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Teacher Activity Notes: Observing Goldfish Capillaries

PLAN

Summary

Students use a microscope to observe the capillaries in the tail of a goldfish. This activity can be done as a whole-class demonstration. However, if you have enough equipment, you may wish to have students work in teams. This activity helps students learn careful handling of and respect for living organisms in the laboratory.

Objectives

Students:

\checkmark determine the direction of the blood flow in goldfish vessels.

\checkmark locate and identify capillaries containing blood cells.

Student Materials

  • Activity Guide
  • Activity Report
  • Goldfish; Cotton; Petri dish; Microscope slide; Microscope; Medicine dropper

Teacher Materials

  • Activity Report Answer Key
  • Photos of capillaries
  • Diagrams or a model of the circulatory system showing location of the major capillary beds
  • Rules for Safety

Advance Preparation

Set up an aquarium and purchase goldfish.

Arrange to have microscopes available.

Post the safety rules for the care and handling of laboratory organisms.

Estimated Time

One 50-\mathrm{minute} period

Interdisciplinary Connection

Language Arts Students write about the journey of a red blood cell in and out of the capillary bed.

Prerequisites and Background Information

Students need to know how to use a microscope. Discuss with students the rules for the care and handling of living organisms.

IMPLEMENT

Steps 1-3

Remind students that the goldfish must be kept moist. Remind them to keep adding water to the cotton. Make sure they are keeping track of the time the goldfish is out of the aquarium.

Step 4

Make sure students are using the low power. Emphasize that they should never focus the mirror of the microscope toward the sun. Sun's reflection can damage the eye.

Steps 5-6

Remind students that the lenses of the microscope turn the image upside down. Therefore, blood that appears to be flowing from the fin to the body is actually flowing from the body to the tail.

As a Journal Writing assignment, have each student in the group represent a component that travels in the blood through the capillaries (e.g., oxygen, carbon dioxide, food nutrients, hormone, enzyme). Have them use the first person to write about a journey through the capillaries.

Helpful Hints

Post the safety rules, or point them out if they are already posted.

Remind students to be careful when handling the goldfish, such as when they are placing the goldfish back in the aquarium.

Make sure students do not use direct sun as the light source for the microscope.

ASSESS

Use your observations of students' working in groups and their written responses to the Activity Report to assess if students can

\checkmark identify capillaries in the goldfish tail.

\checkmark determine the direction of blood flow in goldfish vessels.

\checkmark compare the structure of the goldfish-tail capillary bed to their model capillary bed.

\checkmark determine the direction of blood flow in goldfish vessels.

Observing Goldfish Capillaries - Activity Report Answer Key

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. Draw a small section of the tail showing 1 or 2 capillaries, along with some blood cells. Label: an arteriole, a venule, and a capillary.
  2. Compare what you observed in the goldfish tail to your model of a capillary bed.

Activity Guide: Observing Goldfish Capillaries (Student Reproducible)

Introduction

You can observe the movement of blood in the tail of a goldfish. The tail is so thin that you can see the blood moving through the capillaries. But remember that goldfish are living organisms and should be handled carefully.

Materials

  • Goldfish
  • Cotton
  • Petri dish
  • Microscope slide
  • Microscope
  • Medicine dropper
  • Activity Report

Procedure

Step 1

Saturate a 5-\mathrm{cm} square piece of absorbent cotton or \frac{1}{2} of a tissue with water. Place the cotton on the bottom of a petri dish with a small amount of water.

Step 2

Carefully place the head of a goldfish on the wet, absorbent cotton. Remember to handle the goldfish gently. Saturate another 5-\mathrm{cm} square piece of absorbent cotton with water. Place this piece cotton over the head and gills of the fish.

Step 3

Now put a clean microscope slide under the tail fin of the fish. Hold another slide gently on top of the tail fin to permit observation of the blood vessels in the tail fin. Periodically add fresh water.

CAUTION: The goldfish should not be out of the aquarium for more than 10\;\mathrm{minutes} at a time. After 10\;\mathrm{minutes}, carefully place the goldfish back in the aquarium.

