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Viruses & Bacteria

Name: ________________

Hour: ____

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Vocabulary and Big Ideas

Viruses Bacteria

virus

host parasite

vaccine

bacteria

cytoplasm

ribosome

flagellum

cellular respiration

binary fission

conjugation

endospore

pasteurization

decomposer

Long-term “I Can” Statements

Viruses Bacteria

I can… Date done Activity to support

I can… Date done Activity to support

…list the characteristics of viruses.

...draw and label a bacterial cell and its structures.

…explain how a virus is similar to a parasite.

…classify bacteria by its shape.

...understand how small a virus is.

…list and explain how bacteria get food, get energy, and reproduce.

…draw how a virus attaches to a host cell.

…differentiate between asexual and sexual reproduction.

…explain how viruses interact with the living world.

…understand bacteria’s role in nature.

…describe how a vaccine works.

Unit: Viruses & Bacteria Unit Completion Date:

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How Many Viruses Fit on the Head of a Pin? Problem How small is a virus? Materials straight pin long strips of paper pencil meter stick scissors tape calculator imagination Procedure

1. Carefully, examine the head of a straight pin. Write a prediction about the number of viruses that could fit on the pinhead.

My prediction is: __________________ viruses.

2. Assume that the pinhead has a diameter of about 1 mm. If the pinhead were

enlarged 10,000 times, its diameter would measure 10 m. Create a model of a pinhead by cutting and taping together narrow strips of paper to make a strip that is 10 m long. The strip of paper represents the diameter of the enlarged pinhead.

3. Lay the 10 m strip of paper on the floor. Imagine creating a large circle that had

the strip as its diameter. The circle would be the pinhead at the enlarged size. Calculate the area of the enlarged pinhead using this formula:

A = π x radius2 = __________________ m2

4. A virus particle may measure 200 nm on each side (1 nm equals a billionth of a

meter). If the virus were enlarged 10,000 times, each side would measure 0.002 m. Cut out a square 0.002 m by 0.002 m to serve as a model for a virus. (Hint: 0.002 m = 2 mm).

5. Next, find the area in meters of one virus particle at the enlarged size. Remember that the area of a square equals side x side.

A = __________________ m2

6. Now divide the area of the pinhead that you calculated in Step 3 by the area of

one virus particle (Step 5) to find out how many viruses could fit on the pinhead.

__________________ viruses

7. Exchange your work with a partner, and check each other’s calculations.

Calculations:

d

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How Many Viruses Fit on the Head of a Pin? CONTINUED… Conclusion

1. How does your calculation compare with the prediction you made? If the two numbers are very different, explain why your prediction may have been inaccurate.

2. What did you learn about the size of viruses by magnifying both the viruses and pinheads to 10,000 times their actual size?

3. Explain why scientists sometimes make and use enlarged models of very small things, such as viruses.

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How Viruses Spread Vaccines are substances that help protect against diseases caused by

viruses. In this activity, you will see how vaccines affect the spread of

viral “diseases” in your classroom.

INQUIRY FOCUS Relate Evidence and Explanation

Procedure

1. Study your Vaccination Card. There are five imaginary

viruses that will circulate through the classroom. Your Vaccination Card lists the viruses and indicates which

vaccines you have received.

2. When you are handed a Virus Card, check to see if you are vaccinated for that virus.

3. Then, follow the appropriate instructions on the Virus

Card. When you receive a virus for which you are not vaccinated, you will be immune to that virus in the future.

4. Classmates who are immune to a particular virus or have already had that virus

will not accept that Virus Card from you. Keep trying to give the card to someone

until you succeed.

Think It Over

Based on the summary of how many students “caught” each virus, which viruses

were the most people vaccinated for?

If you had complete immunity for a particular virus, why did you give the Virus

Card back to the person who gave it to you?

Use the evidence you gathered in this activity to explain why vaccines are

important for preventing the spread of a viral disease.

Materials

1 Vaccination Card per student

5 Virus Cards

collection of “aprons” and “goggles”

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7

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Viruses

1. Viruses are considered to be nonliving. How are they similar to living organisms and how are they

different?

