Name
Class
Date
Skills Practice Lab
Perch Dissection
Perch are members of the Class Osteichthyes, or bony fishes. Food enters the
fish’s mouth and passes through the stomach and into the intestine. Digestion is
aided by bile produced by the liver, which is attached to the intestine. Solid waste
passes out through the anus.
Wastes from metabolism are processed by kidneys and pass out through the
urogenital opening. Oxygen is obtained from the water as it passes over the
gills. Waste carbon dioxide is passed into the water at the same time.
Movement is achieved by the action of muscles attached to the bony skeleton
of the fish and is guided by the action of several types of fins. The fish has an air
bladder in its body to help it stay afloat. The amount of gas in the bladder is
adjusted by gas exchange across the capillaries in the air bladder wall. The lateral line, found on the outside of the body, allows the fish to sense differences in
pressure and to sense low-frequency sounds.
In this lab, you will dissect a fish in order to observe the external and internal
structures of fish anatomy.
OBJECTIVES
Describe the appearance of various organs in a perch.
Name the organs that make up various systems of a perch.
Compare the features of a perch to other organisms.
MATERIALS
•
•
•
•
dissecting pins
dissection tray
forceps
• lab apron
• preserved perch
• probe
• safety goggles
• scalpel
• scissors
gloves
Procedure
1. Put on safety goggles, gloves, and a lab apron.
2. Place a fish on a dissection tray with the head on your left. Use Figure 1 to
locate and identify the external structures of the fish. The head includes the
mouth, nostrils, eyes, and operculum (gill cover). Turn the fish as needed.
3. Use your fingers to pry open the mouth, and note the teeth.
4. Use forceps to lift back the operculum, and observe the comblike gills
underneath.
5. Identify the scales on the skin, the lateral line, the anus, and the urogenital
opening. Then locate and identify the different types of fins: dorsal (back),
pectoral (shoulder), pelvic (hip), anal, and caudal (tail).
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Perch Dissection continued
FIGURE 1 EXTERNAL STRUCTURES OF A PERCH
Operculum
Dorsal fins
Lateral line
Eye
Caudal fin
Nostrils
Mouth
Pectoral fin
Pelvic fin
Anal fin
6. Referring to Figure 2, use scissors to cut on one side from the corner of the
mouth to the front lower edge of the gill cover. Then remove the operculum.
CAUTION: Use scissors and other sharp instruments with extreme care.
7. Use scissors to remove a gill, and identify the fingerlike gill filaments. On the
inside of the gill are sturdy projections called gill rakers. They help keep food
away from the gills. Note that the gills open directly into the throat.
FIGURE 2 GILL STRUCTURE
Blood flow
Gill filament
Water
flow
Cut
Blood vessels
8. Refer to Figure 3 for cutting open the trunk of the fish in steps 8–11. With a
scalpel, make an incision through the body wall of the fish. Cut along the
belly of the fish from the front edge of the operculum through the trunk to the
anus (cut a). CAUTION: Use scissors and other sharp instruments with
extreme care.
9. Cut up along the side of the fish to the backbone (cut b).
10. Pin the fish on its side through the edge of the belly and the tail. Lift open the
side of the fish, and cut forward through the ribs along the backbone to the
tip of the operculum (cut c).
11. Remove the portion of the trunk that you have cut away.
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Perch Dissection continued
FIGURE 3 CUTTING DIAGRAM
Cut (c)
Backbone
Ribs
Cut (b)
Cut (a)
Anus
12. Use Figure 4 and your probe to locate and observe the following internal
organs: air bladder, stomach, intestine, liver, kidneys, gonads (ovaries or
testes), heart (atrium and ventricle), muscles, ribs, and vertebrae (backbone).
FIGURE 4 INTERNAL ORGANS OF A PERCH
Vertebrae
Kidney
Ribs
Spinal nerve cord
Air bladder
Brain
Throat
Muscles
Gills
Heart
Liver
Stomach
Gonad
Intestine
Anus
Urogenital opening
13. Dispose of your materials according to your teacher’s directions.
14. Clean up you work area, and wash your hands before leaving the lab.
Analysis
1. Identifying Relationships What is the organ in the fish you observed that is
most closely related in function to a human’s ear? Explain.
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Perch Dissection continued
2. Analyzing Results What type of fin is located just behind the operculum?
(Refer to Figure 1.) In what way do fins function?
3. Analyzing Results What internal organs that you observed connect to the
urogenital opening?
Conclusions
1. Interpreting Information What adaptations for life in the water did you
observe in the perch? Describe what the adaptation does.
2. Drawing Conclusions Describe the difference between a gastrovascular
cavity and a complete one-way digestive system. Which is characteristic of
fish, and what is its evolutionary advantage?
3. Making Predictions Predict how a fish’s behavior would change if it had an
open circulatory system instead of a closed circulatory system.
Extensions
1. Designing Experiments Before disposing of your fish, dissect the central
nervous system, under your teacher’s guidance. Use a textbook illustration to
identify the parts you locate.
2. Research and Communications Use references to investigate the significance of the evolution of bony fish, which have powerful jaws, compared with
the jawless fish, which are generally parasites. Write a report of your findings.
