Unit 1 Target 8-experimental Design Quiz

1. How many independent variables should there be in a controlled experiment?

In a controlled experiment, there should be one independent variable. This is because the purpose of a controlled experiment is to isolate and manipulate a single factor to observe its effects on the dependent variable. By controlling all other variables, the researcher can determine the specific impact of the independent variable on the outcome. Having more than one independent variable would make it difficult to determine which variable is responsible for any observed changes in the dependent variable.

Explanation

In a controlled experiment, there should be one independent variable. This is because the purpose of a controlled experiment is to isolate and manipulate a single factor to observe its effects on the dependent variable. By controlling all other variables, the researcher can determine the specific impact of the independent variable on the outcome. Having more than one independent variable would make it difficult to determine which variable is responsible for any observed changes in the dependent variable.

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2. Other than the independent variable, all other factors in the experiment should be kept ___ for both the experimental group and control group.

In order to accurately determine the effect of the independent variable on the experimental group, it is important to keep all other factors constant or the same for both the experimental group and control group. This ensures that any differences observed between the two groups can be attributed solely to the independent variable and not to any other factors. By maintaining identical conditions, the researcher can isolate the impact of the independent variable and draw valid conclusions from the experiment.

Explanation

In order to accurately determine the effect of the independent variable on the experimental group, it is important to keep all other factors constant or the same for both the experimental group and control group. This ensures that any differences observed between the two groups can be attributed solely to the independent variable and not to any other factors. By maintaining identical conditions, the researcher can isolate the impact of the independent variable and draw valid conclusions from the experiment.

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3. Mrs. Lewis set up a lab for her biology students using a culture of the small crustacean Daphnia, obtained from a pond that was 20°C. The students are to investigate the effect temperature has on Daphnia. The students will observe the crustacean's heartbeat under the microscope, at the following temperatures: 0°C, 10°C, 20°C, 30°C, and 40°C. They will count the number of heartbeats per sec.What is the independent variable in the experiment?

Number of heartbeats/sec

Temperature of the samples

Type of microscope used

Number of Daphnia in the cultures

The independent variable in the experiment is the temperature of the samples. This is because the students are investigating the effect temperature has on Daphnia's heartbeat. They are manipulating the temperature by observing the crustacean's heartbeat at different temperature levels. The number of heartbeats per second is the dependent variable, as it is the outcome that is being measured and observed in response to the changes in temperature. The type of microscope used and the number of Daphnia in the cultures are not mentioned as factors being manipulated or observed in this experiment.

Explanation

The independent variable in the experiment is the temperature of the samples. This is because the students are investigating the effect temperature has on Daphnia's heartbeat. They are manipulating the temperature by observing the crustacean's heartbeat at different temperature levels. The number of heartbeats per second is the dependent variable, as it is the outcome that is being measured and observed in response to the changes in temperature. The type of microscope used and the number of Daphnia in the cultures are not mentioned as factors being manipulated or observed in this experiment.

4. Dr. Hansen performs an experiment testing the effectiveness of different cough syrups. Identify the dependent variable in the experiment.

Type of cough syrup

Effectiveness of the cough syrup

Number of people taking each cough syrup

Number of days people take each cough syrup

The dependent variable in this experiment is the effectiveness of the cough syrup. This is because the effectiveness of the cough syrup is what is being measured and observed in response to the different types of cough syrup being tested. The other options provided, such as the type of cough syrup, the number of people taking each cough syrup, and the number of days people take each cough syrup, are not the variables being measured or observed in this experiment.

Explanation

The dependent variable in this experiment is the effectiveness of the cough syrup. This is because the effectiveness of the cough syrup is what is being measured and observed in response to the different types of cough syrup being tested. The other options provided, such as the type of cough syrup, the number of people taking each cough syrup, and the number of days people take each cough syrup, are not the variables being measured or observed in this experiment.