Step 4

Place the petri dish on the stage of your microscope. Use the low power focus. Focus on a section of tail fin that shows blood flowing through blood vessels. Locate and identify an arteriole, a venule, and a capillary. Examine the thickness of each. Determine if the blood flow is toward the tail, from the tail, or in both directions.

Step 5

Observe the capillaries in the tail. Note how the blood flows through them. Draw a small section of the tail showing 1 or 2 capillaries along with some blood cells. Remember that the lenses of the microscope turn the image upside down. Therefore, blood that appears to be flowing from the fin to the body is actually flowing from the body to the fin.

Step 6

When you are through with your observations, place the goldfish back in the aquarium.

Activity Report: Observing Goldfish Capillaries (Student Reproducible)

1. Draw a small section of the tail showing 1 or 2 capillaries along with some blood cells. Label: an arteriole, a venule, and a capillary.

2. Compare what you have observed in the goldfish tail with your model capillary bed.

Teacher Activity Notes: Transport of Materials - Exploring Diffusion

PLAN

Summary

Students observe the diffusion of potassium permanganate (KMnO_4) crystals and water in a graduated cylinder.

Objectives

Students:

\checkmark describe what happens when several crystals of potassium permanganate are placed at the bottom of a column of water in a graduated cylinder.

\checkmark explain the effect of stirring on the rate of diffusion.

\checkmark explain the effect of heating or cooling on the rate of diffusion.

Student Materials

Activity Report

Teacher Materials

  • Activity Guide
  • Activity Report Answer Key
  • Two 50-1,000\;\mathrm{ml} (milliliter) graduated cylinders
  • One 2-foot long piece of clean, dry glass tubing with an internal diameter of about 3\;\mathrm{mm}
  • 1 container of potassium permanganate (KMnO_4) crystals
  • Water

Advance Preparation

Obtain the KMnO_4, graduated cylinders, and glass tubing. If you don't have these available, they can be borrowed from the science department of your local high school. Or they can be ordered from a scientific supply house.

Carolina Biological Supply Company, 2700 York Rd., Burlington, NC 27215. Call 1-800-334-5551.

Estimated Time

20\;\mathrm{minutes} to set up the demonstration. Setup can be done before class. 5-10\;\mathrm{minutes} will be needed each period over several days. Allow enough time for students to observe the diffusion.

Interdisciplinary Connection

Math Tables and rate determination of diffusion could be completed in math class.

Prerequisites and Background Information

SAFETY CAUTION: Potassium permanganate is poisonous. Be sure that students do not come in contact with it at any time.

Diffusion can be defined as the movement of materials from a region of greater concentration to a region of lesser concentration due to random motion. The energy required for this movement comes from the molecular motion of the materials involved. This energy is available to move materials in systems above -273^\circ C. Diffusion will continue as long as there is a difference in concentration and molecular motion within the system. Diffusion will stop when equilibrium is reached. Once equilibrium is reached, although diffusion stops, molecular motion continues.

Temperature is a net measurement of the molecular motion of the substances in a given system. For example, in an ice cube, water molecules are vibrating as they would in any solid. In liquid water, molecules are moving slowly and randomly. In water vapor, a gas, water molecules are moving very rapidly.

Altering the rate of molecular motion can change the rate of diffusion. Molecular motion can be increased by adding more energy to the system in the form of heat energy (raising the temperature) or mechanical energy (stirring). Removing heat from the system (cooling) can slow the rate of diffusion.

Also, the nature of the substance determines its rate of diffusion. For example, perfume diffuses more rapidly than motor oil.

Helpful Hints

  • It is important that the glass tubing is dry.
  • It is best to select two or three medium-size crystals of potassium permanganate.

IMPLEMENT

Steps 1-4

If you set this demonstration up in advance, you may want to encourage students to try to explain how you put the potassium permanganate in the bottom. As a contrast, take a second cylinder, fill it with water, and drop some crystals into the water. These will dissolve and diffuse on the way down to the bottom.