2. How are viruses similar to parasites?

3. In the diagram below, what is the structure and function of the part labeled “A”?

4. In the diagram below, what is the structure and function of the part labeled “B”?

5. virus

6. host

7. parasite

8. vaccine

a. an organism that lives on or in a host and causes it harm

b. a substance introduced in the body to help produce chemicals that destroy specific viruses

c. an organism that provides a source of energy for a virus or another organism

d. a tiny, nonliving particle that enters and then reproduces inside a living cell

Understanding Main Ideas

Answer the following questions.

Building Vocabulary

Match each term with its definition by writing the letter of the correct definition in the right column on the line beside the term in the left column.

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Viruses

Viral Multiplication

Different kinds of viruses multiply at different rates. The rate at which a virus multiplies and when and how this multiplication takes place can help to identify the virus. The graph below shows the rate of growth of four groups of animal viruses, that is, viruses that infect animal cells.

To collect the data for the graph above, scientists grew viruses in the laboratory. Counting viruses is very difficult because they are so small. It’s much easier to measure how effective a virus is at killing cells. So in the graph, the y-axis of the graph shows the number of cells that have been destroyed because of viral activity. For each kind of virus, a higher number of cells killed by the virus means a higher number of virus particles.

1. Which kind of virus begins multiplying first? How soon after infection does this happen?

2. Which kind of virus begins multiplying last? How soon after infection does this happen?

3. What is similar about the four lines on the graph? What does this mean about the growth rate of the four kinds of virus groups?

4. The upper part of the line representing the growth curve of the herpesvirus is nearly horizontal. What

does this mean about the rate of multiplication of the herpesvirus from 15 to 20 hours after infection?

Read the passage and study the graph below. Then, answer the questions that follow.

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How Quickly Can Bacteria Multiply? A bacterium can reproduce every twenty minutes. At this rate, imagine

how large a bacteria population could become in one day!

INQUIRY FOCUS Graph

Procedure

1. Your teacher will give you some beans and plastic

cups. Number the cups 1 through 8. Each bean will represent a bacterial cell.

2. Put one bean into Cup 1 to represent the first generation of bacteria. Approximately every

20 minutes, a bacterial cell reproduces by dividing

into two cells. Put two beans into Cup 2 to represent the second generation of bacteria.

3. Calculate how many bacterial cells there would be in the third generation if each

cell in Cup 2 divided into two cells. Place the correct number of beans in Cup 3.

4. Repeat Step 3 five more times for each of your cups. All the cups should now

contain beans. How many cells are in the eighth generation? How much time has

elapsed since the first generation?

Think It Over

In the box below, create a line graph to show how the population of bacteria increased in this

activity. The x-axis (horizontal) should represent time (use 20 minute generation time, not the

time it took you to do the activity). The y-axis (vertical) should represent population size.

Based on this activity, explain why the number of bacteria can increase rapidly in a

short period of time.

Materials

260 dried beans

8 plastic cups

marking pen

graph paper

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Bacteria

1. INFER Why would being able to reproduce quickly be advantageous to an organism? Explain.

2. INFER How could an organism able to reproduce quickly be dangerous

to other organisms? Explain.

3. INFER Would it be harder for your body to fight off an infection from

an organism that reproduced quickly or one that reproduced slowly? Explain.

4. DRAWING CONCLUSIONS Based on the results you observed in the

lab, do you think there are more people or more bacteria on Earth? Explain.

Inquiry Warm-Up, How Quickly Can Bacteria Multiply?

In the Inquiry Warm-Up, you investigated how quickly bacteria can reproduce. Using what you learned from that activity, answer the questions below.

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Classifying Bacteria Bacteria are everywhere. Despite their microscopic size, bacteria vary

greatly in size, color, and shape. In this activity, you will observe a few

types of bacteria using a light microscope.

INQUIRY FOCUS Observe

Procedure

1. Your teacher will provide you with at least three different slides of bacteria.

2. Look at each slide under the light microscope. Make a sketch of the bacteria you see on each

slide. If possible, give a size estimate for each

type of bacterium.

Think It Over

Compare and contrast the different bacteria you observed.

Look at the photos provided by your teacher that show the different shapes of

bacteria. Label your sketches of the bacteria as cocci, bacilli, or spirilla.

Materials

light microscope

prepared slides of different bacteria species

Photographs of cocci, bacilli, and spirilla

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Role of Bacteria in Nature NOTES

Process Role of Bacteria

(explain how, if it is helpful/harmful, etc.)

