INVERTEBRATE SURVEY
LAB
Spring 09
CHARACTERISTICS OF ANIMALS
Representatives of the animal kingdom display a
wide diversity in appearance. Regardless, they do
share certain characteristics:
 ALL ANIMALS ARE HETEROTROPHIC
 ALL ANIMALS ARE MULTICELLULAR
 ALL ANIMALS ARE MADE OF EUKARYOTIC CELLS
THAT LACK A CELL WALL
The animal kingdom is divided into several phyla
(categories). Each phylum contains animals which
demonstrate common traits.
 These traits allow for a classification system that shows
progressive change in the phyla from simple to more
complex in forms.
KEY TERMS TO KNOW
Body Symmetry
 Asymmetry – no specific shape
 Radial Symmetry – body plan in which body parts
repeat around the center of the body
 Bilateral Symmetry – a single imaginary plane could
divide the organism in to 2 equal halves
Asymmetry
KEY TERMS TO KNOW
• Cephalization
– Cephalization is a concentration of sense
organs and nerve cells in the front of the
body (toward the head).
KEY TERMS TO KNOW
Coelom
 Coelom means body cavity (a tube within a
tube).
About the Coelom
– Coelom means body cavity (a tube within a tube).
–
–
–
Acoelomates
• Have NO TRUE body cavity!
Pseudocoelomates
• Have a fluid filled cavity BUT – it is not lined like that of higher-order animals.
Coelomates
• Have a body cavity that separates the body into an inner and outer tube (fully lined).
KEY TERMS TO KNOW
Early Development
Protostomes are
organisms that develop
a mouth first and then
an anus.
 Most invertebrates are
protostomes
Deuterostomes are
organisms that develop
an anus first and then a
mouth.
 Echinoderms and all
vertebrates are
deuterostomes.
KEY TERMS TO KNOW
Early Development–
During early development,
the cells of most animal
embryos separate into
three layers called germ
layers:
1.
2.
3.
ENDODERM: innermost
layer; develops into the
lining of the digestive tract
& much of the respiratory
system
MESODERM: middle
layer; develops into
muscles and much of the
circulatory, reproductive,
and excretory systems
ECTODERM: outermost
layer; develops into the
sense organs, nerves, and
outer layer of the skin
KEY CONCEPT TO KNOW
TRENDS IN ANIMAL EVOLUTION:
As animals get more
advanced, they have more
specialized features than
those animals found in the
prior phyla.
PHYLUM PORIFERA - SPONGES
KEY CHARACTERISTICS
Sponges are:
Multicellular, but do not have tissues!
Filter feeders that sift microscopic food particles from
the water.
Asymmetrical – they have no front or back end!
Sessile – they do not move!
No cephalization!
Early development is protostome.
Habitat is water.
No segmentation!
No germ layers!
No coelom!
ECOLOGY OF SPONGES
Sponges play an important part in the
ecology and survival of numerous aquatic
organisms:
They usually live attached to the sea floor.
They form mutually beneficial relationships
with bacteria, algae, and plantlike protists.
They provide a habitat for snails, sea stars,
sea cucumbers, and shrimp.
PHYLUM PORIFERA - SPONGES
PHYLUM CNIDARIA – JELLYFISH,
SEA ANEMONES, & CORALS
Epidermis
Mesoglea
Gastroderm
Tentacles
Mesoglea
Gastrovascular cavity
Mouth/anus
Mouth/anus
Gastrovascular
cavity
Tentacles
Medusa
Polyp
KEY CHARACTERISTICS
 RADIAL SYMMETRY
 CARNIVOROUS
 NO CEPHALIZATION
 MOVEMENT:
 Polyps are sessile
 Medusas are free swimming
 EARLY DEVELOPMENT: protostome & nerve net
 SOFT/SAC-LIKE BODY PLAN
 2 WAY DIGESTION (ONE OPENING)
 Eat & excrete through same hole!
