MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A student wants to look at the chloroplast in the one-celled organism called Euglena. Which instrument would they use?

a. compound microscope

b. telescope

c. the naked eye

d. magnifying glass

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which process produces the energy needed to carry out life activities?

a. circulation

b. digestion

c. excretion

d. respiration

Correct Answer: d

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which of the following terms refers to the movements of molecules from an area of higher concentration to an area of lower concentration?

a. concentration

b. diffusion

c. passive transport

d. collision

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

If a cell that is 80% water is placed in a solution that is 40% water, which way will the net movement of water go?

a. Into the cell

b. Out of the cell

c. Neither way

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A cell that is 30% water is placed in a solution that is 35% water. Which way will the net movement of water go?

a. Into the cell

b. Out of the cell

c. Neither way

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A cell that is 43% water is placed in a solution that is 75% water. Which way will the net movement of water go?

a. Into the cell

b. Out of the cell

c. Neither way

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A cell that is 35% water is placed in a solution that is 35% water. Which way will the net movement of water go?

a. Into the cell

b. Out of the cell

c. Neither way

Correct Answer: c

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A cell that is 50% water is placed in a solution that is 45% water. Which way will the net movement of water go?

a. Into the cell

b. Out of the cell

c. Neither way

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Kelly and Pat are stranded on a desert island in the middle of the ocean. They both are very thirsty and search for water, but don’t find any fresh water on the island. Kelly decides to drink ocean water deciding that although it tastes salty, it doesn’t taste terrible. Pat, on the other hand, decides to drink coconut milk. As the day wears on, Kelly drinks more ocean water and complains of being thirstier. Pat, however, isn’t complaining at all. Why might Kelly still be thirsty?

a. Osmosis has depleted the water of Kelly’s cells, causing thirst.

b. Osmosis has put more salt into Kelly’s cells, causing thirst.

c. The salt from the ocean water has held more water in Kelly’s cells.

d. Coconut milk contains about half the salt that ocean water does.

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Sarah put a carrot slice in a beaker of cold salty water and another slice from the same carrot in a beaker of cold fresh water. After an hour, she found that the one in the fresh water was much crispier than the one in the salt water. Which answer best explains her findings?

a. the fresh water slice must have come from a crisper carrot.

b. the fresh water slice must have been smaller.

c. the fresh water in the beaker absorbed water from the cells of the carrot slice.

d. fresh water in the beaker went into the cells of the carrot slice.

Correct Answer: d

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

A student observes a flower, an apple, a dog, and a tree. Which of the organisms that the student sees has different cells than the rest, and how are the cells different?

a. The flower is different because its cells are the only ones without a nucleus.

b. The apple is different because its cells are the only ones with a cell membrane.

c. The dog is different because its cells are the only ones without a cell wall.

d. The tree is different because its cells are the only ones with chloroplasts.

Correct Answer: c

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which answer best describes the function of the nucleus in the cell?

a. carries the protein to other parts of the cell

b. major controller of cell’s activities

c. allows substances to enter and leave the cell

d. gets rid of the waste produced in the cell

e. aids in the transport of nutrients for the cell

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

What part of the cell contains instructions and information to be sent to all parts of the cell?

a. mitochondrion

b. nucleolus

c. nucleus

d. ribosome

e. vacuole

Correct Answer: c

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which part of the cell contains a green pigment needed for photosynthesis?

a. centriole

b. chromatin

c. chloroplasts

d. cytoplasm

e. ribosomes

Correct Answer: c

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

The brain controls the body. In an individual cell, which of the following is most comparable to the brain?

a. cell membrane

b. cell wall

c. cytoplasm

d. nucleus

Correct Answer: d

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

What is the function of the cell membrane in the cell?

a. To control what goes in and out of the cell.

b. To provide strength for the cell.

c. To package things made in the cell.

d. To direct cell reproduction.

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

What is the function of the cell wall in the cell?

a. To control what goes in and out of the cell.

b. To destroy harmful things in the cell.

c. To provide rigid support for the cell.

d. To hold the cell parts in place.

Correct Answer: c

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

What is the function of the nucleus in the cell?

a. To control what goes in and out of the cell.

b. To kill harmful things in the cell.

c. To package things made in the cell.

d. To control the activities and reproduction of the cell.

Correct Answer: d

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Match the organelles below with the drawing of this plant.

