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Grade Level
Duration
1 - 1 ½ hours
Subject/Subject Area
Science, language arts;
Analysis, application,
communication,
comparing similarities and
differences, description,
discussion, drawing, small
group work, using time
and space, writing.
Materials
For each pair (or group) of
students:
- Whole body fresh fish
- Dissecting trays or thick
pads of newspaper
(Most cuts can be
made with a pair of
classroom scissors)
straightened paper clip
works well)
not necessary)
newspaper
anatomy
- Hands lens
- Student worksheets
(optional)
the teacher)
LSSS
4-LS1-1; 4-LS1-2;
4-ESS2-3; 6-MS-LS2-1;
6-MS-LS2-2; 7-MS-LS1-3;
8-MS-LS4-
EXPLORE A FISH
Focus Overview
Students will examine the external and internal anatomy of various fish
species. They will note similarities and differences. Students will then
use their observations to make inferences about the relationships among
them.
Background information
This activity gives students first-hand experience exploring the
adaptations which allow fish to function in their environment. Students
look at both form and function of different systems to help understand
how specific adaptations assist organisms in adapting to their
environment. How do fish move through the water and keep their vertical
position within the water? Students can make comparisons between their
own anatomy and the anatomy of a fish.
It is important for students to understand the purpose of this activity
is to study the internal and external anatomy of a fish. It requires
concentration, listening skills and being able to follow directions. All
students should be given the option of not participating in the activity
and be allowed an alternate activity. You may want to do a practice run on
your own.
You can either do this activity as a teacher-led class discussion or break
the students into cooperative learning groups and give each group: a fish,
“Explore a Fish” worksheet, dissection and anatomy sheet, newspaper
and something to cut the fish with.
It is helpful to have students read the handouts “What’s a Fish,” “How Do
Fish…” and “Fish Biology” prior to this activity.
Tips on Buying Fish
Whole, uncut (uncleaned) fish are not easy to find. Most markets clean
the fish before putting them on display. Asian food stores generally have a
tremendous variety of whole bodied fish and are relatively less expensive
than most retail fish markets. If you don’t know of an Asian market near
you, look in the yellow pages under “grocers - retail.” You can also look
in the yellow pages for “fish - retail,” but these will probably be more
expensive. Another possibility is to talk with the fish manager at your local
store well in advance of needing your fish. We have limited success with
this as supermarkets generally only receive a few species of fish and it is
hard to obtain them whole body.
FISH DISSECTION
Buy several types of fish with a variety of body shapes, scale size, and other interesting features. Or keep some
of your catch or ask students to keep some of their catch next time they go fishing.
Learning Objectives
Students will:
- Name characteristics of fish.
- Identify internal & external anatomy.
- Describe form and function of different organ systems.
Procedures
Pre-Activity Discussion
Discuss in groups or use to lead class discussion: (answers are in italics)
- What is a fish? ( A fish is a cold-blooded animal with a backbone which lives in water, breathes oxygen
through gills, and has fins .)
- What do fish need to survive? ( Food, water, air, shelter .) - Where do they live? Is it the same for all fish? ( Fresh and salt water. ) ( In the water column; bottom dwellers
vs. swimmers .)
- What body parts do fish have that people lack? ( Gills, fins, body slime, scales, lateral line, cold blood .) - What do both fish and people have in common? ( Backbones, eyes, nose, mouth, teeth, stomach, intestines,
heart, liver, bones .)
- What specialized adaptations do fish have for their aquatic lifestyle? ( Streamlined body, fins, gills, cold
blood, teeth in rows, slime to keep clean .)
- How do people affect fish habitat? ( Pollutants including soaps and other household products enter creeks,
rivers, bays and oceans by way of storm drains: habitat destruction: building along river banks: bank
destabilization .)
Activity
Student Investigation:
- Explain the proper use of each tool.
a. The scissors are used for cutting into the specimen.
b. The probe is used to gently move tissue or organs to gain better access.
c. The forceps are used to grasp small pieces like the gill filament.
- Group students according to age and ability level.
- Provide each group with scissors, a probe, forceps, a fish, and the student worksheets.
- Walk the students through both the external and internal procedures of examining the fish using your own
fish as an example. This ensures that the students can duplicate your actions. Using a document camera to
project your example fish on a large screen would be useful as well.
- As you progress through the procedure, make sure students are following along with you and their
worksheets.
Operculum
- Using the probes, lift the operculum (gill flap) and look at the gills.
- What might be the function of the operculum? ( Separate the gill filament .)
- Count the number of gill arches.
Eyes
- Observe the eye, how does it differ from yours? ( It doesn’t have an iris .)
- Touch it gently. What does it feel like?
- The lens of the fish eye is a spherical shape without being attached to muscles in the eye like our own.
Internal Anatomy Procedure:
Opening the Body Cavity:
NOTE: Demonstrate opening the body cavity before having the students try it.
- Locate the two openings on the ventral side of the fish. One is the vent (anal), the other urogenital.
