There are 20 multiple choice questions on this exam (2 points each), six short answer and two essay question (15 points each).  Please check to make sure you have all 7 pages and remember to put you full name on the top of the first page and the scantron sheet. 
Answer the multiple-choice questions on your scantron sheet by identifying the single most correct answer.

Key
1. e
2. a
3. a
4. e
5. c
6. c
7. b
8. a
9. b
10. c
11. e
12. b
13. b
14. b
15. b
16. b
17. b
18. c
19. d
20. d

21. Draw and completely label the following(8 points)

Myoepithelial cell                                Protonephridia
 

Needed to label:
Epithelial cell                                         Flame cell
Cell contractile process                          Cilia
Orientation of processes
(longitudinal or circular)                         Duct
Basal and apical sides or 
outside and mesoglea                           Nephridopore
Cell nucleus                                         Duct pores
Contractile proteins                              Mesoderm
 
 

22. Describe two functions of each structure (4 points)
a. Choanocyte
They trap food particles via microvilli around collar
They create water currents by beating single flagellum
They trap sperm in microvilli and transport them into the sponge

b. Ameboid cell
Responsible for production of spicules
Responsible for movement of materials throughout the inner layer of the sponge and distribution of food
Responsible for elimination of wastes-move wastes to atrium of sponge
 

23. List three classes of Cnidarians and an example of each (6 points)

 Classes   Example
-Anthozoa    Anemone, corals
-Scyphozoa    Jellyfish
-Hydrozoa    Obelia, hydra, portuguese man of war
-Cubomedusa    Jellyfish that are highly toxic and have box-like shape

24. List three Leuconoid structures that are not found in an Asconoid sponge (3 points)

-Dermal pores

-Incurrent and excurrent canals

-Flagellated chambers
 

25. Define symbiogenesis and list three supporting lines of evidence for this theory (5 points).

Definition:
Theory that suggests that multicellular life can only result from the combination of many species

Evidence:
-There does not appear to be any exceptions-all multicellular life has numerous species 

-endosymbiotic theory

-multiple species appear to be necessary for multicellular life
 

26. Using the Fick law of diffusion, briefly explain why all flatworms are flat (4 points). 
Fick law of diffusion states that molecules can only diffuse rapidly over very short distances.  Since flatworms rely on diffusion for respiration they cannot increase the diffusion distance by increasing in size-must essentially remain a two dimensional animal due to limitations for diffusion.

 27.) In the space provided (no credit for information outside of the box), compare the metazoan fossil record with the Berkner and Marshall hypothesis (15 points). 

Needed to clearly state in an essay that 
1. Fossil record shows the sudden appearance of numerous phyla that we recognize as related to current animal groups.
2. Sudden appearance happened in the Cambrian and termed the cambrian explosion.
3. Fossil record suggest that animals might have had a polyphyletic origin since there is not good fossil record before the cambrian and numerous phyla all appear at the same time in an advanced form and very different from each other.
4. Fossil record also suggest that much of early life is not well represented in fossil form and there must be much information hidden or only presented as trace fossils.

5. B&M hypothesis explains the fossil record in terms of a large physical change.

6. B&M suggest that oxygen was the limiting factor for most of the history of life and it was not until oxygen levels reached 1% (pasteur point) of current day levels that large animals could exist. Low oxygen would limit metabolism and there would have been no ozone layer.

7. Cambrian explosion corresponds to oxygen levels in the earth’s atmosphere.
 
 

28.) In the space provided (no credit for information outside of the box), describe how Cnidarians are able to move without having muscles or bones (15 points). 

Needed to clearly state in an essay that:

1. Cnidarians have no muscles but use parts of their epidermal and gastrodermal cells for contraction
2. Each cell has small contractile processes at its base that can change length due to actin and myosin proteins.
3. Gastrodermal cells have circular processes and are used to change the width of the animal.
4. Epidermal cells have longitudinal contractile processes that are used to change the width of the animal

5. Cnidarians have no bony skeletal system but have a hydrostatic skeleton-physical structure is due to water.

6. Due to the incompressibility of water Cnidarians can contract their cellular processes against the water in the mesoglea and GVC and cause their body to change shape.  Thus as they contract the circular processes the animal will get longer and its tentacles will extend.