5. Morgan hypothesizes that the activity of amylase, an enzyme that catalyses the breakdown of starch, will be greater at 37°C than at 25°C. She prepares 2 tubes: Tube 1 and Tube 2. Morgan adds 2 g of starch and 1 mL of an enzyme suspension to Tube 1 and incubates it at 37°C for 20 min. To accurately test her hypothesis, Morgan should add 2 g of the starch and 1 mL of the enzyme suspension to Tube 2 and incubate it at ______ for ______.

25°C; 20 min

37°C; 20 min

25°C; 10 min

37°C 10 min

Based on Morgan's hypothesis that the activity of amylase is greater at 37°C than at 25°C, she prepares two tubes with the same amount of starch and enzyme suspension. To accurately test her hypothesis, Tube 2 should be incubated at 25°C for 20 minutes. By comparing the activity of amylase in Tube 1 (incubated at 37°C) and Tube 2 (incubated at 25°C), Morgan can determine if the enzyme's activity is indeed greater at 37°C as hypothesized.

Explanation

Based on Morgan's hypothesis that the activity of amylase is greater at 37°C than at 25°C, she prepares two tubes with the same amount of starch and enzyme suspension. To accurately test her hypothesis, Tube 2 should be incubated at 25°C for 20 minutes. By comparing the activity of amylase in Tube 1 (incubated at 37°C) and Tube 2 (incubated at 25°C), Morgan can determine if the enzyme's activity is indeed greater at 37°C as hypothesized.

6. Ebola virus is a potentially deadly virus in the blood which causes Ebola fever. Ebola virus is often spread by monkeys. Scientists used 2 groups of monkey kidney cells in an experiment to confirm the first human case of Ebola fever. The scientists inoculated cells in Group 1 with samples of the Ebola virus taken from a human with Ebola fever. They did not inoculate the cells in Group 2. What was the control group in the experiment?

The Ebola virus

All of the monkey kidney cells

Monkey kidney cells in Group 1

Monkey kidney cells in Group 2

The control group in the experiment was the monkey kidney cells in Group 2. This is because the scientists did not inoculate these cells with samples of the Ebola virus, serving as a baseline comparison to observe the effects of the virus on the cells in Group 1. By not introducing the virus to the cells in Group 2, any changes observed in Group 1 can be attributed to the presence of the Ebola virus rather than other factors.

Explanation

The control group in the experiment was the monkey kidney cells in Group 2. This is because the scientists did not inoculate these cells with samples of the Ebola virus, serving as a baseline comparison to observe the effects of the virus on the cells in Group 1. By not introducing the virus to the cells in Group 2, any changes observed in Group 1 can be attributed to the presence of the Ebola virus rather than other factors.

7. Lydia works in a flower shop after school. She notices that the hydrangeas inContainer 1 have pink blossoms, while the hydrangeas in Container 2 have blueblossoms. She makes sure they all receive the same amount of light and water. Her boss tells her that the flowers were all grown from the same seed variety. Lydia discovers, after testing the soil, that although the same type of soil was used, the soil in Container 1 has a pH of 6.0, and the soil in Container 2 has a pH of 5.0.Lydia most likely conducted her investigation to answer what question about hydrangeas?

How does the chemistry of the soil affect the color of hydrangea blossoms?

What role do genetic factors play in hydrangea color?

Do varying degrees of light affect hydrangea color?

What type of soil will produce a hydrangea with both pink and blue blossoms?

Lydia conducted her investigation to answer the question of how the chemistry of the soil affects the color of hydrangea blossoms. She noticed that the hydrangeas in Container 1 had pink blossoms, while those in Container 2 had blue blossoms. Despite receiving the same amount of light and water, she discovered that the soil in Container 1 had a pH of 6.0, while the soil in Container 2 had a pH of 5.0. This suggests that the pH level of the soil plays a role in determining the color of the hydrangea blossoms.

Explanation

Lydia conducted her investigation to answer the question of how the chemistry of the soil affects the color of hydrangea blossoms. She noticed that the hydrangeas in Container 1 had pink blossoms, while those in Container 2 had blue blossoms. Despite receiving the same amount of light and water, she discovered that the soil in Container 1 had a pH of 6.0, while the soil in Container 2 had a pH of 5.0. This suggests that the pH level of the soil plays a role in determining the color of the hydrangea blossoms.

