Week 5: The Molluscs and Annelids Flashcards
(24 cards)
What are the major clades of clade Mollusca?
- Gastropoda (stomach foot)
- Bivalvia (two valves)
- Cephalopoda
- Polyplacophora
- Scaphopoda
What are the general characteristics of clade Mollusca?
- Triploblastic protostomes
- True coelom - 1st TRUE COELOMATES
- Exoskeleton
- Bilateral symmetry
- Unsegmented
- Complex nervous and digestive systems
- Open circulatory system (except cephalopods)
- Hemolymph instead of blood
What is the common body plan of clade Mollusca?
- Shell (reduced in some species)
- Foot - locomotion of attachment to substrate
- Mantle - secretes the shell
- Visceral mass - contains various organs
What distinguishes an open circulatory system?
- The heart pumps hemolymph instead of blood
- Hemolymph is pumped into open cavities that house organs
- Organs contain sinuses (instead of capillaries) that fill with hemolymph allowing gases/nutrients to reach cells of the organs
What is adaptive radiation?
Evolution of many different morphological types or species from a single common ancestor following migration into new environment
- New niches to explore
- Little competition for resources
What are the major species of Gastropoda?
-Snails, Slugs, Perriwinkles, and Conch
What is the phenomenon that causes gastropods to appear asymmetrical?
-Torsion, the uneven growth of left and right muscles that attach the shell to the head foot.
What are some example species of clade Bivalvia?
-Clams, Mussels, Oysters, and Scallops.
What is a rasping radula, and what clade(s) does it appear in?
It is a tongue-like organ used for feeding. The radula appears in all Gastropoda, Cephalopoda, Polyplacophora, and Scaphopoda.
How do bivalves feed?
They are suspension feeders; they trap food particles from the water in ciliated gills. Particles are then transported to the mouth by the labial palps. NO RADULA.
What is the umbo?
The oldest part of the shell, most resistant to predators.
What are the distinguishing characteristics of clade Cephalopoda?
- “head foot”
- Shell reduced or absent
- Locomotion: the mantle draws in water and contracts to force it through the siphon. creating propulsion.
- Well developed head with radula and eyes
- Closed circulatory system
What some examples of species in clade Cephalopoda?
-Squid, Octopus, Cuttlefish, and Nautilus
What is interesting about the eyes of cephalopods as compared to the eyes of vertebrates?
Eyes of cephalopods and vertebrates are analogous traits, traits which perform a similar function, but are have evolved from a different ancestor (convergent evolution). The cephalopods’ eyes are from skin tissue, and vertebrates’ are from nervous tissue.
What are the characteristics of clade Polyplacophora?
- “many shells”
- Elongated, flat body
- Shells of 8 dorsal plates
- reduced head
- bilateral symmetry
- Foot is broad and flat
- Use radula to feed
What clade do chitons belong to?
Clade polyplacophora.
What are the characteristics of clade Scaphopoda?
- Tusk shells
- Body enclosed in a one-piece shell
- mouth has tentacles
- Absent head
- Marine
What are the characteristics of clade Annelida?
- Triploblastic protostomes
- True coelom
- Closed circulatory system
- More developed organ systems
- Hydrostatic skeletons
- Monoecious (hermamphroditic)
- Metamerism (segmentation) - provides foundation for the specialization of body regions, makes movements more effective.
- Setae - chitinous bristles on ventral side used for locomotion
What are the major clades of Annelida, and what is the defining characteristic of each?
- Polychaeta - many setae
- Oligochaeta - few setae
- Hirudinea - No setae
What are the main characteristics of clade Polychaeta?
- Many bristled setae
- Found on sea floor / reefs
- Beautifully colored
- Parapodia
What are parapodia?
External gills that provide skin surface area for gas exchange and function in locomotion.
What are the major characteristics of clade Oligochaeta?
-Few setae
-Longitudinal and circular muscles
Longitudinal (shorten/thicken)
Circular (lengthen/thin)
-Gas exchange through skin
-Very complex organ systems
-Clitellum present
Describe Oligochaeta mating?
- Two hermaphroditic worms line seminal vesicles with seminal receptacles
- Held together by mucous secreted by the clitellum
- Sperm goes out seminal vesicles and is stored in the seminal receptacle of the other worm.
- Eggs are carried out genital pore
- A chitin-like band forms a cocoon around the clitellum
- This cocoon slides forward, collects eggs and sperm, and fertilization takes place
- The cocoon slides off and is left behind
What are the major characteristics of clade Hirudinea?
- No setae
- Includes leeches
- High level of parental investment
- Secretes an anesthetic and anticoagulant before attachment
- Medicinal leech - relieves edema during surgery
