ACT Science : Biology

Study concepts, example questions & explanations for ACT Science

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Example Questions

Example Question #71 : Biology

Scientists studied a species of termite and looked at their foraging habitats across the United States. The termite’s population in a given tree was measured by the level of decomposition within a tree, due to the termites eating the bark. The experiment also kept track of the level of shade tolerance for each species of tree. For the species of trees in this experiment, shade tolerance fell into two main categorizes- shade tolerant (ST) and intermediate shade (IS). Lastly, they recorded the average amount of rainfall in that given month for the species location being observed. The chart below summarizes the data. Scientists hypothesized that the level of decomposition would be highest in tree species with a higher average rainfall. In addition, they hypothesized that the trees allowing more shade would allow for more termites and, in turn, more decomposition.

 

Tsuga canadensis

Morus rubra

Pinus

strobus

Acer rubrum

Arbutus

menziesii

Quercus

lobata

Juniperus

scopulorum

Decomposition

(in ccm)

2.38

3.21

1.01

.970

2.89

1.31

4.03

Shade tolerance

ST

ST

IS

IS

ST

IS

ST

Average rainfall

47.27

50.89

43.26

41.65

46.87

44.98

52.75

What is the relationship between shade tolerance and the level of decomposition? 

Possible Answers:

Tree species with higher shade tolerance have lower levels of decomposition. 

There is not a consistent relationship between shade tolerance and decomposition levels within the tree species studied. 

The level of decomposition stays the same regardless of shade tolerance. 

Tree species with less shade tolerance have higher levels of decomposition. 

Tree species with higher shade tolerance have higher levels of decomposition. 

Correct answer:

Tree species with higher shade tolerance have higher levels of decomposition. 

Explanation:

According to the chart, the species with a shade tolerance (ST) have levels of decompisition that are higher than species with an intermediate shade tolerance (IS).

Example Question #72 : Biology

Vaccinations have become a controversial topic in the United States. Currently the US Food and Drug Administration (FDA) regulates all vaccines. The federal government does not mandate vaccinations for any individual; however, all states require vaccinations for children entering public school. There are several types of vaccines—live attenuated vaccines, inactivated vaccines, subunit vaccines, toxoid vaccines, and conjugate vaccines, just to name a few. All of these vaccines have the shared purpose of exposing the host body to antigens of a specific disease. When the body receives the antigens, the immune system is activated, remembering the antigens. The next time the individual is exposed to the disease, the body will remember the antigen and have a better probability of not getting infected. Two scientists below discuss their belief on vaccines.

Scientist 1

Vaccines have saved many lives. The risks of not being vaccinated far outweigh the risks of adverse vaccine reactions. Reports linking autism to vaccines have been evaluated by the CDC, which states there is no scientific link between autism and vaccines. The second leading cancer killer in women is cervical cancer. The HPV vaccine protects against the two most common strains causing cancer. This is an example of a vaccine that does much more good than bad. Vaccines also reduce the amount of money spent on healthcare, because the preventative cost of a vaccine is much cheaper than the cost of treating an infected person. The only time a vaccine should not be administered is if the chance of the individual coming into contact with the disease is so rare it is not worth the potential of adverse reactions.

 Scientist 2

Many vaccines nowadays are extraneous. Vaccines for diseases like whooping cough and scarlet fever were once necessary but now outdated. Modern updates on hygiene, waste management, and water filtration have resulted in significantly decreased chances of infection. In addition, diseases like rotavirus have an infection period of a few days, and the main symptom is dehydration. Modern medicine can easily treat severe dehydration, and the risk of rotavirus infection is very slim; therefore, the results of infection are far milder than the results of an adverse reaction. Vaccines for children can cause extremely dangerous adverse reactions. This includes anaphylactic shock, paralysis, and death. While scientists have not been able to conclusively prove this, many believe that these reactions are related to the age of the host and the lack of a developed immune systemor neural network. Vaccines suppress the immune system, which can lead to autoimmune disorders. In addition, vaccines can congest the lymphatic system with proteins molecules from the vaccines; therefore, I would recommend requirements for vaccination to take place at a later stage in a child’s development.

