Invertebrate
Animals
Unit C
Chapter 4
4.1 Most Animals are Invertebrates

Invertebrate

animal that has no backbone

Do not have any bone tissue at all

Found almost everywhere

Frozen tundra to tropical forests

Water or land
In other organisms


Most are small (crickets, oysters, ants)

Some are large (giant squid- can be
59 ft. and almost 1000 pounds)

There are 6 groups of invertebrates

Sponges

Cnidarians

Worms

Echinoderms

Mollusks

Arthropods

Sponges-


Simplest invertebrates

Live in water

Filter food from the water that
surrounds them
sessile organismslive attached to one
spot and do not move
from place to place

Sponges


Most sponges have spicules,
which are needle-like spines
made of hard minerals such
as calcium or silicon

Give the sponge its shape

If they stick out from the body,
they make the sponge a less
likely food source
Can reproduce asexually or sexually
4.2 Cnidarians and Worms have
Different Body Plans

Cnidarians
Have simple body systems

Found only in water

Examples: jellyfish, corals, sea anenome, hydras

Have tentacles with specialized stinging cells


tentacles- long, slender, flexible extensions of the
body used to touch, move, or hold
Reproduce asexually and sexually

Each stinging cell has a nematocyst- a
capsule that holds a barbed filament


The filament is like a tiny, hollow tube coiled up
inside the capsule
When prey comes in contact with stinger cells,
filament is released, sometimes wrapping itself
around the prey

In most species, the stinger stabs the prey and
releases poison from the tip.

Stingers also protect cnidarians from predators

Cnidarian Tissues and Body Systems

Body is made of flexible layers of tissues

The tissues and specialized cells make up the
body systems

Tissues are organized around a central opening
where food is taken in a waste is released

Tentacles bring prey into the opening, which
leads to a cavity, or a gut, where food is digested

Have simple muscles systems for movement

Cnidarian Tissues and Body Systems

They are sessile, but they still move their bodies


Bend from side to side
Extend tentacles

Muscle cells that run alongside the body shorten
or contract to produce movement

When they move, they interact with their
environment

Sense and respond to prey that come in contact with
their tentacles

Body Plan- shape of an animal’s body

Cnidarians usually have radial symmetry


Body is organized around a central point- a
mouth-like opening that leads to a gut
Allows sessile organisms to capture food from any
direction

Worms

Have complex body systems


Food, in many worms, enters at one end and is
processed as it moves through the body


Once nutrients have been absorbed, the remaining
waste is released at the other end
Take in oxygen dissolved in water through their
skin


Tube shaped body with bilateral symmetry
Therefore, they live in moist environments
Many live in water

Bilateral Symmetry

One half looks just like the other

Animals with bilateral symmetry have a forward
end where the mouth is located (head)

The animal moves forward, head first, in search of
food

Works well with mobile animals

Food enters the body through one end, is
processed as it moves through the body, and then
the waste is released at the other end

Types of worms:

Segmented

Flat

Round

Segmented Worms

bodies are divided into individual compartments,
or segments
Called annelids, which means “ringed animals”

Segmented Worms

Organs are organized into body systems

Digestive system includes organs for digestion
and food storage and connects to the excretory
system, which removes waste

Get nutrients from decayed plant or animal matter
in the soil that is passed through their digestive
system

A worm’s feeding and burrowing activity adds
nutrients and oxygen to the soil

Have several layers of muscle tissue in their
body wall

Have hair-like bristles that help anchor the worm
in the soil as it moves

Nervous system- includes brain and nerve cord
that runs through the body


Can detect strong light and vibrations from the soil
which indicate danger
Circulatory system- several hearts that pump
blood through the blood vessels

Can reproduce both sexually and asexually

No distinct male or female worms

Earthworms carry male and female reproductive
structures

Flatworms
Worms with the simplest bodies


Some are so small and flat that they move with
cilia, not muscles
Absorb nutrients directly through skin

Most live as parasites

Example: tapeworm-does not need a digestive
system because it gets digested nutrients from
the host
Flatworm of Nelson Bay,
Australia
Tapeworm

Round worms

Found almost everywhere on earth: saltwater,
freshwater, soil
Bodies more complex than flatworms, but less
complex than earthworms

Not segmented

Have muscles to move

Have nervous and digestive systems

Some roundworms are important decomposers on
land and in water
Examples: hookworm, pinworm (can be harmful to
humans because they are parasites)

Hookworm
4.3 Most Mollusks Have Shells and
Echinoderms Have Spiny Skeletons

Mollusks
Soft bodied animals

Many have an outer shell to protect their body.

