ACT Science : How to find experimental design in biology

Study concepts, example questions & explanations for ACT Science

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Example Question #1 : How To Find Experimental Design In Biology

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The chart above shows the height growth of three different plant species after a period of 2 weeks. Each plant species was grown in 4 different soil mediums. All the plants were grown in the same environment with equal amounts of light, water, and oxygen. 

What factor would weaken the design of this experiment?

Possible Answers:

All four mediums contain different soil nutrients. 

All three plants require equal amounts of oxygen and water. 

The water used by the plants had mineral levels tested through out the experiment. 

Plant 1 requires more light than Plant 2 and Plant 3 in order to reach maximum growth. 

Plant height growth was measured by a computer program. 

Correct answer:

Plant 1 requires more light than Plant 2 and Plant 3 in order to reach maximum growth. 

Explanation:

Since the experiment design leaves light constant for all three plant species, a factor such as a different light preference for one plant species would weaken the control environment for the experiment. 

Example Question #2 : How To Find Experimental Design In Biology

 

Varsitytutor 

The chart above shows the height growth of three different plant species after a period of 2 weeks. Each plant species was grown in 4 different soil mediums. All the plants were grown in the same environment with equal amounts of light, water, and oxygen.

 

Based on the chart, soil Medium C has what effect on plant growth?

Possible Answers:

Soil Medium C does not seem to have a noticable effect on Plant 1, but has a beneficial effect on Plant 2 and Plant 3. 

Soil Medium C is beneficial for Plant 2, but detrimental for Plant 1 and Plant 3. 

Soil Medium C has a negative effect on the height growth of all three plants. 

Soil Medium C is beneficial for all three plant types. 

Soil Medium C is beneficial for Plant 1, but has negative effects on Plant 2 and Plant 3.

Correct answer:

Soil Medium C is beneficial for Plant 1, but has negative effects on Plant 2 and Plant 3.

Explanation:

Plant 1 is the only plant that had an increased height growth in Medium C. Plant 2 and Plant 3 had decreased height when in Medium C.

Example Question #3 : How To Find Experimental Design In Biology

Mitochondria make 90% of the energy needed by the body to sustain life. The Mitochondrial Free Radical Theory of Aging (MFRTA) theorizes that individuals who live longest produce fewer mitochondrial oxygen reactive species than individuals that have a shorter life span. Therefore, lifespan will increase if fewer mtROS are produced, and lifespan will decrease if more mtROS are produced. An experiment was done to test this theory, and the results are shown in the chart below. Four test groups of flies were involved, two groups consisted of females, and two groups consisted of males.

 

 

Test group 1

Test group 2

 

Test group 3

 

Test group 4

 # of mtROS

 3.9

 2.5

 3.2

 2.7

 Lifespan

110 days

120 days

95 days

89 days

 

 

 

 

Does this data support or dispute the MFRTA theory? 

Possible Answers:

The data supports the theory because it shows an inverse relationship, a high mtROS amount correlates to a high lifespan. 

The data does not support the MFRTA theory because it was not able to show an inverse relationship between the number of mtROS and the lifespan of the organisms. 

The data does not support the theory because the experiment does not test the information needed to address the MFRTA theory. 

The data does not support the theory because it shows an inverse relationship between the mtROS amount and the length of lifespan. 

The data supports the theory because some test groups had low numbers of mtROSs and also had long lifespans. 

Correct answer:

The data does not support the MFRTA theory because it was not able to show an inverse relationship between the number of mtROS and the lifespan of the organisms. 

Explanation:

According to the theory, test group 1 had the greatest number of mtROS, therefore it should have the shortest lifespan. However, it has a lifestpan of 110 days, the second longest life span in the experiment. 

Example Question #3 : How To Find Experimental Design In Biology

Mitochondria make 90% of the energy needed by the body to sustain life. The Mitochondrial Free Radical Theory of Aging (MFRTA) theorizes that individuals who live longest produce fewer mitochondrial oxygen reactive species than individuals that have a shorter life span. Therefore, lifespan will increase if fewer mtROS are produced, and lifespan will decrease if more mtROS are produced. An experiment was done to test this theory, and the results are shown in the chart below. Four test groups of flies were involved, two groups consisted of females, and two groups consisted of males.

 

 

Test group 1

Test group 2

 

Test group 3

 

Test group 4

 # of mtROS

 3.9

 2.5

 3.2

 2.7

 Lifespan

110 days

120 days

95 days

89 days

What information would weaken the experiment's results?