According to the passage, how does the opinion of Scientist 1 differ from the opinion of Scientist 2? 

Possible Answers:

Scientist 2 believes many vaccines are no longer needed while Scientist 1 believes all vaccines are necessary.

Scientist 1 believes the benefits of being vaccinated outweigh the risks, while Scientist 2 believes the possible reactions far outweigh the possible protection. 

Both scientists believe vaccinations should be allowed, except Scientist 1 believes the HPV vaccine should not be administered.

Scientist 1 believes vaccines are outdated while Scientist 2 believes vaccines save lives.

Scientist 1 believes the risks of vaccinated outweigh the risks, while Scientist 2 believes the possible reactions far outweigh the possible protection. 

Correct answer:

Scientist 1 believes the benefits of being vaccinated outweigh the risks, while Scientist 2 believes the possible reactions far outweigh the possible protection. 

Explanation:

Scientist 1 believes the risks of not being vaccinated "far outweigh the risks of adverse vaccine reactions." Scientist 2 believes the possible reactions for young children far outweigh the possible protection, recommending that vaccination "take place at a later stage in a child’s development."

Example Question #73 : Biology

There is a certain species of rabbit that is known to reproduce quickly. 250 of these rabbits were introduced into a new environment, and their population was measured in ten year intervals.

Screen_shot_2013-11-12_at_9.55.32_am_1

Following current trends, approximately how many rabbits will there be after 25 years?

Possible Answers:

Correct answer:

Explanation:

Based upon the table, the number of rabbits at 25 years should fall between the second and third decade numbers. Since the value for 20 years is 1,380 and the value for 30 years is 2,330, the correct value should fall between the two. 

The only answer that fits this range is 1,700.

You can also get a rough mathematical estimate by taking the average between the second and third decade.

Example Question #71 : Biology

The Millikin oil drop experiment is among the most important experiments in the history of science.  It was used to determine one of the fundamental constants of the universe, the charge on the electron. For his work, Robert Millikin won the Nobel Prize in Physics in 1923.

Millikin used an experimental setup as follows in Figure 1. He opened a chamber of oil into an adjacent uniform electric field.  The oil droplets sank into the electric field once the trap door opened, but were then immediately suspended by the forces of electricity present in the field.

Figure 1:

Millikin

By determining how much force was needed to exactly counteract the gravity pulling the oil droplet down, Millikin was able to determine the force of electricity.  This is depicted in Figure 2.

Using this information, he was able to calculate the exact charge on an electron.  By changing some conditions, such as creating a vacuum in the apparatus, the experiment can be modified. 

Figure 2:

Millikin_drop

When the drop is suspended perfectly, the total forces up equal the total forces down.  Because Millikin knew the electric field in the apparatus, the force of air resistance, the mass of the drop, and the acceleration due to gravity, he was able to solve the following equation: 

Table 1 summarizes the electric charge found on oil drops in suspension.  Millikin correctly concluded that the calculated charges must all be multiples of the fundamental charge of the electron.  A hypothetical oil drop contains some net charge due to lost electrons, and this net charge cannot be smaller than the charge on a single electron.

Table 1: 

Trial #

Electric Charge Calculated in Coulombs (C)

Vacuum Used?

1

1.602176487 x 10-8

No

2

1.602176487 x 10-2

Yes

3

1.602176487 x 10-6

No

4

1.602176487 x 10-4

Yes

Using his own data, a scientist determines that the fundamental charge on an electron is about 1.602176487 x 10-7 C.  Which of the following findings most substantially undermines these conclusions?

