Simple Invertebrates
Sponges, jellyfish and coral,
flatworms, roundworms, and
segmented worms too!
Phylum Platyhelminthes
(Flatworms)
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More complex than sponges and cnidarians.
Organisms with long, flat body.
Clearly defined head with mouth.
Some have senses, a few even have eyespots.
Some move freely.
Live in ponds, streams, or in a host!
Many are parasites
Flatworms:
planarian
tapeworm
flukes
Characteristics:
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Reproduce
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Simplest of all worms
1 body opening
Flat bodies
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Hermaphrodites
Cellular Level
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Most flatworms are
parasites
Asexuallyregeneration &
fission
Sexually
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Organs
3 tissue layers
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Endoderm
Mesoderm
Ectoderm
Planarians:
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Triangular head with
eyespots that sense
light
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Reproduce asexually
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Parasites
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Digestive system
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Feed on dead plant &
animal matter
Regeneration
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Mouth
Pharynx
intestine
Tapeworms:
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Long, flat ribbons
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Parasites
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Live in bodies of
humans & animals
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head has hooks that
attach to the host
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can grow up to
18 feet long!
Liver fluke:
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Parasite
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Live in the liver or
blood of an animal
host
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Animal hosts:
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Snails
Fish
Humans
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Humans can get liver
fluke by eating raw or
uncooked fish that
contains the parasite.
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Preventions?
Phylum: Nematoda
(Roundworms)
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Another step up the ladder!
Live on land or in the water
Some even have a simple nervous system.
Some have a digestive system that runs
through the entire body -- with two openings,
one for food to enter and one for wastes to
leave.
Most are parasites.
Some are harmless microscopic critters that
live in the soil.
Characteristics:
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Examples: hookworm, heartworm,
pinworm, Trichinella
Described as a “tube within a tube”
First animals with a complete
digestive system
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two body openings: mouth & anus
Trichinella
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Parasite
Lives in the muscle tissue of pigs
Live and reproduce in the intestine of
the host.
Prevention?
The disease is called Trichinosis
Hookworm:
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Parasite
Live in small intestine
where it enters the
bloodstream
From the bloodstream it
enters the lungs, coughed
up, then swallowed and
enters the digestive
system.
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Hookworm eggs are passed
in the feces of an infected
person.
Hookworm infection is mainly
acquired by walking barefoot
on contaminated soil.
Prevention?
Heartworm:
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Parasite
Enters the blood of a dog
through a mosquito bite!
Worm moves to the heart
where they grow and
reproduce.
They block the valves
that lead to and from the
lungs.
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Prevention?
Pinworm:
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Parasite
Adult lives in the
large intestine
Female migrates to
the anal region to
lay her eggs
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Prevention?
Phylum: Annelid
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Live in fresh & salt
water, streams,
and soil
Examples:
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Leech
Earthworm
Most common
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Lubricus terrestris
Characteristics:
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Approximately 100
segments
Outer layer made of
mucus to help the
animal glide
Setae- tiny bristles
that help in
movement
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Systems:
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Closed Circulatory
system- 5 pairs of tube
hearts
Digestive system
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Mouth
Pharynx
Esophagus
Crop
Gizzard
Intestine
Anus
Nervous system
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Respiratory system
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Ganglion
Nerve cord
No organs
O2 enters through the
skin & CO2 leaves
Reproductive
system- sexual
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Sperm is exchanged
at the clitellum
Clitellum- the band
on the earthworm
where the sex cells
are located
How do earthworms help the
environment?
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Enrich and improve soil
for plants, animals &
even humans.
Create tunnels in the soil
by burrowing, which
aerates the soil to allow
air, water and nutrients
to reach deep within the
soil.
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After organic matter is
digested, the earthworm
releases waste from
their bodies called
castings.
Castings contain many
nutrients that the plant
can use.
Some people even use
earthworm castings as
garden fertilizer.
External Earthworm Lab
External Anatomy
Phylum Porifera
(Sponges)
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Simplest animals of all (some of the oldest too).
All are aquatic (freshwater and marine).
Only two layers of cells, no tissues or organs!
Their skeletons are made of tiny spines called
spicules.
Cannot move (grow attached to the bottom).
Mostly filter feeders.
Uses?
The mighty sponge!
Phylum Cnidaria (aka Coelenterata):
Jellyfish and Coral
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More advanced than sponges. (for example, they
have tissues, but still no organs).
Their body is a hollow cavity with only one opening
(for food AND wastes)!
Entirely aquatic (freshwater and marine).
All have stinging cells, but not all can harm people.
Some are pretty nasty predators. Others filter-feed
on small particles and organisms in the water.
Medusae vs. Polyps
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MEDUSAE
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POLYPS
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Ex. Jellyfish
A medusa is free-swimming.
Most are solitary.
Their opening is on the
bottom of their body.
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Ex. Coral
Polyps are like an upside
down medusa.
Their opening is on the top
of their body.
Coral polyps are tiny and live
in huge colonies of
thousands.
Corals build their “home” as
the colony grows larger and
larger.
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Jellyfish
Most jellyfish are harmless to people, although not so
to small fish and other marine organims.
Portuguese man-of-war.
Look out!
Corals: beautiful colonies of polyps.
More Cnidarians: hydra and sea anemones.
Is it a medusa or a polyp?
Roundworms!
One teaspoon of garden soil may
contain as many as 10,000 tiny
nematodes (roundworms) in it!
Phylum Annelida
(Segmented Worms)
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Most complex worms of all.
Tube-like body divided into segments.
Sophisticated digestive system! (mouth, crop and gizzard,
intestine, anus)
Many other specialized organs heart, blood vessels, nerve
cords, simple brains)
Can move well.
Some aquatic (leeches, clam worms), some terrestrial
(earthworms).
Some are parasites (leeches), others are very important
decomposers (earthworms).
Any other uses for annelids?
Phylum Annelida
(Segmented Worms)
So NOW what do you know about the simple
invertebrates?
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Do you know the names of the five phyla of simple
invertebrates?
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Do you know the main characteristics of each of the
five phyla?
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Can you identify examples of animals in each of the
five phyla?