Chapter 33 Flashcards
Clades of protostomes
Lophotrochozoa - gradually get larger, no molting
Ecdysozoa - molting
Lophotrochozoa characteristics
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.
Ecdysozoa
Contains animals that molt. Exoskeleton. Two large groups. Arthropods. Nematodes (C. elegans studied spp.) Lots used in lab studies, easy to grow and rear.
Phylum Platyhelminthes
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.
Flatworm digestion and circulation
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
Flatworms Excretion and osmoregulation Flatowrm
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.
Nervous system and reproduction. Flatworm
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.
Turbellaria
Parasitic Subphyla
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
Schistosoma
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
Cercomeromorpha tapeworms
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
Phylum Rotifera
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.
Phylum Mollusca Characteristics
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.
Ctenidia
gills in aquatic mollusks, also filter food in most bivalves.
Nephridia
Mollusks. Kidney like structure for nitrogenous waste removal. Consists of cilia lined openings called nephrostomes. Tube to excretory pore to mantle cavity.
Mollusk life stages
Trochophore - free swimming larval stage.
Veliger - 2nd free swimming larval stage (only in bivalves and marine snails)
4 Mollusks classes to know
Polyplacophora - chitons
Gastropoda - limpets, snails, slugs
Bivalvia - clams, oysters, scallops
Cephalopoda - squids, octo, cuttlefish, chambered nautilus
ClassPolyplacophora
Chitons. Marine with oval bodies. 8 overlapping dorsal calcareous plates. Body is not segmented, just plates. Grazing herbivores.
Class Gastropoda
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.
Nudibranchs
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.
Class Bivalvia
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
Class Cephalopoda
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.