Chapter 10: Molluscs Flashcards
Phylum ____ is the 2nd largest after Arthopoda
Mollusca
There are almost ____ extant species of Phylum Mollusca
90,000
What is so important about Molluscs?
They are an extremely important food source and extremely commercially harvested.
A healthy ____ depends on healthy oceans
fishery
Explain what happens when CO2 amounts increase in the atmosphere
As CO2 levels rise, the acidity of the oceans does as well which causes the amount of biologically available calcium to decrease. This calcium is used for creating strong, healthy shells of molluscs so without it shells are weak and larvae fail to develop normally
What are the two primary portions of the basic body plan of a mollusc
Head-foot portion and Visceral mass
What is contained within the head food region of a mollusc?
Feeding, cephalic sensory, and locomotor organs
The function of the Head-foot region primarily depends on what?
muscular action
What is contained within the Visceral mass of a mollusc?
Digestive, circulatory, respiratory, and reproductive organs
The function of the Visceral Mass is dependent on what?
Ciliary tracts
Describe the mantle of a mollusc
Formed by two folds of skin
Internal space is the mantle cavity
What is the function of the mantle?
Protection and secretes the shell
Modifications of structures produce great ___ of the body plans
diversity
What other structures are found within the head-foot region?
Mouth, sensory organs, chemoreceptors, statocysts, tactile sensors, brain
Describe a radula (function, feel)
Unique to molluscs, located in mouth, Tongue-like organ
Function- helps feed and carry food particles toward digestive tract
What is the foot portion of the head-foot region adapted for?
Locomotion and attachment to substrate
Describe the modification of the foot that Limpets have
Attachment disc that creates suction
Describe the modification of the foot that Bivalaves have
“hatchet foot”
Describe the modification of the foot that squids/octopuses have
Funnel for jet propulsion
How many layers does a mollusc shell have? What are they called?
3;Periostracum, Prismatic layer, Nacre
What layer of the shell is the outmost?
Periostracum
The Periostratcum is composed of ____.
conchiolins
What are conchiolins? Function?
Composition of the Periostratcum; protective protein, protects from erosion
What is the Prismatic layer composed of?
densely packed prisms of calcium carbonate
What is the innermost layer of a molluscs shell called?
Nacre
What is unique about the nacre layer?
It is secreted continuously through an animals life and become thicker
What special event occurs in the nacre?
Pearl formation
Explain how a pearl is formed
The nacre layer begins to cover a foreign object such as dirt between the shell and the mantle continuously to avoid irritation. Overtime, this dirt becomes a shiny spherical object we call a pearl
What is unique about a molluscs circulation system
It is an open system, blood is not contained within the vessels
_____ have a closed circulatory system
Cephalpods
What does fertilization result in?
An embryo
What is the 2nd swimming larval stage structure called?
Veliger
What classes of Molluscs are discussed in this chapter
Polyplacophora & Gastropoda
____ is the most diverse class of molluscs
Gastropods
Most Gastropods have a hard proteinaceous plate called a _____.
Operculum
What does an Operculum do?
Acts as a trapdoor and covers the shell when the body withdraws inside
What is an example of Herbivore Gastropods
Turban snails
What do scavenger Gastropods feed on? Example
Dead and decaying flesh; mud snails
What do driller/borer Gastropods do? What is an example?
They drills holes into shells with their radula (4 days); Moon snail
What is an example of carnivore Gastropods
Cone snails
What is unique about cone snails
they have a radula that has been modified into a harpoon with venom to kill prey
What are the 3 subclasses of Gastropods
Prosobranchia, Opisthobranchia, & Pulmonata
____ is the largest subclass of Gastropods
Prosobranchia
What are examples of Prosobranchia
Periwinkles, Limpets, Abalones, Cowries
What is an example of subclass Opisthobranchia
Sea hare & Nudibranchs
What is an example of subclass Pulmonata?
Giant land snail
What is different about subclass Pulmonata?
Lack gills, contain land and freshwater slugs/snails
What is the common name for Class Polyplacophora?
Chiton
What Class is described as bearing many plates”
Class Polyplacophora (Chitons)
