Annelids and mollusks
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Annelids and Mollusks. Leech. Clam. Earthworm. Annelids. Annelida  Marine Sandworms, earthworms, and leeches (segmented worms) Classes Polychaetes -> Marine worms, fire worms, feather dusters Oligochaetes  earthworms Hirudinea  leeches. Annelids. Earthworm. Polychaete (Ragworm).

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Annelids and Mollusks

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Annelids and Mollusks

Leech

Clam

Earthworm


Annelids

  • Annelida Marine Sandworms, earthworms, and leeches (segmented worms)

    Classes

  • Polychaetes -> Marine worms, fire worms, feather dusters

  • Oligochaetes  earthworms

  • Hirudinea  leeches


Annelids

Earthworm

Polychaete (Ragworm)

Leech


Reproduction

  • Mostly Sexual

  • Aquatic worms shed sperm and eggs into water

  • Earthworms & leeches are hermaphroditic (individuals fertilize each others eggs)

Earthworm Mating


Characteristics of Annelids

  • “Means tiny rings”

  • Have 5 characteristics of higher organisms

  • Bilateral symmetry

  • Cephalization

  • Tubular gut

  • Coelom

  • Segmentation


Segmentation

  • Allows organism to attain larger size

  • Each segment separated by a wall called a septum

  • Nephridia  found in each segment; removes excess water & wastes

  • Muscle in each segment contract sequentially for movement

  • Each segment contains nerve cords connected to the brain


Digestive System

  • 2 organs for Digestion

  • Crop -> stores food

  • Gizzard  grinds food


Mollusks

  • Includes snails, clams, oysters, scallops, Squid, and Octopus

  • Characteristics of Mollusks

  • 2nd most numerous phylum

  • Ceolomates allows for movement and digestion at same time

  • Trochophore Free swimming larval stage


Body Plan of Mollusks

  • Head-foot region  contains head (ganglia) and foot (muscle used for locomotion)

  • Visceral Mass contains heart + organs

  • Shell shell is made of Calcium carbonate;

  • Mantle epidermal layer that secretes Calcium carbonate; makes the shell

  • Ganglia Central Nerves behind mouth

  • Radula specialized tongue with teeth used for scraping algae or cutting plants


Head-Foot Region


Radula

Circular Rows of Moving Teeth


Gastropods

  • Includes Snails + Conch

  • Land snails are hermaphroditic; aquatic snails have separate sexes

  • Nudibranches “Naked gill” slugs… No shell


Snails and Conch

Conch

Apple Snail

Burgundy Snail


Bivalvia

  • Includes clams, oysters, and scallops

  • Most are filter feeders through tubes called siphons


Bivalves

Clams

Scallops

Oysters


Cephalopods

  • Includes Octopus and Squid

  • Free swimming Mollusks

  • Advanced nervous system with distinct brain (largest invertebrate brain)

  • Chromatophores are epidermal pigment cells that release ink when threatened


Giant Squid Swimming Next to Diver


Cephalopods


Giant Pacific Octopus


Scary-Looking Octopus


I’m an Octopus!


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