mollusca Flashcards
animals in the phylum mollusca are calcareous, what does this mean?
they have a shell enclosing a soft body, but the shell may be lost or reduced in many taxa
what are some characteristics of mollusca?
- they have a complete digestive system with a mouth
- they have a true coelom
- open circulatory system (no blood vessels and the coelom is small)
- not clearly segmented
mollusca have a mantle, what is it?
a thin layer of tissue that secretes the shell
how do molluscs move?
muscular ventral foot
where are a molluscs organs?
inside the visceral mass above the foot
molluscs have a radula, what is it?
a mouthpart that has a strap-like rasping (conveyor belt with hooks/spikes)
how do molluscs breathe?
gills for gas exchange and sometimes feeding
what are the three classes of molluscs?
gastropoda, bivalvia, cephalopoda
what is the most abundant class of molluscs?
gastropoda
what animals does the class gastropoda encompass?
snails and slugs
how do gastropods move?
through slime excretion, then use their muscular foot to move across the substrate
during the larval stage, gastropods undergo _________. what is it?
torsion - visceral mass twists during development where their anal opening is over their head
do gastropods have direct development?
only terrestrial and freshwater species, marine species have a larval stage
how do land snails and slugs exchange gasses?
using a lung, which is the lining of their mantle cavity
gastropods have a division called nudibranchs, what are they and their characteristics?
marine shell-less gastropods (sea slugs)
1. many are bright and vibrantly colored
2. protected by nematocysts of cnidarians (other animals)
how are nudibranchs protected by the nematocysts of cnidarians?
eat cnidarians, but prevent their nematocysts from firing but instead storing it in their own tissues and firing the nematocysts when threatened
where does the term ‘bivalvia’ come from?
having two hinged shells
what animals does the class bivalvia encompass?
clams, oysters, muscles and scallops
what are some characteristics of bivalves?
- filter feed by drawing water through the gills
- no radula (no definitive head)
- most are sedentary (can move if needed)
what animals does the class cephalopoda consist of?
squids, cuttlefish and octopus
do cephalopods have a shell?
no external shell (except nautilus) and some have internal shell remnants (cuttlefish)
how do cephalopods eat?
long tentacles that have suckers or hooks around their mouths
do cephalopods have a radula?
no, it was modified into a biting beak
how do cephalopods move?
they have a siphon (a fused tube of the mantle) in which they propel water though
cephalopods are the only molluscs with a?
closed circulatory system which supports their active lifestyle
do cephalopods have direct development?
yes
cephalopods provide maternal care, what is that?
they protect their eggs until young hatch
what are some characteristics of octopus?
excellent vision and have complex behavior
