Nematodes, Annelids, and Molluscs Flashcards
What organism is Phylum Nematoda?
Roundworms
What are nematodes (roundworms) like?
Cylindrical body hooked at both ends, bilaterally symmetrical, triploblastic, pseudocoelom, no segmentation, complete digestive system, hydroskeleton, no circulatory or respiratory system, simple nervous and excretory system.
How do nematodes transport nutrients?
They lack a circulatory system but have an alimentary canal, so they transport nutrients by fluid in the hemocoel
Trichinella spiralis
A parasite that can be acquired by humans eating undercooked pork, becomes encysted in human muscle tissue and organs and causes trichinosis
Sexual reproduction in nematodes?
Primarily sexual
Endotokia matricida
Intra-uterine birth causing maternal death
Phylum Annelida organism?
Segmented worms that live in marine, freshwater, and damp soil habitats
General characteristics of annelids
-Segmented
-Bilaterally symmetrical
-Elongated Bodies
-Protostomes
-Possess a coelom
-Complete digestive system
-Closed circulatory system
-CNS
-No appendages
-Each segment possesses setae
-hydrostatic skeleton
-Complete digestive system
-Closed circulatory system with beating heart
Setae
Small bristle-like appendages used for locomotion
What excretory system do annelids use?
Nephridia (similar to vertebrate kidneys)
What organisms included in P. Annelida, Class Polychaeta?
Bristle worms, Polychaetes
What are polychaetes?
A diverse group of marine worms; polychaete means many setae
Polychaete general characteristics
-segmented
-bilaterally symmetrical
-coelomate
-distinct head w/ eyes, antennae, and sensory palps
-Parapodia with setae on each segment
-closed circulatory system
-complete digestive system
-respiration through skin, gills, or parapodia
-nephridia for excretion
Parapodia
Appendages on polychaetes that can be used for swimming and gathering food, can also be used as gills or for protection
What organism for P. Annelida Subclass Hirudinea?
Leeches
Tell me about leeches
Most are predators of invertebrates, while some are blood sucking parasites of vertebrates. Some slit the skin of their host and secrete an anesthetic to prevent detection. They secrete hirudin preventing coagulation that lets them gorge on host’s blood.
General characteristics of leeches
Cylindrical
Not segmented
Most freshwater
Suckers used for locomotion and holding prey
Internal structure segregated into 32 separate segments that each have their own brain
4 pairs of eyes but poor eyesight
Open circulatory system
Reduced coelom
Complete digestive system
No respiratory system
CNS
Phylum Mollusca Organisms
Clams, Snails, Slugs, and Squids
Phylum Mollusca General Characteristics
Bilaterally symmetrical
Triploblastic
Coelomate
Unsegmented
Similar body plan with three parts
Many have water-filled mantle cavity housing gills, anus, and excretory pores
Many feed using straplike radula to scrape up food
Complete digestive system
Respirate by gills
Simple nervous system
Open circulatory system
Well-developed excretory system
Exoskeleton/shell made of calcium carbonate
Body plan of Molluscs
-Muscular foot used for movement
-Visceral mass containing most of the internal organs
-Mantle, a fold of tissue draping over the visceral mass that secretes the shell
What excretory system do molluscs use?
Tubular nephridia organized as kidneys
How do molluscs reproduce?
Most have separate sexes, many snails are hermaphrodites
Most aquatic ones lay eggs that hatch into trochophore larvae, then become free swimming larvae called veliger
Some gastropods reproduce via an unfertilized gamete
Parthenogenesis
Asexual reproduction via an unfertilized gamete that’s found among some gastropods
Trochophore
Ciliated larval stage that most aquatic mollusk eggs hatch into
Veliger
Small, free-swimming larvae
What are the four major classes of Phylum Mollusca?
Polyplacophora (chitons), Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves), and Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses)
P. Mollusca, Class Polyplacophora
-Chitons
-Marine animals with oval-shaped bodies
-Foot used to grip and creep along rock
-Radula used to scrape algae off surface
P. Mollusca, Class Gastropoda
-Snails and Slugs
-About 3/4 of molluscs are gastropods (means “foot stomach”)
-Most marine, but some freshwater and terrestrial
-slowly move with cilia or rippling foot
-Most have single, spiraled shell that protects from injury, dehydration, and predation
-Most herbivores
P. Mollusca, Class Bivalvia
-All aquatic; many species of clams, oysters, mussels, and scallops
-Shell divided into two hinged halves held together by adductor muscles
-No distinct head or radula
-Some have eyes and sensory tentacles along edge of mantle
Describe bivalve gills
They are housed inside the mantle cavity, used for suspension feeding and gas exchange
P. Mollusca, Class Cephalopoda
-Squids, Octopuses, Cuttlefish, and Chambered Nautiluses
-Immobilize prey using poison in their saliva
-Foot modified into muscular excurrent siphon and part of the tentacles
-reduced shell and internal or missing in most cephalopods (except chambered nautilus)
-only molluscs with a closed circulatory system
-well developed sense organs and a complex brain
How does siphon work in cephalopods?
Water is drawn into the mantle cavity and shot out through the excurrent siphon for rapid movement
