1. Mr. Gibson Lecture Room 213/Labs 214 w/o March 28 th & April 11th

2. Embryonic Development & Cellular Differentiation Invertebrate Flatworms This week we are building upon your prior knowledge regarding embryonic development & the transition of zygote cells [from] “undifferentiated” [to] “differentiated”.

3. Embryonic Development & Cellular Differentiation Invertebrate Flatworms In particular the differentiation as it pertains to: Ectoderm (outer) Mesoderm (middle) Endoderm (inner) Cells.

4. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Even more specific to our studies over the next two weeks is the further differentiation of Ectoderm/Mesoderm /Endoderm cells into specific structures regarding Invertebrates (no spinal column or backbone)

5. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The first of our invertebrates for our developing Protostome Embryos will be “worms”. And of the worms, we will be dealing with “Flatworms” first.

6. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Flatworms are the “simplest” of the worm invertebrates [as] they have tissues and internal organs [as well as] the three embryonic differentiated cells: Ecto/meso/endoderm

7. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The invertebrate “Flatworms” are studied first due to the fact; biologists state their overall development & structures are less complex than their more evolved “cousins”. But don’t be confused… […] by “less complex” it does NOT imply “simplistic”.

8. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Flatworms have Bilateral symmetry. By that we mean they have a body plan in which only a single, imaginary line can divide the body into two equal halves. This is a characteristics of worms. Plane of symmetry

9. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Flatworms have an area of Cephalization By that we mean they have an area on their body that has a concentration of their sensory organs (allowing for interacting with their surrounding environment) Various flatworms & their areas of cephalization

10. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Flatworms are also called Acoelomates (ay-SEE-luh-mates) Usually in biology if you see the letter “a” in front of a term it means “without”. Flatworms are without a coelom coelom

11. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The “Flatworms” we will study have a much less complex, digestive system and neurosystem… and no real circulatory” system; As these systems have arisen from further differentiation of Ecto/meso/endo- derms cells.

12. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The further differentiation of “Flatworm” endoderm cells. Once the protostome develops for the invertebrate flatworm the endoderm cells continue to further differentiate into a digestive system.

13. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The invertebrate flatworm’s differentiated endoderm cells become a “simple” digestive system. For the planeria @ the right it is nothing more than an endoderm lined cave or cavity called a “gastrovascular cavity”

14. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The invertebrate flatworm’s endoderm lined “gastrovascular cavity” Is really a “tube” that runs through the middle of the animal where secreted enzymes break down ingested food for cellular nutrient needs.

15. Embryonic Development & Cellular Differentiation Invertebrate Flatworms The flat worm… because it IS flat doesn’t really need all that sophisticated of a digestive system. The “flatness” of the worm allows it to act like a sponge… It can readily “absorb” materials through the endoderm cells. Food intake mouth pharnyx

16. Embryonic Development & Cellular Differentiation Invertebrate Flatworms By the time the ingested food reaches the other end of the gastrovascular track what is needed will be absorbed into the animal’s body feeding all the other cells. Anything not needed plus waste coming out of the cells will empty out of the animal. Food intake mouth pharnyx

17. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Materials such as oxygen & nutrients move into a flatworm’s interior (meso/ectoderm) Cells in-spite of the fact the flatworm has NO circulatory system. This is done by diffusion. Cell boundary Waste materials to leave the cell

18. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Diffusion also removes carbon dioxide and other wastes from their body. Because their bodies are so thin and flat, many flatworms do not need a circulatory system to transport materials. Cell boundary Waste materials to leave the cell

19. Embryonic Development & Cellular Differentiation Invertebrate Flatworms There is another structure that the flatworm uses to remove waste material and excess water. That structure is called a FLAME CELL Waste materials also leave the cell via Flame Cells

20. Embryonic Development & Cellular Differentiation Invertebrate Flatworms In addition to handling materials into and out of the animal; The animal must be able to find the food too (as well as be aware of predators and not become food itself).

21. Embryonic Development & Cellular Differentiation Invertebrate Flatworms To help in finding food while avoiding becoming food the animal uses light sensing areas called EYESPOTS And It uses CHEMICAL SENSORY organs that detect good/bad chemicals in the water. Eye spots are light sensing cells

22. Embryonic Development & Cellular Differentiation Invertebrate Flatworms And to process all this information while handling all the interior signals running the animal’s systems; The neural impulses to/from activities route through groups of cells not complex enough to be called a brain -- GANGLIA A group of nerve cells that process electrical impulses.

23. Embryonic Development & Cellular Differentiation Invertebrate Flatworms From the ganglia are a pair of long nerve chords that run either side of the body. These are called Ventral Chords. The long chords that run the length of the animal’s body

24. Embryonic Development & Cellular Differentiation Invertebrate Flatworms And the series of much smaller nerve chords that run laterally (side-to-side) of the animal’s body serving the ganglia are: TRANSVERSE NERVES The much shorter nerves that run side to side of the animal’s body – serving the ganglia

25. Embryonic Development & Cellular Differentiation Invertebrate Flatworms In terms of reproduction… Flatworms are QUITE versatile! They can reproduce: Sexually as hermaphrodites (have both sex organs); Asexually via fission (splitting in half); Asexually via fragmentation Sexual reproduction of hermaphrodites Asexual reproduction by fission reproduction by fragmentation

26. Embryonic Development & Cellular Differentiation Invertebrate Flatworms And speaking of food; Free living flatworms obtain their nutrients [as] heterotrophic carnivores that feed on tiny aquatic animals, or they can be scavengers that feed on recently dead animals.

27. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Flatworms that are “parasitic” (means they live off another living organism). A flatworm with another parasitic flatworm feeding off of it.

28. Embryonic Development & Cellular Differentiation Invertebrate Flatworms There are three types of Flatworms: Turbellarians: free- living flatworms of which most of them live in marine or fresh water.

29. Embryonic Development & Cellular Differentiation Invertebrate Flatworms There are three types of Flatworms: Flukes: parasitic flatworms that are generally found infecting the internal organs of their host

30. Embryonic Development & Cellular Differentiation Invertebrate Flatworms There are three types of Flatworms: Tapeworms: long, flat, parasitic worms that are adapted to life inside the intestines of their hosts

31. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Some special features of the ectoderm structures worth noting with flatworms. Scolex (SKOH-lex): A structure that can contain suckers or hooks and is the head of an adult worm belonging to the parasitic flatworms group.

32. Embryonic Development & Cellular Differentiation Invertebrate Flatworms Some special features of the ectoderm structures worth noting. Proglottids (pro- GLAHT-tidz): Segments that make up most of the worm’s body. Located behind the scolex and belongs to the parasitic flatworms group.