Invert Test 4

What type of symmetry do molluscs have?

Bilateral symmetry

Are molluscs protostomes or deuterostomes?

Protostomes

What type of body cavity do molluscs possess?

A true coelom (eucoelomates)

What are the benefits of gaining a coelom for molluscs?

It allowed the development of more complex organ systems with mesenteries, closed circulation, and antagonistic muscle interactions for movement.

Why are molluscs considered evolutionarily important among protostomes?

They are the FIRST protostome group with a coelom, allowing greater body complexity.

Where are molluscs found?

Marine (all), freshwater (bivalves and gastropods), and terrestrial environments (only gastropods).

What size range can molluscs reach?

From a few centimeters to about 21 meters (giant squid).

What are the 5 mollusca classes?

Polyplacophora- chitons

Scaphopoda- tusk shells

Gastropoda- snails, slugs

Bivalvia- oysters, scallops, Cephalopoda- nautilus, cuttlefish, squid, octopus.

What are the three main body regions of molluscs?

Visceral mass

Mantle

Head/foot

What is the visceral mass in molluscs?

The dorsal body region that contains the internal organs such as digestive, reproductive, and excretory systems.

(main thing is contains the internal organs)

What is the mantle?

A fold of epithelium that covers the visceral mass and secretes the shell.

What is the mantle cavity?

The space around the visceral mass

What types of sensory receptors are found in molluscs?

Chemoreceptors, Mechanoreceptors

What are the gills functions on molluscs?

Excretory, Respiratory, Digestive (food collecting/ sorting), Reproductive

How do the gills work in mollsucs?

Via diffusion

What is the function of the head region in molluscs?

Feeding and sensory functions

What is the function of the posterior/ventral molluscan foot?

A muscular structure used for locomotion

What are some specialized functions of the molluscan foot?

Holdfast (anchor), Wing-like projections, Tentacles.

What does the mantle secrete in molluscs?

The Shell

What is the radula?

A rasping, tongue-like feeding organ with chitinous teeth

Which major mollusc class lacks a radula?

Bivalves

What is the buccal mass?

The radular complex plus its musculature

What structures make up the radular complex?

-Odontophore (cartilage like structure)

-Chitinous teeth

What is the odontophore?

A cartilage-like structure for the radula

What are radular teeth made of?

Chitin

What is the main function of the radula?

Feeding

How does the radula help with feeding?

It scrapes food and moves it like a conveyor belt toward the GI tract

How many teeth can a radula have?

From a few to about 250,000 teeth

Why is the radula effective over time?

Its teeth are replaceable

How do predatory molluscs use the radula?

To puncture or scrape prey

What structure forms the skeletal support in many molluscs?

Shell secreted by the mantle

What type of muscular system do molluscs have?

A ventral muscular foot and additional body muscles

What is the main respiratory structure in molluscs?

Gills located in the mantle cavity

What type of digestive system do molluscs have?

A complete digestive system with salivary glands and rasping (radula)

What feeding structure is commonly part of the molluscan digestive system?

Radula

What glands assist with digestion in molluscs?

Salivary glands

What type of circulatory system do most molluscs have, except Cephalopoda?

Open circulatory system

What is an open circulatory system?

Blood directly bathes internal organs, not always in a blood vessel

Which mollusc group has a closed circulatory system?

Cephalopods

What is a closed circulatory system?

Blood moves in blood vessels at all times, best version of circulatory system, super efficient (what humans have)

Where is the molluscan heart usually located?

In the pericardial cavity

How do molluscs perform excretion?

Nephridia connected to the pericardial cavity

Describe the molluscan nervous system.

A nerve ring with paired ganglia and two pairs of nerve cords; one innervates the foot, one innervates the visceral mass (ventral ladder-like system)

What are the 3 reasons molluscs are considered ecologically important?

They help with water filtration, food web support, and habitat formation.

How do molluscs help with water filatration?

natural cleaners, remove plankton, bacteria and pollutants from water (mostly bivalves)

How do molluscs contribute to food webs?

They act as both predators and prey.

How do molluscs contribute to habitat formation?

Oysters create reefs which give shelter to fish and crabs, shell beds stabilize sediments, this protects coastlines and reduce erosion

Why are molluscs economically important to humans?

Many species are harvested as food, pearls and jewelry, medicine, and research.

Give examples of molluscs commonly eaten by humans.

Clams, oysters, mussels, scallops, and snails.

What materials produced by molluscs have economic value?

