Biology 212 Zoology Lake Tahoe Community College Winter Quarter Instructor: Sue Kloss




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Biology 212 - Zoology Lake Tahoe Community College

Winter Quarter Instructor: Sue Kloss

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Acoelomates

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I. Evolutionary perspective

A. Phyla Platyhelminthes, Gastrotricha and Nemertea.

B. triploblastic acoelomates

C. Platyhelminthes -

1. flatworms

2. tapeworms

3. flukes

D. Nemertea

E. Phylum Gastrotricha includes
II. Phylum Platyhelminthes

A. Characteristics:

1. > 20000 spp.

2. size


3. ectoderm

4. mesodermal tissues

5. organ level system of organization

6. Phylum Platyhelminthes

B. Class Turbellaria

1. niches

2. Body walls

3. Locomotion

4. Digestion and nutrition -

5. Exchange w/ environment

6. Nervous system and sense organs

7. Reproduction and Development

C. Class Monogenea - Only one generation in life cycle - adults develop from egg (no multiple life stages)

1. mostly freshwater and marine parasites of fishes

D. Class Trematoda

1. > 8k spp

2. almost all adult flukes are parasites

3. epidermis is called tegument

4. flukes of medical importance

E. Class Cestoda - Tapeworms - Fig. 10.17

1. most specialized of all flatworms

2. 3500 spp

3. 2 unique parasitic characteristics of tapeworms

4. very stable environment

5. host maintains homeostasis

II. Phylum Nemertea - proboscis worms

A. ~900 spp.

1. elongate flattened worms found in marine mud and sand

2. long proboscis; few mm to several cm; pale yellow, orange, green, red

3. Characteristics of this phylum

4. Digestive system

5. Circulatory system

6. reproduction

III. Phylum Gastrotricha

A. Small phylum,

B. Dorsal cuticle contains scales

C. Syncytial epidermis beneath cuticle

IV. Phylogenetic considerations -

A. tegument is used in phylogeny

B. recent molecular data suggests


Lesson Objective Questions
1. What important evolutionary advantages can be found in Phylums Platyhelminthes, Gastrotricha, and Nemertea?

2. What happens to the 3 embryonic tissue layers in Platyhelminthes?

3. Of what importance is the fact that these phyla have organs and organ systems?

4. List 3 or 4 characteristics of Phylum Platyhelminthes

5. What is the niche of Class Turbellaria?

6. What becomes of the 3 embryonic layers in this group?

7. How do turbellarians move, typically?

8. Describe turbellarian sense organs, and their uses.

9. How do turbellarians digest food?

10. Describe turbellarian structures and processes that allow bodily exchange w/environment.

11. How are neurons organized in turbellarians?

12. Describe 3 classes of Platyhelminthes other than turbellarians, include niches, form of nutrition and reproduction

13. List 3 or 4 characteristics of Phylum Nemertea.

14. What huge evolutionary advances can be seen in this phylum?

15. What niche do members of this phylum occupy?

16. List 3 or 4 characteristics of Phylum Gastrotricha.

17. What niche do members of this phylum occupy?

18. What unusual reproductive feature does this phylum have?



19. If you haven’t already used these terms in this assignment, please define bolded t erms.


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