Name:__________________________________________________________
Date:_______
Frog Dissection Pre-Lab1
Why are we dissecting a frog?
Frogs and humans are vertebrates and they have very similar organ systems. Although all
of the internal organs are not exactly the same, it is helpful to learn about anatomy through
dissection. We will be looking at each body system and exploring the individual organs of the
frog. We will be making comparisons between the frog and yourself.
Some individuals argue that dissecting a frog is cruel. Dissection would be a cruel practice
if the frogs were mistreated. The frogs that we use in lab for our dissection were bred in Mexico
for the sole purpose of scientific study. The companies use a very safe preservative to make the
frogs as safe as possible. The frogs we will be using in class have been prepared for dissection- all
blood has been drained from their bodies. We still need to wear gloves and wash our hands while
working with the frogs.
Computers can be used to simulate a dissection. We will be going through a ‘Virtual
Dissection’ to help prepare for our actual dissection.
The frogs we use, gave their lives for science. They are ‘Organ Donors’ who would like us
to learn more about them (and ourselves). In order to best use this opportunity to learn and
show respect for the frog, we must follow all instructions and safety procedures. But, For our
safety, we will be wearing gloves and goggles during the dissection. Aprons will be available for
students. EVERYBODY must wash their hands before they leave the room. Hair should be tied
back. No gum chewing or eating at all.
1. Why are we doing a dissection?
Characteristics of amphibians
Because their eggs are not in a shell, they must develop in a wet environment. Most amphibians
do not have scales. Their skin is thin, smooth, and moist. They do not drink water! Instead, they
absorb it through their skin. This is a major reason why most amphibians prefer to live in damp
environments (or near water). Amphibians can breathe through their lungs or through their skin.
Ecological Indicators
Amphibians are often called ecological indicators. When large numbers of amphibians begin to
die or show deformities, this may indicate a problem with the environment. Sometimes
deformities are caused by other living organisms. They are good ecological indicator because
their skin is responsible for gas and water exchanges- and thus they are extremely sensitive to
changes in air and water quality.
2. Frogs are amphibians, and do not drink water. How do frogs get their water?
3. Why are amphibians considered to be a good ecological indicator?
1
Adapted from Frog Dissection Pre-Lab activities from Mr. Eric Jacques
Frog Life Cycle
http://allaboutfrogs.org/weird/general/cycle.html
Below you will find questions organized by section.
Use the website above to answer.
4. Spawn (egg-mass). Describe how a male frog fertilizes eggs.
5. Egg. Frogs lay thousands of eggs at a time because most will not survive. Roughly 5% of
all egg laid, even hatch. How long does a tadpole egg take to hatch (on average)?
6. Tadpole. Tadpoles are born with gills, and spend ALL of their time in the water. How long
before the gills start getting grown over (and covered) by skin?
7. Tadpole with Legs. When do legs start to sprout?
8. Young Frog. This life stage looks just like frog, but still have a tail. How many weeks old is
a frog in this stage?
9. Frog. How long does it take a frog to fully develop from tadpole to frog?
10. Frog. What other factors can influence the grow rate of frogs?
Virtual Frog Dissection
http://www.mhhe.com/biosci/genbio/virtual_labs/BL_16/BL_16.html
Below you will find questions organized by section. Use the website above to answer.
Introduction
11. Why Dissect. Why are frogs a good model to use when studying the digestive system (as
well as other systems)?
12. Natural History. Frogs and humans are both vertebrates. What does this mean they both
have?
13. Dissection Tools. What are the probe and scissors used for?
Click on Menu on the bottom at the bottom of the page when you are ready to move on to the next section
External Anatomy
14. Orientation. Is it possible to tell if a frog is male or female by external appearance?
15. Skin. What does the mucus do for the skin?
External Anatomy (continued)
16. Head. Where are the tympanic membranes (eardrums)? Do frogs have a pinna?
17. Cloaca. What materials would pass through a cloaca.
18. Legs. How many hind leg toes does a frog have?
Click on Menu on the bottom at the bottom of the page when you are ready to move on to the next section
Internal Anatomy
19. The Initial Cut. Are you supposed to push the pins in at an angle or straight down? What
is the benefit of pushing the pins in this way?
