Transcript Planarian: A Flatworm

Planarian: A Flatworm
SWBAT define bilateral symmetry; define
free living; describe the nervous system
of the planarian; describe the processes
of digestion and excretion in the
planarian
Planarian
 Bilateral symmetry

Two equal sides to the animal. One side is
a mirror image of the other.
 The planarian is only 2 cm long. Draw a
line estimating how big that would be,
then get a ruler and see how close you
were.
Planarian
 What phylum do flatworms belong to?

Platyhelminthes
 flatworms
 Free-living

An animal that is not a parasite (which
needs a host), it lives on its own.
 Parasites

Fleas, tapeworms
Nervous System
 Neurons

Long, thin nerve cells that are found
throughout the body. They carry impulses
from one point to another.
 Nerve

Collection of neurons wrapped in a
protective coating
 Ganglion
 Simple brain, coordination center –
controls the nervous system
Nervous System
 Describe how the ganglion, nerves and
neurons work together in the planarian.

The nerves interpret a touch and send the
impulse to the ganglion. The ganglion then
sends a response back through the nerves
that creates a response to the stimulus.
Nervous System
 Stimulus

Something an organism can sense
Digestive and Excretory
Systems
 Describe how the process of digestion and
excretion occur in a planarian.

The pharynx shoots out of the mouth and sucks
food to the intestine, where enzymes secreted by
the gastroderm begin to digest it. The cells then
absorb the food and finish breaking it down by
cellular digestion. Non-digestible material is
pushed back out through the mouth. Waste is
excreted through tiny tubes at the end of which are
flame cells, where cilia beat the end and move
waste and water through the tubes.
Other Flatworms
 Tapeworms
 Flukes
 Marine flatworms