Live on land, freshwater, or saltwater

Examples: oysters,
clams, snails,
mussels, squid, and
slugs

Reproduce sexually

Mollusks


Most have a well-developed organ system
Have a muscular foot
Also have a mantle- layer of folded skin that
protects its internal organs

3 groups of Mollusks



Bivalves
Gastropods
Cephalopods

Bivalves
Examples:
clams,
mussels

Named for their hard shell made of 2 matching
halves

When the shell is closed, it encompasses the body

The body looks like a mass of tissue with no distinct
head

Bivalves
They have a mouth and sensory organs

Filter feeders

In order to move, they have to balance
upright, open their shell, extend their foot,
and push the foot in and out
 Foot also used for burrowing
Clam Anatomy

Bivalves
Take in oxygen through a pair of gills
Gill- organ that filters dissolved oxygen
from the water
 Allows organisms to take in a lot of
oxygen in just one area of the body
 Made of many folds of tissue that create
a large surface area
The blood picks up the oxygen and moves
it to the rest of the body
In most bivalves, the gills also filter food
from the water.




Gastropods
Examples: snails, slugs, periwinkles, conches

The most diverse group of mollusks

Many are protected by spiral shaped shells where
they can withdraw to for protection

Their head is at the end of their foot

It has eyes and specialized tentacles for sensing
Snail Anatomy

Gastropods
Many have a radula




Radula- mouth part that shreds food
Some eat animals, but most feed on plants and
algae
If they live in water, they have gills in order to
breathe
Some that live on land have lungs

Lung- organ that absorbs oxygen from the air

Cephalopods- (SEHF-uh-lah-PAHDZ)

Examples: squid, octopus

Live in saltwater

Have well-developed body systems

They have a pair of eyes near their mouth

Their foot, which surrounds their mouth, has
tentacles for capturing prey
Squid Anatomy

Cephalopods
A mantle pushes water through a tube-shaped
structure called a siphon that produces a jet of
water that moves the animal

Gills take in oxygen which is picked up by the
blood vessels and pumped through the body by
the 3 hearts.

Cephalopods
Octopus and squid:

Have no
protective shell

Have protective
behaviors



Can camouflage
themselves
Some release dark clouds of ink-like fluid to confuse predators
Lack of a shell allows them to move freely through the
water

Cephalopods
Nautilus

Only cephalopod that
has a shell

Shell is made of
separate compartments
or chambers

It lives in the outermost
chamber

The inner chambers are filled with gas which
allows it to float

The shell also provides protection
Nautilus Anatomy


http://www.youtube.com/watch?v=HHEdT0Vevus
Clam moving
http://www.oceanfootage.com/vid
eo_clips/DH02_112
Squid moving
4.3 Echinoderms

Echinoderm- invertebrate
sea animal with a spiny
skeleton, a water vascular
system, and tube feet

Echinoderm means “spiny-skinned”

Skeleton is made up of a network of stiff, hard, plates
that lie just under the surface of the skin


Some are more flexible that others
Examples: sea stars, sea urchins, sea cucumbers,
and sand dollars

Have a water vascular system
Water filled tubes that radiate out from the
center of the body

Tiny openings along the upper surface of the body
feed water into these tubes

At the base of the tubes is a series of tube feet

Muscles attached to the top of each tube can close
the tube off, producing suction at the base of the
tube
Tube feet stick to the ocean floor allowing it to pull
itself along


Can also be used to hunt prey



In adult form, bodies have
radial symmetry
Feed off ocean floor as they
move along it
Mouth is at the center of the
body on the underside

Some, like sea urchins and sand dollars, filter
feed from surroundings

Others, like sea stars, feed on clams, snails, and
other echinoderms



http://video.google.com/videosearch?sourcei
d=navclient&rlz=1T4HPND_enUS306US205
&q=echinoderms&um=1&ie=UTF8&sa=N&hl=en&tab=wv#
Sea Star Movement- first 5 minutes
Skip minutes 9 and 10
4.4 Arthropods Have
Exoskeletons and Joints


Most invertebrates are arthropods
Arthropod- invertebrate animal with an
exoskeleton, a segmented body, and jointed
legs

Exoskeleton- strong, flexible outer covering



Completely covers the body
Keeps cells, tissues, and organs from drying out
if they live on land
Has joints, or places where it is thin and flexible

Three types of examples: insects,
crustaceans, and arachnids

Can have many pairs of legs

Are active animals

Feed on all types of food

Can live in water,
but most live on
land

Generally have 3 sections

Head- front end

Thorax- middle

Abdomen- back end

Legs, antennae, and claws are jointed

Muscles attach to exoskeletons at joints,
enabling it to move

Exoskeletons do not grow

Arthropods
must shed
an
exoskeleton
as it grows

Molting- process of an arthropod shedding
its exoskeleton to allow for growth

Times of molting are dangerous
Molting

Have well-developed body systems

Nervous system and brain

Digestive system with stomach and intestines

Open circulatory
system

Reproduce sexually