Possible Answers:

The results of Trial 4

The results of Trial 1

The results of Trials 2 and 3

The results of Trial 3

The results of Trial 2

Correct answer:

The results of Trial 1

Explanation:

The conclusion from the experiment is that the fundamental charge on the electron must be a factor of all the numbers found in the experiment.  The results of Trial 1 would constitute a multiple of the number found by this new scientist.

Example Question #71 : Biology

The Millikin oil drop experiment is among the most important experiments in the history of science.  It was used to determine one of the fundamental constants of the universe, the charge on the electron. For his work, Robert Millikin won the Nobel Prize in Physics in 1923.

Millikin used an experimental setup as follows in Figure 1. He opened a chamber of oil into an adjacent uniform electric field.  The oil droplets sank into the electric field once the trap door opened, but were then immediately suspended by the forces of electricity present in the field.

Figure 1:

Millikin

By determining how much force was needed to exactly counteract the gravity pulling the oil droplet down, Millikin was able to determine the force of electricity.  This is depicted in Figure 2.

Using this information, he was able to calculate the exact charge on an electron.  By changing some conditions, such as creating a vacuum in the apparatus, the experiment can be modified. 

Figure 2:

Millikin_drop

When the drop is suspended perfectly, the total forces up equal the total forces down.  Because Millikin knew the electric field in the apparatus, the force of air resistance, the mass of the drop, and the acceleration due to gravity, he was able to solve the following equation: 

Table 1 summarizes the electric charge found on oil drops in suspension.  Millikin correctly concluded that the calculated charges must all be multiples of the fundamental charge of the electron.  A hypothetical oil drop contains some net charge due to lost electrons, and this net charge cannot be smaller than the charge on a single electron.

Table 1: 

Trial #

Electric Charge Calculated in Coulombs (C)

Vacuum Used?

1

1.602176487 x 10-8

No

2

1.602176487 x 10-2

Yes

3

1.602176487 x 10-6

No

4

1.602176487 x 10-4

Yes

 

In a subsequent experiment, a scientist realizes that the greater the mass of an oil drop, the greater she needs to make the external elecric field to hold it in suspension.  In this experiment, the relationship between mass and necessary electric field must be:

Possible Answers:

Independent

Indirect

Exponential

Logarithmic

Direct

Correct answer:

Direct

Explanation:

Based on this information, the relationship must be direct.  This is defined by the two variables varying in the same direction.  The greater the magnitude of the mass, the greater is the necessary electric field strength.

Example Question #75 : Biology

Clostridium botulinum is a bacterial organism that can cause disease in people after eating improperly canned foods. As a result of this risk, canning foods involves bringing contents to high pressures and temperatures, thus killing the inactive form of Clostridium, called a spore.

Table 1 shows the ability of a scientist to detect spores as a function of the peak temperature and pressure reached during the process used for canning green beans.

Peak Temperature

Peak Pressure

Spores/Cubic Millimeter

100 C

50 PSI

5

100 C

100 PSI

3

150 C

50 PSI

2

150 C

100 PSI

1

 

Table 2 shows the infectious dose of spores per cubic millimeter necessary to cause illness in four populations. 

Population

Minimum Concentration of Spores

Children <1 Year

1

Children 1-4 Years

1

Children 5-10 years

4

Children > 10 years and Adults

8

 

A scientist discovers that, despite adhering to appropriate canning methods as described above, an outbreak of disease due to Clostridium botulinum has taken place in a Minnesota school. She visits the school and collects food samples to determine the cause of the outbreak. While compiling data at the school, she discovers that there are an increasing number of cases of a new strain of Clostridium botulinum. Upon investigation, the scientist finds that all children who attend the school are older than 5 years of age.

 

To create Table 2, a scientist measured the minimum concentrations of spores necessary to cause disease in animal models.