 NO COELOM
 NO SEGMENTATION
 2 GERM LAYERS: ectoderm & endoderm
IMPORTANT FEATURES
 They typically have a
life cycle that includes
two different-looking
stages: a polyp and a
medusa:
 A polyp is a
cylindrical body with
arm-like tentacles.
• In a polyp, the
mouth points
upward.
• Polyps are usually
sessile (do not
move).
 A medusa has a
motile, bell-shaped
body with the mouth
on the bottom.
CNIDARIAN ACTIVITY
 Cnidarians are soft-bodied,
carnivorous animals that
have stinging tentacles
arranged in circles around
their mouths.
– They are the simplest
animals to have body
symmetry and specialized
tissues.
– Cnidocytes are stinging
cells that are located along
their tentacles.
– A nematocyst is a poisonfilled, stinging structure that
contains a tiny coiled dart –
used to paralyze and kill
prey.
 After paralyzing its prey, a
cnidarian pulls the prey
through its mouth into its
gastrovascular cavity.
– Nutrients are then
transported through the
body by diffusion.
– Cnidarians gather
information from their
environment using
specialized sensory cells.
– Most cnidarians reproduce
both sexually and asexually
• Most sexual reproduction
takes place with external
fertilization (outside the
female’s body).
PHYLUM PLATYHELMINTHES FLATWORMS
KEY CHARACTERISTICS
 Three germ layers:
ectoderm, mesoderm,
endoderm
 Bilateral symmetry
 Cephalization is present
 Acoelomates - No
coelom
 Use diffusion to
transport materials
through body
 No segmentation
 Movement w/ muscles or
cilia
 Early development –
protostomes
 Habitat  water or moist
dirt
 Basic body parts:
mouth, pharynx,
intestine, ganglia, flame
cells
MOVEMENT & REPRODUCTION
IN FLATWORMS
Free-living flatworms typically move in 2 ways:
Cilia help them glide through the water.
Muscle cells allow them to twist and turn.
Most free-living flatworms are hermaphrodites
(have both male and female reproductive organs).
Sexual reproduction involves joining in a pair
and delivering sperm to each other.
Asexual reproduction takes place by fission –
where the organism splits in two and each half
grows into a new organism.
GROUPS OF FLATWORMS
• Turbellarians (picture #1): free-living flatworms that
live in marine or fresh water
• Bottom dwellers
• Flukes (picture #2): parasitic flatworms
• Infect the internal organs of their hosts
• Tapeworms (picture #3): long, flat, parasitic worms
• adapted to life inside the intestines of their hosts
1
2
3
FLUKES – PARASITIC
FLATWORMS
PHYLUM NEMATODA ROUNDWORMS
KEY CHARACTERISTICS
Three germ layers
present – ectoderm,
mesoderm, endoderm
Unsegmented
Bilateral symmetry
Cephalization
present
Pseudocoelom
present
Mouth forms first –
protostome
Basic body parts:
mouth, anus,
intestines
Examples: Pinworms
& Nematodes
Roundworms
• Roundworms are unsegmented
worms that have pseudocoeloms
and digestive systems with two
openings – a mouth and an anus
– A pseudocoelom is a “false
coelom” – a body cavity lined
only partially with mesoderm
• Feeding: most are carnivorous
with grasping mouthparts and
spines to catch and eat other
animals
• Respiration, circulation, and
excretion: occurs via diffusion –
they have no internal transport
system
• Response: simple nervous
systems consisting of several
ganglia
• Movement: muscles extend the
length of their body and allow
for movement
• Reproduction: sexual, nonhermaphroditic
ROUNDWORMS & HUMAN
DISEASE
PHYLUM ANNELIDA – EARTHWORMS
& LEECHES
KEY CHARACTERISTICS
Three germ layers
present
Bilateral symmetry
present
Cephalization present
True coelom present
Segmentation present
Movement  Muscles
Mouth develops first –
protostome
Basic body parts:
mouth, anus, crop,
gizzard, body
segments
– Ex: earthworm
FORM & FUNCTION OF ANNELIDS
• Feeding & Digestion: range
from filter feeders to predators
– They extend their pharynx to
collect prey and the food moves
through the crop where it is
stored and then through the
gizzard where it is ground into
smaller pieces
• Circulation: they have a closed
circulatory system
– Blood is contained within a
network of blood vessels
• Respiration: gills (aquatic
annelids) and diffusion (land
annelids)
• Excretion: digestive wastes
passes out through the anus and
liquid waste is eliminated by
nephridia (filter fluid)
• Response: have well developed
nervous systems that include a
brain and several nerve cords
• Movement: have 2 major groups
of body muscles as part of a
hydrostatic skeleton
• Reproduction: most reproduce
sexually (although some use
external fertilization) and some
are hermaphroditic
GROUPS OF ANNELIDS
• Oligochaetes: Typically have streamlined bodies
and relatively few setae (hairs) compared to
polychaetes (most live in soil or fresh water).
