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BIOL 212 Lab Name: Animal Digestion and Digestive Structures OBJECTIVES: · Compare the basic layout and functions of the different forms of animal digestion · Learn proper dissecting techniques · Use histological examinations to help identify functions of various digestive organs INTRODUCTION In this Lab exercise, we will explore the digestive structures of animals. The two main objectives of this lab are to 1) compare the various digestive structures of the animal kingdom and 2) use the histology of the digestive structures to help identify the function of digestive structures as a whole. The evolution of digestive structures and systems play a big part in the differences we see in various animal bodies. Briefly, we began our look at the animal kingdom by examining animals with body cavities that took on numerous roles for the organism. For instance, the gastrovascular cavity of Cnidarians and Platyhelmintheans served the animals as digestive, circulatory, and excretory structures. The spongocoel of a Poriferan serves as the excretory and circulatory structures, and is the only animal we will be viewing that has intracellular digestion – takes food inside its cells via phagocytosis and digests rather than dumping enzymes into an opening within the body. In the “simpler” animals, one cavity must serve many roles. These cavities we considered as “incomplete”. Later, in the more “complex” animals we examined “complete” digestive tracts that functioned almost entirely for digestive function (along with removal of solid waste). These complete digestive tracts were one-way, two-opening tracts, which were often “regionalized” and included specific segments that handled various digestive and absorptive functions. For instance in the earthworm (Phylum Annelida), the digestive tract is organized into a mouth, a pharynx, an esophagus, a crop, a gizzard, an intestine and an anus that all have specific functions for the overall process of the digestive system. Not all animals contain these regions, but the overall processes are basically the same. In Part I of this lab, we will focus our attention on some of the various digestive structures. As you are examining these slides and organisms, try to decipher how the system works based on the layout and the structures you observe. STUDENT PREPARATION AND GENERAL LAB PROCEDURES FOR THIS LAB. Prepare for this laboratory by reading Chapter 41 in Campbell text (particularly Concepts 41.2 to 41.3, pp. 880 to 891). Familiarizing yourself in advance with information and procedures covered in this laboratory will give you a better understanding of the material and improve your efficiency. As you work your way through the lab, you will examine slides and some models. For each slide you view under the scope, draw and label the specimen. When you label the drawings, be sure to include all the structures that you can identify on the specimen and the total magnification you used. I. A Tour through the Animal Kingdom, Gazing at the Digestive Systems and Structures Background: As mentioned above, there is a wide array of digestive systems and structures we have already looked at as we examined the ―evolutionary trendsǁ‖ of the Animal Kingdom. This is an opportunity to bring all of these different digestive structures into view at one time for comparison. As you examine the slides, consider the following questions… · What are the digestive structures you can see and identify? · Is this a complete or an incomplete digestive system (you may have to look and consider beyond the cross-sectional slides)? · How are digestion and absorption processes handled by these structures? · How are the products of digestion (basically organic and inorganic nutrients) distributed from these structures to the other cells of the body? Lab: Animal Digestion 1 Materials Needed Preserved Specimens for dissection, each set of lab partners: one Rat, one earthworm For viewing: Demonstration pigeon Live specimens: Clams (if available) Various slides (listed below) Plastic Earthworm model, Hydra model, Clam model, Human digestion model Structures and cells to look for and identify (some of these slides you may have seen in diversity lab): • Microscope Slides: * Hydra (c.s. and w.m)—Identify gastrodermis, epidermis, gastrovascular cavity, cnidocytes * Planaria digestive(w.m.)—Identify the gastrovascular cavity, pharynx * Mammalian columnar epithelial cells (small intestine) – Identify microvilli, apical surface, basal lamina • Earthworm model: Use this to help identify the regions of the digestive tract. Using your textbook and other resources, label the mouth, pharynx, esophagus, crop, gizzard, and intestine. • Clam model. Identify the palps, intestine, stomach. II. Hydra Model. Identify gastrodermis, epidermis, gastrovascular cavity, cnidocytes, tentacles. III. Animal Dissections Use the pdf files from the website for instructions on proper dissection techniques. There is more information on the pdf files than you are responsible for knowing. However, you will be asked to identify the list of digestive structures and their functions included below for each of the dissected organisms: Earthworm – information specific to dissection technique and digestion are highlighted in yellow in the pdf file! External Anatomy: mouth, anus Internal Anatomy: pharynx, esophagus, crop, gizzard, intestine Rat External Anatomy: mouth incisors, anus Internal Anatomy: epiglottis, liver (medial lobe, left & right lateral lobes, caudate lobe), esophagus, pharynx, stomach, pyloric sphincter, (spleen- not digestive!), pancreas, small intestine (specific area of duodenum as well as entire intestine), cecum, large intestine, rectum, salivary glands, coelom Demo Pigeon: External anatomy: beak, vent Internal Anatomy: esophagus, crop, stomach, gizzard, small intestine, large intestine, cecum, rectum Prelab: 1. How is the shape of the flatworms well suited to their feeding style? 2. How does the cnidaria (hydra) feed? The sponge? The rat? 3. Which of the organisms you will be viewing in lab today have complete digestive systems (digestive tracts)? What is meant by this term complete digestive system? Postlab: Compare and contrast the digestive systems of the bird and the rat, two vertebrate animals. Describe common structures and features, and how these features are modified for the particular organism’s diet and lifestyle. Notebook Check: 1. Labeled drawings of the slides – include specimen name, total magnification, and any notes that will help you with identification for study and for the practicum! 2. Labeled sketches and notes on dissected animals. 3. Any other notes, etc. that my help you in learning the material. I will not be grading your additional notes, but you may find them helpful during practicum! NOTE: Get checked off for each dissection before leaving lab! For Lab Quiz: Be able to identify and describe the function of the different organs and structures you viewed in lab. Be able to discuss how feeding styles, body plans, specific digestive organs, etc. are modified to suit each animal’s environment and lifestyle Lab: Animal Digestion 2