2. HBZ104 GROUP 1 PRESENTATION PRESENTERS : Masamvu Michelle Takunda Mangauzani Paidamoyo fende

3. Question Outline the adaptive radiation in feeding, digestion and absorption in phylum Mollusca

4. General characteristics of phylum mollusca  Soft bodied mostly protected by a hard calcium shell  Billateral symmetry  Usegmented  Usually with a definite head  Have a visceral mass which contains most of the internal organs  tripoblastic  Ventral body wall specialized as a muscular foot  Dorsal body wall forms the mantle which encloses the mantle cavity  Coelomate  Examples include snails, slugs, octopuses, squids

5. Definition of key terms  Adaptive radiation :a process in which organisms diversify particularly when a change in the environment makes new resources available, creates new challenges or opens new environmental niches  Adaptive radiation can also be defined as a process in which an unspecialized ancestor evolves into very different groups of organisms, each adapted to its own environment and own lifestyle  Feeding  Digestion  Absorption

6. Adaptive radiation in terms of feeding class cephalopoda  Carnivorous  Use tentacles to catch prey  Use Beak like jaws to bite prey  Mouth lies within the arm  use radula to pull prey into its mouth  Examples include octopuses, squids and cuttlefish

7. Digestion and absorption in cephalopods  Digestion starts  They have a complete digestive system

8. Class bivalvia (pelycopoda)  Filter feeders  Beating cilia direct flow of water across the gills and also move  Siphon brings water over a filtering structure  Suspended organic matter enters incurrent siphon  Gland on gills and labial pulps secrete mucus  Examples include oysters, scallops and marine mussel

9. Digestion and absorbtion in Bivalvia  Digestive tract consists of oesophogus, stomach and intestines  A number of digestive glands open into the stomach  Stomach aslo contains phagocytotic cells that digest food particle intracellularly

10. Digestion and absorption in gastropoda  Digestion starts in the mouth  Digestion is partially extracellular  Enzymes produced by the salivary gland eosophageal pouches and or digestive glands aid in digestion  The liver is the site for intracellular digestion and absorption  In snails digestive tract is continued by the intestines which is the medium for absorption  There is final absorption of simple sugars

11. Class gastropoda  Most are herbivorous and some are scavenger  Radula use to scrape algae from rock surfaces  Radula modified into a poisonous harpoon that paralyses prey  In some the radula is used to bore holes in the shells of prey  Examples include snails, slugs and limpets

12. Class aplacophora  Food taken in through circum-pharyngeal muscle which forms the oral cavity  Radula scrapes bits of food on aquatic surfaces and draws it into the mouth  They have a complete digestive system  Food is passed into the mid-gut organ that consists of a stomach and a digestive gland  Visceral mass consists of a straight and simple alimentary canal  Radula is part of the gut therefore it grinds food down the alimentary canal  The short intestines absorb nutrients before the waste is passed into cloaca

13. Monoplacophora  Mouth is a cluster of front like appendages that push food into the pharynx  They also have a radula for cutting and ingesting food  Digestion is similar to that of gastropoda

14. Class Polyplacophora  Herbivorous  Use radula to scrape algae of rock surfaces  Complete digestive system  Oesophogus for passage of food towards the stomach  Digestion takes place in the stomach and absorption takes place in the intestines

15. scapholopoda  Their food often consists of a microscopic family of one celled organismsm called foraminifer  The buccal cavity contains a well developed radula with large flattened teeth  The stomach and digestive gland are located in the middle of the body  The intestine then extends anteriorly