Mae Gallego 9 A BIVALVES AND GASTROPODS Kingdom

Mae Gallego 9 A BIVALVES AND GASTROPODS

�Kingdom: Animalia �G. Phyla: Molusca �i. )Sub-phyla: Gastropods/Bivalves

GASTROPODA � From ancient Greek � Prefix γαστήρ gastr- stomach � Sufix πούς pod- foot � 325, 000 species currently existing -only 85 thousand have accepted names

GASTROPOD CHARACTERISTICS � Have shell � Univalves � Torted body � Anus and head are together � Well defined head � 2 -4 sensory tentacles with eyes � Moves gliding along a surface � Leaves mucus or slime produced by glands on the foot. � Invertabrate

BIVALVIA � Name describes the shape of the shell. � Also known as: � Pelecypoda (axe foot) � Acephala (no head) � Lamellibranchia (plate-like gill elements) aprox. 9, 200 species

CHARACTERISTICS � � � � Shell (2 asymmetrically rounded halves) � Made of calcium carbonate Hinge (flexible ligament that joins the valves) Most live in water No defined head Breathe-only one/two pairs of gills Have no brain Can live in water with a p. H greater than 5 Mostly sedentary

GASTROPOD FOSSIL RECORD � Most are fossils of the shell � Few slug fossils � Earliests-exclusively marine (end of Cambrian)

BIVALVE FOSSIL RECORD � 1 st from the Cambrian period � 510 million years ago � Most abundant during the Devonian period � 400 million years ago � During Paleozoic period- near shore enviroments.

GASTROPOD LIFE CICLE

BIVALVE LIFE CYCLE

DIGESTIVE SYSTEM � Gastropods: � Mostly hervibores or scavangers � Use radula to eat � tongue-like structure-rows of rasping teeth. � Adapts to the food it eats � Stomach is above foot � Vivalves: � Filter feeding (gills) � Scraping detritus from bottom (most primitive) � Intercellular digestion

RESPIRATORY SYSTEM � Lungs or gills � Depending on the habitat � Respiratory protein: Hemocyanin � Bivalves � Water currents enable the organism to get fresh oxygen.

CIRCULATORY SYSTEM � Open circulatory system � Gastropods: � 2 chamber heart � Auricle (recieves the haemolymph) � Ventricle (pumps haemolymph into the aorta) � Haemolymph � Circulatory fluid � Short aorta � Divided in 2 main vessels � Bivalves: � 3 chamber heart

SENSORY SYSTEM � Gastropods � Olfactory � Mechanorceptor � Statocyst � Eyes or visual organ � Central nervous system � Bivalves � Poor nervous system and sensory organs � Chemosensory cells at edge of mantle

ANY QUESTIONS, COMENTS ETC?

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