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Review and model appropriate handling of dissection tools. Encourage students to work carefully and respectfully of one another and their specimens. 4.
Typology: Lecture notes
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1 Preserved frogs (look for mail order sources at the end of this activity)
Content Standard C:
Science C(2)
Science Life & Human Biology (6th-8th):
Systems: How can we understand a complex world through its systems?
Structure & Function: How are structure and function interdependent?
This activity was adapted from the Home School in the Woods, Deserts and Rainforests: Lesson 4 web site (see References section for full website listing).
Clay is always fun to use and making models is a good kinesthetic activity. Because not every student may be enthusiastic about dissecting a real frog to learn about its anatomy, you may try making clay models instead.
√ Look at the overhead transparencies showing Figure 1 and 2. Figure 1 shows the dorsal view of a frog. Figure 2 shows the ventral view. Now look at your frog.
√ Verify your frog has both a nictitating membrane and a tympanic membrane. The nictitating membrane is a transparent lower eyelid that cleans and protects the eye. The tympanic membrane is an eardrum that receives sound waves.
√ Verify only the back feet are webbed.
√ Verify the sex of your frog by looking at the thumb pads on its front feet. Males’ thumb pads are bigger at the base, just like in the diagram to the right.
√ Now verify there are no teeth on the lower jaw. Find the vomerine teeth on the upper jaw. They are used for holding food or prey.
√ Next, look for openings in the mouth that lead to eustachian tubes, which connect to the middle ear and equalize pressure.
√ Now find the glottis. The glottis is the opening from the mouth to the respiratory system.
√ Now see if you can find the tongue.
Nictitating membrane
Tympanic membrane
Male (^) Female
enlarged thumb pad
vomerine teeth
eustachian tube
glottis
internal nares
Cloaca
Small Intestine
Pancreas
Stomach
Left Atrium
Vein
Esophagus
Artery
Gall Bladder
Liver
Ventricle
Lung
Right Atrium
Artery
Large Intestine
The adult frog heart has three chambers. See overhead transparency Figure 5 for reference. While it’s more efficient than the two chambered heart of a fish or tadpole, it’s less efficient than the four chambered heart of warm-blooded vertebrates.
The three chambers of your frog’s heart are the right atrium, left atrium and ventricle. The blood returning from the body full of carbon dioxide is pumped by the same chamber as oxygen rich blood coming from the lungs. This means that blood going to the body has carbon dioxide diluting the oxygen.
The second drawing shows the dark ovaries and coiled oviduct of a female. In a female, these organs cover each kidney. If your frog was a female collected in the spring, the body cavity may be full of ovaries and oviducts.
Testes
Male Female
Kidney
Fat Bodies
Ureter
Urinary bladder
Ovary Oviduct
Fat Bodies
Kidney
Urinary Ureter bladder