20. The Initial Cut. Describe the first cut you will be making. Include where you will be
cutting and how deep.
21. The Initial Cut. Why are there so many blood vessels in between the skin and muscle
layers?
Internal Anatomy (continued)
22. Digestive System. Which organ is the pancreas located closest to?
23. Digestive System. The movie asks you to remove the intestines. What other organ(s)
is/are removed with the intestines when you click on the tweezers?
24. Respiratory System. What does the skin do in frogs that it does not do in humans?
25. Respiratory System. Where are the lungs located in a frog (relative to the heart)?
26. Circulatory (Cardiovascular) System. How many chambers does a frogs heart have?
27. Circulatory (Cardiovascular) System What is a frogs heart missing when compared to a
humans (what chamber)?
28. Circulatory (Cardiovascular) System Why is the three chambered heart not as efficient
as a four chambered heart?
29. Reproductive System. In your own words, describe where are the testes located?
30. Reproductive System In your own words, describe where are the ovaries located?
31. Excretory System. What happens to blood that enters the kidneys?
Internal Anatomy (continued)
32. Excretory System What organ connects the kidneys to the (urinary) bladder?
33. Nervous System. This video is long, and parts without sound. Please watch patiently.
What makes up a frogs nervous system?
34. Muscular System. The upper leg muscles in a frog are responsible for moving which part
of the frog’s body?
35. Skeletal System. How many bones are found in the axial region?
36. Skeletal System. How many bones are found in the appendicular?
Follow-up.
After you are done with the website portion of this pre-lab, complete the following questions:
37. What is the purpose of this lab?
38. What will we be doing during this lab to stay safe?
39. Sketch the pattern of where you should cut to
make the first incision on your frog (cut thru the
integument).
Draw directly on the picture to the right.
When you are finished with the WebQuest above here is a list of places to visit/things to do:
1. Take the Pre-Lab quiz the homework site. You must pass this with a score of 85%
or better in order to do the dissection. No notes are allowed.
2. Visit these additional sites for virtual frog dissections. When going through the
dissections think about how they compare to the one we just went through.
 http://www.froguts.com (under DEMO)

http://frog.edschool.virginia.edu/
After you have completed #1 and #2 above, you may choose which of the following to do in any
order you want. I have ranked them based on the quality of the site, and how much I think you
will enjoy them (highest to lowest). Some links (teachertube.com) will require you to watch a
short ad before viewing the video.
1. Teacher guided video of a dissection of a rat. Good site. Awesome accent.
http://www1.teachertube.com/viewVideo.php?video_id=101109
2. Colossal Squid. Here you can view virtual info as well as real photos and videos.
http://squid.tepapa.govt.nz/anatomy/interactive
3. Digital Videos webpage. This page has video of dissection of sheep brain, frog
heart, and crayfish brain. *WARNING* These videos are of live frogs. If you feel this
will disturb you, then do NOT watch. This site is totally optional.
http://www.wellesley.edu/Biology/Concepts/Html/digitalvideos.html
4. Pig Heart dissection video. This Aussie guides you through the dissection of a pig
heart. There is blood in this video. Great review of the heart, and its chambers.
http://www1.teachertube.com/viewVideo.php?video_id=60969
5. Sheep eye dissection video. A little far away from video to see anything great, but
good commentary. Too bad his class won’t be quiet!
http://www1.teachertube.com/viewVideo.php?video_id=145439
6. Frog Dissection Video. Long video, but great step-by-step for what to expect when
dissecting a frog. No Audio.
http://www1.teachertube.com/viewVideo.php?video_id=155411&title=Frog_Diss
ection_Instructions
7. Fetal Pig dissection pictures. This page contains photos that are labeled with the
organs they are showing. http://www.execulink.com/~ekimmel/fetal0.htm
8. Rat dissection pictures. http://www.k-state.edu/organismic/rat_dissection.htm
9. Salmon Virtual dissection. This site is cheesy, but you may enjoy it if you like
cheese. http://library.thinkquest.org/05aug/00548/Dissection.html
10. Perch dissection pictures. This site contains a few pictures of the internal organs of
male and female perch (fish).
http://www.bio200.buffalo.edu/labs/tutor/Perch/Perch.html