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Mollusks, Arthropods, and Echinoderms
Table of Contents
Mollusks
Arthropods
Insects
Insect Ecology
Echinoderms
Mollusks, Arthropods, and Echinoderms
The Animal Kingdom
Chapter 2: Mollusks, Arthropods and
Echinoderms
Mollusks, Arthropods, and Echinoderms
Phylum Mollusca: Snails, Clams,
Squid
• Characteristics:
– All have soft bodies and
bilateral symmetry.
– The Latin word, “mollis”
means “soft”.
– Most secret hard, calcium
carbonate shells to protect
themselves.
Mollusks, Arthropods, and Echinoderms - Mollusks
• Although they don’t look much alike at
first, a snail, a clam, and a squid have the
same basic body structures.
Mollusks, Arthropods, and Echinoderms
• Basic body pattern of most mollusks:
1. Head: containing the mouth
2. Muscular foot: for crawling, digging, or
swimming.
3. Mantle: a thin layer of tissue that
surrounds the main body organs. The
mantle secretes the shell.
4. Gills: used to breath oxygen from water.
Mollusks, Arthropods, and Echinoderms
•
Classes of mollusks include:
1. Gastropoda (stomach-foot) —snails,
slugs, and sea slugs.
*One shell (univalve)
*Live in the water or on land
*Make beautiful sea shells
Mollusks, Arthropods, and Echinoderms
*Use a flexible ribbon of
tiny teeth called a
radula to get food.
*Some are herbivores
*Some are carnivores Mouth
Radula
Radula Teeth
Mollusks, Arthropods, and Echinoderms
2. Bivalvia (two-shells)-- clams, oysters,
scallops and mussels.
*Filter feeders—most are omnivores
*Economically important as food
*Used in production of pearls.
Mollusks, Arthropods, and Echinoderms - Mollusks
• A razor clam digs into the mud by changing
the shape of its foot.
Mollusks, Arthropods, and Echinoderms
3. Cephalopoda (head-foot) —octopus,
squid, cuttlefish, and chambered nautilus.
*Muscular foot is divided into tentacles for
swimming.
*Complex and intelligent.
*Range in size from 1-60 feet.
*Carnivores
*Crawl or swim by jet propulsion
Mollusks, Arthropods, and Echinoderms
Not all cephalopods have a shell
Octopus—no shell
Squid—internal shell
Chambered Nautilus
external shell
Mollusks, Arthropods, and Echinoderms
Cool Videos!!
Never underestimate the skills of the octopus!
Octopus Escape Video
(45 sec)
Octopus Killing Shark Video
(2 min 01 sec)
Mollusks, Arthropods, and Echinoderms
Phylum Arthropoda:
Jointed Legs
• Characteristics:
– Largest group of animals with over 1
million species known. That number may
be as high as 10 million.
Mollusks, Arthropods, and Echinoderms
– Exoskeleton made of chitin. Must be
shed from time to time in a process
called molting.
– Segmented bodies
– All have jointed appendages (legs,
antenna, pinchers and claws)
– Open circulatory system
– Bilateral symmetry
– One-way digestive tract
Mollusks, Arthropods, and Echinoderms
• Five classes: Arachnida, Crustacea,
Chilopoda, Diplopoda, Insecta
Mollusks, Arthropods, and Echinoderms
1. Crustaceans: crabs,
lobsters, crayfish, shrimp and pill bugs.
*Most have two body regions:
cephalothorax and abdomen.
*Five pairs of appendages including large
pinchers on most.
*Most have two pair of antenna
Mollusks, Arthropods, and Echinoderms
Fiddler crab
Pill Bug
Crayfish
Mollusks, Arthropods, and Echinoderms
2. Arachnids: spiders, scorpions, mites
and ticks.
*Most have two body regions:
abdomen
cephalothorax.
*simple eyes
*poison glands,
fangs or stingers
*four pair of legs
Mollusks, Arthropods, and Echinoderms
Spiders are found everywhere.
They spin webs using spinnerets
in their abdomen.
Mollusks, Arthropods, and Echinoderms
Scorpions are found in tropical
areas and hunt insects and
spiders.
Mollusks, Arthropods, and Echinoderms
–Ticks are external
parasites that feed on
the blood of a host.
Some transmit Lyme
Disease and Rocky
Mountain Spotted
Fever.
–Mites are usually
found in dust and are
mostly harmless.
Mollusks, Arthropods, and Echinoderms
3. Chilopoda: centipedes
*Long, flat bodies with one pair of
legs per body segment.
*Carnivores: eat snails, slugs and
worms and can bite humans.
Mollusks, Arthropods, and Echinoderms
4. Diplopoda: millipedes
–Long, rounded bodies with two pairs
of legs per body segment.
