Evolutionary perspective Relationship to other animals Origin of ceolom Referance Presentation BEST OF LUCK

1. PHYLUM MOLLUSCA

2. Content
 Evolutionary perspective
 Relationship to other animals
 Origin of ceolom

3. Phulum molusca

4. Evolutionary perspective
 Most adept predators
 Evolution in..
1. Large brain
2. Complex sensory structure
3. Rapid locomotion
4. Grasping tentacles
 Cephalopods including 550 species
 Posses coelom and coelom of mollusks
Is only a small cavity surrounding heart and gonads.
coelom
 A coelom is a body cavity that arises in mesoderm and lined by sheet known as peritonium.

5. • Evolutionary relationship of molluscans

6.  Outcompeted cephalopods because they make appearance in historic seas also they aquired
active energy and predatory lifestyle.
 declined because of random evolutionary events.
 Molluscan success
 twice as succesful as verteberates
 100,000 spiece belongs to
1. Class gastropoda(snails and sludges)
2. Class bivalvia(clams )

7.  Triploblastic
 First animal that posses ceolom.

8. Relationship to other animal
 Protostomes
 What are protostomes
“any other group of animal such as annelida and mollusca in this mouth formation directly
From blastopore and coelom made from splitting mesoderm”.
 Similarities in mollusca and other phylum
 Molluscan share developmental characteristics with annelids, arthropods and
Brachiopods.

9.  They were earliar grouped together with arthropods but now they are
placed separately in ecdyozoa.
 Mollusks probably evolved from flatworms resembling ancestor during the
precambium era.

10. Origin of coelom
 Hypothesis
1. Schizocoel hypothesis
 (Gr.schizen,to split and koilos,hollow)
 “This is patterened after mathod of mesodermal development and coelom formation in many
protosomes.”
 Coeloam formation from mesoderm
 Forunner of coelomate.

11. Enterocoel hypothesis
 (Gr.enteron,gut and koilos,hollow)
 “suggest that coelom may have arisen as outpocketing of a primitive gut track.”
 Patterend after formation of coelom in deutrostome
 This hypothesis patterened after mathod of coelom formation in
Deutrosome .
• Implication is mesoderm and coelom form from gut of diploblastic animal.

12. Zoologist don’t know which is accurate
 Zoologist believe that coelom may have arisen more than once in different lineage.
 So more than one explanation could be correct.
 Referance ..miller and harlay book 5th edition .