For example, to determine the minimum infectious concentration for children age 5-10 years, he measured the concentration of spores it took to get seven mice to show signs of Clostridium botulinum poisoning.  He then ordered this data as follows:

Mouse 1:  At least 1 spores/cubic millimeter

Mouse 2:  At least 1 spore/cubic millimeter

Mouse 3:  At least 4 spores/cubic millimeter

Mouse 4:  At least 4 spores/cubic millimeter

Mouse 5:  At least 4 spores/cubic millimeter

Mouse 6:  At least 5 spores/cubic millimeter

Mouse 7: At least 16 spores/cubic millimeter

According to this data set, which value did the scientist use to determine the reported minimum infectious concentration in Table 1?

Possible Answers:

Mode of the data set

Median and mode of the data set

Mean and median of the data set

Mean and mode of the data set

Mean of the data set

Correct answer:

Median and mode of the data set

Explanation:

The data set provided in the question has a mean of 5, a mode of 4 and a median of 4. Table 1 reports the minimum infectious concentration as 4, and thus median and/or mode were used to determine this number as reported.

Example Question #76 : Biology

Understanding the biological features of different bacteria that allow them to grow in unwelcoming environments is necessary to treat and prevent human disease. Modern scientific laboratories, such as those in major hospitals, take blood, urine, and mucus samples from patients and culture them for bacterial growth. During the culturing process, laboratory technicians stain the growing bacteria for a component of their cell wall, the structure that provides shape and rigidity to the bacterium, through a process called Gram staining. Bacteria are typically classified as Gram Positive or Gram Negative, a distinction that is important in selecting the most effective antibiotic for treatment. Gram Positive bacteria appear purple under a microscope, while Gram Negative bacteria appear red. However, some bacteria do not Gram Stain and cannot be seen under a microscope when prepared this way.

Technicians also grow the bacteria on various types of plates containing special growth nutrients to determine which bacteria are causing a specific illness. If a bacterium is able to grow on a selective plate, meaning a plate that contains additional nutrients required for a specific bacterium to grow if it is present in the culture, doctors are able to determine the exact cause of a patient’s illness and prescribe targeted antibiotics to eliminate the infection. Bacteria that commonly cause human illness, their growth requirements, and their appearance on specific growth media are presented below in Table 1.

                                                           Table 1 

Screen_shot_2014-04-27_at_11.32.48_pm 

Scientists can take the bacteria cultured on the plate and further analyze their enzymes. Three enzymes—urease, catalase, and beta-lactamase—are important for bacterial survival against the human immune system. Urease is responsible for producing urea, a basic molecule that can counteract the bactericidal (bacteria-killing) activity of stomach acid. Catalase, on the other hand, helps bacteria neutralize toxic substances released from human immune cells, allowing them to survive oxidative stress in high-oxygen areas. Finally, beta-lactamase allows Gram Positive bacteria to break down antibiotics called penicillins. While this ability to break down penicillin and its related antibiotic ampicillin was not initially present, bacteria, especially E. coli, have adapted by developing the new enzyme beta-lactamase that opens the ring responsible for penicillin’s bactericidal activity, rending the antibiotic ineffective. This and other examples of antibiotic resistance are becoming more common and are making treatment of serious human diseases very challenging.

According to information presented in the passage, which bacterium or bacteria is/are not susceptible to penicillin?

Possible Answers:

E. coli

B. cerrius

S. pneumoniae

H. pylori

Correct answer:

E. coli

Explanation:

The passage says that penicillin is used to treat gram positive organisms. Thus, in order to determine which organisms are not susceptible to penicillin, we need to see which organisms are gram negative. We are told in the first paragraph that "Grame Negative bacteria appear red." Using the provided chart, we can see this corresponds to E. coli. Alternatively, in the last paragraph, we are told "While this ability to break down penicillin and its related antibiotic ampicillin was not initially present, bacteria, especially E. coli, have adapted by developing the new enzyme beta-lactamase that opens the ring responsible for penicillin’s bactericidal activity, rending the antibiotic ineffective." This tells us that E. coli are not susceptible to penicillin.

