1. OUTLINE THE ADAPTIVE RADIATION IN LOCOMOTION, FEEDING AND DIGESTION IN PHYLUM MOLLUSCA GROUP 3 PRESENTATION

2. D EFINITION OF KEY WORDS : Adaptive radiation - The evolutionary diversification of a species or single ancestral lineage into various forms that are each adaptively specialized to a specific environmental niche. Locomotion - ability to move from one place to another Feeding - How an organism attains its food Digestion - the process of treating a substance with heat, enzymes, or a solvent to promote decomposition or extract essential components.

3. G ENERAL CHARACTERISTICS OF PHYLUM M OLLUSCA Have visceral mass- it contains most of the internal organs i.e digestive system, circulatory system, reproductive system and respiratory organs Have a muscular foot- variously modified, but chiefly used for locomotion Have mantle- this encloses the mantle cavity and it secretes the shell in some

4. T HE 7 CLASSES OF THE PHYLUM M OLLUSCA Aplacophora- Aquatic bottom grazer Monoplacophora- Deep sea bottom grazer Polyplacophora- All are marine, live on rock surfaces and are bottom grazers Gastropoda - Some are freshwater and some are marine, terrestrial and are either herbivores, carnivores, scavengers or detritus feeders Bivalvia- Fresh water or marine, these are suspension feeders Scaphopoda- are marine inhabitants that live partially buried in sand or gravel all their lives Cephalopoda- Marine carnivores

5. A PLACOPHORA Habitat: Aquatic Locomotion They are cylindrical and worm-shaped They glide on a mucous film which it secretes Presence of cilia which also aids in movement Feeding Food is taken in through the circumpharyngeal muscle the oral cavity They have a radula, which rasps/scrapes bits of food on aquatic surfaces and draws it into the mouth The fine food then passes it into a mid-gut organ that consists of a stomach and digestive gland Digestion The visceral mass consists of a straight and simple alimentary canal The radula is part of the gut, therefore it grinds food down the alimentary canal The mid-gut is separated into stomach and digestive organ The short intestines absorb nutrients before the waste passed in the cloaca They have a complete digestive system

6. A PLACOPHORA

7. M ONOPLACOPHORA Habitat: deep sea where there are soft sediments Locomotion Possess a broad, flat ventral foot which is not very muscular and is responsible for locomotion in a creeping motion Feeding Mouth is a cluster of front-like appendages that push food into the pharynx Have radula for cutting and ingesting food Digestion Similar to that of gastropods

8. M ONOPLACOPHORA ANATOMY

9. POLYPLACOPHORA Habitat: all are marine. Some live on rocks in sea shore on soft sediments Locomotion Have expanded broad flat foot which covers most of the ventral surface for locomotion and adhesion Creep on rock surfaces using their muscular foot which secretes a small amount of mucous Only move when in search of food e.g chiton Feeding Use of radula to scrape algae off rock surfaces since they are herbivores Digestion They have a complete digestive system Have esophagus for passage of food towards the stomach Have a stomach were digestion takes place Nutrients absorbed in the intestines

10. P OLYPLACOPHORA

11. GASTROPODA Habitat: live in fresh water and terrestrial environments, though some are marine Locomotion Move by rippling motion of their muscular creeping foot from the anterior to the posterior Pedal mucous glands open onto the ventral or dorsal surface of the foot and secretes a slime train over which the animal glides over (the layer of mucus also aid against injury Feeding Some are herbivores and they feed by scraping and cutting using the radula Some are scavengers of dead animals and they tear of pieces with radula teeth Some are carnivores, radula and chemicals to get through the shells of other molluscs Digestion Its always at least partially extracellular Enzymes needed for extracellular digestion produced by salivary glands, esophageal pouches and/or the digestive glands, or by a combination of all three Stomach is the site for extracellular digestion and liver is site for intracellular digestion and absorption

12. S NAIL ANATOMY

13. G IANT A FRICAN SNAIL IN N IGERIA

14. Gastropoda (slug)

15. BIVALVIA Habitat: fresh water and marine Locomotion Some are sessile. They secrete strong threads and tether them to rocks Some move with their foot via a muscle that can be projected through their shells Some swim by clapping their shells together to create a jet propulsion. Feeding They lack the radula, therefore they are filter feeders They use their gills to separate water and food Gland cells on gills and labial palps secrete mucus to entangle food particles Digestion The digestive tract of typical bivalves consists of an oesophagus, stomach, and intestine A number of digestive glands open into the stomach,these secrete enzymes to digest food in the stomach also include cells that phagocytose food particles, and digest them intracellularly.

16. BIVALVE ANATOMY

17. S CAPHOPODA T HE TUSK OR TOOTH SHELLS, AS THEY ARE MORE COMMONLY KNOWN, HAVE THE SIMPLEST SHELL STRUCTURE AND ANATOMY OF ALL THE MOLLUSCS Locomotion The foot extends from the larger end of the shell and is spade or cone shaped. It is projected downwards, so the animal can burrow with it. It also serves as a means of an anchor for the animal. Finally, by the contracting and expanding motions, the foot also keeps water passing in and out of the posterior half of the mantle cavity which in turn causes blood circulation. Feeding Their food often consists of a microscopic family of one-celled organisms called foraminifer, some of which live on sand or silt The Scaphopod head is reduced to a short conical projection or proboscus, bearing the mouth. On each side of the head are lobes bearing a large number of thread-like appendages called captacula The buccal cavity contains a well-developed radula with large flattened teeth

18. S CAPHOPODA (C ONTIUED …) Digestion The stomach and digestive gland are located in the middle of the body. The intestine then extends anteriorly, and then loops around to open through the anus into the mantle cavity. Details of scaphoda digestion and absorption are still fairly unknown

19. CEPHALOPODA Habitat: marine water Locomotion Built for speed Have arms which help them swim Squid start about backwards drawing water into its mantle cavity, firing a jet-stream of water through the excurrent siphon Octopuses creep on the ocean floor Feeding Some have tentacles which help them sting and capture prey Beak-like jaws to bite prey They also inject poisons to immobilise their prey Digestion Complete digestive system

20. A NATOMY OF A SQUID

21. A NATOMY OF C EPHALOPOD ARM

22. G ROUP III NAMEREG NUMBER Kaneunyenye Simba Chatora Yolander Chidzana Winnie Chirilele Praise Makonyere Brenda Bright Tom Mtisi Layton Masakadza Tatenda Wisani Nyengeterai Foroma Bernadette Kadzungwa Lorraine Chitanga Brian Gukuta Nyasha Hlatshwayo Lisa Chapenyama George Gwanzura Luanne-May Chakanza Ngonidzashe R169202R R169196U R1611456 R1610333 R1610323 R1611457 R167120A R1610428 R165806N R167121G R167146W R167162A R167161U R167160P R164438A R167134Q R167127J