INVERTEBRATES
Diverse life on Earth
Evolutionary Stages in Animals
STAGE
MILESTONE
1
2
3
4
5
6
7
8
9
Multicellularity
Tissues
Bilateral symmetry
Body cavity
Coelom
Segmentation
Jointed appendages
Deuterstomes
Notochord
General Invert Characteristics
All invertebrates share the following
characteristics:
 Heterotrophic
 Most animals have to move from place to
place to search for food
 All animals are multicellular.
 Invertebrates have cells that lack cell walls
General Invert Characteristics




Invert cells are organized into tissues
They have specialized muscle cells that
allow for complex movements
Reproduce sexually
99% of all animals on Earth are
invertebrates (& have no backbone)
General Invert Characteristics

Body organization:
CELLS  TISSUES  ORGANS
ORGAN SYSTEMS
SYMMETRY

All animals, including invertebrates display
one of three types of symmetry in their
body plans:
ASYMMETRY
BILATERAL SYMMETRY
RADIAL SYMMETRY
ASYMMETRY


Asymmetrical
animals do not
display any
particular form
of symmetry
Example:
sponges
BILATERAL SYMMETRY

Bilaterally
symmetrical
animals, if cut
down the middle,
would have two
halves that mirror
each other.

Example: dragonfly
RADIAL SYMMETRY


Animals that
display radial
symmetry have a
central point from
which the rest of
the body radiates
out of.
Example: sea star
Development of Organ Systems

The organ systems of all animals develop
from 1 of 3 embyonic tissue layers:
Layer:
ECTODERM
MESODERM
ENDODERM
Organ Systems Formed:
Skin, body coverings &
nervous system
Skeleton, muscles &
circulatory system
Digestive system
SPONGES: Phylum Porifera
Barrel sponge
SPONGES: Phylum Porifera


Sponges are the simplest of all animals
Most live in saltwater
SPONGES: Phylum Porifera


Sponge

Asymmetrical
Have cell
recognition
ability– can
recognize other
cells & their own
without having a
nervous system
Sessile (do not
move)
SPONGES: Phylum Porifera


Sponges are filterfeeders
They suck water in
through pores
using cells called
choanocytes with
flagella and filter
out food to “eat”
CNIDARIANS:
Phylum Cnidaria
CNIDARIANS: Phylum Cnidaria



The cnidarians were
the first eumetazoans
or true animals
First to develop 3
distinct cell layers as
embryos
Includes animals like
jellyfish, hydras, sea
anemones & corals
Sea anemone
CNIDARIANS: Phylum Cnidaria



Jellyfish
Radially symmetric
Are carnivores that
capture prey using
tentacles located
around their mouths
Tentacles containing
stinging cells
(cnidocytes) used to
spear prey
CNIDARIANS: Phylum Cnidaria


Cnidarians digest
food externally, like
fungi
Cnidarian body types
come in two forms:
Polyp (Ex. hydra)
Medusa (Ex. jellyfish)
Medusa body form
Polyp body form
Bilateral Symmetry Begins
One important evolutionary advancement shared by more
advanced animals is bilateral symmetry. In bilaterally
symmetric animals an imaginary line drawn down the
middle would produce mirror images on each side of the
organism.
Dorsal
Posterior
Anterior
Ventral
FLATWORMS: Phylum
Platyhelminthes
Marine flatworm
FLATWORMS: Phylum
Platyhelminthes



Bilaterally symmetric
This is the first phylum to display
cephalization, or the evolution of a definite
head that contains organs with which they
monitor their environments
Flatworms are the simplest animals that
have organs.
FLATWORMS: Phylum
Platyhelminthes



Flatworms have an
eyespot to detect light
They are
acoelomates, which
means they do not
have any body
cavities except a gut.
Most species are
parasitic.
Fluke
PHYLUM NEMATODA:
Round worms
Ascaris
PHYLUM NEMATODA:
Round worms



Display bilateral symmetry
Are pseudocoelomates, which means they
have an internal body cavity
Presence of the body cavity is important
because it allows for the following to be
present:
- circulation
- movement
- complex organ functions
PHYLUM NEMATODA:
Round worms


Hookworm
Have a one-way
gut through which
food passes in the
mouth and out the
anus
Most are freeliving in soil, but
many are parasitic
PHYLUM NEMATODA:
Round worms


The blister below is
caused by a parasitic
worm
To the right is a
guinea worm exiting
a person’s ankle.
PHYLUM NEMATODA:
Round worms

