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
Majority of those in phylum mollusca live in what kind of environment? What are the other two not as common environments ?
- 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
- 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?
- 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??
- 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?
- heart , vessels and capillaries
Most molluscs have a pair of ____ also called metanephridia
The ___ ducts also discharge what?
-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
- 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