Flatworms and cnidarians share some basic characteristics like having simple tissue organization but differ in key aspects like flatworms having bilateral symmetry and a digestive system while cnidarians do not. Some flatworms like tapeworms are parasitic and can infect humans, causing illnesses if meat or water is ingested that contains the parasite larvae. Roundworms also infect many humans and include parasites like hookworms that burrow into the skin and travel to the bloodstream, feeding on blood.

1. Warm up
1. What are some characteristics that flatworms
and cnidarians share?
2. What are some characteristics that are
different?

2. Platyhelminthes
The flatworms

3. Bilateral Symmetry
3 tissue layers

4. No body cavity
Mouth but no anus
Branched intestines
Feed on small animals;
scavengers
Parasites; tapeworms

5. No skeleton; Body cavity is fluid filled to move and keep shape
Sexual reproduction, but hermaphroditic
Live in all environments
Primitive muscles!
Many parasitic for humans
Definite nerve organs including eyespots for sensing light
Most primitive of the bilateral animals!!! 

6. CEPHALIZATION:
definite head end
Collection of nerves in
the head; ganglia

7. Hymenolepis dimunata
This is how tapeworm attach to a host.
They are found in uncooked meat and fecal material.
The host can become VERY SICK!!!

8. Bilharzia burrows through you skin and
moves to your gut.
The host becomes very sick.
It comes from fouled water.
~250,000,000 people are infected

9. Sparganosis is from infected water.
Humans can get it from
reptiles, birds, & other mammals that
have it.
They can grow up to 14 inches.
This flatworm can infect the brain or
eyes.
Most
common
in eastern
Asia!

10. Nematoda
The roundworms

11. Bilateral

12. Digestive cavity
Mouth and anus
Feed on just about
anything
Many harmful parasites
to humans!

13. No skeleton
Sexual reproduction
Found everywhere
Name means thread-like

14. No circulatory
system
Look like
worms, but are
NOT!
Coelom (body cavity
type body plan)
Two nerve cords that
transmit impulses

16. These parasites have
teeth-like plates to
attach them to the
intestinal tract.
Hookworms can each
drink 1.0 ml (1/2 cup)
of blood per day.
You can get them by
walking barefoot then
they burrow into your
skin and move to your
blood.

17. Trichinella roundworms
in human muscle
Whipworm found in
50% of puppies;
Transmitted to human
owners
Most common
childhood intestinal
parasite