ACT SAMPLE SCIENCE TEST 15
DIRECTIONS: This test consists of seven passages, each followed by several questions. Read each passage
and select the best answer for each question following the passage. Then, on your answer sheet, mark the
oval corresponding to the best answer. You may NOT use a calculator on this test.
Passage I
Nitrates are substances that occur naturally at low concentrations in water (including drinking
water), plants, and the soil. In nature, nitrates are relatively nontoxic and are not likely to be a health
hazard. In higher concentrations, however, nitrates can be potentially threatening contaminants.
Human activities are responsible for increased levels of nitrates in groundwater. The most
common sources of nitrates produced by human activity can be traced to industrial pollution, human
waste septic systems, and agricultural processes. Industrial wastewaters and refuse dumps contaminate
the soil and can contribute to excess nitrate levels if pollutants seep into groundwater supplies.
Nitrogen fertilizers, widely used to promote growth of plants, wash into rivers and streams and seep
into the groundwater when it rains. In addition, animal feed lots contribute to runoff that can also enter
the water supply. Septic systems, if poorly constructed or leaky, also allow contaminants to seep into
the soil and eventually into the groundwater.
Figure 1 shows the nitrate concentration, in milligrams per liter (mg/l), for each of four locations
(A, B, C, and D) of drinking water supplies in a city. Figure 1 also shows the water quality standards (set
by officials in this particular city) and the Maximum Contaminant Level (MCL) set by the Environmental
Protection Agency (EPA). Any drinking water source that exceeds the MCL is considered unsafe for
consumption.
Figure 1
Concerned with the high levels of nitrates in Location A, several scientists attempt to determine
the source of nitrate pollution in a lake within Location A. Table 1 shows the nitrate concentration of
water samples collected from three different rivers that empty into the lake at Location A. The rivers
chosen for the study collect runoff from nitrogen fertilizers used at a nearby farm. Two samples were
collected from each river, one in the late fall (F) and one in early spring (S).
Table 1
Nitrates (mg/l)
River 1
F
29.5
S
36.7
River 2
F
9.8
S
12.4
River 3
F
17.8
S
21.8
1) To better understand the relationship between nitrate levels in the lake and their sources, which
of the following activities should be performed next?
A) Decrease the Water Quality Standard for all of the locations that show evidence of high
nitrate levels.
B) Increase the MCL in each of the three rivers and study how it affects nitrate levels.
C) Observe the nitrate levels in Locations A, B, C, and D for an extended period of time.
D) Determine the respective contribution of nitrates from fertilizers, septic systems, and
industrial processes.
2) Studies have shown that runoff from agricultural processes is greater during the time of year
when farmers apply nitrogen fertilizers to their crops. Based on this information and Table 1,
which of the following is most likely true?
F) The farmers in the study apply more fertilizer to their crops in the late fall.
G) The farmers applied less fertilizer in 2000 than in 1985.
H) The farmers in the study apply more fertilizer to their crops in the early spring.
J) The farmers in the study did not use nitrogen fertilizer on their crops.
3) According to Figure 1, water with a nitrate concentration below the MCL is most likely:
A) contaminated by human waste.
B) considered safe and healthy for consumption.
C) considered unsafe for human consumption.
D) contaminated by fertilizer runoff.
4) According to Figure 1, all of the following are most likely true, EXCEPT:
F) the MCL for drinking water supplies is approximately 10 milligrams of nitrates per liter of
water.
G) the water at Location D is safe for human consumption.
H) more nitrates were detected in 2000 than in 1985.
J) the water in Location B may be harmful if consumed.
5) According to information in the passage, all of the following would reduce nitrate
concentrations EXCEPT:
A) changing the water quality standard to 8.
B) reducing the amount of nitrogen fertilizer used.
C) constructing better septic systems.
D) reducing the number of industrial wastewater locations.
Passage II
Carbon-14 dating is a process that uses radioactivity to determine the age of an organic
material. Carbon-14 dating is typically used to establish the age of archaeological artifacts such as
bones, insect remains, plant fibers, or any material that was once living or was derived from something
that was living.
Each radioactive substance has a half-life, which is the amount of time that it takes for the initial
amount of a substance to be halved (also called radioactive decay). The half-life of carbon-14 is
approximately 5,730 years, which means that it takes carbon-14 approximately 5,730 years to be
reduced by 50%. Figure 1 shows the half-life decay of carbon-14, with each increment on the x-axis
representing 1 half-life.
