1. Patterns of Organization
Just like body symmetry, body patterns are another form of organization used to classify animals.
Unicellular
Diploblastic
Triploblastic

2. Diploblastic Organization Derived from 2 embryological layers:
Ectoderm: gives rise to the epidermis (outer layer of body wall)
Endoderm: gives rise to the gastrodermis (lining inside the gut)
Figure 7.10

3. Diploblastic Organization
Functionally interdependent tissue layers.
Gastrodermis-digestive and muscular cells
Epidermis-epithelial and muscular cells
Ex: Hydra & jellyfish
Figure 7.10

4. Triploblastic Organization Derived from 3 embryological layers
Mesoderm: gives rise to supportive, contractile, and blood cells
Most have organ-system level organization (excretory, nervous, digestive, reproductive, circulatory, etc.)

5. Triploblastic Organization
Body cavity is a fluid-filled space in which the internal organs can be suspended and separated from the body wall.
3 subgroups………….

6. Coelomate (SEE lom ate)
Body cavity completely surrounded by mesoderm
Organs suspended in the body cavity

7. Pseudocoelomate Body cavity not entirely lined by mesoderm
No suspended organs, muscular or connective tissue

8. Acoelomate Without a coelom
Mesoderm forms a solid mass between ectoderm and endoderm called parenchyma (no particular function)

10. The Triploblastic, Acoelomate Body Plan
Chapter 10

11. Triploblastic, Acoelomate Body Plan
1st animals to exhibit bilateral symmetry and a body organization more complex than that of the sponges.
Triploblastic (3 primary germ layers)
Acoelomate (without a coelom)

12. Phyla
Platyhelminthes
Nemertea
Gastrotricha

13. Platyhelminthes Greek platys=flat and helmins=worms “Flat Worms”

14. Phylum Platyhelminthes
34,000 species
Range from 1 mm or less to 25 m
Mostly worm like creatures that are flattened body design
Tapeworms, Flatworms, Flukes and Planarian.

15. Characteristics Bilateral symmetry Usually flattened & unsegmented
Degree of cephalization
Sac-like digestive system; absorb food
Ladder nervous system
Monoecious: complex reproductive systems

16. Digestion
Varies from simple unbranched chamber to a highly branched system of tubes

17. Class Turbellaria Freshwater & marine free living bottom dwellers
Crawl on rocks, sand and vegetation
Predators and scavengers
Colorization mostly black, brown & gray (marine groups brightly colored)
Blind gut (one-way gut); mouth but no anus
Photophobic; have eyespots that detect light

18. Outer Body Covering Covered by a ciliated epidermis
Rhabdites: rod-shaped cells that swell to form a protective mucous sheath around the animal, possibly in response to attempted predation or desiccation
Adhesion glands: produce a chemical that attaches part of the animal to a substrate
Releaser glands: secrete a chemical that dissolves the attachment

19. Locomotion
Bottom dwellers glide over substrate using cilia and muscular contractions help twist & turn
Lay down a sheath of mucous that aides in adhesion and helps the cilia gain traction

20. Nutrition
Most are carnivores and feed on small, live invertebrates or scavenge on larger dead animals
Chemoreceptors (auricles): Sensory cells on their head help detect food
Feeding is via a pharynx: muscular opening to the one-way gut that is located mid-body
The pharynx will pin down the prey while enzymes secreted from the mouth soften the tissue. The mouth sucks in the food and digestion is completed inside the cells.

21. Figure 10.5

23. Class Turbellaria Internally, no body cavity: organs are held in parenchyma, non-contractile muscle cells that take up space

24. Reproduction & Environment
Use cross-fertilization
Monoecious: Hermaphroditic
Can reproduce asexually by transverse fission
Produce zooids
Figure 10.8