Possible Answers:

An experiment suggesting mitochondria make more than ninety percent of the body's energy. 

An experiment testing the lifespan of flies in an oxygen-deprived environment. 

An experiment consisting of a control group of both males and females.  

An experiment suggesting there is a high-percent error in measuring mitochondrial oxygen reactive species. 

A separate experiment done with a different test species that had similar results. 

Correct answer:

An experiment suggesting there is a high-percent error in measuring mitochondrial oxygen reactive species. 

Explanation:

An experiment casting doubt on the accuracy of mtROS measurement, which is the independent variable, would drastically weaken the experiment's results.

Example Question #3 : How To Find Experimental Design In Biology

Mitochondria make 90% of the energy needed by the body to sustain life. The Mitochondrial Free Radical Theory of Aging (MFRTA) theorizes that individuals who live longest produce fewer mitochondrial oxygen reactive species than individuals that have a shorter life span. Therefore, lifespan will increase if fewer mtROS are produced, and lifespan will decrease if more mtROS are produced. An experiment was done to test this theory, and the results are shown in the chart below. Four test groups of flies were involved, two groups consisted of females, and two groups consisted of males.

 

 

Test group 1

Test group 2

 

Test group 3

 

Test group 4

 # of mtROS

 3.9

 2.5

 3.2

 2.7

 Lifespan

110 days

120 days

95 days

89 days

What, if added, would strengthen the results of the experiment? 

Possible Answers:

Two test groups consisting of a mixed male and female population that had a mtROS amount of 5 and a lifespan of 150 days. 

A test group living in an isolated environment that showed a lifespan of 100 days and a mtROS amount of three. 

All of the answers listed. 

Two test groups, one male and one female, having a genetic mitochondrial disease but a significantly long lifespan. 

Two test groups consisting of a mixed male and female population that showed an overall decrease in lifespan with higher mtROS amounts. 

Correct answer:

Two test groups consisting of a mixed male and female population that showed an overall decrease in lifespan with higher mtROS amounts. 

Explanation:

The experiment's results would be strengthened if the influence of sex was addressed. Two test groups with mixed sex populations would eliminate the sex variable from the results.  Showing the inverse relationship with males and females in a mixed group would add another layer to the experiment. 

Example Question #4 : How To Find Experimental Design In Biology

An experiment was done to test the antibiotic resistance of the bacteria Pseudomonas flourescens and Escherichia coli by using the antibiotic disk sensitivity method. Four different antibiotics were tested on each bacterium. Media were prepared with each type of bacterium and a drop of each antibiotic was added to each corner of the plates, a different antibiotic in each corner. The cultures were observed for eighteen hours. After this period of time, the zones of inhibition (where the bacteria was not able to grow due to the antibiotic) were measured. The table below shows the results of the four antibiotics on the two bacteria, Pseudomonas flourescens and Escherichia coli.

 

 

Antibiotic 1

Antibiotic 2

Antibiotic 3

Antibiotic 4

Pseudomonas flourescens

11mm

2mm

5mm

20mm

Escherichia coli

 

10mm

8mm

3mm

10mm

Which of the following changes would weaken the experimental results?

Possible Answers:

Two of the antibiotics tested had synergistic effects

The zone of inhibition was measured after five hours of plating

The experiment tested one bacterial strain instead of two

The experiment looked at two antibiotics instead of four

All of the scenarios listed would weaken the experiment

Correct answer:

All of the scenarios listed would weaken the experiment

Explanation:

All of the answer choices would weaken the experiment. If the experiment only tested one bacterial strain, it would remove data relevant to the effectiveness of the antibiotic on multiple diseases. Testing two antibiotics instead of four would weaken the ability to compare the zones of inhibition. If two of the antibiotics had synergistic effects, it would be impossible to make conclusions because you would not know to what degree the resistance was due to the combination of two antibiotics. Lastly, looking at the results after only five hours would stunt any possible progress made by an antibiotic. The zone of inhibition might double from four hours to eighteen hours.

Example Question #5 : How To Find Experimental Design In Biology

An experiment was done to test the antibiotic resistance of the bacteria Pseudomonas flourescens and Escherichia coli by using the antibiotic disk sensitivity method. Four different antibiotics were tested on each bacterium. Media were prepared with each type of bacterium and a drop of each antibiotic was added to each corner of the plates, a different antibiotic in each corner. The cultures were observed for eighteen hours. After this period of time, the zones of inhibition (where the bacteria was not able to grow due to the antibiotic) were measured. The table below shows the results of the four antibiotics on the two bacteria, Pseudomonas flourescens and Escherichia coli.

