Class Turbellaria Notes

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1. Phylum: PlatyhelminthesPhylum: Platyhelminthes
Class: TurbellariaClass: Turbellaria
By By
Mr. “I wish I could regenerate” ChapmanMr. “I wish I could regenerate” Chapman

2. PlatyhelminthesPlatyhelminthes
Class Turbellaria –
Are free-living flatworms, are scavengers
that can be found in 3 different habitats:
1. Freshwater species like planaria

3. PlanariansPlanarians
Planarians are frequently used to Planarians are frequently used to
demonstrate the regenerative capabilities demonstrate the regenerative capabilities
of lower invertebrate animals. of lower invertebrate animals.
If cut in half, two Planaria will result. If the If cut in half, two Planaria will result. If the
head is split lengthwise, two heads will head is split lengthwise, two heads will
result after healing is complete.result after healing is complete.

4. Not all Planarians will look the same. There
are hundreds of species and they all vary in
color, shape and size. Planarians live on land
in tropical rainforests and in freshwater lakes,
rivers, and streams.

5. Eyespot
Planarian StructurePlanarian Structure
Planaria’s eyespots allow Planaria’s eyespots allow
them to detect light but them to detect light but
they cannot focus like they cannot focus like
your eyes. your eyes.
The The ganglionganglion, their , their
primitive brain is visible primitive brain is visible
along the inside margins along the inside margins
of each eyespot, giving of each eyespot, giving
Planarians a “cross-eyed” Planarians a “cross-eyed”
appearance.appearance.

6. Planarian StructurePlanarian Structure
Two long nerves that extend Two long nerves that extend
from the Planarian’s head to from the Planarian’s head to
posterior end fuse at the posterior end fuse at the
anterior end to form the anterior end to form the
ganglion. ganglion.
Having sensory organs Having sensory organs
concentrated at the anterior concentrated at the anterior
end of an animal is called end of an animal is called
cephalization. cephalization.
Cephalus means head. Cephalus means head.

7. Planarian StructurePlanarian Structure
Therefore flatworms are the first animals to have a head. Therefore flatworms are the first animals to have a head.
Consequently if they have a head, they then have a right and left Consequently if they have a head, they then have a right and left
side. Cephalization then, leads to a new kind of organization among side. Cephalization then, leads to a new kind of organization among
animals called bilateral symmetry. animals called bilateral symmetry.
Animals with bilateral symmetry have two sides. Bi = two and Animals with bilateral symmetry have two sides. Bi = two and
lateral = sides.lateral = sides.

8. PlatyhelminthesPlatyhelminthes
2. Marine flatworms
like sea slugs
There is also a There is also a
diversity of marine diversity of marine
flatworms. Many are flatworms. Many are
brightly colored brightly colored
warning (Apsomatic) warning (Apsomatic)
fish that they taste fish that they taste
bad.bad.

9. Others are cryptically
colored allowing them to
camouflage with their
surroundings. Marine
flatworms, like Planaria, are
in the class Turbellaria.

10. Examples of TurbellariansExamples of Turbellarians
3. Terrestrial species
like ribbon worms
Scavengers
Mistaken for
earthworms

11. The End