• Leeches: external parasites that suck the blood
and body fluids of their host.
• Polychaetes: marine annelids that have paired,
paddlelike appendages tipped with setae (hairs).
Polychaetes
Oligochaete
Leech
PHYLUM MOLLUSKA – SNAIL,
CLAM, SQUID, OCTOPUS, ETC.
KEY CHARACTERISTICS
 Ex. Clam, squid, octopus,
snail, oyster, scallop...
 Three germ layers
present: ectoderm,
mesoderm, endoderm
 Have an external or
internal shell for support
 Bilateral symmetry &
Radial Symmetry (Squid)
 Cephalization present
 Segmentation present
 Movement  with
muscles
 Has a TRUE COELOM
 Mouth develops first –
protostome
 Basic body parts: gills,
specialized “foot”
THE MOLLUSK BODY PLAN
BODY PLAN & OTHER PROCESSES
•
Body Plan: contains 4 parts –
foot, mantle, shell, visceral mass
– The muscular foot has many
forms, including flat structures for
crawling, spade-shaped structures
for burrowing, and tentacles for
capturing prey
– The mantle is a thin layer of
tissue that covers most of the
mollusk’s body
– The shell is made by glands that
secrete calcium carbonate and
has been reduced or lost in snails
and some other mollusks groups
– The visceral mass lies just below
the mantle and contains the
internal organs
•
Respiration: breathe using gills
(aquatic) or by diffusion (land)
•
Circulation: either open or closed
circulatory system
– Open - blood is pumped through
vessels by a simple heart and
then diffusion into other systems
– Closed – blood is transported
through the body much quicker
than an open circulatory system
and is always contained in vessels
•
Excretion: nephridia
•
Response: complexity of nervous
systems varies
•
Movement: secretion of mucous or jet
propulsion
•
Reproduction: sexually by external
fertilization, sexually by internal
fertilization, and some are
hermaphrodites
GROUPS OF MOLLUSKS
GIANT CLAM
VARIOUS MOLLUSKS
PHYLUM ARTHROPODA –
CRAYFISH, SPIDERS, LOBSTERS,
ETC.
KEY CHARACTERISTICS
Three germ layers
present
Exoskeleton present
that requires molting
(shedding)
Jointed appendages
Bilateral symmetry
Cephalization
present
True coelom present
Segmentation present
Movement  Yes
(muscles & skeleton)
Habitat  In or Near
Water
Early Development 
Protostome
– Ex. Insects, spiders,
crayfish, millipedes,
and centipedes
CRUSTACEAN PARTS
 Cephalothorax: formed by fusion of the head
with the thorax (which houses most of the
internal organs)
 Abdomen: posterior part of the body
 Carapace: part of the exoskeleton that covers
the cephalothorax
 Mandible: mouthpart adapted for biting and
grinding food
DECAPODS
The largest group of crustaceans are the
decapods:
– They have 5 pairs of legs
– The 1st pair of legs are chelipeds and bear
large claws
– The walking legs are the next pair
– Behind the walking legs are the swimmerets
(flipper-like appendages for swimming)
Examples: crayfish, lobsters, crabs
HORSESHOE CRABS
• Horseshoe crabs are among the oldest
living arthropods!