  

 

Antibiotic 1

Antibiotic 2

Antibiotic 3

Antibiotic 4

Pseudomonas flourescens

11mm

2mm

5mm

20mm

Escherichia coli

 

10mm

8mm

3mm

10mm

Which change to the experimental design would strengthen the results?

Possible Answers:

Focusing on only two antibiotics instead of four

Testing the four antibiotics on separate plates

Focusing on only one bacteria strain and using more than four antibiotics

All of the choices listed would strengthen the experiment

Observing the cultures after two hours instead of eighteen hours

Correct answer:

Testing the four antibiotics on separate plates

Explanation:

Testing the antibiotics on different plates would eliminate any possible combination reactions. All of the other answer choices would weaken the results instead of strengthen. 

Example Question #7 : How To Find Experimental Design In Biology

A biologist wanted to do an experiment involving two species of large cat (species A and species B) around a potential new food source.

He isolated the populations of each cat in a location that closely approximated their natural environment, except this potential new food source was the only food source available to them. 

Experiment 1:

When species A was left alone with the new food source, their numbers decreased rapidly until none were left.

Experiment 2:

When species B was left alone with the new food source, their numbers increased and the species flourished.

Experiment 3:

When an equal number of species A and B were placed with the new food source, both species maintained relatively constant numbers.

Which of the following changes would most alter the results of the experiments?

Possible Answers:

Decreasing the starting number of each species of animal

Introduction of an alternative food source

Increasing the amount of fresh water in the environment

Raising the temperature in the environment

Correct answer:

Introduction of an alternative food source

Explanation:

This experiment, at its heart, is to determine the relationship between the species of cat, a new food source, and the change in population. If an alternative food source is introduced into the experiment, that would most likely change the results of the experiment by introducing a second independent variable. Fluctuations in population size could be attributable to either of the food sources, and the effects of a single food source could not be determined.

Changes in temperature, water availability, and sample size would likely have some impact on the results, but nearly as severe of an effect as adding a secondary food source.

Example Question #8 : How To Find Experimental Design In Biology

A biologist wanted to do an experiment involving two species of large cat (species A and species B) around a potential new food source.

He isolated the populations of each cat in a location that closely approximated their natural environment, except this potential new food source was the only food source available to them. 

Experiment 1:

When species A was left alone with the new food source, their numbers decreased rapidly until none were left.

Experiment 2:

When species B was left alone with the new food source, their numbers increased and the species flourished.

Experiment 3:

When an equal number of species A and B were placed with the new food source, both species maintained relatively constant numbers.

The biologist wants to recreate this experiment, but with fish. Which of the following will he NOT need?

Possible Answers:

Environments that recreate the natural habitat of the fish

Two different species of fish

Similar-sized aquariums

Only one food source for both fish

Correct answer:

Similar-sized aquariums

Explanation:

The experiment requires two different species of the animal, only one food source, and for the location to closely mimic their natural environment. The size of the aquarium is irrelevant, as long as it mimics each fish's natural environment.

Example Question #6 : How To Find Experimental Design In Biology

A biologist wanted to do an experiment involving two species of large cat (species A and species B) around a potential new food source.

He isolated the populations of each cat in a location that closely approximated their natural environment, except this potential new food source was the only food source available to them. 

Experiment 1:

When species A was left alone with the new food source, their numbers decreased rapidly until none were left.

Experiment 2:

When species B was left alone with the new food source, their numbers increased and the species flourished.

Experiment 3:

When an equal number of species A and B were placed with the new food source, both species maintained relatively constant numbers.

Why is it important that each species was in a location that closely approximated their natural environment?

Possible Answers:

This is the safest way to keep them away from predators

This will make the cats more comfortable, and thus more agreeable to the experiment

This is the only way to isolate their response to the new food source

It is irrelevant data

Correct answer:

This is the only way to isolate their response to the new food source

Explanation:

For this experiment, the goal is to isolate the response of the cats to the food source. Everything else must be controlled; there can only be one indirect variable: the food source. Any variation aside from the variable being tested could result in unwanted additional changes in the cats' behaviors. By keeping their environments constant, any changes can be assumed to be the result of the altered food source.

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