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CHAPTER 26
Sponges, Cnidarians, Flatworms, and Roundworms
Phylum Porifera (Sponges)

Characteristics:
 Simple body structure with no true tissues;
multicellular, (hermaphrodites—animal has both
male and female structures), asymmetrical
 Sessile—no movement as adults; are filter feeders
(catch food as it floats through them)
 Have pores that absorb water
 Spicules—tiny hard particles of calcium or silicon
compounds that make up skeleton
Phylum Porifera (Sponges)

Reproduction: can be asexual (budding) or sexual
by releasing sperm that enters other sponges
through pores where it will fertilize the egg.
 After
fertilization, larvae will develop. Larvae are
immature stages of an animal.
Sponge Reproduction
Sperm
cells
Egg
cell
Flagella
Larvae
New sponge
Sponges
Review Questions
1. What word means that a sponge does not move?
Sessile
2. How do sponges eat?
By filtering the water around them
3. What tiny, hard particles make up the sponge
skeleton?
Spicules
Phylum Cnidaria and Cnetophora

Mouth
Characteristics
Tentacle
 Radial symmetry with true
tissues; cup/bell shaped
 Have stinging cells called
Cavity
Inner cell
nematocysts to help capture
layer
food
Jellylike
Bud
 Sting can be fatal to humans
layer
 examples: hydra (very tiny
Outer cell
Disc
layer
jellyfish-like animal),
Has one body opening made of two
jellyfish, coral, sea
layers of cells
anemones
Body Form of Cnidarians
 Has
2 life forms during their life cycle:
 Polyp- has a tube-shaped body with a mouth
surrounded by tentacles.
 Medusa- has an umbrella-shaped body called a
bell.
Polyp
Medusa
Reproduction in Cnidarians

Reproduction: Sexually and
asexually through budding
Review Questions
1. What type of symmetry do cnidarians have?
Radial
2. What are nematocysts?
Stinging cells
3. Give an example of a cnidarian.
Coral, jellyfish, sea anemone, hydra
4. What are the 2 life forms of a cnidarian?
Polyp & medusa
Phylum Platyhelminthes “Flatworms”

Characteristics
 Simplest animal with bilateral symmetry; have long,
thin flat bodies. Usually hermaphroditic.
 Many are parasitic (ex: tapeworms, liver flukes)
Phylum Platyhelminthes “Flatworms”

Reproduction
 Usually
hermaphroditic and reproduce sexually. During
mating, they fertilize each other at the same time.

Some can reproduce asexually by regenerating
(regrowing) lost parts. (ex: cut planarian: will grow
back lost parts!)
Flatworms
Life Cycle of a Flatworm
Adult flukes
Embryos
released
Larva
Human
host
Snail host
Larva
Phylum Nematoda “Roundworms” and
Rotifera

Characteristics
 Bilateral
symmetry, have both mouth and anus
 Live in soil, fresh and marine water.
 Nematodes: roundworms that are often parasitic
 Examples:
Ascaria (intestinal roundworm about 1 ft long),
hookworms, trichinella (from undercooked pork), pinworms,
heartworms
Phylum Nematoda “Roundworms” and
Rotifera

Reproduction
 Most
have separate sexes. Lay eggs.
FYI: Roundworm parasites of
humans
 Hookworm infections are common in
humans in warm climates where they
walk on contaminated soil in bare feet.
 Hookworms cause
people to feel weak and
tired due to blood loss.
FYI: Roundworm parasites of
humans
 Pinworms are the most common human
roundworm parasites in the United States.
 Pinworms are highly contagious because eggs
can survive for up to two weeks on surfaces.
FYI: Ascaris

Eggs of Ascaris are found in
soil and enter a human’s body
through the mouth.
Ascaris worm coming out of a
pig.
Beard worm
Christmas tree worm
- Also have: (turn to pink
sheet)
 Setae—external
Phylum:
ANNELIDA
“Segmented worms”
movement
 Coelom—true fluid-filled
body cavity


