Name: ___________________________________________________________ Honors Biology

Welcome to Honors Biology! In order to start the new school year off on the right foot, complete these practice problems. There are

readings and helpful videos to watch if you need them. Identifying variables, creating hypotheses and

making and interpreting graphs are skills needed throughout all of your high school science career.

Starting your freshman year off understanding how to accomplish these skills with mastery is key to being

successful. Please bring this finished packet with you in the fall, either electronic or paper copy.

We look forward to meeting you and a year full of experimenting together!

- Biology Honors Teachers

Identifying Variables & Hypothesis Review HELPFUL VIDEOS

“Independent and Dependent Variables” - https://youtu.be/-mVHzIDN0A8

“ What are Independent, Dependent and Controlled Variables” - https://youtu.be/iaewZmc4TYQ

“Independent and Dependent Variables Made Easy” - https://youtu.be/_VdOB4JJE_8

“Writing a Hypothesis” - https://youtu.be/2sb6gw688Co

“What is a Hypothesis?” - https://youtu.be/id1OrxsIhQ0

HOW TO IDENTIFY VARIABLES Independent Variable- One thing that the experimenter changes on purpose

Dependent Variable- Something that changes as a result of the independent variable (often what is measured)

Constant/Control Variable – Something kept the same on purpose

EXPERIMENT SET-UP

Experimental Group- is a test sample or the group that receives an experimental procedure. This group is exposed to

changes in the independent variable being tested. The values of the independent variable and the impact on the dependent

variable are recorded. An experiment may include multiple experimental groups at one time.

Control Group- is a group separated from the rest of the experiment such that the independent variable being tested

cannot influence the results. This isolates the independent variable's effects on the experiment and can help rule out

alternative explanations of the experimental results.

HOW TO WRITE A GOOD HYPOTHESIS USING “IF… THEN… BECAUSE…” An “If… then…because” statement in a hypothesis tells the readers what you believe will happen in an investigation when

something is changed, so you can see the effect of the change.

IF…tells the readers what will be changed. This is the manipulated (independent) variable in the

investigation.

THEN… tells the reader what will happen because of the change (manipulated variable) described in the If…

statement. This is the responding (dependent) variable in the investigation.

BECAUSE… tells the reader how you know this will occur. It should be based on something you have

experienced, or perhaps something you infer.

Examples:

If 7th graders and 8th graders complete the same math problems, then the 8th graders will have more

answers correct, because they have studied math for one year longer than the 7th graders.

If some students eat breakfast before school and others do not, then the ones who do eat breakfast will

have better grades in their morning classes, because their brains have more energy to think.

Practice Problems #1-6

DIRECTIONS: For each testable question (1 thru 6), UNDERLINE the independent variable, circle the dependent

variable, and list 3 constant/control variables. Then write a hypothesis in correct form.

1) How does the distance from an eye chart affect the number of letters that are recognized on a line?

Constant/Control Variables: optometrist’s office , not wearing contact lenses or glasses, both eyes open.

Hypothesis: If a person getting their eye exam stands closer to the eye chart, such as 10 feet,

then they will recognize more letters

because the eye exam was created for a person to stand 20 feet away

2) How does the amount of light affect the growth of a plant?

Constant/Control Variables: _________________________________________________

Hypothesis: If_____________________________________________________________________

then __________________________________________________________________

because _______________________________________________________________

3) How does the amount of oxygen in the water affect the oyster population?

Constant/Control Variables: _________________________________________________

Hypothesis: If_____________________________________________________________________

then __________________________________________________________________

because _______________________________________________________________

4) How will the amount of fertilizer used on a field affect the number of earthworms found there?

Constant/Control Variables: _________________________________________________

Hypothesis: If_____________________________________________________________________

then __________________________________________________________________

because _______________________________________________________________

5) How does the length of a string affect the number of times a pendulum will swing back and forth in 10 seconds?

Constant/Control Variables: _________________________________________________

Hypothesis: If_____________________________________________________________________

then __________________________________________________________________

because _______________________________________________________________

6) How does the size of a bicycle tire affect the distance it will travel when it is pedaled in a given number of times?

Constant/Control Variables: _________________________________________________

Hypothesis: If_____________________________________________________________________

then __________________________________________________________________

because _______________________________________________________________

Practice Problems # 7 – 9

DIRECTIONS: For each scenario (7 thru 9), identify the independent, dependent and constant variables. Then state

the control and experimental groups.

7) Mr. Smith wanted to see if the color of light shined on a plant had an effect on the number of leaves it had. He

gathered a 2 groups of the same species of plants, gave them the same amount of water, and did the test for the

same amount of time. On one group of plants he used white light. On the second group he changed the light color to red. Identify:

Independent variable: Color of light

Dependent variable: Number of leaves

Constants: species of plant & amount of water, amount of time

Control group (What would Mr. Smith use as a control group?): The plants he used white light on

Experimental group (what would Mr. Smith use as a experimental group?) The plants he used red light on

8) You are managing a large feed lot of cattle. A pharmaceutical company wants you to try a new antibiotic to treat

shipping fever in newly arrived cattle. You are currently not using any antibiotic to treat shipping fever in your

cattle. The company claims that it is more effective and will save you money using this antibiotic. You will use the

same feed, water and conditions of the cattle. You will measure the temperature of the cattle’s fevers to see whether or not the new antibiotic works on treating shipping fever.

