Introduction:  The digestive system, in all organisms, serves to break down foods, which can later be used to supply energy.  In this MicroViewer lesson you will be examining various organisms and their modes of digestion.  

Procedure:
1. Using the micro-slide-viewer, microslide, and text folder you will work through the procedure.
2. Read and follow all directions.
3. Examine each slide and study the descriptions in the text folder.  Answer the questions that accompany each section.
4. Draw what you see, when you are asked to do so.
 

Slide # 1 – Paramecium (Protozoan)

1. Draw what you see on the slide.
2. Label the following:  mouth, oral groove, gullet, and vacuole.

Questions
1. Food is pushed into the mouth and gullet by ______________. (cilia or pseudopodia)
2. Why do the yeast cells turn blue in the food vacuoles?
3. Is this organism unicellular or multicellular?

Slide # 2 – Hydra

Questions
1. What has this hydra eaten?
2. The hypostome serves as a ______________ and a ______________.
3. What are the two types of digestion that this organism exhibits?
4. Is this organism unicellular or multicellular?

Slide # 3 – Planaria

Questions
1. The function of the pharynx is _______________. (ingestion or locomotion)
2. Digestion in the planaria is similar to that in the hydra because it is ___________ and ___________.
3. The pharynx in a planaria has the same function as the _____________ in a hydra.
4. What is a disadvantage of having a two-way digestive system?

Slide # 4 – Earthworm

1. Draw what you see in this slide.
2. Label the crop and the gizzard.

Questions
1. Where does an earthworm get its “food?”
2. What is the function of the crop?
3. What is the function of the gizzard?
4. What type of plant material can an earthworm digest that is not digested by humans?
5. Surface area in the earthworm’s intestinal wall is increased by ___________. (villi or typhlosole)

Slide # 5 – Grasshopper

1. Draw the mouth parts of the grasshopper.
2. Label the following:  mandibles, palps, and maxillae.

Questions
1. What is the function of the labium and labrum?
2. What is the function of the crop in the grasshopper?
3. What is the function of the gizzard?
4. Gastric glands in the stomach _____________.  (absorb food or secrete juices)

Slide # 6 – Frog Intestine

Questions
1. What adaptation increases the absorption rate in a frog’s intestine?
2. Absorption is the function of which cell type?
3. Frogs do not have to conserve water.  WHY???

Slide # 7 – Villi / Intestinal Glands

Questions
1. Name the parts of the grasshopper that function like teeth in humans.
2. Name the part of the grasshopper that functions like the liver and pancreas in humans.
3. Absorptive surface in human intestines is increase by:  ________________, _______________, ___________________, and ___________________.
4. How long is the human intestine?

Slide # 8 – Large Intestine (Human)

1. Draw what you see in this slide.
2. Label the tubular glands, goblet cells, and epithelial cells.

Questions
1. What do goblet cells secrete?
2. Why are the bacteria found naturally in the human intestine important?  What do they do?
3. State the three functions of epithelial tissue.
4. Diarrhea causes a loss of _____________.
 

Summary:

Write a short paragraph explaining the purpose of this lab.  What did you learn, why did we perform this lab, and how does this activity fit into our discussion of nutrition and digestion?