Figure 1
Carbon-14 is a naturally occurring radioactive isotope that is continually generated in the upper
atmosphere. Carbon-14 is absorbed by all living things and is ingested by humans and animals. The
ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things is nearly constant. As
soon as something that was living dies, it stops taking in new carbon; carbon-12 will remain constant
and carbon-14 will continue to decay. To determine the object’s age, the ratio of carbon-12 to carbon14 must be observed and compared to the ratio of carbon-12 to carbon-14 in all living things. With this
information, scientists can determine the age of something that is no longer living.
Figure 2 shows the ages of different organic materials and each material’s carbon ratio. The
carbon ratio is a ratio, or comparison, of the present amount of carbon-14 (A) to the original amount of
carbon-14 (Ao) in an object. The original amount of carbon-14 is the amount that the organic material
contained while it was still living.
Figure 2
6) According to Figure 1, approximately what percentage of carbon-14 isotopes remain after 2 halflives?
F) 100%
G) 75%
H) 50%
J) 25%
7) What is the approximate age in years of an organic material with 12.5% of carbon-14 remaining?
A) 2,000
B) 5,730
C) 17,190
D) 28,650
8) According to information in the passage, which of the following in NOT true? Carbon-14:
F) remains constant as carbon-12 decays after death.
G) has a half-life of 5,730 years.
H) decays as carbon-12 remains constant after death.
J) is used to determine the age of organic materials.
9) Which of the following best explains the relationship between the carbon ratio and the age of
an object?
A) As the carbon ratio decreases, age increases.
B) As the carbon ratio decreases, age decreases.
C) A ratio close to 1 signifies an older object.
D) A ratio close to 0 signifies an age of less than 1,000 years.
10) Rocks, which are nonliving, cannot be dated using the carbon-14 method. Which of the
following best explains why?
F) Only animals and humans contain carbon-12 and carbon-14.
G) The carbon ratio of inorganic materials is too high.
H) Only materials that were once living can be dated using the carbon-14 method.
J) The carbon ratio of inorganic materials is too low.
11) According to Figure 2, a material with a carbon ratio of less than 0.2 would most likely be:
A) less than 1,000 years old.
B) between 2,000 and 3,000 years old.
C) between 2,500 and 3,500 years old.
D) greater than 4,500 years old.
Passage III
The blood type of a human being depends on the presence or absence of certain proteins that
appear on the surface of red blood cells and in the fluid substance (plasma) of the blood. The proteins
found on the surface of red blood cells are called antigens, and the proteins found floating in the plasma
are called antibodies. Table 1 shows how the ABO blood grouping system determines blood type as A,
B, AB, or O, based on the combination of proteins within the blood.
Table 1
Protein Combinations
Blood Type
Type A
Type B
Type AB
Type O
Antigens
A
Yes
No
Yes
No
Antibodies
B
No
Yes
Yes
No
A
No
Yes
No
Yes
B
Yes
No
No
Yes
Blood type can also be distinguished by an Rh factor. The Rh factor refers to an antigen on the surface
of red blood cells that is either positive (+), if the antigen is present, or negative (−), if it is absent. Any
of the aforementioned blood types (A, B, AB, or O) are either Rh+ or Rh−.
In order for a blood transfusion, or the giving of blood from one person to another, to be
successful, the ABO and Rh blood types must be compatible. If the blood is not compatible between the
donor (the one who gives the blood) and the recipient (the one who receives the blood), then the red
blood cells from the donor with clump together, or agglutinate, often leading to fatal consequences.
Table 2 charts the compatibility of the four ABO blood types. The blood types under “Donate” indicate
to which blood types each can give blood, and “Receive” indicates which blood types each can receive.
Blood Type
Type A
Type B
Type AB
Type O
Table 2
Donate
A, AB
B, AB
AB
A, B, AB, O
Receive
A,O
B, O
A, B, AB, O
O
12) Which of the following best explains why type O is considered the “universal donor?” Type O
donors can:
F) receive blood from all of the four ABO blood types.
G) give blood only to other O blood types.
H) give blood to all of the four ABO blood types.
J) receive blood from most of the ABO blood types.
13) According to information in the passage, all of the following are true EXCEPT:
A) type O recipients can only receive blood from type O donors.
B) recipients can only receive blood from donors of the same blood type.
