Transcript Phylum Mollusca - MissReidClasses

Phylum Mollusca
Phylum level Characteristics
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soft-bodied with single muscular “foot”
internal or external limestone shell
complete digestive system
coelomates
grouped together because of similar
developmental patterns
• live everywhere:
– ocean, freshwater, on land
General Body Plan
• Foot
• Mantle
– tissue that hangs or covers some
or all of the body
• Shell
– hard structure can be internal or
external
• Visceral mass
– contains all internal organs
• Radula
– unique to mollusks
– it’s a rasping organ with file like
teeth to scrape, crush food
• Gills
– to extract oxygen from water and
can filter food
Feeding
• Every form of feeding is represented by the
various types of mollusks
• Some utilize a radula
– Herbivores use it to scrape algae off surfaces
– Carnivores us it to drill into the shells of prey
• Octopi and sea slugs produce poison to
subdue prey then use sharp jaws to eat them
• Filter feeders use gills to sift food from the
water
• slug video
Respiration
• Aquatic species use gills (found within the
mantle cavity) to extract dissolved oxygen
from the water
• Land molluscs breathe via an adapted mantle
cavity lined with blood vessels. Must be kept
moist for oxygen to enter the cells
Circulatory System
• Slow moving or sessile species have an open
circulatory system
– Blood not always within blood vessels
– Works through body tissues in open spaces called
sinuses
• Faster movies species (like octopi) have a
closed circulatory system
– Blood always within vessels
– More efficient
Excretory System
• Complete digestive system
– Solid waste expelled through anus
– Metabolic wastes (ammonia) excreted by
nephridia (simple kidney like organs)
• Nephridia remove wastes and excrete to outside
through skin
Nervous System
• Varies greatly between species
– Bi-valves have extremely simple systems
consisting of a couple ganglia, nerve chords and
sense organs
– Octopi and other complex molluscs have
developed brains with memory and learning
capacity
Reproduction
• Again, varies between species
• Most have separate sexes and fertilization is
external (in open water)
• More complex species have internal
fertilization
Ecological & Economic Importance
• clams, oysters, scallops all farmed or fished for
food
• octopus some food value, recreational diving
to observe
3 Main Classes
• Take some time to read over pages 590 – 592
to learn about the:
– Gastropods
– Bivalves
– Cephalopods
• Complete Phylum Mollusca handout
Squid External View
Squid Internal Anatomy
Assignment:
1. Complete Phylum Mollusca handout from
last class
2. With your partner, read over the handout for
tomorrows dissection
3. Begin to fill in as much of the handout as
you can.