What do you know about frogs?

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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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Which is a frog? Which is a toad?
How can you tell the difference?
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How do frogs differ from toads?

• 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.

• 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

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How are these frogs similar? How are these frogs
different?
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Classification of the Frog

• Kingdom AnimaliaPhylum ChordataSubphylum
  VertebrataClass AmphibiaSubclass
  LissamphibiaOrder AnuraSuborder
  NeobatrachiaFamily RanidaeGenus Rana

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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

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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.

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Frog Dissection
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Part 1 External Anatomy
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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 frogs eyes
  relative to the head
• -How might this be an adaptation for its way of
  life?

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B. Tympanic Membranes
3 ?
Tympanic membrane

• 3. Right behind the eyes are dark circular
  structures called the tympanic membranes.
• -What is their function?

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D. Feet

• 4. Observe the frogs feet. Compare the frogs
  feet to that of humans. Why do you think the
  frogs feet are shaped as they are?
• -How is the structure of the frogs feet related
  to its function?
• -How many toes are on the front legs? How many
  toes are on the back legs?

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Part 2 Digestive SystemThe Mouth
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A. The Tongue

• Cut the edges of the jaw with scissors. Cut back
  till hear crack (hit jaw bone)
• Compare the frogs tongue to a humans
• 1. How do the tip ends differ?
• 2. How do the points of attachment to the lower
  jaw different?

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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
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C. Teeth
Maxillary teeth

• Rub your fingers along the inside edge of the
  frogs upper jaw. You should feel the maxillary
  teeth.
• Compare these teeth to human teeth
• 7. Why do you think a frogs teeth are this way
• Extending from the roof of the mouth are two
  vomerine teeth
• -8. What is their function?

Vomerine teeth
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Part 3 Digestive System Internal Organs
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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

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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.
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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.

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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.

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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.

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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.

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liver
A
B
Smallintestine
C
stomach
D
Large intestine

• General Structures Inside Frog

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A. Liver and Gall Bladder
Locate the liver and gall bladder
Liver (large brown lobes)
Gall Bladder (greenish-brown sac) -is located
behind liver
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B. Stomach
Locate the stomach and compare it to a humans
Using scissor, cut along the outer curvature of
the stomach toward the pylorus. Examine the
contents of the stomach and its lining
stomach
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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.
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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
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Part 4 Circulatory System The Heart
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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
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Part 5 The Urogenital System
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Is Your Frog a Girl or a Boy?
Female
Male
ovary/eggs
oviduct Functions transport eggs, add jelly
coating
Testes Function Make sperm
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• 1 ?
• 2 ?

Ovary with eggs
oviducts
2
1
female
This frog is a ______________ female
male
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?
?
testes

• ? _______________
• This frog is a ______________ male
  female

male
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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
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Part 6 The Respiratory System
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A. The Lungs
Locate the lungs situated near the heart. Make
noteworthy observations of the exterior of them.

Pink arrows point to lungs
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Frog Diagrams
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THE END