C) type AB donors can only give blood to type AB recipients.
D) blood types are dependent upon proteins found in plasma.
14) Which of the following is true of a person with Rh− blood?
F) A person with Rh− blood cannot by Type O.
G) Rh− blood contains negative Rh factors in the plasma.
H) Rh− blood does not contain the Rh antigen.
J) A person with Rh− blood cannot donate blood.
15) Suppose that a person with type A blood donates to a person with type B blood. Which of the
following statements about the results of this transfusion is most consistent with the
information given in the passage?
A) The red blood cells mix together smoothly because the blood types are compatible.
B) The transfusion would be successful only if the recipient was type O.
C) The transfusion would be successful if the donor had Rh+ blood.
D) The red blood cells will agglutinate because the blood types are not compatible.
16) According to the passage, which of the following best describes the main difference between
antigen and antibody proteins in the blood?
F) The location of the proteins
G) The color of the proteins
H) The number of proteins
J) The size of proteins
Passage IV
All living organisms derive their nutrients through the process of metabolism. Organisms
metabolize, or break down, food in their digestive tracts. During the final stages of the digestion
process, nutrients such as amino acids and simple sugars are absorbed by the organisms’ cells, allowing
the cells to grow and reproduce. In mammals, blood cells carry nutrients from the intestine directly to
the liver. The liver plays an important role in regulating the nutrient content in the blood that is
eventually pumped throughout the body.
Certain hormones help to regulate digestion. Table 1 shows these digestive hormones, as well
as where they are produced, what stimulates the production, and what the effect is of the hormone
once it is produced.
Gastrin
Table 1
Production Site
Production Stimulus
Stomach wall
Food in stomach
Secretin
Small intestine
Partially digested food
in small intestine
Cholecystokinin (CCK)
Small intestine wall
Amino acids produced
by partial digestion
Hormone
Effect
Sustained secretion of
gastric juice in stomach
Stimulates pancreas to
release bicarbonate in
small intestine
Stimulate pancreas to
release enzymes in
small intestine;
stimulates gall bladder
to contract and release
bile into small intestine
17) According to Table 1, partially digested food in the small intestine stimulates the production of:
A) gastrin only.
B) secretin only.
C) CCK only.
D) CCK and secretin.
18) Based on information in the passage, the human liver is responsible for:
F) breaking down food in the digestive tract.
G) regulating the level of nutrients in the blood.
H) pumping blood throughout the body.
J) secreting digestive hormones into the body.
19) According to Table 1, bile is released from:
A) the stomach lining.
B) the pancreas.
C) the liver.
D) the gall bladder.
20) Certain substances in the food we eat stimulate the production of gastrin in the stomach. An
initial burst of gastrin during a meal is followed by sustained secretion. The most likely reason
for this is that:
F) additional gastric juices are needed to continue to break down the food that we eat.
G) the small intestine continually absorbs the gastrin.
H) sustained secretion of gastrin stimulates the pancreas to release enzymes into the small
intestine.
J) the food that we eat contains nutrients that cannot be broken down.
21) Based on information in the passage, the process of metabolism:
A) occurs only in the liver.
B) is a necessary component of digestion.
C) releases bile into the blood.
D) is responsible for regulating reproduction.
Passage V
Remote sensing of the environment is defined as any technique for obtaining information about
certain objects, through the analysis of data collected by special instruments. These instruments are not
in direct, physical contact with the objects being investigated, and they can include photographic
cameras, mechanical scanners, and radar systems. Two scientists present their views on different types
of remote sensing techniques.
Scientist 1
Remote sensing is best achieved through the use of aerial photographs. These photographs
supply researchers with a vast amount of data, which can often be used for additional studies. Large
areas can be covered rapidly and at a very low cost. In fact, it is often possible to share the charges for
aerial photography with scientists conducting different research in the same area. Large-scale
phenomena can be more easily identified in aerial photographs. In addition, wetlands, rugged terrain,
and prohibited areas can be accessed via the air. It is often not necessary to get permission to fly over
restricted or hard-to-reach locations.
Scientist 2
The best way to remotely sense the environment is to conduct a ground survey. Measurements
are very precise, and field operators become familiar with the physical and cultural features of the
landscape. This familiarity allows researchers to gain a deeper understanding of the environment.
Minute details can be closely observed and documented. Weather factors that may impede or inhibit
aerial photography are generally not a problem during ground surveys. Remote sensors can be
strategically placed throughout an area to record data that can be collected at a later date.