–Plant eaters: will not bite humans
Mollusks, Arthropods, and Echinoderms
5. Insects: largest group of arthropods
– Three body segments: head, thorax and
abdomen.
– Three pairs of legs attached to the thorax.
– One pair of antenna.
– Some have one or two pairs of wings; some
have no wings.
– Large, compound eyes; some also have
simple eyes.
– Open circulatory system.
Mollusks, Arthropods, and Echinoderms
Wings
Abdomen
Antenna
Thorax
Head
Compound
Eyes
3 Pair of Legs
Mollusks, Arthropods, and Echinoderms - Arthropods
Links on Arthropods
• Click the SciLinks button for links on
arthropods.
Mollusks, Arthropods, and Echinoderms
–All insects undergo metamorphosis
*This is a process in which an
animal’s body undergoes dramatic
changes in its life cycle.
*Two types of metamorphosis:
Complete and Gradual
Mollusks, Arthropods, and Echinoderms
-Stages of Complete Metamorphosis:
*Egg, Larva, Pupa, Adult
(Beetles, bees, butterflies, flies and
ants use complete metamorphosis)
Mollusks, Arthropods, and Echinoderms - Insects
Life Cycle
• An insect with complete metamorphosis
has four different stages: egg, larva, pupa,
and adult.
Mollusks, Arthropods, and Echinoderms
–Stages of Gradual Metamorphosis:
*Egg, Nymph, Adult
(Grasshoppers, termites, cockroaches and
dragonflies use gradual metamorphosis)
Mollusks, Arthropods, and Echinoderms - Insects
• An insect with gradual metamorphosis has
no distinct larval stage. An egg hatches
into a stage called a nymph, which usually
looks like the adult insect without wings.
Mollusks, Arthropods, and Echinoderms - Insects
More on Insect Metamorphosis
• Click the PHSchool.com button for an
activity about
insect metamorphosis.
Mollusks, Arthropods, and Echinoderms - Arthropods
Lyme Disease Cases
• The graph shows the
number of cases of
Lyme disease by age
group reported by
Connecticut during
one year.
Mollusks, Arthropods, and Echinoderms - Arthropods
Lyme Disease Cases
• Reading Graphs:
What variable is plotted
on the y-axis? What
does the first bar tell
you?
Cases per 100,000
people; the first bar
indicates that for every
100,000 children under
the age of 10, 200 had
Lyme disease.
Mollusks, Arthropods, and Echinoderms - Arthropods
Lyme Disease Cases
• Interpreting Data:
Which age group is
least at risk for Lyme
disease? Explain.
20–29 year-olds;
just over 50 per
100,000 people
were infected.
Mollusks, Arthropods, and Echinoderms - Arthropods
Lyme Disease Cases
• Interpreting Data:
Which two age
groups are most at
risk?
Children under 10
and people
between the ages
of 50 and 59
Mollusks, Arthropods, and Echinoderms - Arthropods
Lyme Disease Cases
• Calculating:
Suppose a particular
school in Connecticut has
1,000 students aged 10–
19. About how many of
these students would you
expect to get Lyme
disease per year?
One or two students
Mollusks, Arthropods, and Echinoderms - Insects
Insect Adaptations
• Click the Video button to watch a movie
about
insect adaptations.
Mollusks, Arthropods, and Echinoderms
•
•
•
•
Phylum Echinodermata: Seastars
6,000 species of spinyskinned animals
All have radial symmetry.
“Echinoderm” means
“spiny-skin”.
Have an internal skeleton
made of spines that extend
out through the body.
Mollusks, Arthropods, and Echinoderms
• All live in the ocean.
• Move using a water-vascular system
and tube feet.
• Most can regenerate lost body parts
and can occasionally reproduce this
way.
Mollusks, Arthropods, and Echinoderms
Characteristics of Echinoderms
• Echinoderms, such as this sea star, have a
water vascular system that helps them move
and catch food.
Tube
Stomach
Feet
Madreporite
Water Vascular
System
Mollusks, Arthropods, and Echinoderms - Echinoderms
Water Vascular System Activity
• Click the Active Art button to open a
browser window and access Active Art
about the water vascular system.
Mollusks, Arthropods, and Echinoderms
• Examples of echinoderms:
1. Sea stars and brittle stars: have 5 or
more arms lined with tube feet. Feed on
clams by inserting their stomach into the
clam and digesting it inside the shell.
Mollusks, Arthropods, and Echinoderms
2. Sea urchins and sand dollars: do
not have arms. Covered with
movable spines used for defense
and movement.
Mollusks, Arthropods, and Echinoderms
3. Sea cucumbers: leathery skin
with no spines. Spits out its
internal organs to confuse
predators.