___ 1. Cytoplasm

___ 2. Cell Membrane

___ 3. Cell Wall

___ 4. Nucleus

Correct Answer:

1. d

2. c

3. a

4. b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Plant cells are often rectangular or square. Which organelle gives plant cells their definite rigid shape and structure?

a. cell membrane

b. cell wall

c. chloroplast

d. cytoplasm

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Plant cells can be distinguished from animal cells because plant cells have a second outer layer giving them additional shape and support. What is the name of this additional layer?

a. cell membrane

b. cell wall

c. chloroplast

d. cytoplasm

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Two students set up two experiments to see if both plant and animal cells have cell walls. Which of the following statements best describes correct conclusions?

a. Both student experiments show that plant cells have cell walls and animal cells do not have cell walls so it does not matter that each student used different experimental methods and procedures.

b. Both experiments showed that plant cells and animal cells have cell walls so it does not matter that each student used different experimental methods and procedures.

c. Both experiments showed that plant cells have cell walls and animal cells do not have cell walls so the two students obviously did the exact same experiment so they could get the same conclusion.

d. Both experiments showed that plant cells and animal cells have cell walls so the two students obviously had the same exact experiment so they could get the same conclusion.

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which cell structure is found only in plant cells?

a. cell membrane

b. cell wall

c. cytoplasm

d. nucleus

Correct Answer: b

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Which of the following structures let substances pass in and out of animal cells?

a. cell membrane

b. cell wall

c. epidermis

d. mitochondria

e. mucous membrane

Correct Answer: a

MC	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Plant and animal cells are distinguished from each other by several factors. One of these factors is:

a. Plant cells have cell walls but not cell membranes.

b. Plant cells have both cell membranes and cell walls.

c. Animal cells have both cell membranes and cell walls.

d. Animal cells have cell walls but not cell membranes.

Correct Answer: b

I	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Use the diagram above to answer the following questions.

1. Which best describes the function of a cell wall?

a. aids in cell reproduction

b. controls the activity of the cell

c. supports and protects the cell

d. moves material through the cell

2. Which is a plant cell, A or B?

3. What evidence did you use to determine your answer to #2?

4. Predict what difficulties an animal might have if each of its cells had a cell wall.

5. Why do plants need cell walls and animals do not?

Correct Answers:

1. c

2. a

3. presence of cell wall

4. Accept any reasonable answers difficulty moving, predators may be slower, pests may be tougher, etc.

Cell walls provide support and protection for plants, support for animals comes from skeletons and they protect themselves in many different ways.

I	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

This item refers to an investigation in which cells were cut in half. They were cut in a way that one half of each cell contained a nucleus and one half had no nucleus. One hundred fragments from each group were placed in containers with uniform conditions. The table below shows the results.

	Number of Cell Fragments Without Nuclei	Number of Cell Fragments With Nuclei
Number Studied	100	100
Surviving 1 day	80	79
Surviving 2 days	60	74
Surviving 3 days	30	72
Surviving 4 days	3	72

1. Which of the following hypotheses is being tested by this experiment?

a. Twice as many cells will grow if each is cut in half.

b. The size of the cell fragment will determine how long it lives.

c. A nucleus is necessary for the continued life of a cell.

d. Any cell fragment will eventually die.

2. Construct a graph to describe and summarize the survival data for the 2 groups.

Correct Answers:

1. c

2. Graph should include:

number of days surviving

number of fragments studied

number of fragments with nuclei for each day

number of fragments without nuclei for each day

a curve connecting the data points for each graph

I	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

The next 4 questions refer to the following diagram of a plant cell.

1. Which cell part is the major controller of the cell’s activities?

a. A

b. B

c. C

d. D

2. Which cell part is majorly responsible for the movement of materials into and out of the cell?

a. A

b. B

c. C

d. D

3. Which cell part is not found in animal cells?

a. A

b. B

c. C

d. D

4. Which label designates the cytoplasm?

a. A

b. B

c. C

d. D

Correct answers:

1. c

2. b

3. b

4. d

I	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Each diagram below represents a cell in a solution. Water percentages in the cells and solutions are written in the diagram. For each diagram, tell which way the net movement of water will go. Use the key to answer the questions.

Key

a. Water moves into the cell

b. Water moves out of the cell

c. No net movement of water into or out of the cell

Correct Answers:

1. b

2. a

3. c

4. b

5. a

6. b

I	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

From the following list, select a specific instrument and explain how it has influenced our ability to study cells.