Independent variable: ________________________________________

Dependent variable: _________________________________________

Constants: ___________________________________ & ____________________________________

Control group: _____________________________________________________________________________________

Experimental group: _________________________________________________________________________________

9) A shopping mall wanted to determine whether the more expensive “Tough Stuff” floor wax was better than the

cheaper “Steel Seal” floor wax at protecting its floor tiles against scratches. One liter of each brand of floor wax

was applied to test sections of the main hall of the mall. The test sections were all the same size and were covered

with the same kind of tiles. After 3 weeks, the number of scratches in each of the test sections was counted to

observe the wax’s effectiveness.

Independent variable: ________________________________________

Dependent variable: _________________________________________

Constants: ___________________________________ & ____________________________________

Control group: _____________________________________________________________________________________

Experimental group: _________________________________________________________________________________

Practice Problems # 10 – 13

DIRECTIONS: For each scenario (10 thru 13) write a hypothesis.

10) The cooler the temperature in a lake, the more oxygen the water holds. Daniel notices that he catches more fish in a

lake that is cooler than 55 degrees. He wants to conduct a study so he can catch the most fish possible this year. He’s having trouble writing a hypothesis. Please help him.

Hypothesis: If the temperature of the lake is cooler than 55 degrees (independent variable)

Then the amount of fish available to catch is greater (dependent variable)

Because cold water can hold more oxygen, thus providing the fish more oxygen which leads greater

population numbers .

11) Kasey lives in Moab, Utah. She likes to mountain bike for miles and miles until she can’t bike anymore. She thinks that she can bike further when she drinks more than a liter of water before her bike ride. Please assist her in developing a hypothesis, so she can make the best of her future bike rides.

Hypothesis: If ____________________________________________________________ (independent variable)

Then __________________________________________________________ (dependent variable)

Because ________________________________________________________ .

12) Jimmy likes to work with his friend Joe on 7th grade science class labs. However, he notices that he tends to get lower grades when he does work with Joe, because he and Joe like to talk about basketball and not science. He’s decided to investigate if his science lab grades are higher when he works with Joe or if they’re higher when he works with someone else. He has set goals to become a better student, so could you please help him write a hypothesis for his study?

Hypothesis: If ____________________________________________________________ (independent variable)

Then __________________________________________________________ (dependent variable)

Because ________________________________________________________ .

13) Mr. Montanari has noticed that there is a wide range of grades that students get on tests, even though they are all in the same class. He wonders whether students, who study for 20 minutes per night, every night, get higher scores on tests or not. Mr. Montanari wants as many kids to be successful as possible. Please help him write a hypothesis about this problem.

Hypothesis: If ____________________________________________________________ (independent variable)

Then __________________________________________________________ (dependent variable)

Because ________________________________________________________ .

Graphing Review

INTRODUCTION Line graphs compare two variables. Each variable is plotted along an axis. A line graph has a vertical axis and a horizontal axis. For example, if you wanted to graph the height of a ball after you have thrown it, you would put time

along the horizontal, or x-axis, and height along the vertical, or y-axis.

HELPFUL VIDEOS “A Beginners Guide to Graphing” - https://youtu.be/9BkbYeTC6Mo

“Graphing Data by Hand” - https://youtu.be/GUYRMdcEs00

LINE GRAPHS ARE IMPORTANT TO SCIENCE FOR SEVERAL REASONS, SUCH AS:

• showing specific values of data. If one variable is known, the other can be determined.

• showing trends and relationships in data clearly. They visibly depict how one variable is affected by the other as

it increases or decreases.

• allowing the viewer to make predictions within recorded data, called interpolation, and to make predictions

about data not yet recorded, called extrapolation.

INTERPOLATION vs. EXTRAPOLATION Determine which of the examples below is interpolation and which is extrapolation. Explain why.

1. The value of Sarah’s car in 2004 was $17,500. ______________________________________________________

2. The value of Sarah’s car in 2008 was $1,900. _______________________________________________________

HOW TO CONSTRUCT A LINE GRAPH: 1. Identify the Variables & Label the Axes

a. Independent Variable – factor that is varied in an experiment and specifically controlled by the experimenter

i. Label along the x-axis (horizontal) – include units

ii. Typically found on the left side of a data table

b. Dependent Variable – factor that is measured in an experiment and will change as a result of the

independent variable

i. Label along the y-axis (vertical) – include units ii. Typically found on the right side of a data table

Independent vs. Dependent Variable Practice

A student wanted to observe how changing the temperature of the aquarium water would affect the

breathing rate of his goldfish.

o What is the independent variable? ___________________________________________

o What is the dependent variable? ____________________________________________

A student wanted to determine how tall corn would grow if different types of fertilizer were used.