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TEACHER RESOURCE PAGE
Skills Practice Lab
Perch Dissection
Teacher Notes
TIME REQUIRED One 45-minute period
SKILLS ACQUIRED
Identifying and recognizing patterns
Inferring
Interpreting
RATING
Teacher Prep–4
Student Set-up–3
Concept Level–3
Clean up–3
Easy
1
2
3
4
Hard
THE SCIENTIFIC METHOD
Make Observations Students observe various organs and systems in a perch.
Analyze the Results Analysis questions 2 and 3 require students to analyze their
results.
Draw Conclusions Conclusions question 2 asks students to draw conclusions
from their data.
MATERIALS
Materials for this lab can be ordered from WARD’S. Use the Lab Materials
QuickList Software on the One-Stop Planner CD-ROM for catalog numbers
and to create a customized list of materials for this lab.
SAFETY CAUTIONS
• Discuss all safety symbols and the caution statement with students.
• Do not use specimens preserved with formaldehyde.
• Prolonged contact with WARDSafe, which should be used to store the
specimens, may be irritating to skin and eyes and may cause allergic reaction
in hypersensitive individuals. Discontinue use if redness or swelling occurs.
In case of contact, flush with water, including under eyelids, for 15 minutes.
Contact physician if irritation or redness persists. May be toxic if swallowed.
If conscious, drink 8–10 oz (240–300 mL) water to dilute material. Induce vomiting. Get prompt medical attention.
• Instruct students on the correct, careful handling of all dissecting instruments,
especially the scalpel. Do not allow students to use razor blades.
DISPOSAL
Wrap the remains of the dissected fish in newspaper, place them in a plastic bag,
and tie the bag securely. Inform the school custodian of the bag’s contents, and
hand it over personally for its safe disposal.
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Perch Dissection continued
TECHNIQUES TO DEMONSTRATE
Demonstrate dissection techniques, including the use of the probe, forceps, and
scalpel, as well as how to pin the specimen. Show students how to properly hold
the scalpel and how to use short strokes to make an incision.
Demonstrate with a volunteer the appropriate way to hand scissors or a
scalpel to another student. (Scissors are offered handle first, not blade first. A
scalpel is placed on a tray for another student to pick up, not handed over.)
TIPS AND TRICKS
This lab works best in groups of two students. There should be no more than four
students per fish.
All WARD’S specimens are treated with WARDSafe. These specimens require
no additional preparation. They greatly minimize student discomfort, especially
eye irritation.
Have students line the dissection trays with paper towels. This will make
cleanup easier.
If you place the specimens in the dissecting trays, do not place them in any
particular position.
You may want only one student from each group to do the dissection, while
the others comment, take notes, and record data.
Emphasize to students that dissection is not “cutting and slicing.” Except for
major incisions, such as removing layers of the skin and muscle to open a body
cavity, dissection is not cutting. Rather, it is making careful incisions to expose
parts, and then using a probe to separate organs from their coverings. Point out
that the intent is to carefully unwrap the animal’s structures without damage.
As a prelab, have students use colored pencils to color the diagrams and highlight any incision lines indicated. This will help students become familiar with the
procedure they will use in the dissection. By using different colors to shade each
of the internal organs shown in the figures before the lab, students will be better
able to visualize the target organs during the dissection.
Give the following instructions to students who carry out Extensions item 1:
Use scissors to snip off the tip of the nose. Then use a scalpel to scrape away
pieces of the skull to expose the brain. Follow the backbone, which contains the
spinal cord, forward to the area of the head above the gills. Have everyone in the
class observe the completed dissection and identify the olfactory lobes, optic lobes,
cerebrum, cerebellum, medulla, cranial nerves, spinal cord, and spinal nerves.
If you do not wish to have your students perform this dissection, or if some students object to dissection, alternative methods of studying these structures are
available. These include models, filmstrips, videotapes, and computer simulations.
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Chapter Labs
Title
TEACHER RESOURCE PAGE
Name
Class
Date
Skills Practice Lab
Perch Dissection
Perch are members of the Class Osteichthyes, or bony fishes. Food enters the
fish’s mouth and passes through the stomach and into the intestine. Digestion is
aided by bile produced by the liver, which is attached to the intestine. Solid waste
passes out through the anus.
Wastes from metabolism are processed by kidneys and pass out through the
urogenital opening. Oxygen is obtained from the water as it passes over the
gills. Waste carbon dioxide is passed into the water at the same time.
Movement is achieved by the action of muscles attached to the bony skeleton
of the fish and is guided by the action of several types of fins. The fish has an air
bladder in its body to help it stay afloat. The amount of gas in the bladder is
adjusted by gas exchange across the capillaries in the air bladder wall. The lateral line, found on the outside of the body, allows the fish to sense differences in
pressure and to sense low-frequency sounds.
In this lab, you will dissect a fish in order to observe the external and internal
structures of fish anatomy.
OBJECTIVES
Describe the appearance of various organs in a perch.
Name the organs that make up various systems of a perch.
Compare the features of a perch to other organisms.
