Mollusca Identify the distinguishing characteristics of Phylum Mollusca, in terms of body plan, embryonic development, symmetry, organ systems, etc Describe the process of torsion and identify which class of mollusk undergoes torsion Describe differences among the different classes of mollusks as discussed in class, give examples of each What are the distinguishing characteristics of Phylum Rotifera? Understand the differences in cephalization among the mollusk classes and be able to give reasons why. Know the difference between external and internal fertilization. Solution Identify the distinguishing characteristics of Phylum Mollusca, in terms of body plan, embryonic development, symmetry, organ systems, etc ANS: some characcteristic of phylum Mollusca are : they have unsegmented and have bilateral symmetry,they have reduced coelom,have complete digestive sysytem,have large complex metanephridia,Mantle for braething and excretion,head foot and visceral mass. Describe the process of torsion and identify which class of mollusk undergoes torsion Ans: A visceral mass is present which starts twisting during development in such a way that one side of the mass grows faster than the other side.This leads to the uneven growth.This uneven growth rotates visceral mass and take to the position of 1800 relative to head.This is called Torsion.This is a important or key characterictic of this group,along with a foot which is modified for crawling. Describe differences among the different classes of mollusks as discussed in class, give examples of each Ans: different classes of Mollusks are: a) Aplacophora-eg Worms like animals. b) Monoplacophora:eg- Neopilina galatheae c)Polyplacophora: eg- Chitons -Lepidopleurus. d) Bivalvia:eg oysters,musseles. e) Gastropoda eg: garden snails,conispiral f) Cephalopoda: eg:octopus What are the distinguishing characteristics of Phylum Rotifera? Ans: They are tiny multicellular organisms,They have pseudocoelum,have alimentary canal.separate mouth and anus. Understand the differences in cephalization among the mollusk classes and be able to give reasons why. ANS:The cephalization in different classes of mollusks are in cephalopoda they are moslty cephalised and used for camouflage. And polyplacophoda they are nomewhat cephalized and used for survival. Know the difference between external and internal fertilization. ANS: Fertilization is a process in which sperm and egg unite to form a new individual. The difference between internal and external fertilization is that in internal fertilization sperm fertilizes the egg within the female and female give birth to a live individual whereas in external fertilization both sperm and egg release into external environment and sperm will fertilize egg in outside environment . for example in spawning..

1. Mollusca
Identify the distinguishing characteristics of Phylum Mollusca, in terms of body plan, embryonic
development, symmetry, organ systems, etc
Describe the process of torsion and identify which class of mollusk undergoes torsion
Describe differences among the different classes of mollusks as discussed in class, give examples
of each
What are the distinguishing characteristics of Phylum Rotifera?
Understand the differences in cephalization among the mollusk classes and be able to give
reasons why.
Know the difference between external and internal fertilization.
Solution
Identify the distinguishing characteristics of Phylum Mollusca, in terms of body plan, embryonic
development, symmetry, organ systems, etc
ANS: some characcteristic of phylum Mollusca are :
they have unsegmented and have bilateral symmetry,they have reduced coelom,have complete
digestive sysytem,have large complex metanephridia,Mantle for braething and excretion,head
foot and visceral mass.
Describe the process of torsion and identify which class of mollusk undergoes torsion
Ans: A visceral mass is present which starts twisting during development in such a way that one
side of the mass grows faster than the other side.This leads to the uneven growth.This uneven
growth rotates visceral mass and take to the position of 1800 relative to head.This is called
Torsion.This is a important or key characterictic of this group,along with a foot which is
modified for crawling.
Describe differences among the different classes of mollusks as discussed in class, give examples
of each
Ans: different classes of Mollusks are:
a) Aplacophora-eg Worms like animals.
b) Monoplacophora:eg- Neopilina galatheae
c)Polyplacophora: eg- Chitons -Lepidopleurus.
d) Bivalvia:eg oysters,musseles.
e) Gastropoda eg: garden snails,conispiral
f) Cephalopoda: eg:octopus
What are the distinguishing characteristics of Phylum Rotifera?

2. Ans: They are tiny multicellular organisms,They have pseudocoelum,have alimentary
canal.separate mouth and anus.
Understand the differences in cephalization among the mollusk classes and be able to give
reasons why.
ANS:The cephalization in different classes of mollusks are in cephalopoda they are moslty
cephalised and used for camouflage. And polyplacophoda they are nomewhat cephalized and
used for survival.
Know the difference between external and internal fertilization.
ANS: Fertilization is a process in which sperm and egg unite to form a new individual. The
difference between internal and external fertilization is that in internal fertilization sperm
fertilizes the egg within the female and female give birth to a live individual whereas in external
fertilization both sperm and egg release into external environment and sperm will fertilize egg in
outside environment . for example in spawning.