22) Scientist 1’s viewpoint contains the basic assumption that:
F) remote sensing is the only means to gather important data.
G) aerial photographs can be effectively and accurately interpreted.
H) ground surveys are the primary remote sensing techniques used today.
J) aerial photographs cannot provide adequate information.
23) Scientist 1 would most likely state that which of the following is an important consideration in
deciding upon a remote sensing technique?
A) Cost
B) Culture
C) Climate
D) Education
24) According to information in Scientist 2’s viewpoint, accurate measurements are possible
because:
F) large areas can be easily accessed.
G) field operators are not familiar with the landscape.
H) a vast amount of data can be gathered.
J) details can be more easily observed.
25) Both scientists would most likely agree that:
A) it is necessary to get permission to remotely sense restricted areas.
B) remote sensing of the environment can yield useful data.
C) remote sensing is best achieved using photographic cameras.
D) it is impossible to identify large-scale phenomena.
26) Scientist 1 would most likely support which of the following statements about remote sensing
instruments?
F) Strategic placement of remote sensors is critical in gathering useful data.
G) Remote sensing instruments cannot tolerate high altitudes.
H) Photographic cameras can be modified to instantaneously capture an entire ground area.
J) Rugged terrain cannot be remotely sensed with any of the sensing instruments currently in
use.
27) Scientist 2 states that:
A) aerial photographs often supply researchers with an excess of data.
B) physical and cultural features of the landscape can often be overlooked during a ground
survey.
C) large-scale phenomena can easily be seen from the air.
D) ground surveys can yield highly accurate data, despite potentially bad weather conditions.
Passage VI
In the United States, one in four people suffer from some type of allergy. An allergy is an
overreaction of the body’s immune system to a foreign substance, called an allergen. An allergen can be
ingested (eaten), injected, inhaled into the lungs, or absorbed by the skin. Once an allergen has been
introduced to the body, the body can react by producing a variety of symptoms, including coughing and
sneezing; itchy, watery eyes; a runny nose; and a scratchy throat. In extreme cases, a person may
experience a rash, hives, low blood pressure, difficulty in breathing, an asthma attack, or even death.
Although allergies and their symptoms can be managed, there is no known cure.
Allergies are characterized by the specific allergens that trigger symptoms, as well as by which
method the allergy can be introduced. The most common types of allergies, their method of
introduction, and their common triggers are listed in Table 1.
Allergy Type
Indoor
Outdoor
Food and drug
Skin
Insect
Table 1
Method
Inhalation
Inhalation
Ingestion
Injection
Absorption
Injection
Common Triggers
Pet dander, dust mites, mold spores
Trees, grass, and weed pollen, mold spores
Peanuts, shellfish, wheat, dairy
Penicillin
Latex, poison ivy/oak/sumac
Hornets/wasps/bees
Fire ants
Many people suffer from “seasonal allergies,” which occur at specific times of the year. The
most common seasonal allergies occur from outdoor allergies occur from outdoor allergens such as tree,
grass, and weed pollen, and mold spores. The pollen and spores from these allergens all vary in
concentration throughout the year, thus making reactions greater at certain times of the year than at
others.
Pollen and spores can be counted at research stations and measured in terms of the number of
pollen or spores per cubic meter of air. Table 2 shows the scale for determining the intensity of allergen
counts.
Intensity
Not Present
Low
Moderate
High
Very High
Table 2
Allergen in Terms of Number of Pollen or Spores per Cubic Meter of Air
Grass
Tree
Weed
Mold
0
0
0
0
1−5
1−16
1−9
1−5,999
6−20
17−90
10−50
6,000−13,999
21−200
91−1,500
51−500
14,000−49,999
>201
>1,500
>500
>50,000
A study was conducted to measure the allergen counts for grass pollen, tree pollen, weed
pollen, and mold spores in an area over the course of one year. The results are shown in Figures 1 and
2. Figure 1 shows the counts for grass, tree, and weed pollen, and Figure 2 shows the counts for mold
spores.
Figure 1
Figure 2
28) Based on the results of the study, one could generalize that allergic reactions:
F) to weed pollen are greatest from mid-August to October.
G) to all allergens are greatest during summer months.
H) to all pollens is least from May to July.
J) to grass pollen is greatest during the winter months.