- Insert the sharp point of your scissors into the opening that is closest to the pelvic fins (the vent).
- Make an incision from the vent along the belly of the fish to underneath the gills. Be careful not to cut
too deep or you’ll damage the internal organs. (Students often have trouble cutting through the bone and
cartilage between the pelvic fin especially if the scissors are dull.)
- Using the ventral fin to lift the rib cage, snip along the incision carefully until you’ve cut through the ribs
and entered the body cavity.
The first obvious organs you’ll see are the liver and heart.
Heart
- Locate the fish’s heart which is directly below and just behind the gills.
- Why would it be important for the heart to be located close to the gills? (Allows fish to quickly get oxygen
to the heart.)
- Notice that there are two main chambers of the heart (some text will list it as four chambers). Blood flows
from the heart to the gills and then directly to the body where oxygen is used and carbon dioxide is made.
The blood carrying carbon dioxide goes back to the heart.
Liver
- The largest and easiest internal organ to find is the liver. The liver is a chemical factory and a storehouse.
It produces bile which is stored and concentrated in the gall bladder and used to break down fats in the
digestive system.
- Cut the connective tissue of the liver and fold it back.
- The upper part of the liver is connected to the stomach. It can be carefully snipped away from the stomach
and underneath is the gall bladder.
Gall Bladder
- The gall bladder is attached to the liver. It is a pretty hard organ to find. It looks like a little greenish-bubble
attached underneath the liver.
- The gall bladder stores bile which is transmitted into the digestive tract. Fold the liver back with the probe
and trace the complete digestive tract.
Digestive Tract
- The digestive tract consists of the esophagus, stomach, and intestines.
- The stomach is the larger sac leading from the esophagus.
- Some fish have a pyloric stomach which is an organ that increases the amount of surface area for digestion
with little finger-like appendages.
- If you fold the stomach back you will find the spleen; a dark, black-red organ attached to the posterior end
of the stomach. It is part of the circulatory system. It stores and forms blood.
- The rest of the digestive tract is the intestines for absorption of nutrients.
- The anal opening is for excretion.
- The stomach can be cut open to examine the contents but it is rather smelly and sometimes hard to
identify the contents.
Reproductive Organs
- The reproductive organs are attached to the urogenital opening located directly behind the anus.
- The ovaries, if the fish is female, may be in different stages of development.
- The testes, if the fish is male, are white flaccid organs that produce sperm.
- The digestive system and reproductive organs can be scraped away at this point to reveal the air bladder.
Air Bladder
- How does the air bladder help the fish? (It helps the fish remain suspended without exerting a lot of
muscular energy from its fins.)
- How does the air get inside the bladder? (Some fish gulp air into the bladder. However, in most fish, it is a
sealed sack, and the gas comes from the fish’s blood.)
Kidney
- If you cut away the membrane just below the vertebral column, you will expose the kidneys. They are long
and dark in color.
- The kidneys filter waste from the blood and are key organs in balancing the salt in the blood.
Post work/Clean-up:
- When students are finished with the dissection, have them fold all materials into their paper towels/
newspaper and set aside a separate trashcan for dissection materials.
- Remind each group to thoroughly rinse and sanitize dissection equipment (water and mild bleach solution,
vinegar solution, or other sanitizing agent). Have them dry the equipment and return it to your storage
area. Make sure they rinse and dry their tray as well.
- Dispose of dissection material appropriately (ex. Outside dumpster) and immediately.
- Wipe all dissection stations with a sanitizer (mild bleach or vinegar solution).
Review
- What was the most interesting thing you learned about fish?
- What adaptations have fish developed to survive in their environment?
- What anatomical structures do fish have in common with humans?
Assessment Method
- Grade students based on their overall execution of the lesson and their answers to part I of the worksheet.
- You can also use a rubric to score their drawings based on labeling of anatomical features.
- Add a discussion question to a regular weekly test.
FISH ANATOMY
EXTERNAL FISH ANATOMY
INTERNAL FISH ANATOMY
Spines
Two-part Dorsal Fin
Rays
Adipose Fin
Caudal Fin
Anal Fin Pelvic Fin
Pectoral Fin
Operculum
(or gill cover)
Lateral Line
Gills
Swim Bladder
Stomach
Kidney
Gonad
Urinary Bladder
Liver Anus Intestines
Heart
Pharynx
Gills
Gallbladder
Scales
Mouth
Eye
Nares
(nostrils)
Vent
1. WHAT IS A FISH?
In a small group, answer the following questions:
A. What is a fish? (List some characteristics of fish.)
B. What is their habitat? Is it the same for all fish?
C. What do fish need to survive?
D. What body parts do fish have that people lack?
E. What do both fish and people have in common?
F. What specialized adaptations do fish have for their aquatic lifestyle?
“Explore a Fish” Student Worksheet
USE THIS SHEET TO DRAW AND LABEL THE PARTS OF YOUR FISH
