous tubes. -The lophophore is extended with the phoronid is feeding. It is withdrawn when it feels threatened.

-Brachiopods resemble clams and other bivalve mollusks.

-Dorsal and ventral sides -Marine

7.Phylum Nemertea: Proboscis worms known for the prey-capturing apparatus. -Resemble flatworms like tapeworms, but have fluid-filled sacs that resemble a true coelom. -Sometimes called “ribbon worms” -Have complete digestive and circulatory system. -Proboscis sticky, barbed, or poisonous

8.Phylum Mollusca have a muscular foot, a mantle, and a visceral mass. -Slugs, snails, oysters, clams, octopus, and squids. -Marine and freshwater -Soft bodied with hard shell; slugs, octopus, and squids have lost or reduced during their evolution.

-Foot: used for locomotion -Visceral mass: contains the organs -Mantle: secretes the shell -Radula: used to scrape up food

-Most mollusks are separated sexes, but some snails are hermaphrodites. -The life cycle of many mollusks include a ciliated larva called a trophophore (also in Annelids). -8 classes: 1. Polyplacophora (chitons), 2. Gastropoda (snails and slugs), 3. Bivalvia (clams, oysters, and other bivalves), and 4. Cephalopoda (squids, octopuses, and nautiluses).

-Unique among the mollusks, the cephalopods have a well-developed brain and nervous system. -They also have a closed circulatory system.

9.Phylum Annelids: Segmented worms -Septa between the segments. -Digestive system -Closed circulatory system -Each segments contains a metanephridia, which excretes wastes  Wastes excreted out through pores.

-Two brain-like ganglia in head -Hermaphrodites -Some can reproduce asexually by fragmentation and then regeneration

-True coelom

-3 Classes: 1. Oligochaeta (earthworms) 2. Polychaeta (marine segmented worms) 3. Hirudinea (leeches) Polychaeta Leech

-In annelids, the coelom plays a hydrostatic role. -Segmentation allows for specialization of body regions.

10.Phylum Nematodes: Roundworms are non- segmented pseudocoelomates covered by a tough cuticle. -90,000 species (with probably 10x more) -Size: 1mm to more than 1m -Lack a circulatory system -Complete digestive tract -Move by moving back and forth due to longitudinal muscles -Reproduce sexually with internal fertilization -Female can lay over 100,000 eggs

-Over 50 species of nematodes are parasitic to humans.  Trichinella spiralis causes trichinosis when the nematode worms encyst in a variety of human organs, including skeletal muscle.

11.Phylum Arthropods: Segmented coelomates with exoskeletons and jointed appendages. -Population: 1 billion billion (10 18 ) -Nearly 1 million species (most successful animal phylum)

-Evolutionary success due to segmentation, exoskeleton, and jointed appendages.  specialized body parts  efficient labor