29) According to the study, grass and tree pollen are similar to each other in that:
A) neither allergen is present from February to May.
B) all people experience the same symptoms from both allergens.
C) both experience elevated allergen counts from May to August.
D) tree and grass pollen produces identical symptoms for all sufferers.
30) According to the study, which factor most affects the presence of mold spores and grass, weed,
and tree pollen?
F) The method of introduction
G) The symptoms produced
H) The allergic reactions of people in the area
J) The time of year
31) Seasonal allergies most likely result from allergens that are:
A) inhaled into the lungs.
B) ingested.
C) injected.
D) absorbed by the skin.
32) According to Table 2, a tree pollen count of 1,000 would be considered:
F) Low
G) Moderate
H) High
J) Very High
33) It has been discovered that mold allergies peak during late December to early January. Does the
data presented in Figure 2 support this discovery?
A) Yes, because the mold allergen count is highest in December and January
B) Yes, because the mold allergen count is less than 12,500 in December and January
C) No, because the mold allergen count is below zero for several months during the year
D) No, because the mold allergen count cannot be recorded when the temperature is too low
Passage VII
Metallic substances such as iron have many uses around the world. These substances are
created by taking a naturally occurring ore (like iron ore) and adding energy in the form of heat,
chemicals, electricity, etc. The addition of this energy transforms the ore into a specific metallic
substance. From the minute a metal is formed, it begins to release stored-up energy. This natural
process is called corrosion. Some environmental factors will accelerate corrosion by causing the metal
to release energy faster than normal.
A group of students designed an experiment to test the corrosion process of the metallic
substance iron.
Experiment 1
Three iron nails were thoroughly cleaned with fine sandpaper. Each nail was placed in a
separate glass container. Two of the containers were filled with room-temperature water, just enough
to cover the nails. The students poured olive oil into one of these glass containers so that a layer of oil
approximately ¼-inch thick covered the surface of the water. The third container was left dry.
Figure 1
After 6 hours, the students observed the nails and recorded the results of their observations in Table 1.
Container
1
2
3
Table 1
Condition of the Nail after 6 hours
Severely corroded; rusty red color; rust flakes prevalent in water
Some corrosion; slight evidence of rust
No corrosion
34) Based on Table 1, what is a by-product of the corrosion of iron?
F) Water
G) Oil
H) Rust
J) Ore
35) The students recorded their observations again after 12 hours had elapsed. The nail in
Container 1 was even more severely corroded, but the nail in Container 2 had not corroded any
further. What is the most likely explanation for this?
A) The oil in Container 1 accelerated the corrosion process.
B) The oil in Container 2 stopped the corrosion process at some point.
C) The water in Container 1 had totally evaporated after 12 hours.
D) The oil in Container 2 caused the corrosion process to accelerate.
36) According to the passage, corrosion results from:
F) adding heat energy to metal.
G) rubbing metal with sandpaper.
H) the mining of iron ore.
J) the release of stored energy.
37) Based on the results of the experiment, you can reasonably conclude that:
A) water causes iron to release energy faster than normal.
B) oil prevents corrosion from occurring in iron.
C) only the presence of oxygen is required to accelerate corrosion.
D) the presence of rust in the water will accelerate corrosion.
38) According to the passage, which of the following is an environmental factor that accelerates
corrosion?
F) Oil
G) Rust
H) Moisture
J) Metal
39) Suppose that the students removed the nail from Container 1 after 6 hours. You can most
reasonably predict that:
A) the nail would continue to corrode at an accelerated rate.
B) the nail would eventually stop corroding.
C) the oil would coat the nail, stopping the corrosion process.
D) the corrosion process would be reversed.
40) According to the passage, metallic substances can be created by:
F) heating naturally occurring ores until the ores are transformed.
G) transforming iron into rust through application of heat.
H) releasing stored energy faster than normal.
J) placing naturally occurring ores into containers filled with water.
Sample Science Test 15 Answers
1)
2)
3)
4)
5)
6)
7)
D
H
B
G
A
J
C
8)
9)
10)
11)
12)
13)
14)
F
A
H
D
H
B
H
15)
16)
17)
18)
19)
20)
21)
D
F
D
G
D
F
B
22)
23)
24)
25)
26)
27)
28)
G
A
J
B
H
D
F
29)
30)
31)
32)
33)
34)
35)
C
J
A
H
A
H
B
36)
37)
38)
39)
40)
J
A
H
B
F