Molluscs and Annelids

Question 1

Why is the Phylum Mollusca very morphologically diverse?

Answer 1

No constraint of body plan

Question 2

Does Phylum Mollusca have a true coelem?

Answer 2

Yes

Question 3

What organ systems does phylum mollusca have?

Answer 3

Gill, heart, kidneys

Question 4

How does the external shell form on phylum mollusca?

Answer 4

The mantle secretes the external shell

Question 5

What is the rasping tongue used for grazing in phylum mollusca?

Answer 5

The Radula

Question 6

What does the diversity of phylum Mollusca reflect?

Answer 6

It reflects the various feeding strategies of the Phylum

Question 7

What kind of embryological development does Phylum Mollusca experience?

Answer 7

Sprial mosaic/determinate cleavage

Question 8

What group is Phylum Mollusca a part of?

Answer 8

Lophotrochozoan Protostomes

• Lophophore: feeding tentacle
• Trochophore larva: Have band of hair growing around widest part

Question 9

What are the characteristics of the Mollusca body plan?

Answer 9

• Large Foot
• Radula
• Heart
• Open blood vascular system (hemocoel)
• Gills
• Coelem reduced to pericardium

Question 10

What are the characteristics of the Mollusca digestive system?

Answer 10

Break-down food for delivery to bloodstream and cells

• Digestive gland: breaks down the food molecules
• Radula

Question 11

What is the function of the Mollusca Circulatory system?

Answer 11

Move blood around body to deliver O2/soup molecules and remove CO2 and N waste.

Question 12

What is the Mollusca Hemocoel? What system is it a part of?

Answer 12

(NOT coelom) where organs are and blood is not in vessels
-space where blood is dumped

Part of Circulatory system

Question 13

What is the Mollusca 3-Chambered Heart? What system is it a part of?

Answer 13

Sucks blood from gill and pushes to body
-pushes especially to the nervous system

Part of Circulatory system

Question 14

What is the Mollusca Pericardium? What system is it a part of?

Answer 14

Coelomic space around heart

Part of Circulatory system and excretory system

Question 15

What is the function of the Mollusca Excratory system?

Answer 15

Removes nitrogenous wastes and excess water from body

Question 16

What is the Mollusca Kidneys? What system is it a part of?

Answer 16

Uses pressure of beating heart against the pericardium to remove excess water and nitrogenous wastes

Excretory System

Question 17

What is the function of the Mollusca Respiratory system?

Answer 17

Provides a surface for rapid exchange of gases between the blood supply and surrounding water
-O2 in and CO2 out

Question 18

What is the Mollusca Gills? What system is it a part of?

Answer 18

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

Question 19

What is the function of the Mollusca Nervous system?

Answer 19

Controls muscles and coordinates movement with sensory input

Question 20

What is the Molluscan shell made of?

Answer 20

Mostly CaCO3

-some collagen

Question 21

How do Molluscs reproduce?

Answer 21

Mostly Dioecious, some hermaphrodites

• External fertilization: trocophore larva to veliger larva
• Direct Development: develop in egg then hatch

Question 22

What is the least derived (most close to ancestor) class of Mollusca?

Answer 22

Gastropoda (stomach foot) - the grazers

• Radula
• Foot
• Gill
• Shell

Question 23

What is the 2nd least/most derived (most close to ancestor) class of Mollusca?

Answer 23

Bivalvia - filter feeders

• No radula, eyes or head
• Foot for burrowing or byssus thread to attach to rock
• Large Gills
• Shell completely surrounds body

Question 24

What is the most derived (most close to ancestor) class of Mollusca?

Answer 24

Cephalopoda - predators

• beak replaced radula
• Foot became funnel to direct water
• Gills
• Mantle became tentacles
• Closed blood system
• shell lost or modified for buoyancy

Question 25

Why is the Phylum Annelida not morphologically diverse?

Answer 25

Constrained body plan due to hydrostatic skeleton

Question 26

What group do Phylum Annelida belong to?

Answer 26

Lophotrochozoan protostomes

Question 27

Where do Phylum Annelida get their names from?

Answer 27

"segmented worms" | -metameric segments

Question 28

What kind of skeleton do phylum annelida have?

Answer 28

hydrostatic skeleton from spetate coelomic cavities

Question 29

How do phylum annelida move?

Answer 29

Bristles (chaete or setae) used to move or burrow

Question 30

Metamerism, or segmentation, results from what?

Answer 30

Trochophore larva grows from the pygidium by metamere addition

Question 31

Describe the body plan of Phylum Annelida. What is the result?

Answer 31

- 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

Question 32

What are the characteristics of the Annelida Nervous System?

Answer 32

Ventral nerve cord has a paired ganglia in each segment | -controls the contraction of the muscle groups (circular and longitudinal muscles)

Question 33

What are the characteristics of the Annelida Excretory System?

Answer 33

Pair of metanephridia per segment uses blood supply and pressure to eliminate water and nitrogenous waste

Question 34

What is unique about Class Polychaetes (phylum annelida)?

Answer 34

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

Question 35

What is Clade Clitellata in Phylum Annelida?

Answer 35

Have a Clitellum - band of secretory cells - Class Oligochaeta and Hirudinea