Example Question #77 : Biology

Understanding the biological features of different bacteria that allow them to grow in unwelcoming environments is necessary to treat and prevent human disease. Modern scientific laboratories, such as those in major hospitals, take blood, urine, and mucus samples from patients and culture them for bacterial growth. During the culturing process, laboratory technicians stain the growing bacteria for a component of their cell wall, the structure that provides shape and rigidity to the bacterium, through a process called Gram staining. Bacteria are typically classified as Gram Positive or Gram Negative, a distinction that is important in selecting the most effective antibiotic for treatment. Gram Positive bacteria appear purple under a microscope, while Gram Negative bacteria appear red. However, some bacteria do not Gram Stain and cannot be seen under a microscope when prepared this way.

Technicians also grow the bacteria on various types of plates containing special growth nutrients to determine which bacteria are causing a specific illness. If a bacterium is able to grow on a selective plate, meaning a plate that contains additional nutrients required for a specific bacterium to grow if it is present in the culture, doctors are able to determine the exact cause of a patient’s illness and prescribe targeted antibiotics to eliminate the infection. Bacteria that commonly cause human illness, their growth requirements, and their appearance on specific growth media are presented below in Table 1.

                                                           Table 1 

Screen_shot_2014-04-27_at_11.32.48_pm 

Scientists can take the bacteria cultured on the plate and further analyze their enzymes. Three enzymes—urease, catalase, and beta-lactamase—are important for bacterial survival against the human immune system. Urease is responsible for producing urea, a basic molecule that can counteract the bactericidal (bacteria-killing) activity of stomach acid. Catalase, on the other hand, helps bacteria neutralize toxic substances released from human immune cells, allowing them to survive oxidative stress in high-oxygen areas. Finally, beta-lactamase allows Gram Positive bacteria to break down antibiotics called penicillins. While this ability to break down penicillin and its related antibiotic ampicillin was not initially present, bacteria, especially E. coli, have adapted by developing the new enzyme beta-lactamase that opens the ring responsible for penicillin’s bactericidal activity, rending the antibiotic ineffective. This and other examples of antibiotic resistance are becoming more common and are making treatment of serious human diseases very challenging.

Ampicillin is not able to treat which of the following illnesses, according to information in the passage?

Possible Answers:

Diarrhea

Pneumonia

Stomach Infection

Urinary Tract Infection

Correct answer:

Urinary Tract Infection

Explanation:

As described by the last paragraph of the passage, ampicillin is a penicillin derivative. E. coli are resistant to penicillin and ampicillin; thus, using the chart, we can see that treating a urinary tract infection would not be possible with ampicillin.

Example Question #71 : Act Science

In contrast to prokaryotes, eukaryotes have membrane-bound organelles that allow their cell(s) to compartmentalize different cellular functions. These different functions, which occur only within membrane-bound organelles, include the synthesis and breakdown of different macronutrients fatty acids and proteins. Other processes like glycolysis (the breakdown of carbohydrates) and nucleic acid breakdown can occur outside membrane-bound organelles. Synthesizing different macronutrients is known as anabolism, while breaking down these same nutrients into Adenosine Tri-Phosphate (ATP) is called catabolism.

Macronutrient anabolism and catabolism are balanced by the supply of available energy. In the fed state, where a high concentration of sugar is dissolved in your blood stream, the body prefers to use glucose as its energy source through a pathway called glycolysis. When the supply of glucose in the blood runs low, however, the liver is able to synthesize new glucose in a process called gluconeogenesis. In gluconeogenesis, oxaloacetate, the product of another cycle called the Krebs Cycle is used as the starting point to run glycolysis in reverse, making a new glucose molecule. When these precursors needed to initiate gluconeogenesis run low, the body then turns to the catabolism of proteins and free fatty acids.

Proteins, composed of strands of amino acids, are broken down to generate ATP and oxaloacetate. People who have not eaten for an extended period of time experience low muscle mass due to catabolism of skeletal muscle proteins. Only after available protein is broken down does beta oxidation of free fatty acids begin.

