Lab 7: Phylum Mollusca Flashcards
Define rapid radiation
a pattern of evolution in which there are multiple divergences from a common ancestor in a relatively short period of time
When radiation is accompanied by ecological diversification, this is called _____ _______
adaptive radiation
Define adaptive radiation
the genetic differentiation between populations evolves in response to differences in the environments they inhabit and the resources they use
What type of symmetry does a mollusc have?
Bilateral
Is a mollusc triploblastic or diploblastic?
Triploblastic
Unsegmented protostomes belong to the clade _____
spiralia
Do molluscs have complete digestive systems?
Yes, they have a complete gut with regional specialization, kidneys (excretory organs), and a circulatory system that is of the open type in most although few have a closed.
How do molluscs do gas exchange?
With gills; there are some molluscs that have a primitive lung
The molluscan plan is referred to as having _____
plasticity; their body plan can be molded like plastic to fit a variety of ecological niches
What is a modular body plan?
parts of the body can be removed, and different ones put in their place
What are the basic parts of a mollusc?
Ventral foot, dorsal visceral mass, mantle, and shell
Homocoel
a series of interconnected spaces between tissues and organs. Blood leaves vessels and flows through these spaces outside of vessels
What is a Gastropoda?
Most possess coiled shell; well-defined head, foot for crawling. Largest class of molluscs.
What is a Bivalia?
Two shells dorsally hinged; suspension feeder
What is a Polyplacaphora?
Broad flat foot and shell divided into 8 plates
What is a Cephalopoda?
Free swimming, highly developed nervous system, predator, foot modified into tentacles, shell absent in most.
In molluscs, the coelm is much _____. It only exists as a fluid-filled space surrounding the ____.
Reduced; heart
What is the principal body cavity in a mollusc?
Hemocoel; functions as hydrostatic skeleton in molluscs.
Production of what in molluscs aids in locomotion?
mucus
Ventral foot is involved in ____
locomotion
What is a radula?
Feeding structure located in the mouth of the cavity D; ribbon of teeth composed of chitlin
What is located in the dorsal visceral mass
circulatory system, the reproductive system, the excretory system, and the digestive system
What is the mantle?
a sheet of skin located between the visceral mass and the shell; the mantle secretes the shell
What is the mantle cavity?
the space between the outside wall of the visceral mass and the mantle is called the mantle cavity; is open to the environment. (At the posterior of the generalized mollusc)
Where are gills located?
Mantle cavity
The gills are covered with _____
cilia
What does the cilia do?
creates a current that draws water into the mantle cavity and over the gills
How is oxygen diffused?
from the water into the blood in the gills; hemocyanin binds the oxygen. When blood reaches cells of the body it releases the oxygen to the cells
What is the shell composed of and and secreted by?
Calcium carbonate; secreted by the mantle
Describe a molluscs nervous sytem
consisting of a ganglion encircling the esophagus and nerve cords extending to the organs and foot
Molluscs have what kind of circulatory system?
Open
Why is blood flow slow in an open circulatory system?
it empties into a large space and the pressure cannot be maintained
What is a molluscs digestive tract composed of?
Mouth, esophagus, stomach, intestine, and anus. Mouth is in the radula
What is step one of a gas exchange in a generalized mollusc?
Exchange with environment and blood
What is the second step of gas exchange in a mollusc?
exchange with the blood and individual cells
