1. Flat Worms

2. Embryonic Development

3. Nerdy Science Quote
“The most important moment in your life is not birth or marriage, but gastrulation.”
Gastrulation is when the blastula (pretty much the zygote that has divided a whole bunch) folds – it determines whether or not a protostome or deuterostome

4. Embryonic Development
Protostome - “mouth first” – most inverts
Deuterostome – “second mouth” – echinoderms and vertebrates

5. 3 Germ Layers Ectoderm (outermost) Mesoderm (middle)
Endoderm (innermost)

6. Questions
What does protostome mean?
What does deuterostome mean?

7. Questions What is the middle germ layer?
What is the outside germ layer?
What is the inside germ layer?

8. Platyhelminthes aka flatworms
Usually no more than a few mm thick
Have tissues and internal organ systems
Simplest animals with 3 embryonic germ layers, bilateral symmetry, and cephalization

9. Questions Why is it advantageous to be only a few cells thick?
What is cephalization?
What are the 3 germ layers?
What does bi mean?

10. cephalization
Has most sense organs and nerve cells at the anterior (front) end of the body
Aka has a head region with sense organs 

11. Bilateral symmetry
Bilateral symmetry has 2 parts that are the same if cut down the middle

12. Acoelomates “without coelom” What is a coelom?
A fluid filled body cavity lined with mesoderm

13. Classes Within Platyhelminthes
Turbellaria – free living flat worms (most in marine or fresh water)
Tematoda – aka flukes. They are parasitic
Cestoda – aka tapeworms. They are parasitic

14. Planaria (Turbellaria)

15. Turbellaria

16. Tematoda (flukes)
Parasitic – means it lives in/on a host and harms the host to get what it needs
Flukes can live in any organ
Schistosomiasis is a disease where the eggs clog blood vessels

17. Fluke Life Cycle Summary
Flukes mature & reproduce sexually. Embryos are passed through feces
Once in water embryos turn into larva & infect intermediate host

18. Fluke Life Cycle Summary
Asexual reproduction happens in the intermediate host & new larvae are released into water.
Larvae bore through primary host’s skin (humans)

19. Cestoda
Live in intestines of host
The head = scolex

20. Tapeworm Anatomy
Proglottids- when mature have both male and female reproductive organs. Sperm is produced in the testes. Eggs are made in the ovary.
When mature the proglottid breaks off and bursts – releasing the embryos.

22. Tapeworm Life Cycle

23. Tapeworm Lifecycle Summary
1. Proglottids/embryos are relased in human feces.
These embryos are eaten by intermediate hosts.
Cyst forms in intermediate host, which is eaten by human

24. Preventing Parasites
How can you keep from getting a fluke or tapeworm?