Description: (PG.16 Purple Sheet)
Bilateral symmetry,
segmented body, closed
circulation (have vessels)
and true digestive system,
oxygen diffuses through
skin
bristles for

Ex: Earthworms, leeches
Earthworms loosen soil
and make it better for
growing plants
Reproduction
 Sexual: hermaphrodites
(have sperm and eggs), cannot
fertilize themselves.
Earthworm
Phylum:
ANNELIDA
“Segmented worms”
Leeches
CHARACTERISTICS:
Body Temp - Ectothermic
Symmetry - Bilateral
Digestive System – Complete
Skeletal System – None
Circulatory System – Closed
Reproductive System –
Sexual
Heart Chambers – Heart
Body
Mollusks
• Class Gastropoda
(snails & slugs)…2nd
largest class after Class
Insecta
• Class Bivalvia
“Bivalves” (scallops,
oysters, clams, mussels)
• Class Cephalopoda
(squid & octupi)…Only
mollusks with brains!
Phylum: MOLLUSCA
*from Latin word, “molluscus” - soft
Description:
*2ND Largest Phylum of Animals
 3 Main Body Parts:
1. Muscular foot
2. Head
3. Visceral mass (its insides)
 FYI: terrestrial and marine
Giant clam
Sea
Slug

Reproduction
 Sexual: most have separate
sexes, produce gametes
CHARACTERISTICS:
Squid
Ectothermic
Symmetry - Bilateral
Digestive System – Complete
Skeletal System – None
Circulatory System – *OPEN*
Reproductive System –
Sexual
Nervous System - Simple
Heart Chambers - 2 or 3 in
some
Phylum:
MOLLUSCA
Nautilus
octopus
o Subphylum Crustacea
(lobsters, crabs, crayfish…GILLS)
o Class Insecta (all insects have 6
legs)
o Class Arachnida (spiders &
scorpions…all have 8 legs)
o Class Diplopoda (millipedes)
o Class Chilopoda (centipedes)
Arthropods
Crabs
Phylum:
ARTHROPODA
“Arthropods”
Bull Ant
Description:
• Have segmented appendages
(joints) that allow for flexibility
•Molting—since exoskeletons
do not grow, arthropods have
to shed exoskeleton and form
new one
Crabs
Phylum:
ARTHROPODA
“Arthropods”
Bull Ant
Description:
• Mandibles—mouthparts for
holding, chewing, sucking, biting
•Have segments fused into
three main body sections:
head, thorax, abdomen; a
fusion of the head & thorax =
cephalothorax
-
Oxygen obtained through: gills,
tracheal tubes, or lungs

Metamorphosis—series of 4
changes in shape and body
structure during development.

Incomplete metamorphosis—
only has 3 stages; once such an
insect hatches, it looks almost like
the adult version and is called a
nymph
•
Many have camouflage to blend in with surroundings
Locust molting
“Evil” Butterflies
Lobster
CHARACTERISTICS:
Body Temp - Ectothermic
Symmetry - Bilateral
Digestive System – Complete
Skeletal System – Exoskeleton
Circulatory System – Open
Reproductive System –
Very diverse
Nervous System - Simple
Heart Chambers – Muscular
Tube
A termite mound made by the cathedral termite
The Arachnids: Ticks & Mites
Tick
American House Mites
Spiny Cushion Sea Star
Description:
 Move with tube feet—
appendages with suction cups
on tips
 FYI: Have mouth, stomach,
intestines, but no head/brain
 All echinoderms have
exoskeletons made of calcium
carbonate.
Feather
Star

Egyptian Sea Star
Sand Dollars
Reproduction
 Sexually with gametes,
asexually with
regeneration
CHARACTERISTICS:
Phylum:
Echinodermata
“Echinoderms”
Body Temp - Ectothermic
Symmetry - Radial
Digestive System – Complete
Skeletal System –
Exoskeleton
Circulatory System – Open
Reproductive System –
Sexual & asexual
Heart Chambers – No true heart