Mollusks/Annelids Flashcards
Symmetry Type of Mollusks
Bilateral Symmetry
Visceral Mass
Contains the internal organs
Mantle
Delicate tissue that produces shell. Thin layer of tissue that covers the entire body.
Foot
Usually contains the mouth and used for locomotion and food capture. Different forms for different animals
Shell
Used for protection, but not all mollusks still retain it (eg. octopi)
Diet (Mollusks)
Can be herbivores, carnivores, filter feeders, scavengers, or parisites.
Radula
Tongue shaped structure with teeth all over. used to drill through animal shells or scrape algae off rocks.
Gills in Clam and Oysters
Filter Food.
Method of Respiration (Mollusks)
Usually gills
Mantle Cavity
In snails and slugs. Lined with blood vessels as they have no gills.
Type of Circulatory System (Mollusks)
Open Circulatory System.
Sinuses
Blood goes through sinuses which lead to blood vessels
Respiration Process & Where it is Located (Mollusks)
Oxygen and CO2 exchange in gills
Nephridia
Tube shaped, ammonia leaves through here. Solid waste leaves through anus
Simple Nervous System (Mollusks)
Ganglia near mouth, few nerve cords, simple sense organs. Eg. Clams
Complex Nervous System (Mollusks)
Octopi. Very intelligent with well developed brains, can remember for long time.
Reproduction (Mollusks)
Most have separate sexes and have external fertilization (eggs and sperm released into water), which develop into larvae. Some are hermaphrodites.
Class Division Basis (Mollusks)
Divided based according to foot and shell
Class Bivalvia
Two large shells, filter feeders, grows up to 2m diamater. Eg. Clams, oysters, mussels, scallops.
Class Gastropoda
Translates to “stomach” “foot”. All have radula and are snails, and are shell-less or single shelled that move using muscular food located on ventral side. Eg. Slugs, ground snails
Class Cephalopoda
Translates to “head” “foot”. Internal shell or no shell in return for speed, making them good hunters. Head attached to single foot which is divided into arms or tentacles. Eg. Octopi and squid.
Septum
Internal walls that separate the segments of an annelid
Habitat (Annelids)
Mostly in mud or oceans
Nervous System (Annelids)
Most have brain and several nerve cords
Pharynx
Catches prey and pumps food/soil into esophagus
Esophagus
Tube where food/soil is pumped through
Crop
Location where food is first stored
Gizzard
Food is ground into smaller pieces
Intestine
Digests food
Nephridia
Filters fluid
Type of Circulatory System (Annelids)
Closed Circulatory System
Two Types of Blood Vessels (Annelids)
Dorsal - top, moves blood toward head of worm
Ventral - bottom, moves blood toward end of worm
Aortic Arches
5 hearts of the Annelid
Two Groups of Muscles (Annelids)
Longitudinal - front to rear, contract to make worm shorter/fatter
Circular - wrap around each body segment and contract to make the worm longer and thinner
Reproduction (Annelids)
Most sexual, some hermaphrodites, some budding.
Clitellum
When eggs are ready for fertilization, clitellum excretes a mucus ring in which sperm and eggs are released. Fertilization takes place inside ring, which slips off and forms a cocoon before hatching a few weeks later.
Polychaetes
Many bristles. Eg. Marine bristle worm, bloodworm, sandworm
Hirudinae
Parasite that sucks blood and bodily fluids of host. Used to reduce swelling after surgery and secretes a fluid that stops blood from clotting. Ex. Leech
Oligochaetes
Few Bristles. Sold in pet stores as food. Eg. Earthworm, tubiflex worm
Ecological Significance of Annelids
Enriches soil, slows down erosion, aerates soil, helps decompose plant matter, makes passageways for plant roots and water, increases nitrogen fixation.
