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CHAPTER 2 Section 1. Background information about Mollusks – They belong to the phylum Mollusca – Live nearly everywhere on Earth – Most live in water.

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Presentation on theme: "CHAPTER 2 Section 1. Background information about Mollusks – They belong to the phylum Mollusca – Live nearly everywhere on Earth – Most live in water."— Presentation transcript:

1 CHAPTER 2 Section 1

2 Background information about Mollusks – They belong to the phylum Mollusca – Live nearly everywhere on Earth – Most live in water Mountain streams to the deep ocean – Some live on land in damp locations. ABOUT MOLLUSKS

3 Background Information about Mollusks – Bilateral symmetry – All organs are located in 1 area. – Open circulatory system for the 1 st time. This allows an animal to be bigger ABOUT MOLLUSKS

4 What is a mollusk? – Invertebrate with a soft, unsegmented body that is protected by a hard outer shell. – They have a thin layer of tissue called a mantle over their internal organs. – The mantle also produces the mollusks shell. Respiratory organ for land mollusks MOLLUSKS

5 What is a mollusk? – They move with a muscular structure called a foot. – Different mollusks have feet adapted for different uses such as crawling, digging, or catching prey MOLLUSKS


7 TYPES OF MOLLUSKS Clam Oyster Scallop Snails Octopus

8 MOLLUSK VIDEOS the-ultimate-guide-octopus-octopus- ancestry-video.htm the-ultimate-guide-octopus-octopus- sense-of-touch-video.htm the-ultimate-guide-octopus-octopus- defenses-video.htm

9 Organs within a Mollusk – Pair of Kidneys: organs that remove waste – Gills: Organs that remove oxygen from water – Radula: Flexible ribbon of tiny teeth MOLLUSK ORGANS

10 Gills: found in most water- dwelling mollusks – They are attached to the mantle – Have a rich supply of blood vessels – Oxygen from the surrounding water diffuses into the blood and carbon dioxide diffuses out MOLLUSK ORGANS – Covered with tiny, hair like structures called cilia. – The beating movement of the cilia makes water flow over the gills.

11 Radula: Flexible ribbon of teeth – Unique to this Phylum – Act like sandpaper – Scrape food from a surface such as a leaf – May have as many as 250,000 teeth – The arrangement of teeth are used to classify mollusks MOLLUSK ORGANS

12 What was the 1 st evidence of mollusks? – Living in the oceans about 540 million years ago – The evidence for this comes from fossil shells in limestone rocks EARLY MOLLUSKS After a mollusk died the shell broke into pieces due to waves and currents. – The broken pieces piled up on the ocean floor – The hard materials underwent a chemical change and became cemented together to form limestone – During this process some shells become fossils

13 Based on the presence of: 1.Presence of a shell 2.Type of shell 3.Type of foot 4.The arrangement of teeth in the radula 5.Complexity of the nervous system HOW ARE MOLLUSKS CLASSIFIED?

14 1.Gastropods – most numerous 2.Bivalves 3.Cephalopods 3 GROUPS OF MOLLUSKS

15 Gastropod means stomach foot – Foot is on the same side of their body as their stomach Snails have a single, coiled shell Slugs have no shell Creep along on their broad foot Some are herbivores, some are scavengers, and others are carnivores When a snail is threatened it can pull into its shell also when it is dry out GASTROPODS

16 Ex: Clams, oysters, scallops, and mussels Have 2 shells that are held together by hinges Do not have a radula – Instead food sticks to the mucus that covers the gills – Cilia on the gills then removes the food BIVALVES

17 Found in all kinds of watery environments – As adults bivalves stay in 1 place or move slowly – After their larval stage oysters and mussels attach to a surface underwater – Clams are active and burrow into the sand or mud – Scallops move from place to place BIVALVES

18 Octopuses, cuttlefish, nautiluses, and squids are all cephalopods Tentacles can be 5 meters long Capture food with flexible tentacles – Suckers on the tentacles receive taste sensations – They dont have to touch something to taste it Large eyes and excellent vision Swim by jet propulsion CEPHALOPODS

19 Largest and most varied class – Aquatic and terrestrial Many marine snails have poison-tipped mouthparts – Many serve as an intermediate host for trematode parasites in humans. – Mantle used as respiratory organ in land snails CLASS GASTROPODA – Undergo torsion: movement of the anus Advantage: Balance and protection because the head retreats first into the shell Disadvantage: Anus is near the mouth If torsion didnt happen the foot would go in before the head


21 Bivalves – 2 shells – 2 nd largest class of Mollusks – Marine & Freshwater – 3 shell layers Outer protective layer Middle layers made of calcium carbonate Inner layer CLASS BIVALVIA

22 Between the mantle and inner layer a pearl is made. The pearl is formed by the mucus fluid covering bacteria or a grain of sand that is irritating the muscle. They have no radula – filter feeders Mussels make pearls – clams do not. CLASS BIVALVIA

23 Minnesota has one of the greatest diversities of freshwater mussels in the U.S. Introduced zebra mussel larvae in 1985/1986 to the Great Lakes region from Europe MUSSELS Problems: – Outcompete native mussels – Disrupt spawning of game fish – Prolific breeders which damage property – Settle on native mussels so that they cannot open – Damage pipelines

24 Most complex of all invertebrates – Octopus: shell is absent – Squid/ Cuttlefish: Shell is internal – Nautilus: Shell is external CLASS CEPHALOPODA

25 – Large brain: capable of learning – Image-forming eye similar to vertebrates – Closed circulatory system – Blue-ring octopus have salivary glands with venom CLASS CEPHALOPODA – Anterior foot is divided into a series of arms – Marine – Active Predators – Powerful beak-like jaw and radula

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