Oxygen Production

Food Production

Health & Medicine

Environmental Cleanup

Environmental Recycling

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Drawing Conclusions: Bacteria

Decomposers are organisms that break down large molecules within

organisms into smaller molecules. In this activity, you will investigate the

role of bacteria as decomposers.

INQUIRY FOCUS Draw Conclusions

Procedure

1. Put several lettuce leaves on two different plates.

2. Place one plate in the refrigerator. Place the other plate in a warm place. Allow the plates to sit for several days.

3. After several days, observe the lettuce. Describe what you see.

_________________________________________________________________________

_________________________________________________________________________

4. Wash your hands with warm water and soap.

Think It Over What has made the lettuce change as it did?

________________________________________________________________________

________________________________________________________________________

How does temperature affect the growth of some bacteria?

________________________________________________________________________

________________________________________________________________________

What can you conclude about how bacteria on the lettuce are similar to the

bacteria that act as decomposers in the environment?

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Materials

lettuce leaves

2 plates

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Bacteria

1. How are bacterial cells different from the cells of eukaryotes?

2. List four ways that bacteria are helpful to people.

3. bacteria

4. cytoplasm

5. ribosomes

6. flagellum

7. cellular respiration

8. binary fission

9. conjugation

10. endospore

11. pasteurization

12. decomposers

a. tiny structures that produce proteins inside bacteria

b. a process by which bacteria reproduce asexually

c. organisms that break down large, complex chemicals in dead organisms into small, simple chemicals

d. the region inside the cell membrane of a bacterium

e. a process by which bacteria reproduce sexually

f. the process of breaking down food to release energy

g. tiny single-celled organisms that live almost everywhere

h. a method of slowing down food spoilage

i. a small, rounded, thick-walled resting cell inside a bacterial cell

j. a whip-like structure that helps a bacterial cell to move

Building Vocabulary

Match each term with its definition by writing the letter of the correct definition in the right column on the line beside the term in the left column.

Understanding Main Ideas

Answer the following questions.

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Bacteria

Identifying Bacteria

Thousands of different kinds of bacteria inhabit Earth. Each kind can be distinguished from the others by

its characteristics. In addition to shape, these characteristics include: whether it will grow in water hotter

than 45°C; whether it will grow in very salty water; whether it will grow in the presence of air; whether

it will grow without air; and whether it forms endospores.

Scientists who study bacteria use these and about 15 other characteristics to identify a bacterium. In

the table below, a plus (+) sign means the bacterium has the characteristic. A minus (−) sign means the

bacterium does not have the characteristic.

1. What characteristic do all of the bacteria have in common?

2. How could you distinguish bacterium 1 from bacterium 2?

3. Which bacteria might be found in hot springs?

4. What characteristic(s) can you use to distinguish the spherical bacteria from one another?

5. Sea water is about 3.5% salt. In some places, sea water gets trapped when the tide goes out. The heat of the sun will cause some of this water to evaporate. Which bacteria are most likely to survive in such water? Explain your answer.

The table below shows the characteristics of some bacteria. Read the passage below and study the table. Then, answer the questions that follow.

Bacterium Rod Sphere Grows at 45°C

Grows in 6.5% Salt Water

Grows in Air

Grows Without Air

Endospores

1 + − + unknown + + +

2 + − + unknown − + +

3 − + − + + + −

4 + – + − − + −

5 − + − − + + −

6 − + + − + + −

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Name Date Class

Lab Investigation

Comparing Disinfectants Reviewing Content

Television commercials and magazine ads make

claims that disinfectants are effective in killing

almost all bacteria and viruses. Yet, when you

use a disinfectant on your kitchen counter, how

can you be sure it has done its job? Because

bacteria are invisible to the naked eye, it is

impossible to know immediately whether or not

a disinfectant is actually killing the germs.

It is possible, however, to conduct an

experiment to measure the effectiveness

of a disinfectant. Agar plates are petri dishes

filled with agar. You can inoculate an agar plate

with bacteria. Over a period of a few days, the

bacteria will reproduce so much that you will

actually be able to see colonies of bacteria with

your naked eye. In this activity, you will put disinfectants

on some of the agar plates to determine how effective the

disinfectants are at preventing bacterial growth.

Reviewing Inquiry Focus

Drawing conclusions involves explaining what the data from an

experiment mean. Why are the data important? What trends do the

data show? In the process of drawing a conclusion, scientists analyze

and interpret the data from their experiment and determine whether

their hypothesis is supported. If the hypothesis is unsupported

by the data, a scientist might decide whether to do more research

on the subject. Read through the lab procedure and answer the

following questions.