Pearls and shells. lead to jewelry

How do molluscs contribute to medicine and research?

Pain management drugs

Neuroscience discoveries

Cancer treatments

Antibiotic development

Intermed, hosts of many parasites

Biomaterial Engineering

Environmental health monitoring

(just know like 2-3)

What is the taxonomy of polyplacophora?

Kingdom- Animalia

Subkingdom- eumetazoa

phylum- Mollusca

class- polyplacophora

common name- chitons

What does Polyplacophora mean?

Many plate bearing

What is the common name for Polyplacophora?

Chitons

Where are chitons typically found?

Marine rocky shore habitats

About how many species of chitons exist?

About 800 species

How many shell plates do chitons have?

Eight overlapping dorsal calcareous plates

What structure secretes the plates in chitons?

The mantle

Why are chiton shell plates segmented?

To provide flexibility

What is the girdle in chitons?

A thick lateral mantle that surrounds the shell plates

What structure allows chitons to cling to rocks?

A ventral holdfast (muscular foot)

What are the 3 functions of the ventral holdfast (muscular foot)?

-Mucus secretions

-Maintains position in surf

-Locomotion via pedal waves

How do chitons move?

Using pedal waves of the muscular foot

Where are the gills located in chitons?

In lateral grooves along the sides of the body

What do most chitons eat?

Algae scraped from rocks using the radula

How do some carnivorous chitons capture prey?

Using the radula like a spear

What are 4 major defenses of chitons?

-Heavy overlapping plates

-Cryptic coloration (camo)

-Strong attachment

-Ability to curl into a ball

What is the taxonomy for Scaphopoda?

kingdom- animalia

subkingdom- eumetazoa

phylum- mollusca

class- Scaphopoda

common name- Tooth or Tusk Shells

What does Scaphopoda mean?

Spade foot

What is the common name for Scaphopoda?

Tusk shells or tooth shells

About how many species of scaphopods exist?

About 300-400 species

Where do scaphopods typically live?

Buried in sandy marine sediments, worldwide

What type of environments can scaphopods inhabit?

Shallow coastal waters, continental shelf regions, deep sea

What is the shape of the scaphopod shell?

Long slender tubular shell that is open at both ends

What major molluscan body structures do scaphopods possess?

Foot, mantle and shell, visceral mass, radula

What important structures are absent in scaphopods?

Gills, circulatory system

How do scaphopods breathe?

diffusion

What type of feeders are scaphopods?

Selective deposit feeders

What are captacula?

Prehensile feeding tentacles used to capture food

About how many captacula can a scaphopod have?

About 100-200

How is food transported to the mouth in scaphopods?

By cilia for small particles or muscular contraction for larger prey

What is the taxonomy for Gastropods?

Kingdom- Animalia

Subkingdom- eumetazoa

Phylum- mollusca

Common name- Gastropods

What are the 4 distinctive traits of Gastropods?

-Univalves (in shelled species)--> Torsion

-Distinct Cephalization

-Large foot that is highly omdified among the subclass

-Scraping and/or predatory redula

True or false, Torsion is unique to Gastropods?

True

What does Torsion lead to in Gastropods (funny)?

anus head proximity

What does Gastropoda mean?

Stomach foot

What percentage of living molluscs are gastropods?

About 80%

Which mollusc group has the widest range of ecological niches?

Gastropods

Which mollusc group is the only one that invaded land?

Gastropods

What type of shell do most gastropods have?

Univalve shell (only in shelled species)

What does univalve mean?

A shell made of a single piece

What structure acts as a door that closes the shell opening in gastropods?

Operculum

What are the functions of the operculum?

Protects the animal, prevents water loss, covers aperture

What causes torsion in gastropods?

A twisting of the visceral mass during development leading to asymmetry due to differential growth

Why does torsion cause asymmetry in gastropods?

Because the twisting shifts organs and mantle cavity structures

What does dextral shell coiling mean?

Shell coils to the right, reducing or absent gills, nephridia, and heart on the right side

What does sinistral shell coiling mean?

Shell coils to the left, reducing structures on the left side

What is cephalization?

Development of a distinct head with sensory organs

What 2 types of eyes can gastropods have?

-Pit eyes= simple, open, light-sensitive cup used for detecting light direction

-Vesicular eyes= closed, camera-type structure containing a lens for focusing light into a crude image ("pinhole lens")

What sensory organs are commonly found on gastropod heads?

Tentacles with sensory receptors (statocysts, mechanoreceptors, chemoreceptors)