Biology - Mollusks
Phylum
Mollusca
Unit 4
Mollusk Introduction
Phylum Mollusca
Molluscus = soft
Soft-bodied animals that usually have an internal or external shell.
Includes snails, slugs, clams, squids, and octopi.
True coelom
Complex, interrelated organ systems
Body Plan
The body plan of most mollusks have 4 main parts: foot 2. mantle
3. shell
4. visceral mass
1.
Foot: muscular; may be used for crawling, burrowing, or tentacles for capturing prey
Mantle: thin tissue layer that covers the body (cloak)
Shell: made by glands in the mantle that secrete calcium carbonate
Visceral mass: internal organs
Body Plan
Body Plan
Feeding
Many (snails, slugs) use radula: flexible, tongue-shaped structure with hundreds of tiny teeth to scrape food, or drill into other animals
Octopus: sharp jaws to eat prey
Feeding
Clams, oysters, scallops: filter feeders; use siphon – tube-like structure through which water flows
Respiration
Aquatic mollusks use gills
Land mollusks use mantle cavity; large surface area lined with blood vessels. It is kept moist and oxygen diffuses across.
Circulation
Open circulatory system:(snails, clams) blood is pumped through vessels by a simple heart and works its way into the sinuses; blood then passes to the gills, where oxygen and carbon dioxide are exchanged.
Closed circulatory system: (octopi, squid) capable of transporting blood faster
Open vs. Closed
Open vs. Closed
Response
Clams (bivalves): simple nervous system, small ganglia, nerve cords and simple sense organs
(eyespots, chemical receptors)
Octopi: active predators; most highly developed nervous system of all invertebrates; welldeveloped brains; capable of complex behaviour, such as opening jars, responding to rewards. Reproduction
Variety of methods; snails and bivalves reproduce sexually by external fertilization
External fertilization: large number of eggs are released into the water, then fertilized by
Mollusca
Unit 4
Mollusk Introduction
Phylum Mollusca
Molluscus = soft
Soft-bodied animals that usually have an internal or external shell.
Includes snails, slugs, clams, squids, and octopi.
True coelom
Complex, interrelated organ systems
Body Plan
The body plan of most mollusks have 4 main parts: foot 2. mantle
3. shell
4. visceral mass
1.
Foot: muscular; may be used for crawling, burrowing, or tentacles for capturing prey
Mantle: thin tissue layer that covers the body (cloak)
Shell: made by glands in the mantle that secrete calcium carbonate
Visceral mass: internal organs
Body Plan
Body Plan
Feeding
Many (snails, slugs) use radula: flexible, tongue-shaped structure with hundreds of tiny teeth to scrape food, or drill into other animals
Octopus: sharp jaws to eat prey
Feeding
Clams, oysters, scallops: filter feeders; use siphon – tube-like structure through which water flows
Respiration
Aquatic mollusks use gills
Land mollusks use mantle cavity; large surface area lined with blood vessels. It is kept moist and oxygen diffuses across.
Circulation
Open circulatory system:(snails, clams) blood is pumped through vessels by a simple heart and works its way into the sinuses; blood then passes to the gills, where oxygen and carbon dioxide are exchanged.
Closed circulatory system: (octopi, squid) capable of transporting blood faster
Open vs. Closed
Open vs. Closed
Response
Clams (bivalves): simple nervous system, small ganglia, nerve cords and simple sense organs
(eyespots, chemical receptors)
Octopi: active predators; most highly developed nervous system of all invertebrates; welldeveloped brains; capable of complex behaviour, such as opening jars, responding to rewards. Reproduction
Variety of methods; snails and bivalves reproduce sexually by external fertilization
External fertilization: large number of eggs are released into the water, then fertilized by