Frog Dissection

Biology Do NowGlossary of Terms• Get Your Lab notebooks

• Title the Lab FROG DISSECTION

• Leave space for Purpose section

• Label Background Section• Copy the following terms

into the background section of your lab notebook:

Dorsal: toward the backVentral: toward the bellyLateral: toward the sidesMedian: near the middleAnterior: toward the headPosterior: toward the hind end (tail)Superficial: on or near the surfaceDeep: some distance below the surfaceSagittal: relating to the midplane with bisects the left and right sidesTransverse: relating to the plane separating anterior and posteriorHorizontal: relating to the plane separating dorsal and ventralProximal: near to the point of referenceDistal: far from the point of referencePectoral: relating to the chest and shoulder regionPelvic: relating to the hip region

• Dermal - relating to the skinLongitudinal - lengthwise

• Describe the appearance of various organs found in the frog.• Name locate and identify the organs that make up various systems of the frog.• Compare and contrast frog anatomy to our past dissections.• Contrast and compare various frog's organs to human.

Objective

• Materials:Safety goggles, dissecting pins, gloves, forceps, scissors, paper towel, dissecting probe, preserved frog, dissection tray.

• Purpose:In this lab, you will dissect an frog in order to observe the external and internal structures of frog anatomy

BACKGROUND INFORMATION:• Frogs are classified as amphibians "live a double life". Frogs are

part of the amphibian order, Anura. Tadpoles are aquatic and herbivores. Adult frogs can live on land and in water and are carnivores. Strong muscles and special fused bones help frogs be powerful swimmers and jumpers. Frogs have loose, mucous lined skin to help them escape from predators, and keep them wet which aides in cutaneous respiration (breathing through the skin). Tadpoles breath through gills. Frogs breath though underdeveloped lungs and their skin. Cutaneous respiration limits the frogs body size. The backs of frogs are dark, while their undersides are light, to camouflage them on land and water. Frog brains are smaller and less developed than other vertebrates, they also have a 3 chambered heart.

IntroductionIn this laboratory exercise, the anatomy of the bullfrog will be examined in some detail. You may recall that in your first year biology course you dissected a very similar organism knows as the grass or leopard frog (Rana pipiens). The bullfrog (Rana catesbeiana) which we will be using is much larger than the grass frog, enabling us to find and relate to more structures.

The classification of the bullfrogKingdom AnimaliaPhylum ChordataSubphylum VertebrataClass AmphibiaOrder AnuraFamily RanidaeGenus Rana

The frog is a vertebrate, which means that many aspects of its structural organization are common with all other vertebrates, including man. The similarity of structures among related organisms shows evidence of common ancestry. In a way, studying the frog is like studying a human. As the leading theme of this lab, ask yourself: for every structure observed in the frog, there is an equivalent structure in your own body - what is the structure and where is it located.As the second leading theme, pay particular attention to the relationships among organs and groups of organs. Structural parts are not "just there" in random locations. Their specific layout within the body contributes to making certain functions possible. Therefore, for every structure seen, you should determine the following:•What organ system it belongs to •How it is connected with other components •Its general function •Its specific function (if applicable)

SEXING YOUR FROG:Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the difference between males and females.

 

SEXING YOUR FROG:Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in the diagram below. Male frogs are

also usually smaller than female frogs. Observe several frogs to see the difference between males and females.

Group Roles

• 4 people per group– Dissector 1

• gloves– Dissector 2/Lab material person

• gloves– Observer/recorder 1

• Read instructions out loud to group– Observer/recorder 2

• Record observations (those dissecting can copy later)

Pre-Lab Procedures

• Turn in a sheet of paper to teacher with group members names and group roles of each person

• Collect hand out from teacher• EVERYONE in group needs to copy materials and

procedures into lab notebooks• Get two pairs of glovers per group (for the 2

dissectors)• All hair must be tied back, all loose clothing as well• Absolutely no cell phones permitted in lab

You are expected to have exhausted all

possibilities in attempting to

located structures BEFORE asking for

assistance.

DissectionDissecting tools will be used to open the body cavity of the frog and observe the structures. Keep in mind that dissecting does not mean "to cut up"; in fact, it means "to expose to view". Careful dissecting techniques will be needed to observe all the structures and their connections to other structures. You will not need to use a scalpel. Contrary to popular belief, a scalpel is not the best tool for dissection. Scissors serve better because the point of the scissors can be pointed upwards to prevent damaging organs underneath. Always raise structures to be cut with your forceps before cutting, so that you can see exactly what is underneath and where the incision should be made. Never cut more than is absolutely necessary to expose a part.

Lab Guidelines• Carefully follow instructions on procedure

sheet• No horsing around!• Listen carefully to teacher for directions• Answer all questions on hand out• Dispose of specimen properly when

completed