** Animals without a
backbone or spinal column.
Sponges & Cnidarians
A. Characteristics:
1. Sessile = do not move
2. Asymmetrical
3. Filter feeders- sift food particles
from water
Phylum Porifera: “pore
bearers”= Sponges!!
Sponges & Cnidarians
4. Movement of water provides for
feeding, respiration, circulation
and excretion
5. Skeleton composed of spongin
(soft) and spicules (hard).
Sponges & Cnidarians
A. Specialized Cells:
1. Choanocytes= collar cells– layer of
cells with flagella keeps water moving;
food vacuoles inside digest plankton
(filter feeder).
2. Osculum- large opening at top of
sponge; water exits.
3. Ostia- small openings at the side;
water enters = pores!
Phylum Cnidaria: Hydras,
Jellyfish, Sea Anemone, Coral
Sponges & Cnidarians
A. What are they?
1. Soft bodied, carnivorous animals with
stinging tentacles around their mouth.
2. Nematocysts- poison-filled, stinging
structure that contains a coiled dart.
Sponges & Cnidarians
B. Form and Function
1. Body plan
a) Polyp- usually sessile; mouth points
upward
b) Medusa- motile, bell-shaped body
with mouth on bottom
2. Feeding- paralyze prey and pull it into
gastrovascular cavity.
(Gastro= feeding, Vascular= circulation)
Sponges & Cnidarians
C. Groups of Cnidarians
1. Jellyfish
• Vary in size with the largest being
almost 4 meters in diameter and
tentacles more than 30 meters long;
smallest is a few inches in diameter.
• Australian box jelly: deadly to
humans.
• **Both polyp and medusa forms.
Sponges & Cnidarians
Australian
Box Jellyfish
The top prize for The World Most Venomous
Animal would go to the Box Jellyfish. It has
caused at least 5,567 recorded deaths since
1954. Their venom is among the most deadly
in the world. It toxins attack the heart,
nervous system, and skin cells. And the worst
part of it is that jelly box venom is so
overpoweringly painful, that human victims go
in shock, drown or die of heart failure before
even reaching shore. Survivors experience
pain weeks after the contact with box jellies.
Sponges & Cnidarians
Irukandji jellyfish– world’s smallest!!
The deadly Irukandji jellyfish is a tiny
killer and can be unnoticed in the water.
With bell and tentacles just 2.5
centimetres across, it is almost
impossible to detect. A sting by the
Irukandji jellyfish, on the other hand, is
often felt as nothing more than a painful
irritant with a rash akin to that of prickly
heat. By the time more serious
symptoms appear, it may be too late to
save a life.
Sponges & Cnidarians
Lion’s Mane Jellyfish=
World’s Largest!
Although capable of attaining a bell diameter of
2.5 m (8 feet), these jellyfish can greatly vary in size,
those found in lower latitudes are much smaller than
their far northern counterparts with bells about 50 cm
(20 inches) in diameter. The tentacles of larger
specimens may trail as long as 30 m (90 feet) or
more. These extremely sticky tentacles are grouped
into eight clusters, each cluster containing over 100
tentacles,[5] arranged in a series of rows.
At 120 feet in length, the largest known specimen
was longer than a Blue Whale and is generally
considered the longest known animal in the
world.[6][7][8]
Sponges & Cnidarians
C. Groups of Cnidarians
2. Hydras and their relatives
• Hydras have only polyp form
• Texas coast– Portuguese man-ofwar has a polyp that forms a balloonlike float for the colony with stinging
tentacles that can be meters long!
Phylum Cnidaria
Hydras and relatives
Size:
Float, 12 in (30 cm) long, 5 in (12.7 cm) wide;
tentacles, up to 165 ft (50 m) long
Size relative to a 6-ft (2-m) man:
Sponges & Cnidarians
C. Groups of Cnidarians
3. Sea Anemones and Corals
• Sea anemones are individual polyps
• Hard corals secrete skeleton of limestone
and live as colonies for hundreds or
thousands of years (many together create
a coral reef)
• Largest reef is the Great Barrier Reef in
Australia- can be seen from space!!
Phylum Cnidaria
Sea Anemones and Corals
Great Barrier Reef as seen from space
Worms and Mollusks
1. Phylum Platyhelminthes = flatworms
A. Form and function
1. Pharynx: muscular tube to suck in
food (digestive)
2. Rely on diffusion for transport of
oxygen and nutrients (because of
flatness) (circulatory)
3. Flame cells: remove excess water
from the body (excretory)
Worms and Mollusks
4. Ganglia: group of nerve cells (no brain)
(nervous system)
5. Eyespots: can detect changes in amount
of light
6. Most reproduce sexually; are
hermaphrodites– have both male and
female reproductive organs
Worms and Mollusks
B. Groups
1.Turbellarians- flatworms (planarians)
- Most live in marine or fresh water
2. Flukes- parasitic flatworms that infect internal
organs of host
•
•
Blood fluke Schistosoma lives in multiple hosts
during life cycle (human and snail)
Affects millions worldwide in areas that lack
proper sewage systems
Worms and Mollusks
1. Tapeworms
• Adapted to life inside intestines of host;
attach with scolex: head with suckers or
hooks.
