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.
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 )
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 .