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What do you know about frogs?. What class are frogs placed in? Why are they placed in this class? How do frogs differ from humans in terms of their habitats and eating habits? How do frogs differ structurally from humans? Why do you think these differences exist?.
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What do you know about frogs? • What class are frogs placed in? Why are they placed in this class? • How do frogs differ from humans in terms of their habitats and eating habits? • How do frogs differ structurally from humans? Why do you think these differences exist?
Which is a frog? Which is a toad? How can you tell the difference?
Frogs Need to live near water Have smooth, moist skin that makes them look “slimy”. Have a narrow body Have higher, rounder, bulgier eyes Have longer hind legs Take long high jumps Have many predators Toads: Do not need to live near water to survive Have rough, dry, bumpy skin Have a wider body Have lower, football shaped eyes Have shorter, less powerful hind legs Will run or take small hops rather than jump Do not have many predators. Skin lets out a bitter taste and smell that burns the eyes and nostrils of its predators. How do frogs differ from toads?
Classification of the Frog • Kingdom: AnimaliaPhylum: ChordataSubphylum: VertebrataClass: AmphibiaSubclass: LissamphibiaOrder: AnuraSuborder: NeobatrachiaFamily: RanidaeGenus: Rana
Rules for Dissection • 1. Do not mutilate the organism. Any unnecessary cutting or abuse of the specimen will not be tolerated. Follow the directions and do not go off on your own. • 2. Do not even pretend to threaten classmates with any tool found in the dissection kit. Any threat made will be taken as real and the student will be turned into the school for violent intent. • 3. Act accordingly. No horseplay. No throwing of anything. Once you get started, stay in your seat with your group and focus on the dissection. If you have questions – ask! *Any violation of the above rules will result in the student being instructed to put everything away, they will lose all dissection privileges, and the will have a visit to the local office and receive a detention*
Procedures for Dissection • 1. You will be working with a partner • If you do not want to dissect the frog, make sure that you a pick a partner who will do the dissection • 2. You will need to obtain the following materials before you begin • Dissection tray • Scissors (Be careful, they are sharp) • Probe (Be careful, they are sharp) • Frog (Place the frog in your dissection tray) • 3. We will be doing the lab together one section at a time. When you have finished answering the questions for one section, wait for instructions before beginning the next section.
A. Skin and Eyes • 1. Observe the exterior of the frog. Describe the texture and color of the skin. • 2. Observe the location of the frog’s eyes relative to the head • -How might this be an adaptation for its way of life?
B. Tympanic Membranes #3 = ? Tympanic membrane • 3. Right behind the eyes are dark circular structures called the tympanic membranes. • -What is their function?
D. Feet • 4. Observe the frog’s feet. Compare the frog’s feet to that of humans. Why do you think the frog’s feet are shaped as they are? • -How is the structure of the frog’s feet related to its function? • -How many toes are on the front legs? How many toes are on the back legs?
A. The Tongue • Cut the edges of the jaw with scissors. Cut back till hear crack (hit jaw bone) • Compare the frog’s tongue to a human’s • 1. How do the tip ends differ? • 2. How do the points of attachment to the lower jaw different?
B. The Glottis and Esophagus • Locate the slit-like glottis in the center of the back of the mouth. Use a probe to determine where the glottis leads. • -3. To where does the glottis lead? • Locate the esophagus. Using a probe, determine where it leads • 4. To where does the esophagus lead? glottis
Maxillary teeth C. Teeth • Rub your fingers along the inside edge of the frog’s upper jaw. You should feel the maxillary teeth. • Compare these teeth to human teeth • 7. Why do you think a frog’s teeth are this way • Extending from the roof of the mouth are two vomerine teeth • -8. What is their function? Vomerine teeth
Dissection Cuts • 3 main cuts total • -1. Cut from abdomen up to neck • -2. Cut across front legs • -3. Cut across rear legs • *Have to perform cuts twice. Once to cut through skin, then again to cut through muscle* • *When finished, fold back skin flaps*
Dissection Cuts http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin1_first.html Skin First 1. Make the first incision in the skin along the center of the frog between the rear legs. (Take care to cut only the skin.) 2. Use the scissors to continue the incision up the midline all the way to the frog's chin. 3. Stop cutting when your scissors reach the frog's chin.
Dissection Cuts http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin2_horiz.html Skin Horizontal 1. Use the scissors to make sideways incisions in the skin. 2. The first incisions are made between the front legs. 3. The next incisions are made just above the rear legs. 4. Be careful to only cut through the skin, not the muscle.
Dissection Cuts http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle1_first.html First Muscle Incision 1. Repeat the incisions, this time through the muscle layer. 2. Make a small cut with the scissors at the rear legs of the frog. 3. Using the scissors, continue the incision up the midline to a point just below the front legs. 4. Be careful that you don't cut too deeply. The muscle is thin. It is easy to damage the organs underneath.
Dissection Cuts http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle3_horiz.html Muscle Horizontal 1. Make the horizontal incisions. 2. Just as you did with the skin, make a sideways incision in the muscle with the scissors. 3. Make the first incision between the front legs. 4. The next incision is just above the rear legs.
Removal of Eggs • If you have a female frog, you will have many black circle shaped structures on the inside of the frog. • These are eggs and need to be removed so that you can see the organs below them.
liver A General Structures Inside Frog B Smallintestine C stomach D Large intestine
A. Liver and Gall Bladder • Locate the liver and gall bladder Gall Bladder (greenish-brown sac) -is located behind liver Liver (large brown lobes)
B. Stomach • Locate the stomach and compare it to a human’s • Using scissor, cut along the outer curvature of the stomach toward the pylorus. Examine the contents of the stomach and its lining stomach
C. Small Intestine Follow the stomach to the small intestine. The small intestine in the frog has three portions just as in humans The small intestine is surrounded by a thin membrane called the mesentery.
D. Large Intestine • Locate the large intestine • -8. To where does it lead? Large intestine leads to cloaca. -function of cloaca = collecting space for urine, feces, and eggs or sperm cloaca
A. The Heart Remove the heart, leaving as much of the blood vessels attached as possible. Examine the front side. Locate the right atrium, left atrium, and ventricle. *A frog heart only has 3 chambers: 2 atria and 1 ventricle* Right atrium Left atrium Ventricle
Is Your Frog a Girl or a Boy? Female Male ovary/eggs oviduct Functions: transport eggs, add jelly coating Testes Function: Make sperm
Ovary with eggs #1 = ? #2 = ? oviducts #2 #1 female This frog is a ______________ female male
? ? = _______________ This frog is a ______________male female ? testes male
A. Urinary Bladder, Kidneys, and Oviducts Locate the cream colored oviducts through which eggs pass from the anterior of the body cavity to the posterior opening, the cloaca. Remove the oviducts to reveal the brownish kidneys. The kidneys lie along the back of either side of the spine. kidney
A. The Lungs Locate the lungs situated near the heart. Make noteworthy observations of the exterior of them. Pink arrows point to lungs
