Molluscs and Annelids Flashcards
Why is the Phylum Mollusca very morphologically diverse?
No constraint of body plan
Does Phylum Mollusca have a true coelem?
Yes
What organ systems does phylum mollusca have?
Gill, heart, kidneys
How does the external shell form on phylum mollusca?
The mantle secretes the external shell
What is the rasping tongue used for grazing in phylum mollusca?
The Radula
What does the diversity of phylum Mollusca reflect?
It reflects the various feeding strategies of the Phylum
What kind of embryological development does Phylum Mollusca experience?
Sprial mosaic/determinate cleavage
What group is Phylum Mollusca a part of?
Lophotrochozoan Protostomes
- Lophophore: feeding tentacle
- Trochophore larva: Have band of hair growing around widest part
What are the characteristics of the Mollusca body plan?
- Large Foot
- Radula
- Heart
- Open blood vascular system (hemocoel)
- Gills
- Coelem reduced to pericardium
What are the characteristics of the Mollusca digestive system?
Break-down food for delivery to bloodstream and cells
- Digestive gland: breaks down the food molecules
- Radula
What is the function of the Mollusca Circulatory system?
Move blood around body to deliver O2/soup molecules and remove CO2 and N waste.
What is the Mollusca Hemocoel? What system is it a part of?
(NOT coelom) where organs are and blood is not in vessels
-space where blood is dumped
Part of Circulatory system
What is the Mollusca 3-Chambered Heart? What system is it a part of?
Sucks blood from gill and pushes to body
-pushes especially to the nervous system
Part of Circulatory system
What is the Mollusca Pericardium? What system is it a part of?
Coelomic space around heart
Part of Circulatory system and excretory system
What is the function of the Mollusca Excratory system?
Removes nitrogenous wastes and excess water from body
What is the Mollusca Kidneys? What system is it a part of?
Uses pressure of beating heart against the pericardium to remove excess water and nitrogenous wastes
Excretory System
What is the function of the Mollusca Respiratory system?
Provides a surface for rapid exchange of gases between the blood supply and surrounding water
-O2 in and CO2 out
What is the Mollusca Gills? What system is it a part of?
Cilia move and suck in water across gills (opposite direction of blood flow - countercurrent exchange)
- epithilieal layer of gills diffuse O2 out of the H2O
- blood circulates inside of gills and absorbs O2 to be transported to rest of body
Respiratory System
What is the function of the Mollusca Nervous system?
Controls muscles and coordinates movement with sensory input
What is the Molluscan shell made of?
Mostly CaCO3
-some collagen
How do Molluscs reproduce?
Mostly Dioecious, some hermaphrodites
- External fertilization: trocophore larva to veliger larva
- Direct Development: develop in egg then hatch
What is the least derived (most close to ancestor) class of Mollusca?
Gastropoda (stomach foot) - the grazers
- Radula
- Foot
- Gill
- Shell
What is the 2nd least/most derived (most close to ancestor) class of Mollusca?
Bivalvia - filter feeders
- No radula, eyes or head
- Foot for burrowing or byssus thread to attach to rock
- Large Gills
- Shell completely surrounds body
What is the most derived (most close to ancestor) class of Mollusca?
Cephalopoda - predators
- beak replaced radula
- Foot became funnel to direct water
- Gills
- Mantle became tentacles
- Closed blood system
- shell lost or modified for buoyancy
Why is the Phylum Annelida not morphologically diverse?
Constrained body plan due to hydrostatic skeleton
What group do Phylum Annelida belong to?
Lophotrochozoan protostomes
Where do Phylum Annelida get their names from?
“segmented worms”
-metameric segments
What kind of skeleton do phylum annelida have?
hydrostatic skeleton from spetate coelomic cavities
How do phylum annelida move?
Bristles (chaete or setae) used to move or burrow
Metamerism, or segmentation, results from what?
Trochophore larva grows from the pygidium by metamere addition
Describe the body plan of Phylum Annelida. What is the result?
- Cuticle around body
- Septa separate each coelomic cavity
- Hydrostatic skeleton
- Mesentaries split each Coelem in two and hold gut
Results in the ability to control each segment differently
What are the characteristics of the Annelida Nervous System?
Ventral nerve cord has a paired ganglia in each segment
-controls the contraction of the muscle groups (circular and longitudinal muscles)
What are the characteristics of the Annelida Excretory System?
Pair of metanephridia per segment uses blood supply and pressure to eliminate water and nitrogenous waste
What is unique about Class Polychaetes (phylum annelida)?
Parapodia
-Paired outgrowths of body wall
Can also be tube dwelling filter feeders
Hydrothermal vent worms have remnants of gut called trophosome filled with bacteria
-Chemoautotrophs
What is Clade Clitellata in Phylum Annelida?
Have a Clitellum
- band of secretory cells
- Class Oligochaeta and Hirudinea