Compound Microscope

Electron Microscope

Computer

Video Microscope

Possible Answers:

compound microscope – allows cells and many of their components to be magnified and made visible.

electron microscope – allows cells and sub-cellular structures to be observed at magnifications greater than those obtainable with a compound microscope.

computer – accessing, interpreting, gathering, and compiling vast data on cell function.

video microscope – filming and showing cells dividing in real time.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Describe the differences between a cell wall and a cell membrane in a plant cell.

Correct Answer: The cell membrane of a plant cell determines what goes in and out of the cell. It lets in useful substances such as water and ions, and tries to keep out harmful substances. The cell wall, on the other hand, does not keep molecules, substances, or things in or out, but instead provides rigid support for the plant.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Describe two main ways that plant cells differ from animal cells. Also describe how these structural differences relate to functional differences.

Possible Answer:

Plant cells have cell walls and generally chloroplasts. Cell walls give support, and chloroplasts allow plants to produce food through photosynthesis.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Tell three ways plant and animal cells are similar, and two ways they are different.

Possible Answer:

Similarities: Both plant and animal cells have a cell membrane, nucleus, and cytoplasm.

Differences: Plant cells have a cell wall and usually chloroplasts.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Describe the differences between plant and animal cells. How do these differences affect the function of these cells?

Rubric:

4—plant cells have a cell wall and chloroplasts, at least 2 effects are stated

3—mentions either cell wall or chloroplasts, plus 2 effects

2—mentions either cell wall or chloroplasts, plus 1 effect

1—mentions either cell wall or chloroplast or 1 effect

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Draw both an animal cell and a plant cell. Draw each cell at least 2 inches in diameter. Label the following parts: nucleus, cell membrane, cell wall, chloroplast, cytoplasm. Then describe how the function of the plant cell differs from that of an animal cell.

Ideal Answer: Students must label all parts. A plant cell differs from an animal cell in that it contains a cell wall and chloroplast.

Rubric:

4—Labels all 5 parts. Draws both cells. Describes the 3 differences between cells.

3—Draws both cells. Labels some parts. Describes differences between cells.

2—Draws cells. Doesn’t label. Describes some differences between cells.

1—Draws cells.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Draw both an animal cell and a plant cell. Draw each at least 2 inches in diameter. Label the following parts (nucleus, cell membrane, cell wall, chloroplast, cytoplasm).

Ideal Answer: Must label: nucleus, cell membrane, cell wall, chloroplast, cytoplasm

Scoring Guide:

4 - Labels all 5 parts. Draws both cells.

3 - Draws both cells. Labels some parts.

2 - Draws cells. Doesn't label.

1 – Drawings are incomplete and unlabeled.

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Imagine a unique organism and a draw a picture of it. Use the 7 characteristics of life and explain why your organism is living.

Scoring Guide:

10 pts total:

0-3 pts - creative picture

0-7 pts - 7 characteristics

E	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

How has the technology of science helped to further the progress of the study of cells?

Possible Answer:

Using instruments developed from various forms of technology (e.g.: optical, electronic equipment), allows us to see and understand cells better.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

YEAST CELL DIVISION

Directions:

1. Get a microscope, a clean slide and a cover slip.

2. Put one drop of the yeast solution on the slide and then add one drop of Iodine solution. (The iodine will stain the yeast cells.)

3. First focus the microscope with the low power objective, then move through the lenses until it is focused on high power.

4. Draw the yeast cells you see here:

5. Watch the yeast cells closely and look for a cell that is getting ready to divide. As soon as you see a yeast cell dividing, record the time here:

6. Make a hypothesis as to how long you think it will take for that same cell you just saw dividing to divide again:

7. Now keep watching the same cell that you saw divide once. (Remember, now it is 2 cells!) Record the next time that it divides:

8. How accurate were your estimates?

9. Now assume that yeast cells always divide in the same amount of time that you observed. Make a graph that shows the reproduction of yeast cells over time. Assume you start with one cell and indicate the number to be expected after a subsequent series of divisions.

10. If you started with one yeast cell and it divided every hour, how many yeast cells would you have after 12 hours?

Correct Answers:

(Teacher Suggestions):

For a yeast solution, mix yeast with warm water and sugar. Let it sit for about 15 minutes before class starts to get it active. Yeast typically divides every 30 minutes, so this test will take up one class period.