MATERIALS
•
•
•
•
dissecting pins
dissection tray
forceps
• lab apron
• preserved perch
• probe
• safety goggles
• scalpel
• scissors
gloves
Procedure
1. Put on safety goggles, gloves, and a lab apron.
2. Place a fish on a dissection tray with the head on your left. Use Figure 1 to
locate and identify the external structures of the fish. The head includes the
mouth, nostrils, eyes, and operculum (gill cover). Turn the fish as needed.
3. Use your fingers to pry open the mouth, and note the teeth.
4. Use forceps to lift back the operculum, and observe the comblike gills
underneath.
5. Identify the scales on the skin, the lateral line, the anus, and the urogenital
opening. Then locate and identify the different types of fins: dorsal (back),
pectoral (shoulder), pelvic (hip), anal, and caudal (tail).
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Name
Class
Date
Perch Dissection continued
FIGURE 1 EXTERNAL STRUCTURES OF A PERCH
Operculum
Dorsal fins
Lateral line
Eye
Caudal fin
Nostrils
Mouth
Pectoral fin
Pelvic fin
Anal fin
6. Referring to Figure 2, use scissors to cut on one side from the corner of the
mouth to the front lower edge of the gill cover. Then remove the operculum.
CAUTION: Use scissors and other sharp instruments with extreme care.
7. Use scissors to remove a gill, and identify the fingerlike gill filaments. On the
inside of the gill are sturdy projections called gill rakers. They help keep food
away from the gills. Note that the gills open directly into the throat.
FIGURE 2 GILL STRUCTURE
Blood flow
Gill filament
Water
flow
Cut
Blood vessels
8. Refer to Figure 3 for cutting open the trunk of the fish in steps 8–11. With a
scalpel, make an incision through the body wall of the fish. Cut along the
belly of the fish from the front edge of the operculum through the trunk to the
anus (cut a). CAUTION: Use scissors and other sharp instruments with
extreme care.
9. Cut up along the side of the fish to the backbone (cut b).
10. Pin the fish on its side through the edge of the belly and the tail. Lift open the
side of the fish, and cut forward through the ribs along the backbone to the
tip of the operculum (cut c).
11. Remove the portion of the trunk that you have cut away.
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Perch Dissection continued
FIGURE 3 CUTTING DIAGRAM
Cut (c)
Backbone
Ribs
Cut (b)
Cut (a)
Anus
12. Use Figure 4 and your probe to locate and observe the following internal
organs: air bladder, stomach, intestine, liver, kidneys, gonads (ovaries or
testes), heart (atrium and ventricle), muscles, ribs, and vertebrae (backbone).
FIGURE 4 INTERNAL ORGANS OF A PERCH
Vertebrae
Kidney
Ribs
Spinal nerve cord
Air bladder
Brain
Throat
Muscles
Gills
Heart
Liver
Stomach
Gonad
Intestine
Anus
Urogenital opening
13. Dispose of your materials according to your teacher’s directions.
14. Clean up you work area, and wash your hands before leaving the lab.
Analysis
1. Identifying Relationships What is the organ in the fish you observed that is
most closely related in function to a human’s ear? Explain.
The lateral line is most closely related to the human ear because both share
the same basic mechanism. Sensory cells with cilia detect vibrations and
send the information to the brain. The lateral line also senses position and
orientation like the inner ear does.
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Perch Dissection continued
2. Analyzing Results What type of fin is located just behind the operculum?
(Refer to Figure 1.) In what way do fins function?
The pectoral fin and other fins orient the fish and facilitate movement.
3. Analyzing Results What internal organs that you observed connect to the
urogenital opening?
The kidneys and gonads (ovaries and testes) connect to the urogenital opening.
Conclusions
1. Interpreting Information What adaptations for life in the water did you
observe in the perch? Describe what the adaptation does.
Gills allow the perch to obtain oxygen from the water. The air bladder helps the
perch to maintain buoyancy. The fins help guide movement through the water.
2. Drawing Conclusions Describe the difference between a gastrovascular
cavity and a complete one-way digestive system. Which is characteristic of
fish, and what is its evolutionary advantage?
A gastrovascular cavity is a digestive chamber with only one opening that is
found in some invertebrates, such as hydras and flatworms. Fish have a
compete one-way digestive system. The advantage is that food can be moved
in one direction through specialized regions for more efficient processing.
3. Making Predictions Predict how a fish’s behavior would change if it had an
open circulatory system instead of a closed circulatory system.
The complex body structures and behavior of a fish require rapid circulation
and transport of heat, hormones, hemoglobin, and nutrients. It is likely that
the fish would resemble an insect in behavior, size, and complexity if it did
not have the advantage of a closed circulatory system.
Extensions
1. Designing Experiments Before disposing of your fish, dissect the central
nervous system, under your teacher’s guidance. Use a textbook illustration to
identify the parts you locate.
2. Research and Communications Use references to investigate the significance of the evolution of bony fish, which have powerful jaws, compared with
the jawless fish, which are generally parasites. Write a report of your findings.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt Program
BioSources
Title
Lab Program
156
Skills Practice
Chapter Labs
Title