Chapter 16: Phylum Mollusca Flashcards Preview

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Flashcards in Chapter 16: Phylum Mollusca Deck (22):

What are the four types of food acquiring capabilities of those that fall under the phylum Mollusca?

- herbivorous grazers
- predaceous carnivores
- filter feeders
- parasites


Majority of those in phylum mollusca live in what kind of environment? What are the other two not as common environments ?

- marine
- terrestrial
- fresh water aquatic


Are Organisms belonging to phylum Mollusca protosomes or deuterostomes

- protosomes ( mouth first, anus second)


The body plan of a Mollusc is divided into what two parts?

- head foot region
- visceral mass


What is included in the head-foot portion of the Mollusc?(3)

- feeding, cephalic sensory and locomotor organs


What is included in the visceral portion of a Mollusc ?(4)

- digestive, circulatory, respiratory and reproductive organs.


Explain what the mantle cavity is?
- what makes up the mantle?
- whats the space between the mantle and body wall?
- The space contains what? (2)
- The mantle secretes what?

- two folds of skin form protective mantle
- mantle cavity
- gills (ctenidia) or a lung
- shell over the visceral mass


Head- Foot region:
- Mollusc's have a well developed head bearing what? (2)
- Photosensory receptors range from?
- what may be present but not always?
- Posterior to the mouth is the chief locomotor organ called the?

- mouth and some sensory organs
- simple to complex eyes
- tentacles
- the foot


- Is this specific to Mollusc's or not?
- In the mollusca phylum this is present in all organisms except what?
- Describe the organ? Physical characteristics
- Functions? In regards to prey and the digestive tract

- specific to molluscs
- all except bivalves
- protruding , rasping, tongue like organ
- ribbon like membrane contains rows of tiny teeth
- it rasps particles of food off surfaces
-moves particles to digestive tract
-teeth that are very worn out are replaced
- pattern and number of teeth help in classification
-some are specialized to bore through hard material or harpoon prey


Characteristics of the Foot:
- it's usually located how? Ventral or Dorsal?
- It functions in what two basic concepts?
- What Are the modifications it has for varying organisms ? (3)
- Secreted mucus aids in what two things?
- Snails and bivalves do what to extend the foot?
- Burrowers extend the foot into what and do what?
- Free swimming forms have a modified the foot into what?

- ventral
- locomotion or substrate attachment
- A) attachment disc of limpets
B) hatchet foot of clams
C) siphon jet of squids
- locomotion allowing it to glide across the substrate via cilia OR in adhesion
- extend the foot hydraulically via engorgement of blood
- extend it into mud or sand, enlarge the tip as an anchor and draw forward
- into a wing or fin like swimming agents


Mantle and Mantle Cavity Characteristics:
- The mantle is a sheath tissue located where?and secretes what when present?
- Mantle cavity : houses what that develop from what?
- The exposed surface of the mantle functions in what?
- In aquatic molluscs continuous flow of water does what? (3)
- Products of what three systems empty into the mantle cavity?

- on each lateral side
L> secretes the shell when present
- houses the gills or lungs that develop from the mantle
- gaseous exchange
- brings in oxygen, good and flushes out wastes
- Digestive, excretory and reproductive systems


Cephalopods use the head and mantle to create what?

- jet propulsion


Describe the mollusc gill?
- countercurrent blood movement?
-In most molluscs there are how many and form what?

-has leaf like filaments - cilia propel water across the surface
-countercurrent (blood moves one way and water in the other ) blood movement in gill absorbs oxygen efficiently
- In most molluscs two ctenidia on opposite sides form an incurrent and excurrent chambers


Describe the characteristics of the Shell:
-If present it has been secreted and lined by what?
- Periostracum is located where and is composed of what?
- Middle prismatic layer?
- Inner Nacreous layer?
* A thick periostracum for fresh water molluscs protects them against what??

- mantle
- outer horny layer
L> composed of conchiolin, a tanned protein
- closely packed prisms of calcium carbonate
- next to the mantle, the nacre is laid down in thin layers
- acid from leaf decay in streams


Describe the formation of a pearl?

- dirt gets into the outer mantle epithelium and is passed down slowly pushing through the mantle
- protects them against irritation via foreign material


Why do fresh water molluscs have a thicker periostracum?

- protects them against acid water due to leaf litter in water


What kind of circulatory system do they have? What is it comprised of?

- open circulatory system
- pumping heart, blood vessels and blood sinuses


What class does not have a open circulatory system?

- cephalopods
- heart , vessels and capillaries


Most molluscs have a pair of ____ also called metanephridia
The ___ ducts also discharge what?

- kidneys
-kidney, sperm and eggs


What is the nervous system comprised of and is also very simpler in comparison to what other phylum?
- In air breathing snails the nervous system produces what hormones?
Within the phylum Mollusca what organisms do not have a simple nervous system ?

- pairs of ganglia
- annelids
- growth hormones
- squids/octopus aka Cephalopoda


Reproduction and Life History:
- Most organisms in this group are what? Monoecious or Dioecious?Some may possibly be what as well?
- Eggs hatch and produce what? This units them with what other phylum?
-Larva undergoes what process producing a small juvenile chiton?
- In many gastropods and bivalves there is an intermediate larval stage which is called what?

- dioecious but some may be hermaphroditic
- free swimming trochophores, uniting them to annelids and marine turbellarians
- direct metamorphosis
- Veliger


Molluscs are true ______ animals. They are ____ coelomates. They have ___ cleavage. They undergo determinate development which means what? Are they protosomes or deuterostomes?

- coelomate, schizocoelous, spiral
L> Fate of the blastopore is determined very early in development
- Protosomes meaning the mouth forms from the blastopore

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