9. The students should plot an exponential graph of number of yeast cells vs. time

10. 4096 cells

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Microscope Skill Test

Teacher Guide

Materials: microscope, prepared slide

Time needed per student: 3-5 minutes

Directions to Teacher:

When students feel ready they come to take the test (another lab or activity would be in progress)

1. Ask the student to retrieve a microscope and bring it to a lab desk and set it up.

2. Hand the student a prepared slide and ask him/her to center the object and focus on high power.

3. Ask him or her to adjust diaphragm.

4. Check to see if the specimen is in focus and centered.

Scoring Guide: 6 pts-one point each task

1. Properly carry microscope - 2 hands, one on arm and one on base

2. Positions microscope with nosepiece away from body

3. Positions objective correctly - starts with low power first and move to higher powers

4. Focus with coarse adjustment then fine adjustment

5. Knows location of diaphragm

6. Slide was in center of view and focused

• If performance not satisfactory, the student may repeat 1 time only within 1 week of the date the test was originally given.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Microscope Quiz

Instructions:

1. Get a microscope and turn it on.

2. Get the slide for this quiz from your teacher and put it on the microscope.

3. Focus the slide on low power and draw here what you see:

4. Focus the slide on medium power and draw here what you see:

5. Focus the slide on high power and draw here what you see:

6. Put the slide and the microscope away in the appropriate place.

Teacher's Guide (Microscope Quiz):

1. This is a simple quiz to help you determine if your students understand how to operate a microscope.

2. The quiz should be taken individually by each student, not in groups. You may wish to have one table or area designated for the quiz.

3. Any slide may be used for the quiz, but it may be helpful to pick one that has cells to go along with what you are studying.

4. Be sure that you have looked at the slide and made sketches so you will know what the objects look like at each power level and how many items they should see.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

Cell Organelles

Teacher's Guide:

1. This quiz will help you determine if your students can identify some of the basic structures when looking at real cells.

2. You need 2 microscope stations set up with the microscopes clearly labeled Microscope 1 and Microscope 2.

3. At Microscope 1, have a slide containing animal cells focused clearly on the best cells you can find. You can use a pre-made slide, or human cheek cell slides (easy to prepare). Make sure you can identify the cell membrane, cytoplasm and the nucleus of the cells.

4. At Microscope 2, have a slide containing plant cells focused clearly on the best cells that you can find. You can use a pre-made slide, or Elodea or onion skin cell slides (easy to prepare). Make sure you can identify the cell membrane, cell wall, cytoplasm, chloroplasts and the nucleus of the cells.

Cell Organelles

1. Look at the cells in Microscope 1. Draw a few of the cells below and be sure to sketch everything that you see.

2. Label the following cell parts in the cells you have drawn in #1: Cell Membrane, Cytoplasm, and Nucleus.

3. Look at the cells in Microscope 2. Draw a few of the cells below and be sure to sketch everything that you see.

4. Label the following cell parts in the cells you have drawn in #3: Cell Membrane, Cell Wall, Cytoplasm, Chloroplast and Nucleus.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

COMPARING AND CONTRASTING CELLS

Directions:

1. Look at the slides in the microscopes that your teacher has set up for you.

2. Write down all of the similarities of the two types of cells that you can see (Ignore color and size):

3. Now write down all of the differences between the two types of cells that you can see (Ignore color and size):

4. Slide A is an animal cell and Slide B is a plant cell. Look up these two types of cells in your test and write down other similarities in addition to those that you observed:

5. Now write down the differences that you did not observe:

Correct Answers:

2. There can be a variety of answers here but will probably include: both have a nucleus, both have a cell membrane, both have cytoplasm, etc.

3. There can be a variety of answers here but will probably include: one cell has a thick cell wall, one cell has green organelles and the other doesn't, they are different shapes, etc.

4. This answer will depend on the student's observations and what they find in their text.

5. This answer will depend on the student's observations and what they find in their text.

Teacher instructions:

Set up pairs of microscopes--one with an animal cell in focus and one with a plant cell in focus. You can use prepared slides, or prepare your own slides using onionskin or Elodea leaf cells and dyed cheek cells.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

OSMOSIS INVESTIGATION--1

This experiment will demonstrate osmosis, which is the movement of water from a higher to a lower concentration across a selectively permeable membrane.