o What is the independent variable? ___________________________________________

o What is the dependent variable? ____________________________________________

2. Determine the Graph Scale

a. Determine the magnitude (numeric value) of each variable

b. Establish a scale that best fits the range of each variable

c. Spread the graph to use the MOST available space (use at least ¾ of the graph)

d. Be consistent throughout each axes’ scale

3. Plot the data points

a. Plot each data value on the graph with a dot

b. If multiple sets of data are being plotted, use different colored lines and include a key

4. Draw the Graph

a. DO NOT connect the dots unless specifically told to do so

b. Draw one of the following types of graphs:

5. Title the Graph

a. Titles are used to clearly portray what the graph is about so be specific.

b. Titles are typically written as “Y-axis variable” vs. “X-axis variable” and are written at the top of the graph.

i. B est fit Straight Line

ii. Best fit Curved Line

iii. Best fit Peak Line

CONSTANT RELATIONSHIP - Change in one

variable has no effect on the other

DIRECT RELATIONSHIP - Both variables increase

together

INDIRECT RELATIONSHIP - As one variable increases,

the other decreases

Shows an optimum

Graphing Practice Practice Problem #14 Background: The thickness of the annual rings indicates what type of environmental situation was occurring the time of

the tree’s development. A thin ring usually indicates a rough period of development such as lack of water, forest fires,

or insect infestation. On the other hand, a thick ring means a prosperous period of development. Use the information

from the data table below to create a proper scientific graph and to answer the corresponding questions.

Age of Trees (in years) Average Thickness of Annual Rings in

Forest A (millimeters)

Average Thickness of Annual Rings in

Forest B (millimeters)

10 20 24

20 24 28

30 30 35

35 34 38

50 41 45

60 46 51

1. What is the dependent variable? ________________________________________________________________

2. What is the independent variable? _______________________________________________________________

3. What was the average thickness of annual rings for 40 year old trees in Forest A? _________________________

4. What is it called when you make predictions within given data, such as made in question #3? ________________

5. What was the mean thickness of annual rings for all trees found in Forest B? _____________________________

6. Based on the data shown, what can be concluded about the comparative health of Forest A & B? ____________

___________________________________________________________________________________________

7. What type of relationship (constant, direct, or indirect) exists between the age of trees and the average

thickness of the tree’s rings? Explain. ____________________________________________________________

Practice Problem #15 Background: Clams were placed into various temperatures of water. Use the information in the data table below in

order to create a proper scientific graph and to answer the corresponding questions.

Water Temperature (°C) Number of Developing Clams

15 72

20 92

25 120

30 140

35 99

40 72

45 36

50 0

1. What is the dependent variable? ________________________________________________________________

2. What is the independent variable? _______________________________________________________________

3. What is the optimum temperature for clam development? ___________________________________________

4. What is the mean number of clams per sample? ____________________________________________________

5. Approximately how many clams would be developing in 10 degree Celsius water? _________________________

6. What is it called when you make predictions about data not yet recorded, such as the prediction we made in

question number 5? ___________________________________________________________________________

Practice Problem #16 Background: Natalie sets out to run 15 kilometers. Every 30 minutes she checked her pedometer to determine how far

she had run. Use the data below to create a proper scientific graph and to answer the corresponding questions.

Time (minutes) Total Distance (km)

0 0

30 6.8

60 10.1

90 12

120 13.3

150 15

1. What is the dependent variable? ________________________________________________________________

2. What is the independent variable? _______________________________________________________________

3. How many kilometers had Natalie run after 40 minutes? _____________________________________________

4. What was Natalie’s average speed (in kilometers per hour) over the course of her run? ____________________

Practice Problem #17 Background: Match each story on the left with the graph it represents on the right. Each graph compares the distance a

car is from home compared to time.

____1. I had just left home when I realized I had forgotten my books, so I went back to pick them up.

____2. The battery on my electric car started to run down.

____3. Things went fine until I had a flat tire.

____4. I started out calmly, but sped up when I realized

I was going to be late.

Practice Problem #18 Background: The pie chart shows the

approximate percentages teenagers spend

doing various activities in a day. Use the

information in the pie chart to answer the questions below.

1. What percent of the day is spent

watching TV? _____

2. How many hours are spent sleeping? _____

3. What activity takes up the least

amount of time? _____________

4. What activity takes up a quarter of the day? ____________________

5. What two activities take up 50% of

the day? ____________________

6. What two activities take up 25% of the day? ____________________

Practice Problem #19 1. What is the dependent variable? ____________________

_______________________________________________

2. Does the price per bushel always increase with demand?

_______________________________________________

3. What is the quantity demanded when the price is $5

per bushel? ____________________________________

4. What is the price per bushel when the quantity

demanded is 80? ______________________________

B A

Time

D C

School 25 %

Phone 17 % Sleep

33 %

TV 13 %

Eat 8 %

Study 4 %

Teenage Activities in a Day

0

20

40

60

80

100

$1 $2 $3 $4 $5

Price per Bushel (dollars)

Quantity Demanded vs. Price Per Bushel

Series 1