Lab 7: Vertebrate Anatomy: Difference between revisions

A central argument for the common ancestry of vertebrates is the presence of the same body systems in all subgroups. Despite extensive similarities, body systems in different vertebrate subgroups have been adapted over evolutionary time for survival in different habitats.<br><br>

Perch, genus <i>Perca</i> - a member of the Class Osteichthyes (bony fish)<br>

Mudpuppy, genus <i>Necturus</i> - a member of the Class Amphibia<br>

Rabbit, genus <i>Sylvilagus</i> - a member of the Class Mammalia<br>

Rattlesnake, genus <i>Crotalus</i> - a member of the Class Reptilia

 

Each group of four should choose one of the four systems below and consider the questions posed as you compare the anatomy of the various specimens. Be prepared to briefly present your ideas and discoveries to the rest of the class before you leave today.  

Observe the skulls and teeth of the four animals. What role do the teeth play in the digestive system? Do any of the organisms have teeth that you think are used for specific functions (grinding, tearing, etc.)? How does the shape of the animals' teeth vary based on diet?  Based on your observations of the skulls and teeth of each of these animals, how would you classify their diets’ (herbivorous, carnivorous, or omnivorous)?<br>

Note the size of the stomach relative to the total length/size of the digestive tract in each organism. Which diet (herbivore, carnivore, or omnivore) correlates to the largest stomach relative to overall size of the digestive tract? What do your observations about the relative size of each organism's digestive organs suggest about the  volume of food consumed in one feeding? Do you think each animal can eat more sporadically than others due to the size of the stomach? What does this tell you about the nutrient content of the food consumed by each organism per feeding?   <br>

Note the large relative size/length of the esophagus of the snake compared to the other animals. How might this adaptation help them to consume large prey? <br>

Note the large sac at the beginning of the large intestine of the rabbit. It is called the caecum. Do you see a similar structure in the other vertebrates available for comparison, including your fetal pig? What is the main difference in diet between these animals and the rabbit? Suggest a likely function for the larger caecum in the rabbit:  Is the diet of a rabbit  easier or harder to digest than the diet of a Necturus, perch or snake? <br>

Note the clear, membranous balloon-like structure in the body cavity of the perch. It is not pinned since it would break if a sharp structure is stuck into it. This structure is called the swim bladder, and it is formed by an outpocketing of the digestive system. However, it does not serve a role in the digestive tract. What do you think is the function of the swim bladder? (Hint: Think of the environment in which you would find a perch!)

Overall, how do you think length/complexity of the digestive tract is related to diet? <br>

1. Ovary <br>

2. Oviduct (Necturus, rattlesnake, rabbit [present but not visible in the perch])<br>

3. Uterus (Rabbit)<br>

4. Vagina (Rabbit)<br>

5. Urinary bladder (Necturus, rabbit)<br>

6. Urethra (Rabbit) or urogenital opening (perch)<br>

7. Cloaca (Perch, Necturus, rattlesnake)<br>

Based on your observations which animals bear eggs and which bear live young? How might this difference be reflected in the number of eggs that are produced? If animals bear live young, where are they "housed" while they undergo embryological development? What is the source of nutrition during development for each of the organisms? How is mode of fertilization tied to the site of embryological development? <br>

 

Follow the path of liquid waste production (kidney to urinary bladder (if present) to the urethra or cloaca). Do all of the organisms have a single external opening through which urinary and reproductive products exit? <br>

 

Organisms must remove nitrogenous wastes in the form of uric acid (solid), ammonia (gas), or urea (liquid). Humans and other mammals excrete urea, a non-toxic waste product, while fish secrete ammonia and many reptiles and birds excrete uric acid. Do the animals that produce uric acid and ammonia possess a bladder? Why or why not? <br>

5. Left ventricle (Rabbit)<br>

6. Right ventricle (Rabbit)<br>

7. Aortic arch (Rabbit)<br>

8. Anterior vena cava (Rabbit) <br>

9. Posterior vena cava (Rabbit) <br>

Based on your observations of these organisms and the fetal pig, how many chambers of the heart (atria and ventricles) does each animal possess? <br>

Observe the diagrams that display the path of blood flow to and from the heart in each of the specimens. In each organism, compare and contrast blood flow from the heart to the respiratory structures? Does the oxygenated blood re-enter the heart after entering the blood vessels of the respiratory structures? If so, how is it pumped to the rest of the body? What might this mean in terms of efficiency of the circulatory system?  What can you suggest about the functional implications of division of the heart into  chambers? <br>