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 generationsthat 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 flukeSchistosoma 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 knownfor 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, amantle, 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 coelomateswith exoskeletons and jointed appendages.

-Population: 1 billion billion (1018)-Nearly 1 million species (most successful animal phylum)

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