Invertebrates
Chapter 2
March/April, 2012
Invertebrates
• Invertebrates
– 1. Animals without a backbone
– 2. Come in many different shapes and sizes
• Can be compared by looking at:
– 1. Type of body plan
– 2. Whether or not the animal has a head
– 3.The way food is digested
Body Plans
• Invertebrates have 2 basic body types or
types of symmetry
– Definition of Symmetry
• exact reflection of the form on opposite sides of a
dividing line or plane
Bilateral Symmetry
• 1. Bilateral symmetry
– 2 similar halves
– If you draw a line there
are 2 similar halves on
each side
Radial Symmetry
• 2. Radial symmetry
– Body parts are
arranged in a circle
around a central point
Asymmetrical
• 3. Asymmetrical
– No symmetry
3 Types of Symmetry
Presence or Absence of Head
• 1. All animals except for sponges have
nerves
• 2. Nerves- carry signals to control
movements of the body
• 3. Simple invertebrates have nerves
arranged in nerve cords throughout the
body
– These simple animals have no brain or head
Presence or Absence of Head
• Some invertebrates have
– A. Dozens of nerve cells that come together
and are called GANGLIA
– B. Ganglia
• Are found throughout the body controlling different
parts
Presence or Absence of Head
• C. More complex
animals have a
brain and a
head…………where
the brain is stored
• D. Brain controls
many different
nerves in different
parts of the body
Bell Work
• 1. What are nerves cells that help to
control movement of different body parts?
• 2. What is a part of the animal that is a
pouch lined with cells that help break
down food?
• 3. What type of symmetry has 2 similar
halves?
Don’t you have any guts?
• 1. Almost all animals digest food in the
central gut
– A. Gut
– Pouch lined with cells that break down food
– B. These enzymes break down food in smaller
particles so that cells can absorb them
Don’t you have any guts?
• 2. Complex animals have
a space in the body for
the gut
– A. called a coelom
– B. Space in the bodies for
the gut
– C. Allows the gut to move
food without interference
from movements of the
body
– D. Other organs like the
heart and lung are in the
coelom but separated from
the gut
Sponges
•
•
•
•
Phylum: Porifera
1. Simplest animals
2. Asymmetrical
3. Regeneration- ability to replace itself.
New sponges can form from pieces
broken off another sponge
• 4. If cells are separated, they can come
back together and form a sponge
How do sponges eat?
• 1. Water enters the
sponge through its pores.
Pore cells pump water
into the sponge.
• 2. Inside the sponge,
cells called collar cells,
filter food and
microorganisms from the
water
• 3.Then the water flows
into the central cavity and
out the top of the sponge
through a hole called a
osculum
Cnidarians
• Phylum: Cnidaria
• 1. Cnidaria means “nettles” Nettles are plants
that release stinging barbs in the skin
• 2. More complex than a sponge
• 3. Have complex tissues, a gut, and a nervous
system
• 4. In some of these species, if the cells are
separated they can come back together like a
sponge
Cnidarians
• 5.Come in 2 forms
– a. Medusa- looks like
a mushroom with
tentacles
– b. Polyp- look like a
vase and are usually
attached to a surface
Cnidarians
• 5. 3 classes
• a. hydras- live in fresh
water
• b. jelly fish- usually
have medusa form
• c. anemones and
corals usually have
polyps forms
Cnidarians
• “Catching Lunch”
• 7.All cnidarians have
long tentacles
covered in stinging
cells that catch small
fish and other
organisms by having
these stinging cells
that release
paralyzing toxin
Cnidarians
• 8. Cnidarians do not
think
• 9.They have a simple
network of nerve cells
called a nerve net that
controls movement
• 10. Medusa have a
nerve ring that allows
them to swim
Flatworms
• 1. Simplest group of
worms “Planarians”
• 2. Bilateral symmetry
• 3. Have a head and
eye spots
• 4. 2 sensory lobes on
each side of its head
used for finding food
Planarians
• 5. Small- usually size of
your fingernail
• 6. Live in water and land
• 7. Predators (eat on other
animals or their parts)
• 8. Has head, eyespots,
sensory lobes and a
small brain
Flukes and Tapeworms
• 1. Parasites
• 2. Live inside other
animals bodies
• 3. Host is usually killed
• 4. Have heads without
eyespots or sensory
lobes
• 5. No stomachs, they
absorb nutrients of their
host
Roundworms
• 1. Have a simple
nervous system and a
primitive brain
• 2. Parasites
• 3. Live in their host
• 4. Pinworms and
hookworms infect
humans!
Mollusks and Annelid Worms
Mollusks and Annelid Worms
• More complex than
the invertebrates that
we have studied so
far
• Have a
– 1. Coelom
– 2. Circulatory system
Mollusks
• 1. Phylum: Mollusca
• 2. Second largest
phylum of animals
• 3. Includes
–
–
–
–
–
–
Snails
Slugs
Clams
Oysters
Squid
Octopuses
Mollusks
• 3 Classes
• 1. Gastropods (slugs and
snails)
• 2. Bivalves (clams and
other two-shelled
shellfish)
• 3. Cephalopods (squids
and octopuses)
Mollusks Characteristics
• 1. Most mollusks live
in the ocean
• 2. Some live in fresh
water
• 3. Soft body
• 4.Usually covered by
a shell
4 Main Parts of Mollusks
1.Foot- large muscle that mollusks use to move
– Gastropods foot secrete mucus to help it slide
2.Visceral mass-contains gills, gut, and other
organs in the coelom
3.Mantle- covers the visceral mass and protects
the body of mollusks that don’t have a shell
4. Shell- protects the mollusks from predators and
keeps them from drying out
How do mollusks eat?
