Chapter 33

Question 1

Clades of protostomes

Answer 1

Lophotrochozoa - gradually get larger, no molting
Ecdysozoa - molting

Question 2

Lophotrochozoa characteristics

Answer 2

Embryo develops using spiral cleavage and creates spiral body, Most live in water. Move using cilia or contractions of the body musculature.
Two defining characteristics. Trochophore - free living larva. Lophophore - a horseshoe shaped crown of ciliated tentacles surrounds the mouth used in filter feeding.

Question 3

Ecdysozoa

Answer 3

Contains animals that molt. Exoskeleton. Two large groups. Arthropods. Nematodes (C. elegans studied spp.) Lots used in lab studies, easy to grow and rear.

Question 4

Phylum Platyhelminthes

Answer 4

Flatworms are ciliated, soft-bodied animals, flattened dorsoventrally. Simple bodies with no circulatory system or respiratory systems, but complex reproductive system. Use diffusion to perform respiration. Bodies are solid aside from an incomplete digestive cavity. Many spp are parasitic (flukes and tape worms). Others are free living, planarians. Includes marine and freshwater.
Carnivores or scavengers, move with cilia on bottom of body.

Question 5

Flatworm digestion and circulation

Answer 5

Most only have one opening to digestive cavity. Muscular contractions in the pharynx allows food to be ingested and torn into small bits.
Lack circulatory system. Diffusion for gas transport. Gut functions in digestion and food distribution. Some particles digested extracellularly. Cells engulf particles by phagocytosis (lining guts). Tapeworms (parasitic flatworms) lack digestive systems - absorb food directly through body wall.
Network of fine tubules, flame cells for osmoregulation located on side branches of tubules
Anterior cerebral ganglion - Mass of tissue
Hermaphrodite, ovary and testies

Question 6

Flatworms Excretion and osmoregulation Flatowrm

Answer 6

Network of fine tubules run through body, flame cells for osmoregulation located on side branches of tubules. Flagella move water and excretory substances into tubules and then to pores located between the epidermal cells through which liquid is expelled. Metabolic wastes are excreted into the gut and eliminated through the mouth.

Question 7

Nervous system and reproduction. Flatworm

Answer 7

Simple nervous system. Anterior cerebral ganglion and nerve cords. Eyespot can distinguish light from dark and prefer dark. Reproduction, hermaphroditic, undergo sexual reproduction, have capacity for asexual regeneration. Need copulation of 2 individuals, each deposits sperm in egg. Can regen if cut in 1/2. Freshwater lay cocoons, marine do spiral cleavage.

Question 8

Turbellaria
Parasitic Subphyla

Answer 8

Turbellaria - free living (minority) Have eyespot, probably multiple ancestors. Dugesia common planarian in bio labs
Parasitic - Neodermata (Trematoda and Cercomeromorpha). Skin surface resistant to digestive enzymes and immune defenses from host. Attach with suckers, anchors, or hooks, no eyespot. Life cycle has 2 or more hosts. Oriental liver fluke, schistosoma

Question 9

Schistosoma

Answer 9

Important to human health. Blood flukes. 200 mil in tropical Asia, Afr, Latin Am, and Middle East. 200k die each year. Fertilized egg must break through wall of blood vessels in intestine or urinary bladder to get out

Question 10

Cercomeromorpha tapeworms

Answer 10

Adult hangs in inner wall of host intestine using scolex (sucker or hooks). Lack digestive cavity or enzymes. Consumes fluids. Develop at base of neck and gets moved down.
Most of the body is proglottids (complete hermaphroditic unit containing male and female). Formed continuously. Beef tapeworm

Question 11

Phylum Rotifera

Answer 11

Bilateral symmetry, unsegmented pseudocoelomates. Highly developed internal organs. Cytoskeleton rigid but flexible. Freshwater although some soil and mosses and ocean spp.
Corona wheel animals. Conspicuous ring of cilia at anterior end used for locomotion and sweeping food into the mouth. Micrometer size.

Question 12

Phylum Mollusca Characteristics

Answer 12

Second in diversity. Snails, slugs, clams, octos, squids. Some have shells.
Mantle - Thick epidermal sheet bounds cavity. Calcium carbonate secreted. 2 layers, internal layer may be mother of pearl or nacre (coat foreign objects to reduce irritation.)
Foot - Primary means of locomotion for many. Divided into arms or tentacles in cephalopods. Capture or digging.
Internal organs. Coelom is highly reduced. Limited spaces around excretory organs, heart and part of intestine. Digestive, excretory, and reproductive organs are concentrated in a visceral mass.
Ctenidia - gills in aquatic mollusks, also filter food in most bivalves.
Radula - Rasping tongue like structure used in feeding. Scrape up algae. In pred gastropods, modified to drill through clam shells. Bivalves do not have a radula.
Nephridia - Kidney like structure for nitrogenous waste removal
Open circulatory system (except cephalopods) - Hemolymph (blood) sloshes around hemocoel. 3 chambered heart. 2 for O2 and 1 pumps into hemocoel.
Most are gonochoric. Most external fertilization (gastropods internal). Zygote undergoes spiral cleavage.

Question 13

Ctenidia

Answer 13

gills in aquatic mollusks, also filter food in most bivalves.

Question 14

Nephridia

Answer 14

Mollusks. Kidney like structure for nitrogenous waste removal. Consists of cilia lined openings called nephrostomes. Tube to excretory pore to mantle cavity.

Question 15

Mollusk life stages

Answer 15

Trochophore - free swimming larval stage.
Veliger - 2nd free swimming larval stage (only in bivalves and marine snails)

Question 16

4 Mollusks classes to know

Answer 16

Polyplacophora - chitons
Gastropoda - limpets, snails, slugs
Bivalvia - clams, oysters, scallops
Cephalopoda - squids, octo, cuttlefish, chambered nautilus

Question 17

ClassPolyplacophora

Answer 17

Chitons. Marine with oval bodies. 8 overlapping dorsal calcareous plates. Body is not segmented, just plates. Grazing herbivores.

Question 18

Class Gastropoda

Answer 18

Limpets, snails, slugs. Primarily marine group. Some freshwater and only terrestrial mollusks. Most have a single shell if not lost (slugs and sea slugs). Heads typically have pairs of tentacles with eyes to sense chem. Torsion - not same as coiling. Mantle cavity and anus are moved from posterior to the front by twisting.

Question 19

Nudibranchs

Answer 19

Active predators of gastropods. Exposed gills. Secrete distasteful chem but no shell. Some extract nematocysts from cnidarian prey and transfer them to their body surface.

Question 20

Class Bivalvia

Answer 20

2 Shells hinged together, Adductor muscles counter hinge ligament.. Includes clams, scallops, mussels, oysters, and others. Most marine, some freshwater. No radula or distinct head. Water enters through inhalant siphon and exits through exhalant siphon, Food and breathing

Question 21

Class Cephalopoda

Answer 21

More than 700 spp, marine only. Active preds, swim quickly. Only mollusk with closed circulatory system. Foot has evolved into a series of arms equipped with suction cups. Beak like jaws, toxic saliva. Largest relative brain size among inverts. Highly developed nervous system.