CHAPTER 13 Mollusks, Echinoderms, and Arthropods

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CHAPTER 13Mollusks, Echinoderms, and Arthropods
p. 360
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Mollusks PHYLUM MOLLUSCA

• means soft.
• second largest phylum.
• Ex. Snails, clams, squids
• all have bilateral symmetry.

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• SOME
• LIVE
• ON
• LAND

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MOST LIVE IN WATER
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MOLLUSK BODY PLAN

• FOUR BASIC PARTS
• MANTLE
• - creates the shell.
• VISCERAL MASS
• - internal organs.
• SHELL
• - for protection.
• FOOT (or head-foot)
• - for movement.

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• most have an open circulatory system.
• (the blood is not contained in vessels).

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CLASSIFYING MOLLUSKS

• Bivalves
• - ex. clam, oyster, scallops.
• Class Bivalvia
• - also known as Class Pelycepoda
  

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• have a two-part shell linked by a hinge.
• - have a strong muscular foot for movement.

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Bivalves are filter feeders.
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MORE BIVALVES
Scallops
Oyster
Giant Clam
Scallop
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Bivalve Body Plan
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Gills
Visceral mass
Foot
Mantle
Shell
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2) Univalves

• Ex. snails, conches, slugs.
• in Class Gastropoda
• because they walk on their stomach.
• - have only one shell.

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Univalves are the largest class of mollusks.
Triton
Murex
Slug
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Gastropods obtain food by scraping material off
rocks.

• - they have a tongue-like organ called a radula.

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MORE GASTROPODS
Land Snails
Slug
Conch
Edible Snail
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SNAILS

• Crawl on a layer of slime.
• Land snails breathe with lungs. Water snails
  have gills
• Snails cannot hear.
• Snails are hermaphrodites.
• Most travel about 23 inches per hour!

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3) CLASS CEPHALOPODA

• means head-foot.
• includes octopus and squid.

Squid
Octopus
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• Cephalopods are the most complex class.
• - have a closed circulatory system.
• - their foot is their tentacles.

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MOVEMENT JET PROPULSION
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CEPHALOPODS

• Chambered Nautilus
• - an ancient cephalopod.
• Octopus
• - eight tentacles.
• Squid
• - ten tentacles

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CEPHALOPOD FACTS

• A cepholopod eye is somewhat similar to ours and
  is the animal kingdoms largest.
• The Giant Squid is over 65 feet in length.
• Octopus swim backwards.
• Squid and octopus do not have shells.
• Some can release an ink to escape predators.
• Most have a beak which can tear apart their
  prey.

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Importance of Mollusks

• Food
• - clams, oysters, snails, calamari, octopus, etc.

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2) Pearls

• Created by the mantle.
• It secretes nacre over an irritant (like a grain
  of sand).
• Nacre is also called mother of pearl.
• It takes many layers of nacre to make a pearl.

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REVIEW THE THREE MAJOR CLASSES
lt CLASS GASTROPODA
CLASS BIVALVIA gt
lt CLASS CEPHALOPODA
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ECHINODERMS (p. 380) Phylum Echinodermata

• ex. starfish, sea urchin
• - have radial symmetry.

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- some seastars have the ability to regenerate.
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- starfish have tubefeet on their tentacles which
act like suction cups.

• - for movement and feeding.

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Starfish can extend their stomachs to digest
their prey.
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More echinoderms
Pacific Seastar
Crown of thorns seastar
Sea Cucumber
Sand Dollar
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ASSIGNMENTWORKSHEET MOLLUSCA
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PHYLUM ARTHROPODA

• p. 370
• largest phylum of animals - more than all of the
  other phylums put together.
• - an estimated 10 million species.

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Arthropods are more complex.

• they have
• respiratory
• circulatory
• nervous
• systems.

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- all have an open circulatory system.

• Respiratory System
• water arthropods have gills.
• - land arthropods have air sacs/trachea.

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• air enters the book lungs thru holes called
  spiracles.

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Arthropods can have several pairs of appendages.

• Ex. legs, wings, pincers.

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Their bodies have a hard outer covering called an
exoskeleton
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The exoskeleton does not grow. It must be molted
or shed.

• - the new exoskeleton is soft and takes time to
  harden.

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ARTHROPOD CLASSES

• Class insecta
• - largest class of arthropods.
• Ex. ants, grasshoppers, beetles, etc.

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• Insects have three body regions.

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• all have six legs.
• - the only class able to fly.

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• Insects have a compound eye (many lenses)

and a pair of antennae (to sense)
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Insects are classified into orders according to
its mouth parts (or how it eats).

• chewing - grasshopper

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• piercing - mosquito

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• sucking - fly

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ASSIGNMENTWORKSHEETCLASS INSECTA
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INSECT DEVELOPMENT

• Metamorphosis (p.372)
• - a change in form that an organism goes thru to
  become an adult.

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• A) Complete metamorphosis
• Ex. butterfly
• 1) egg
• 2) larva
• (caterpillar)
• 3) pupa
• -inactive stage
• - forms a chrysalis
• (cocoon)
• 4) Adult

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Monarch larvae
Chrysalis
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Complete Metamorphosis
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• B) Incomplete metamorphosis
• Ex. grasshopper
• 1) egg
• 2) nymph
• - small adult
• - no wings
• - many molts
• to
• Adult
• No real change - it just grows larger.

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Which type of metamorphosis?
Incomplete
Complete
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2) Class Arachnae Arachnids p. 374

• Ex. spiders, ticks, scorpions.
• have eight legs.
• no antennae.

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Spiders have book lungs

• air moves over structures that look like pages of
  an open book.
• - openings are called _____.

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Arachnids have two body parts.

• 1) cephalothorax
• - head and chest area.
• 2) abdomen
• - internal organs

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• arachnids have simple eyes
• - they can sense light/dark but cannot see
  images.

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Arachnids have more appendages than insects.

• stingers
• - at the end of the abdomen.
• Ex. scorpion

fangs - inject poison - a
paralyzer. - it
also liquifies the preys inner parts. - the
spider sucks it out.
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spinnerets - are tubes which spit out material
make webs and capture food.
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ASSIGNMENTWORKSHEETMETAMORPHOSIS
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Class Myriapoda myriapods p. 375

• Centipede
• - hundred legged
• many body segments.
• eats other insects
• - has poison fangs.

• Millipede
• thousand legged
• many body segments.
• - eats dead plants.

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• - two pair of legs per segment.
• - can move both sides at a time.
• - smooth movement
• stink glands if threatened.
• - slower.

• - one pair of legs per segment.
• - can move only one side at a time.
• - wriggle.

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ASSIGNMENTWORKSHEETARTHROPODS
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4) Class Crustacea Crustaceans p. 377

• Ex. crab, lobster, shrimp
• similar characteristics to arachnids.
• - two body parts

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- but has many more appendages.

• two pair of antennae to sense info about their
  environment.
• claws
• - used to capture or hold prey.
• - also the first pair of legs.

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• four pairs of walking legs.
• - five pairs of swimmerets.

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• uropod
• - the fan shaped part of the tail.
• - used for swimming.

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• some can regenerate appendages.
• have mandibles
• - jaws for chewing.
• - they also molt.

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- have compound eyes usually located on long
stalks

• more than one lense
• can see movement better.
• - see over a wider area.

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most live in water not pill bugs

• - a huge source of food for people.

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More crustaceans
Crayfish
Fiddler Crab
Blue Crab
Shrimp
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ASSIGNMENTWORKSHEETCRUSTACEANS
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What are these structures?
3.
2.
1.
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