BIVALVES AND GASTROPODSMae Gallego 9A

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 pH 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 1st 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?

BIBLIOGRAPHY http://www.google.es/imgres?q=snail+circulatory+system&um

=1&hl=es&biw=1360&bih=634&tbm=isch&tbnid=F36RH2-OyisixM:&imgrefurl=http://myclasses.naperville203.org/staff/NNHSBiology/KraftsonEco/Animal%2520Kingdom%2520%2520Period%25202/Mollusca.aspx&docid=WyxdXLXKu-cJXM&imgurl=http://www.biologie.uni-hamburg.de/b-online/library/onlinebio/circsys_2.gif&w=502&h=314&ei=Yh5BT6eZBcTE0QX6sJ2PDw&zoom=1&iact=hc&vpx=348&vpy=308&dur=5644&hovh=177&hovw=284&tx=60&ty=71&sig=101967442354638864406&page=1&tbnh=110&tbnw=176&start=0&ndsp=18&ved=0CF0QrQMwBw

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http://www.manandmollusc.net/advanced_introduction/mollusca_101_intro.html

http://www.kgs.ku.edu/Extension/fossils/bivalve.html http://infusion.allconet.org/webquest/PhylumMollusca.html http://www.waterencyclopedia.com/Bi-Ca/Bivalves.html#b