Which is a frog? Which is a toad?

How can you tell the difference?

How do frogs differ from toads?

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.

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, they will get a zero on the dissection lab, 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.

Frog Dissection

Part 1: External Anatomy

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. Develop a hypothesis as to why 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?

Part 2: Digestive System:The Mouth

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

C. Teeth• Rub your fingers along the inside edge of the frog’s upper jaw. You should feel the maxillary teeth.

-5. Are any maxillary teeth also along the lower jaw edge.

• Compare these teeth to human teeth

-6. How does their structures differ?

-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?

Maxillary teeth

Vomerine teeth

Part 3: Digestive System: Internal Organs

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

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.

http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin1_first.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.

http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin2_horiz.html

Dissection Cuts

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 Cutshttp://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle1_first.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.

Dissection Cutshttp://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle3_horiz.html

Removal of Eggs

• If you have a female frog, you will have many black circle shaped structures on the inside of the frog when you it.

• These are eggs and need to be removed so that you can see the organs below them.

General Structures Inside Frog

liver

A

BC

Dstomach

Smallintestine

Large intestine

A. Liver and Gall BladderLocate the liver and gall bladder

-1. How many lobes does the liver have?

-2. Describe the appearance and location of the gallbladder.

Liver (large brown lobes)Gall Bladder (greenish-brown sac) -is located behind liver

B. StomachLocate the stomach and compare it to a human’s

-3. How do their shapes and locations compare?

Using scissor, cut along the outer curvature of the stomach toward the pylorus. Examine the contents of the stomach and its lining

-4. Describe the lining of the stomach and compare to a human

-5. Describe the contents. Did the frog eat right before it was preserved? What did it eat?

stomach

C. Small IntestineFollow the stomach to the small intestine. The small intestine in the frog has three portions just as in humans

-6. What are the three portions

The small intestine is surrounded by a thin membrane called the mesentery.

-7. What do you think is the function of the mesentery?

D. Large IntestineLocate the large intestine

-8. To where does it lead?

Remove the large intestine and cut it open

-9. Describe its interior

Large intestine leads to cloaca.-function of cloaca = collecting space for urine, feces, and eggs or sperm

cloaca

Part 4: Circulatory System: The Heart

A. The HeartRemove the heart, leaving as much of the blood vessels attached as possible. Examine the front side. Locate the right atrium, left atrium, and ventricle. The large vessel arising from the ventricle and forming a “Y” at the top of the heart is the conus arteriosus

-1. Make a sketch (below) of the heart, labeling the right and left atria, ventricle, and conus arteriosus

*A frog heart only has 3 chambers: 2 atria and 1 ventricle*

Right atriumLeft atriumVentricle

Part 5: The Urogenital System

Is Your Frog a Girl or a Boy?

Female Maleovary/eggs

oviduct

Functions: transport eggs, add jelly coating

Testes

Function: Make sperm

#1 = ?

#2 = ?

Ovary with eggs

This frog is a ______________

female male

oviducts

#1

female

#2

? = _______________This frog is a ______________

male female

testes

?

?

male

A. Urinary Bladder, Kidneys, and OviductsLocate 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. Notice they are covered by a thin, tough membrane, the peritoneum, which lines the body cavity. Locate a small twisting tube, the ureter, leading from each kidney to the cloaca. Attached to the cloaca is the urinary bladder.

-1. What is the function of the urinary bladder

-2. What is the function of the kidneys

-3. Make noteworthy observations of the following: oviducts and kidneys

kidney

Part 6: The Respiratory System

A. The LungsLocate the lungs situated near the heart. Make noteworthy observations of the exterior of them. Now remove one lung and nearly slice it in half to expose the interior surface. Make noteworthy observations of the interior.

-1. Lung observations: exterior and interior

Pink arrows point to lungs

Frog Diagrams

THE END