8. Mrs. Lewis set up a lab for her biology students using a culture of the small crustacean Daphnia, obtained from a pond that was 20°C. The students are to investigate the effect temperature has on Daphnia. The students will observe the crustacean's heartbeat under the microscope, at the following temperatures: 0°C, 10°C, 20°C, 30°C, and 40°C. They will count the number of heartbeats per sec.If the experiment is designed correctly, what will the students choose for the experimental treatment?

Placing 5 identical cultures of Daphnia at 20°C

Placing 5 of each identical cultures of Daphnia at a different temperature

Placing 5 cultures, each with a different type of crustacean, at 20°C

Placing 5 cultures, each with a different type of crustacean, at a different temperature

The students will choose to place 5 identical cultures of Daphnia at different temperatures. This is because the objective of the experiment is to investigate the effect of temperature on Daphnia's heartbeat. By having 5 identical cultures at different temperatures, the students can compare the heartbeats per second at each temperature and determine the effect of temperature on Daphnia's heartbeat.

Explanation

The students will choose to place 5 identical cultures of Daphnia at different temperatures. This is because the objective of the experiment is to investigate the effect of temperature on Daphnia's heartbeat. By having 5 identical cultures at different temperatures, the students can compare the heartbeats per second at each temperature and determine the effect of temperature on Daphnia's heartbeat.

9. Aisha wants to conduct an experiment to determine whether sun and shade varieties of the same plant species prefer the same wavelengths of light. She plans to measure rates of photosynthesis. Which design would be best for her experiment.

1 plant of the sun variety tested under blue light only, and 1 plant of the shade variety tested under blue light only

4 plants of the sun variety: 1 tested under blue light, 1 under green, 1 under red, and 1 under yellow light with 4 plants of the shade variety: 1 tested under blue light, 1 under green, 1 under red, and 1 under yellow light

10 plants of the sun variety tested under blue light only; and 10 plants of the shade variety tested under blue light only

40 plants of the sun variety: 10 tested under blue light, 10 under green, 10 under red, and 10 under yellow light with 40 plants of the shade variety: 10 tested under blue light, 10 under green, 10 under red, and 10 under yellow light

The best design for Aisha's experiment would be to have 40 plants of the sun variety and 40 plants of the shade variety, with each group being tested under blue, green, red, and yellow light. This design allows for a more comprehensive comparison between the sun and shade varieties, as well as the different wavelengths of light. By having a larger sample size and testing each variety under different light conditions, Aisha can gather more reliable data and draw more accurate conclusions about the preferences of each variety for different wavelengths of light.

Explanation

The best design for Aisha's experiment would be to have 40 plants of the sun variety and 40 plants of the shade variety, with each group being tested under blue, green, red, and yellow light. This design allows for a more comprehensive comparison between the sun and shade varieties, as well as the different wavelengths of light. By having a larger sample size and testing each variety under different light conditions, Aisha can gather more reliable data and draw more accurate conclusions about the preferences of each variety for different wavelengths of light.

10. Scientific experimentation can most likely answer which question regarding a bird population?

How does a baby bird learn to recognize the type of food it can eat?

How does the type of food a bird eats affect the number of offspring it produces?

What is the relationship between beak size and the number of offspring a bird produces?

Why does a bird with a very short beak produce more offspring than a bird with a very long beak?

Scientific experimentation can most likely answer the question of what is the relationship between beak size and the number of offspring a bird produces. By conducting experiments and collecting data on birds with different beak sizes and their reproductive success, scientists can determine if there is a correlation between beak size and the number of offspring produced. This type of experimentation can help understand the evolutionary adaptations of birds and how beak size may impact their reproductive fitness.

Explanation

Scientific experimentation can most likely answer the question of what is the relationship between beak size and the number of offspring a bird produces. By conducting experiments and collecting data on birds with different beak sizes and their reproductive success, scientists can determine if there is a correlation between beak size and the number of offspring produced. This type of experimentation can help understand the evolutionary adaptations of birds and how beak size may impact their reproductive fitness.