Materials:

2 beakers

10% salt solution

string

carrot

ruler

Directions:

1. Fill one beaker half full with the 10% salt solution and fill the other beaker half full with water out of the tap.

2. Cut the carrot in half. Tightly tie a piece of string 2 cm from the cut end of both parts.

3. Place one carrot half in the beaker of salt water with the cut end down. Mark this beaker "salt".

4. Place the other carrot half with the cut end down into the beaker of tap water. Mark this beaker "tap".

5. Answer the preliminary questions below.

6. Allow the beakers to remain undisturbed for 24 hours. Remove the carrots and observe the tightness of the threads. Record your observations.

Preliminary questions:

1. What do you think will happen to the carrot in the "salt water" beaker? Why?

2. What do you think will happen to the carrot in the "tap water" beaker? Why?

Observations after 24 hours:

Follow up Questions:

1. In which situation did the carrot lose water? How can you tell?

2. In which situation did the carrot gain water? How can you tell?

3. Did the data support, or invalidate, your hypothesis?

4. How does this experiment demonstrate osmosis?

5. How does osmosis affect plant cells?

Correct Answers:

1. The carrot in the salt water--the string will be loose.

2. The carrot in the tap water--the string will be tight.

3. Answers will vary.

4. Water moved either in or out of the carrot cells through the in membranes, depending on the concentration of salt.

5. Plant cells in a salty environment will lose water, and those in fresh water will gain water.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

OSMOSIS INVESTIGATION--2

This experiment will demonstrate osmosis, which is the movement of water from a higher to a lower concentration across a selectively permeable membrane.

Materials:

2 beakers

10% salt solution

Potato

Balance

Directions:

1. Fill one beaker half full with the 10% salt solution and fill the other beaker half full with water out of the tap.

2. As best you can, cut two identically sized pieces of potato.

3. Weigh each piece of potato carefully on the balance and record their respective weights.

Weight of Potato #1 _____ Weight of Potato #2 _____

4. Place Potato #1 in the salt solution. Mark the beaker "Salt".

5. Place Potato #2 in the beaker of tap water. Mark the beaker "tap".

6. Answer the preliminary questions below.

7. Allow the beakers to remain undisturbed for 24 hours. Remove the potatoes weigh each one again. Record these weights and any other observations.

Preliminary Questions:

1. What do you think will happen to the potato in the "salt" beaker? Why?

2. What do you think will happen to the potato in the "tap" beaker? Why?

Weight of Potato #1 _____ Weight of Potato #2 _____

Observations:

Follow Up Questions:

1. In which situation did the potato lose water? How can you tell?

2. In which situation did the potato gain water? How can you tell?

3. Did the data support, or invalidate, your hypothesis?

4. How does this experiment demonstrate osmosis?

5. How does osmosis affect plant cells?

Correct Answers:

1. The potato in the salt water--it will weigh less.

2. The potato in the tap water--it will weigh more.

3. Answers will vary.

4. Water moved either in or out of the potato cells through the in membranes, depending on the concentration of salt.

5. Plant cells in a salty environment will lose water, and those in fresh water will gain water.

P	7^th Grade Integrated Science	Standard: 03
Objective: 01. Observe and describe cellular structures and functions.
ILO:

OSMOSIS INVESTIGATION--3

This experiment will demonstrate osmosis, which is the movement of water from a higher to a lower concentration across a selectively permeable membrane.

Materials:

Microscope

3 slides and cover slips

Aquarium water

10% salt water

Distilled water

Elodea leaves

Grease pencil

Directions:

1. Use the grease pencil to label the first slide “a” for “Aquarium water”, the second slide “s” for “Salt water”, and the third slide “d” for "Distilled water".

2. Place several drops of the liquid named on the label onto the center of the slide that bears that label.

3. Select three small Elodea leaves, and place each one in the liquid on the center of the slide. Add a cover slip.

4. Examine each slide under the microscope using first low power, then high power. In the space provided, draw and label a typical cell from each leaf as it appears under high power. Notice the size of the vacuole in each cell.

Cells in aquarium water:

Cells in salt water:

Cells in distilled water:

Follow Up Question:

1. Explain what you observed in each of the leaf cells and how that relates to osmosis.

Correct Answer: The cells will be isotonic in respect to the aquarium water so there will be no net loss or gain of water due to osmosis. The cells in the salt water will lose water and the vacuoles will be small and maybe non-existent. The cells in the distilled water will gain water by osmosis and the vacuoles will be large and swollen.