Nematodes have
muscles that
extend the length
of their bodies
which enable their
wiggling
movement
-ENDInvertebrate Notes - Part One
 Study
for QUIZ over
Invertebrate Notes (Part 1)
at the beginning of next
class!!
PHYLUM MOLLUSCA:
Mollusks
PHYLUM MOLLUSCA:
Mollusks



Coelomates
Display bilateral
symmetry
Mollusks are the
only advanced
coelomate that do
not have a
segmented body
Snail
PHYLUM MOLLUSCA:
Mollusks


Mollusks have body plans with 3 distinct
regions:
1. Visceral mass
2. Mantle
3. Foot
They use gills, skin or simple lungs to
breathe.
PHYLUM MOLLUSCA:
Mollusks

There are 3 main classes in
Phylum Mollusca to include:
 Gastropods
 Bivalves
 Cephalopods
PHYLUM MOLLUSCA:
Mollusks


Banana slug
Gastropods include
snails and slugs
They have a
muscular foot, a
radula for feeding
and a shell (except
slugs)
PHYLUM MOLLUSCA:
Mollusks



Bivalves include
organisms like
clams, oysters and
scallops
They have a twopart shell held
together by a hinge
Filter-feeders
Scallop
PHYLUM MOLLUSCA:
Mollusks

Bivalve body
structure
PHYLUM MOLLUSCA:
Mollusks


Octopus
Cephalopods are
organisms like
octopuses & squids
Their name means
“head foot”
because most of
their body consists
of their heads
PHYLUM MOLLUSCA:
Mollusks


Cephalopods are considered the most
intelligent animals of all invertebrates
They have a well-developed brain and a
complex nervous system
PHYLUM ANNELIDA:
Segmented Worms
Polychaete
PHYLUM ANNELIDA:
Segmented Worms


This phylum
includes organisms
such as
earthworms,
polychaetes and
leeches.
Bilaterally
symmetric
Leech
PHYLUM ANNELIDA:
Segmented Worms


Earthworm
Are coelomates,
which means they
have a true body
cavity which allows
for specialized tissues
to form.
Have repeated,
specialized internal &
external body
segments
PHYLUM ANNELIDA:
Segmented Worms



Have an advanced circulatory system
Annelids breathe through their skin,
thus they must live in moist
environments
Earthworms are important soil
dwellers as they function to aerate
soil.
PHYLUM ARTHROPODA:
Arthropods
Scorpion
PHYLUM ARTHROPODA:
Arthropods




This is an extremely diverse phylum
Includes insects, crustaceans and
arachnids
These are the first animals with
jointed appendages
Arthropod = “jointed foot”
PHYLUM ARTHROPODA:
Arthropods



Class Insecta includes
all insects like bees,
butterflies, ants,
centipedes & roaches
to name a few.
6 legs
This the most
successful group of
all the animals
PHYLUM ARTHROPODA:
Arthropods


Class Crustacea are
mostly marine
animals
This class includes
such animals as crabs,
lobsters, shrimp,
crawfish and
horseshoe crabs
PHYLUM ARTHROPODA:
Arthropods


Class Arachnida
includes such
animals as
spiders, mites,
scorpions and
pseudoscorpions
8 legs
PHYLUM ARTHROPODA:
Arthropods



Arthropods use spiracles to breathe;
spiracles are openings to tubes that transmit
oxygen to the arthropod
They have compound eyes, which are made
up of a bunch of individual visual units that
come together to form an image.
Arthropods comprise more than ½ of all
life on Earth (insects mostly)
PHYLUM ARTHROPODA:
Arthropods


Cockroach
Arthropods have a
hard exoskeleton
made of chitin that
serves to protect
them.
For many their
exoskeleton must
“molt” in order for
them to grow
PHYLUM ECHINODERMATA:
Echinoderms
PHYLUM ECHINODERMATA:
Echinoderms


This phylum
includes such
organisms as sea
stars, brittle stars,
sea cucumbers, sea
urchins and sand
dollars.
They display radial
symmetry.
Sea cucumber
PHYLUM ECHINODERMATA:
Echinoderms


Sea star
Echinodermata
refers to the “spiny
skin” that most
organisms of this
phylum have.
Most echinoderms
have an
endoskeleton made
of ossicles.
PHYLUM ECHINODERMATA:
Echinoderms

Echinoderms are
unique because
they have a water
vascular system,
which is
essentially a series
of canals & tube
feet that they use
for movement.
Sea urchin
PHYLUM ECHINODERMATA:
Echinoderms


Echinoderms do not
have a head or brain,
but they do have a
nervous system.
Their nervous system
consists of a ring of
nerves that branch
into each arm.
THE END
 Study
for Invertebrate
Note Quiz (part 2) at the
beginning of next class!!