The rate of diffusion also can be influenced by concentration. For example, you can change the rate by increasing or decreasing the substance added or by increasing or decreasing the amount of liquid in the system.

You may wish to do the demonstration at different temperatures, with varying concentrations or amounts of mechanical energy (stirring). Encourage students to record the time required for diffusion and to make a drawing, table, or graph of the results.

Step 5

You and your students should see a clearly distinct band of the purple dye at the bottom of the cylinder. Over a period of several days, have students observe the process of diffusion. Have them record their observations each day. The size and number of crystals will influence the time necessary for diffusion.

ASSESS

Use observations of the diffusion of potassium permanganate (KMnO_4), crystals and water in a graduated cylinder and the written answers or the Activity Report to assess if students can:

\checkmark describe what happens when potassium permanganate crystals are placed at the bottom of a column of water in a graduated cylinder.

\checkmark explain the effect of stirring on the rate of diffusion.

\checkmark explain the effect of heating or cooling on the rate of diffusion.

\checkmark explain the process of diffusion.

Transport of Materials Exploring Diffusion Activity Report Answer Key

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. Explain the process of diffusion.
  2. Draw the apparatus.
  3. Describe the color of the water in the cylinder.
  4. \text{Day 1} && \text{Day 2} && \text{Day 3} && \text{Day 4}
  5. How long did it take for the diffusion process to reach equilibrium?

Activity Guide: Transport of Materials - Exploring Diffusion (Student Reproducible)

Introduction

SAFETY CAUTION: Potassium permanganate is poisonous. Be sure that you do not come in contact with it at any time. Because of the poisonous nature of potassium permanganate, it is recommended that this Enrichment be done as a whole-class demonstration.

The diffusion of potassium permanganate (KMnO_4) crystals in water can be used as a colorful (purple) and simple demonstration.

In this demonstration a few crystals of KMnO_4 are placed by your teacher at the bottom of a column of pure water in a graduated cylinder. The diffusion of the KMnO_4 is easily observed as it diffuses throughout the column of water.

Predict what will happen to the crystals when placed at the bottom of the cylinder of water and how long it will take for equilibrium to be reached.

Describe why and how the process of diffusion occurs.

Procedure

Step 1

Fill 2 graduated cylinders (50-1,000\;\mathrm{ml}) with water. One cylinder will serve as a control. The potassium permanganate (KMnO_4) will be placed in the bottom of the other. Discuss the value of controls in experiments.

Step 2

Select a 2-foot long piece of clean, dry glass tubing with an internal diameter of about 3\;\mathrm{mm}. The teacher places a thumb over one end of the tube and puts several crystals of KMnO_4 into the other end of the tube. The teacher inverts the tube, allowing the Crystals to fall down to the other end of the glass tube where the teacher's thumb is positioned.

Step 3

The teacher's thumb is tight against one end of the tube while it is placed into the graduated cylinder. It is important that the cylinder is tipped slightly without spilling the water as the tube is placed carefully into the cylinder. The end of the tube is in contact with the bottom of the cylinder.

Step 4

Once the tube is on the bottom of the cylinder, the cylinder is returned to an upright position to allow the crystals to fall to the bottom. Then the teacher quickly removes the tube from the cylinder without removing the thumb from the end of the tube.

Step 5

You should see a clearly distinct band of the purple dye at the bottom of the cylinder. Over a period of several days, observe the process of diffusion. The size and number of crystals will influence the time necessary for diffusion.

Activity Report: Transport of Materials - Exploring Diffusion (Student Reproducible)

1. Explain the process of diffusion.

2. Draw the apparatus.

3. Describe the color of the water in the cylinder.

Day 1

Day 2

Day 3

Day 4

4. How long did it take for the diffusion process to reach equilibrium?

Image Attributions

Description

Authors:

Grades:

6 , 7 , 8

Date Created:

Feb 23, 2012

Last Modified:

Apr 29, 2014
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