Coulter
WORMS
CHARACTERISTICS OF WORMS
Biologists classify worms into three major
phyla:
 flatworms, belong to the phyla Platyhelminthes
(plat ee hel minth eez)
 Roundworms, belong to the phyla Nematoda
 Segmented worms, belong to the phyla
Annelida

BODY STRUCTURE
All worms are invertebrates
 Long narrow bodies without legs
 They all have tissue, organs, and body system

NERVOUS SYSTEM
Worms are the simplest organism with a brain.
 Because its brain and other sense organs are
located in its head, it can detect objects, food,
mates, and predators quickly.
 Sense organs are sensitive to light, touch and
vibrations pick up information from the
environment.

FLATWORMS
Flatworms are flat and as soft as jelly.
 Many flat worms are parasites. Parasite is an
organism that lives inside or on another organism.
 Parasites take their food from the host. Host is an
organism in or on which a parasite lives.
 Parasites may injure their host but rarely kill the
host.
 Some flatworms are free living, does not live in or
on other organisms.

PLANARIANS
Free-living flatworms.
 They are scavengers (they feed on dead or
decaying material).
 They are also predators and will attack an
animal that is smaller.
 Feeds like a vacuum cleaner.
 Planarians glide onto their food, insert a feed
tube, inject the prey with digestive juices, then
suck up the digested portion.

TAPEWORM
Parasitic flatworm
 Can get 10 to 12 meters long
 Tapeworms absorb food from the hosts
digestive system.
 Some tapeworms can live in human hosts.
 Many tapeworms can live in more than one
host in its lifetime.

ROUNDWORMS
Roundworms have a digestive system that is
like a tube, open at both ends.
 A one-way digestive system is efficient. Its like a
conveyer belt; start where food enters,
nutrients are absorbed, then remaining is
wasted.
 This type of digestive system enables animal’s
body to absorb a large amount of food.

SEGMENTED WORMS
Earthworms and other segmented worms have
bodies made up of many linked sections called
segments.
 On the inside each segment has organs. For
example each segment has tubes that remove
waste.
 Some organs are only found in certain segments.
 All segmented worms have a nerve cord and
digestive tube that runs the length of the body.
 They have a one way digestive system.

SEGMENTED WORMS
Circulatory system is closed.
 Much like the human body the blood moves in
a closed circulatory system.

EARTHWORMS IN THE ENVIRONMENT
Earthworms tunnel for a living.
 During rainy days they come up out of the
ground to get leaves and other decaying matter
that they will bring under ground and eat.
 Earthworms obtain oxygen through moisture on
its skin.
 Earthworms help the soil in which plants grow.
They burrow tunnels which allow air, water and
plant roots to move through it.
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