SPIDERS & INSECTS
• Horseshoe crabs, spiders,
ticks, and scorpions are
chelicerates
– They have 2 pairs of
appendages attached near
the mouth
• One pair are the chelicerae
that includes fangs
• The other pair, the
pedipalps, are modified to
capture prey
– They have two body sections,
a cephalothorax and abdomen
– nearly all have 4 pairs of
walking legs
– They lack antennae
– They respire using book
gills or lungs
•
The largest group of arachnids are spiders!
– Spiders are arthropods that do not have
jaws for chewing, so they must liquefy
their food to swallow it.
– All spiders produce silk which is stronger
than steel!
• To spin silk into webs, spiders force
liquid silk through spinnerets, which
are organs that contain silk glands
ANATOMY OF SPIDER &
GRASSHOPPER
INSECT RESPONSES
 Insects use a multitude of
sense organs to respond to
stimuli:
– Compound eyes are
made of many lenses.
– Chemical receptors are
used for taste and smell.
– Sensory hairs detect
slight movements in
surrounding air or water.
– Well developed ears
detect sounds far above
the human range.
INSECT METAMORPHOSIS
•
The growth and development of insects usually involve metamorphosis
– Metamorphosis is the process of changing shape and form
– Most insects undergo either incomplete or complete metamorphosis
• Incomplete metamorphosis: immature nymphs look much like adult
form
• Complete metamorphosis: immature larvae look nothing like parents
INSECT COMMUNICATION &
SOCIETIES
• Many insects
communicate using
chemical signals
called pheromones.
– Insects can also
communicate using sound,
visual, and other types of
signals.
– Insect communication
usually involves finding a
mate.
• Ants, bees, termites, and
some of their relatives
form complex associations
called societies.
– A society is a group of
closely related animals of
the same species that work
together for the benefit of
the whole group.
– Within a society, individuals
may be specialized to
perform particular tasks in
groups called castes.
PHYLUM ECHINODERMATA –
STARFISH, SEA URCHINS, SAND
DOLLARS & SEA CUCUMBERS
Eyespot
Endoskeletal plates
Anus
Stomach
Digestive glands
Ring canal
Radial canal
Madreporite
Reproductive glands
Tube foot
Sucker
KEY CHARACTERISTICS
 3 germ layers present
 Bilateral & Radial
symmetry (adults)
 No cephalization in
adults
 True coelom present
 Segmentation present
 Movement  Tube feet &
water vascular system
 Anus forms first –
deuterostome!!! (the only
invertebrate deuterostome)
 Basic body parts: spiny
skin, endoskeleton, water
vascular system, tube feet
– Ex: starfish, sea urchins, sand
dollars, sea cucumbers
ENDOSKELETON & WATER
VASCULAR SYSTEM
• Echinoderms are characterized • A unique feature of
echinoderms is a system of
by spiny skin, an
internal tubes called a water
endoskeleton (internal
vascular system:
skeleton), a water vascular
– This system is filled with fluid
system, and suction-cuplike
and carries out many
structures called tube feet.
– Most adult echinoderms
exhibit five-part radial
symmetry
– The body parts are arranged
around a central body like the
spokes of a wheel
essential body functions
(respiration, circulation,
movement)
– It opens to the outside
through filter-like structures
called madreporites
• A tube foot is a structure
that operates much like a
suction cup
CLASSES OF
ECHINODERMS
•
•
•
•
•
Sea urchins and sand dollars
– Unique echinoderms in having
large, solid plates that form a box
around their internal organs
– Many detritivores & Grazers
Brittle Stars
– Common in coral reefs; detritivores &
filter feeders
– Can shed one or more arms if
attacked; arm will distract their
predators
Sea Cucumbers
– Look like pickles; detritus feeders
that move across sea floor
Sea Stars
– Carnivorous & prey on bivalves
– Can repair itself  when pulled
apart, each section can become a
new sea star if a portion of the
central cavity still remains.
Sea Lilies and Feather Stars
– Filter feeders with long, feathery arms
– Common in tropical oceans around
coral reefs
ECHINODERMS