Mollusca

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Author:
crimsonblaze
ID:
95534
Filename:
Mollusca
Updated:
2011-07-28 11:45:42
Tags:
clams
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Description:
Mollusca
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  1. Mollusca: Symmetry
    Bilateral
  2. Mollusca: # Germ Layers
    • 3 (ecto, meso, endoderm)
    • protostome
  3. Mollusca: Metamerism
    only in one group
  4. Mollusca: Coelom
    • yes (protostome)
    • well developed
  5. Mollusca: Skeletal System
    • none
    • hard exoskeleton ( none/reduced in cephalopods)
    • CaCO3 shell in most except cephalopods
  6. Mollusca: Cephalization
    • minimal in bivalves
    • some in gastropods
    • extensive in cephalopods
  7. Mollusca: Nervous System
    • Various, highly developed cephalopods
    • limited cephalization (except cephalopods -> highly developed w/ complex sensory system and image forming eyes)
  8. Mollusca: Digestive System
    • complete: specialized for filtering small food particles out of water
    • GI tract
    • clam: filter-feed with ctenidia, stomach, intestine
  9. Mollusca: Circulatory System
    • hemocyanin dissolved in plasma membrane
    • open in bivalves and gastropods
    • closes in cephalopods
  10. Mollusca: Respiratory System
    • Ctenidia in most
    • sinuses collect hemolymph and transport to ctenidia for gas exchange
  11. Mollusca: Respiratory Pigment
    hemocyanin
  12. Mollusca: Excretory System
    • Nephridia to kidney
    • nephrostome (kidney like) -> metanephridia -> metanephridiopore
    • nitrogenous wastes excreted into excurrent siphon by pair of kidneys
    • some ammonia eliminated by ctendia
  13. Mollusca: Sexual Cycle
    • most dioecious
    • pair of gonads empties gametes into excurrent siphon
  14. Mollusca: Asexual Cycle
    none
  15. Mollusca: Locomotion
    • most slow movnig via foot
    • Cephalopods fast swimming via jet propulsion
  16. Mollusca: Classes
    • Gastropoda: snail, slug, nudibranch, abalone
    • Bivalvia: clams, mussels, scallops
    • Cephalopoda: octopi, squid, cuttlefish, nautillus
    • Polyplacophora: chitons
  17. Mollusca: Notes
    • heart is located dorsally and is orange
    • 100,000 species (2nd largest phylum)
    • 540mya
  18. Shell
    • external skeleton
    • protects softer parts of animal
    • hardened by CaCO3
    • internal in cephalopods
  19. Ctenidia
    • lined with cilia
    • draws in water into mantle
  20. Digestive pathway of Bivales
    • Water w/ food -> Incurrent siphon -> Mantle cavity -> Ctenidia (lined w/ cilia that beat pulling water in) -> Anus -> excurrent siphon
    • stomach , digestive glands, and intestine not visble w/o cutting visceral mass
  21. Mollusca: Derived features
    • mantle
    • foot
    • radula
    • ctenidium
    • shell
  22. Mollusca: Ancestral Features
    • protosome development
    • bilateral symmetry
    • coelomate
    • segmentation (some)
    • cephalization
  23. Mantle
    • think skin-like structure
    • excloses internal organs
    • secretes external skeleton (the shell)
    • most active secretion at mantle edge -> how shell "grows"
    • can repair damaged shell by secreting CaCO3
  24. Foot
    • muscle used for creeping, crawling, grabbing
    • modified depending on use
  25. Radula
    • ribbon-like string containing rows of "teeth"
    • used for scrapping algae from rocks (limpets)
    • tearing into smaller pieces (marine snails)
    • harpooning prey (cone snails)
    • boring through shells (to eat whats inside)
    • new teeth constantly secreted
    • Bivalves, some Cephalopods, and snails lack radula
  26. Ctenidia
    • gas exchange and filter feeding (some)
    • long feature-like shape with many blood vessels
    • filaments extend from central axis to increase SA
  27. Labial Palps
    sorts and transfers food particles into mouth

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