• 1. Clams and bivalves
stay in one place and
filter tiny plants,
bacteria and other
particles from the
water
How do mollusks eat?
• 2. Octopuses and
squids use tentacles
just like we use our
fingers
How do mollusks eat?
• 3. Snails and slugs
eat with a tongue
covered in curved
teeth called radula
• 4. Slugs and snails
use the radula to
scrape algae off
rocks, or pieces of
leaves off plants
Circulatory System
• Open circulatory systemsimple heart pumps blood
through blood vessels
that empty into spaces in
the animals body called
sinuses
• Closed circulatory
system- heart pumps
blood through blood
vessels that form a
closed loop (cephalopods
have closed system)
Brain
• Mollusks have complex
ganglia
– 1. That control breathing
– 2. Move the foot
– 3. Control digestion
• Cephalopods have a
more complex nervous
system than any other
mollusk
Brain
• 3. Octopus can find
their way through a
maze, pick out
different shapes and
colors, and when
given bricks or stones
will build a cave to
hide in………………
SCARY!!!!!!!!!
Annelid Worms
• Phylum: Annelida
• Characteristics
• 1. Segments- identical or almost identical
repeating body parts
• 2. Have a coelum
• 3. Have a closed circulatory system
• 4. Ganglia in each segment
• 5. Brain found in the head and a nerve cord that
connects the brain to the ganglia
Annelid Worms (3 Classes)
1st Class are Earthworms
• A. Most common are annelids
• B. Some segments are specialized for eating
and reproduction
• C. Break down matter in the soil and excrete
wastes called castings
• D. When they burrow in soil, they allow water
and air to reach deep in the soil
• E. Stiff bristles on the outside of their body help
them move
Bristle Worms
• 2nd Class is Bristle Worms
• A. Come in many and bright colors
• B. Live in water and burrow through sand
and mud to find food
• C. Some crawl on the bottom and eat
mollusks and other small animals
Leeches
• 3rd Class are leeches
• A. Some are parasites and suck other
animals’ blood, others eat dead animals
• B. Doctors used to use them to “suck the
bad blood” out of patients
• C. Today some doctors use them to
prevent swelling near a wound
• D. Leeches also make a chemical that
keeps blood from clotting
Bell Work
• 1. What are the 3 main classes of
mollusks?
• 2. How do herbivorous snails and slugs
use their radula to get food?
Arthropods
Arthropods
75% of all animals are arthropods
Characteristics of arthropods
• 1. Jointed limbs
• 2. Segmented body with specialized
parts
• 3. Well-developed nervous system
Jointed Limbs
1.
2.
3.
4.
5.
Jointed limbs gives
arthropods their names
“Arthro” means joint
“Pod” means foot
Jointed limbs are arms,
legs, or other similar
body parts
Jointed limbs let
arthropods to move
easily
Segmented and Specialized
• 1. Most segments in arthropods are
identical
• 2. Some segments include specialized
parts such as
– A. wings
– B. antenna
– C. gills
– D. pincers
– E. claws
Segmented and Specialized
• 3. These specialized parts form during the
animal’s development
– A. head
– B. thorax
– C. abdomen
Segmented and Specialized
• 4. Exoskeleton- external
(outside) skeleton on
arthropods made of protein
and chitin
A. does the same thing as
an internal skeleton
B. allows the animal to
move
C. all muscles attach to
the exoskeleton and move
that part of the animal when
the muscles contract
D. acts like a suit of armor
to protect internal organs and
muscles
Segmented and Specialized
• 5. All arthropods have a head and a well
developed brain
• 6. Some arthropods can detect light but
can not form an image
• 7. Some arthropods can see images
because they have compound eyes
– Compound eyes- are made of identical lightsensitive cells
Kinds of Arthropods
• 1. Arthropods are
classified according to the
kinds of body parts they
have
• 2. They are classified by
their number of legs, and
the antennae they have
• 3. Antennae- are the
feelers that arthropods
use for touch, taste, and
smell
Insects
• 1. Largest group of arthropod
• 2. Insects live everywhere EXCEPT the ocean
• 3.Insects are beneficial when they
– A. pollinate
• 4. Insects are harmful when they
– A. eat crops
– B. carry diseases
Insect Development
• Metamorphosis- the development of an
insect from an egg to an adult
Bell Work
• 1. Name 2 characteristics that classifies
arthropods?
• 2. Can arthropods see?
• 3. What is an exoskeleton?
Echinoderms
• 1. Phylum: Echinodermata
means “spiny skinned”
echinoderm
– Includes star fish, sea urchins, sea
cucumbers, brittle stars, and sand dollars
Echinoderms
•
•
•
•
Characteristics
1. Live on the sea floors
2. Endoskeletons
3. Echinoderm embryos form a mouth
like vertebrates when they first start to
develop (this makes echinoderms more
closely related to vertebrates than any
other invertebrates)
Echinoderms
• Characteristics
• 4. simple nervous system that contains
nerve rings around the mouth and
radial nerves that controls arms
• 5. water Vascular System- uses water
pumps to help the animals move eat,
breathe, and sense the environment
The End!
Invertebrates
Test Review
Words all 7th graders should know
about invertebrates!
Ganglia
Medusa
Polyp
Open circulatory system
Closed circulatory
system
Exoskeleton
Coelum
Collar cells
• Osculum
• Characteristics of
Invertebrates
• Porifera
• Mollusca
• Arthropods
• Annelids
• Cnidarians
• Echinoderms