If a bacterium can divide every

10 minutes, how many bacteria

could there be in a petri dish after two hours if there was only one

bacterium to begin with? How

many will there be in four hours?

What will you be drawing a conclusion about in this lab?

A scientist conducts an experiment to determine the effect of fertilizer on tomato

plant growth. Which of the following could be a conclusion from that experiment?

• Fertilizer improves tomato plant growth.

• Tomato plant A grew 10 cm.

• Fertilizer provides plants with additional nitrogen.

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Comparing Disinfectants

Problem

How well do different disinfectants limit the growth of bacteria?

How well do different of ba?

1. Work with a partner. Obtain three petri dishes containing sterile nutrient agar. Without opening them, use a grease pencil to label the bottoms A, B, and C. Write your initials on each plate.

2. Wash your hands thoroughly with soap, and then run a fingertip across the surface of your worktable. Your partner should hold open the cover of Petri Dish A, while you run that fingertip gently across the agar in a zig-zag motion. Close the dish immediately.

3. Repeat Step 2 for dishes B and C.

4. Use a plastic dropper to transfer two drops of one disinfectant to the center of Petri Dish A. Open the cover just long enough to add the disinfectant to the dish. Close the cover immediately. Record the name of the disinfectant in your data table. CAUTION: Do not inhale vapors from the disinfectant.

5. Repeat Step 4 for Dish B but add two drops of the other disinfectant. CAUTION: Do not mix any disinfectants together.

6. Do not add any disinfectant to Dish C.

7. Seal the covers by taping them all around so that they will remain tightly closed. Allow the three dishes to sit upright on your work surface for at least five minutes. CAUTION: Do not open the petri dishes again. Wash your hands with soap and water.

INQUIRY FOCUS Observe, Control Variables, Draw Conclusions

Materials

clock

grease pencil

2 plastic droppers

transparent tape

2 household disinfectants

3 plastic petri dishes with sterile nutrient agar

Procedure

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Name Date Class

Lab Investigation

8. As directed by your teacher, store the petri dishes upside down in a warm, dark place where they can remain for at least three days. Remove them only to make a brief examination each day.

9. After one day, observe the contents of each dish without removing the covers. Estimate the percentage of the agar surface that shows any changes. Record your observations. Return the dishes to their storage place when you have finished making your observations. Wash your hands with warm water and soap.

10. Repeat Step 9 after the second day and again after the third day.

11. After you and your partner have made your last observations, return the petri dishes to your teacher unopened. Wash your hands with soap and water.

COMPARING DISINFECTANTS continued

Data Table

Petri Dish Disinfectant Day 1 Day 2 Day 3

A

B

C

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Name Date Class

Lab Investigation

Analyze and Conclude

Observe How did the appearance of Dish C change during the lab?

Interpret Data How did the appearance of Dishes A and B compare

with Dish C?

Draw Conclusions How did the appearance of Dishes A and B

compare with each other? What can you conclude about the two

disinfectants from your observations?

Control Variables Why was it important to use one petri dish that did

not contain any disinfectant?

COMPARING

DISINFECTANTS continued

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Name Date Class

Lab Investigation

Comparing Disinfectants

Design an Experiment Describe how you would design an experiment

to test how well antibacterial soaps control the growth of bacteria.

Interpret Data Compare your results with those of the other groups

in your class. How can you account for similarities and differences

among the results?

Summarize Explain what you have learned about the use of disinfectants

to control bacteria and what you would still like to know.

What I learned

What I still want to know

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Virus and Bacteria Venn Diagram

Living or non-living?

_____________________________

Living or non-living?

________________________________

What are the basic shapes?

________________________________

_______________________________

How does it reproduce?

________________________________

________________________________

How does it reproduce?

________________________________

________________________________

How does it act in your body?

________________________________

________________________________

How does it act in your body?

________________________________

________________________________ How is it treated/prevented?

________________________________

_______________________________

How is it treated/prevented?

________________________________

_________________________________

What are some common examples?

______________________________

_______________________

What are some common examples?

_______________________________

_______________________

What are the basic shapes?

________________________________

________________________________

Virus Bacteria

Size?

_____

_____

Enters body?

__________

__________ Prevented by?

___________

__________

___________ Called?

________

_______