Worms and Mollusks
Phylum Nemotoda- unsegmented worms
(roundworms)
A. Roundworms and Human Diseases
1. Trichinella- reproduce in host and larvae
burrow themselves into organs causing
terrible pain.
Worms and Mollusks
2. Filarial worms:
(mostly in tropical regions of Asia) that live in
the lymph vessels and cause
elephantiasis, which causes extreme
swelling.
Worms and Mollusks
3. Ascarid worms– cause malnutrition in
more than 1 billion people worldwide;
absorbs digested food from humans,
horses, cattle, dogs, pigs, chickens;
humans get it from unclean vegetables not
properly washed.
Ascarid Worms
Worms and Mollusks
4. Hookworms- ¼ of the people in the world
are infected; eggs develop in soil and
when unprotected foot comes into contact
it uses sharp tooth like plates and hook to
burrow into skin and eventually to
intestines where they suck blood and
cause weakness and poor growth.
Worms and Mollusks
Phylum Annelida- segmented worms
(earthworms and leeches)
A. Form and Function- have complex organ
systems
1. crop- to store food and gizzard to grind it
up
2. closed circulatory system- blood is
contained within blood vessels
3. have a brain and nerve cords.
Worms and Mollusks
B. Groups
1. Earthworms- common in woods, gardens;
aerate soil.
2. Leeches- external parasites that suck
blood and body fluids of host; used medically to
reduce swelling or for reattaching body parts;
can suck up to 5 times its weight; secrete
anesthetic so host does not know it’s there. Also,
in its saliva is a fluid that prevents clotting of
blood.
Worms and Mollusks
Phylum Mollusca- snails, slugs, clams,
squid, octopus.
A. Form and Function
1. snails and slugs feed with radula:
tongue with hundreds of tiny teeth
2. siphon: tubelike structure where water
enters and leaves the body
3. closed or open circulatory system
(blood not always in vessels).
Worms and Mollusks
B. Groups
1. Gastropods- snails, slugs. Shell-less
or single shelled that move with muscular
foot on ventral side.
2. Bivalves- clams, oysters, mussels,
scallops (have 2 shells)
3. Cephalopods- octopi, squid, nautilus.
Head is attached to foot which may be
divided into tentacles or arms.
Arthropods and Echinoderms
Phylum Arthrpoda- insects, crabs,
centipedes and spiders.
A. What are they?
1. segmented body; tough exoskeleton
made of chitin
2. jointed appendages: structures such
as legs or antennae that extend from the
body.
Arthropods and Echinoderms
B. Form and Function
1. open circulatory system with well
developed heart
2. well developed nervous system with
brain– cephalization.
3. when they outgrow their skeleton,
they molt: sheds exoskeleton and makes a
new one.
Arthropods and Echinoderms
C. Groups
1. Crustaceans- crabs, shrimp, lobster,
barnacles, pill bugs.
*Two pairs of antennae, 2 or 3 body
sections, and chewing mouthpieces called
mandibles.
Arthropods and Echinoderms
2.
-
Chelicerates- horseshoe crab, spiders, ticks, scorpions
Chelicerae: fangs used to stab and paralyze (spider)
Pedipalps: longer than chelicerae; used to grab prey
(scorpion)
Spiders don’t have jaws, so must liquefy food to
swallow it.
Ticks can transmit bacteria that cause Rocky Mountain
Spotted Fever or Lyme disease
Scorpion pedipalps are enlarged into claws; found in
Southern US; venomous stinger kills or paralyzes prey
and can chew their prey.
Arthropods and Echinoderms
3. Uniramia- centipedes, millipedes
- jaws, one pair of antennae, unbranched
appendages
- Centipedes- up to 100 pairs of legs; one
pair of legs per segment; carnivorous with
poisonous mouthparts.
- Millipedes- two pairs of legs per segment;
feed on dead plants
Arthropods and Echinoderms
4. Insects- bees, ants, beetles, butterfly
- Body divided into: head, thorax, abdomen
- Three pairs of legs attached to thorax
- Types of metamorphosis:
- Incomplete: gradual change (immature form
looks like adult)
- Complete: dramatic change (immature form
looks nothing like adult)
- Some insect groups work as societies
Indirect development
Incomplete
Direct development
Complete
Arthropods and Echinoderms
Phylum Echinodermata- sea urchin, sea stars,
sand dollars
- Spiny skin, internal skeleton, water vascular
system, suction cuplike structures called tube
feet
- Sea urchins help control distribution of algae
- Sea stars are predators that control numbers of
clams and corals
- Crown of thorns is poisonous and feeds on
coral.