Beta oxidation uses free fatty acids floating in the blood to generate the greatest amount of ATP per gram of starting material of any of the macronutrients. Carried out by enzymes called lipases, beta oxidation splits a long fatty acid chain into two carbon units called acetyl-CoA. Per acetyl-CoA that enters the Krebs Cycle, three NADH and one FADHare produced that enter the Electron Transport Chain to drive ATP production. 1 NADH molecule can generate 3 ATP, while 1 FADH2 molecule can generate 2 ATP. Lipases continue to cleave acetyl-COA units off the parent lipid chain until it either produces its last acetyl-CoA molecule or ends in a 3 carbon molecule called propyl-CoA. Propyl-CoA can further undergo catabolism to yield one final acetyl-CoA molecule.

The correlation between the rates of gluconeogenesis and glycolysis may best be described as which of the following?

Possible Answers:

Indirect

Inverse

Direct

Cannot Be Determined

Correct answer:

Inverse

Explanation:

The passage states that gluconeogensis and glycolysis run in opposite directions to keep the level of glucose in the blood at a constant level. Thus, when gluconeogenesis is high, glycolysis is low and visa versa. This describes an inverse relationship - when one value is high, the other value is low.

Example Question #79 : Biology

In contrast to prokaryotes, eukaryotes have membrane-bound organelles that allow their cell(s) to compartmentalize different cellular functions. These different functions, which occur only within membrane-bound organelles, include the synthesis and breakdown of different macronutrients fatty acids and proteins. Other processes like glycolysis (the breakdown of carbohydrates) and nucleic acid breakdown can occur outside membrane-bound organelles. Synthesizing different macronutrients is known as anabolism, while breaking down these same nutrients into Adenosine Tri-Phosphate (ATP) is called catabolism.

Macronutrient anabolism and catabolism are balanced by the supply of available energy. In the fed state, where a high concentration of sugar is dissolved in your blood stream, the body prefers to use glucose as its energy source through a pathway called glycolysis. When the supply of glucose in the blood runs low, however, the liver is able to synthesize new glucose in a process called gluconeogenesis. In gluconeogenesis, oxaloacetate, the product of another cycle called the Krebs Cycle is used as the starting point to run glycolysis in reverse, making a new glucose molecule. When these precursors needed to initiate gluconeogenesis run low, the body then turns to the catabolism of proteins and free fatty acids.

Proteins, composed of strands of amino acids, are broken down to generate ATP and oxaloacetate. People who have not eaten for an extended period of time experience low muscle mass due to catabolism of skeletal muscle proteins. Only after available protein is broken down does beta oxidation of free fatty acids begin.

Beta oxidation uses free fatty acids floating in the blood to generate the greatest amount of ATP per gram of starting material of any of the macronutrients. Carried out by enzymes called lipases, beta oxidation splits a long fatty acid chain into two carbon units called acetyl-CoA. Per acetyl-CoA that enters the Krebs Cycle, three NADH and one FADHare produced that enter the Electron Transport Chain to drive ATP production. 1 NADH molecule can generate 3 ATP, while 1 FADH2 molecule can generate 2 ATP. Lipases continue to cleave acetyl-COA units off the parent lipid chain until it either produces its last acetyl-CoA molecule or ends in a 3 carbon molecule called propyl-CoA. Propyl-CoA can further undergo catabolism to yield one final acetyl-CoA molecule.

A 9-carbon free fatty acid is processed through the process of beta oxidation. How many acetyl-CoA could it be expected to provide? 

Possible Answers:

4

1

2

9

Correct answer:

4

Explanation:

The question asks us to determine how many acetyl-CoA could be made from a 9 carbon chain. According to the last paragraph, acetyl-CoA is a 2 carbon molecule. Thus, the full number of Acetyl-CoA molecules that could be made is 4, leaving one carbon molecule remaining in the presenting chain. 

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