Transcript group_3_diversisity_Molluscax

OUTLINE THE ADAPTIVE RADIATION
IN LOCOMOTION, FEEDING AND
DIGESTION IN PHYLUM MOLLUSCA
GROUP 3 PRESENTATION
DEFINITION 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.

GENERAL CHARACTERISTICS
MOLLUSCA
OF PHYLUM
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

THE 7 CLASSES OF THE PHYLUM
MOLLUSCA
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

APLACOPHORA
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
APLACOPHORA
MONOPLACOPHORA
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
MONOPLACOPHORA ANATOMY
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
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Creep on rock surfaces using their muscular foot which secretes a small amount of mucous
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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
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Have a stomach were digestion takes place
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Nutrients absorbed in the intestines
POLYPLACOPHORA
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
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Some are scavengers of dead animals and they tear of pieces with radula teeth
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Some are carnivores , radula and chemicals to get through the shells of other
molluscs
Digestion

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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
SNAIL ANATOMY
GIANT AFRICAN SNAIL IN NIGERIA
Gastropoda (slug)
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.
BIVALVE ANATOMY
SCAPHOPODA
THE TUSK OR TOOTH SHELLS, AS THEY ARE MORE COMMONLY KNOWN, HAVE
THE SIMPLEST SHELL STRUCTURE AND ANATOMY OF ALL THE MOLLUSCS
Locomotion

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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
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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
SCAPHOPODA (CONTIUED…)
Digestion

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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
CEPHALOPODA
Habitat: marine water
Locomotion

Built for speed
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Have arms which help them swim
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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
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Some have tentacles which help them sting and capture prey
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Beak-like jaws to bite prey
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They also inject poisons to immobilise their prey
Digestion

Complete digestive system
ANATOMY OF A SQUID
ANATOMY OF CEPHALOPOD ARM
GROUP III
NAME
REG 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