PRETEST
Science
This Science Pretest is designed to introduce you to this section of the GED® test and to give you a good idea of your current skill level in this subject area.
This test has 40 items. The questions are in the same formats as the ones on the real exam and are designed to measure the same skills. Many of the questions are based on short reading passages on science topics. Some are based on scientific illustrations, diagrams, or other graphics. Most of the questions are in multiple-choice format, but you will also see questions that ask you to draw a line or indicate a point on a diagram, fill in a blank, or write a short answer. On the real GED® test, you will indicate your answers by clicking on the computer screen. For this paper-and-pencil practice test, mark your answers directly on the page. Type or write your short-answer responses on a separate sheet of paper. You may use a calculator.
To get a good idea of how you will do on the real exam, take this test under actual exam conditions. Complete the test in one session and follow the given time limit. If you do not complete the test in the time allowed, you will know that you need to work on improving your pacing.
Try to answer as many questions as you can. There is no penalty for wrong answers, so guess if you have to. In multiple-choice questions, if you can eliminate one or more answer choices, you can increase your chances of guessing correctly.
After you have finished the test, check your answers in the Answers and Explanations section that follows the pretest. Then use the Evaluation Chart at the end of the Answers and Explanations section to determine the skills and content areas in which you need more practice.
Now turn the page and begin the Science Pretest.
PRETEST
Science
40 questions 
90 minutes
Use the table for Items 1 and 2:
Surface Temperature Ranges per Star Class
1. Using the information in the table, which color star is produced by the widest range of surface temperatures?
A. white
B. yellow
C. orange
D. blue-white
2. Write the appropriate class from the table in the blank.
The Sun is classified as a Class ________________ star because it has a surface temperature of approximately 5778 K.
Use the following passage for Items 3 through 5:
Blood calcium levels are tightly regulated in the human body by the hormones calcitonin and parathyroid hormone (PTH). When calcium levels become too high or low, the thyroid or parathyroid gland produces the appropriate hormone to return the body to homeostasis. The diagram shows the feedback mechanism for regulating blood calcium levels.
3. Which food is most likely to cause the greatest increase in calcitonin production when eaten?
A. rice, because it is an easily digested carbohydrate
B. orange, because it is a good source of vitamin C
C. yogurt, because it is high in bone-strengthening minerals
D. squash, because it is a rich source of vitamins and fiber
4. The ability to maintain blood calcium homeostasis depends on the interactions of several different body systems. Draw a line to connect each body system to the role it plays in maintaining calcium homeostasis.
5. Short answer
Osteoporosis is a disease in which decreased bone mineral density leads to an increased risk of bone fractures. One risk factor for developing osteoporosis is a diet low in calcium.
Explain how a diet low in calcium can affect the body’s ability to regulate blood calcium levels and ultimately contribute to the development of osteoporosis.
Include multiple pieces of evidence from the passage and diagram to support your answer.
Write your response in the space provided. This task may take approximately 10 minutes to complete.
Use the passage and diagram for Items 6 through 8:
The following diagram identifies homologous structures in the forelimbs of seven different species.
The term homologous means similar. Scientists use homologous structures as evidence of common ancestry. Through the process of natural selection, structures inherited from a common ancestor become modified to allow each descendant species to best adapt to its unique environment.
Homologous Structures
6. The homologies in the seven species’ forelimbs result from similarities in
A. metabolism.
B. genetic code.
C. environments.
D. reproductive strategies.
7. Considering the homologies shown in the diagram, humans likely share the most recent ancestor with which species?
A. cat
B. bat
C. bird
D. whale
8. Short answer
Consider the different functions of the forelimbs shown in the diagram. Each forelimb is adapted to best support one of four functions: flying, grasping, swimming, or walking.
Explain how natural selection can lead to adaptation in forelimbs. Give specific examples of structural adaptations and the functions they support.
Include multiple pieces of evidence from the text and diagram. Discuss specific species as examples to support your answer.
Write your response in the space provided. This task may take approximately 10 minutes to complete.
Use the passage for Items 9 and 10:
Photosynthesis is the chemical process of using the energy in sunlight to produce glucose. Respiration is the chemical process of converting glucose to energy that can be used by the cell. The chemical equations for both processes are shown below.
9. Write the appropriate number from the photosynthesis equation in each of the blanks.
Photosynthesis requires ________________ molecules of carbon dioxide and ________________ molecules of water to produce 1 molecule of glucose.
10. Which statement correctly describes the relationship between the processes of photosynthesis and respiration?
A. The reactants of photosynthesis are also used as the reactants for respiration.
B. The energy produced by respiration is used to fuel the photosynthesis reaction.
C. Photosynthesis and respiration are two different processes for producing glucose.
D. The chemical products of photosynthesis are used as the reactants for respiration.
Use the maps for Items 11 and 12:
Heat Maps of U.S. Hazard Areas
In areas where natural hazards occur frequently, specific precautions are often taken to reduce the impact when natural hazards do occur. Examine the areas in the maps with the highest incidence of each type of natural hazard.
11. Draw a line to connect each state to the precaution that would be most useful.
12. Using the information in the maps, which state most likely lies closest to a tectonic plate boundary?
A. Colorado
B. Louisiana
C. New Jersey
D. Washington
Use the passage for Items 13 and 14:
The carbon cycle describes the constant exchange of carbon among the atmosphere, land, and ocean. The following diagram depicts carbon cycle processes. The numbers on the diagram represent the approximate number of gigatons of carbon located in different portions of the cycle.
13. On the diagram, indicate the process that removes the greatest proportion of carbon from the atmosphere.
14. Using the information in the diagram, how many gigatons (GT) of carbon are estimated to be stored in fossil fuel deposits?
A. 7 GT
B. 300 GT
C. 2000 GT
D. 2300 GT
Use the passage for Items 15 through 17:
Velocity is defined as an object’s speed in a given direction. Velocity is positive when an object is moving forward, and negative when the object is moving in reverse. Acceleration is the change in an object’s velocity over time.
A race car driver is practicing on a linear track. The following graph tracks the race car’s velocity, in meters per minute, during the practice session.
Velocity of a Race Car (meters/minute)
15. Using the information in the passage, mark an X on the graph at the point where the race car changes direction from forward to reverse. (Note: On the real GED® test, you will click on the graph to mark the point.)
Use the prompt for Item 16:
Acceleration can be calculated using the following formula:
16. According to the graph, what is the race car’s acceleration between 0 and 10 minutes?
A. 600 m/min
B. 600 m/min2
C. 600 m2/min2
D. 600 (m/min)2
Use the passage for Item 17:
Newton’s Second Law of Motion states that an object’s acceleration is proportional to the total net force acting on the object, or force = mass × acceleration.
17. An object traveling at a constant velocity has no acceleration. According to the graph, the race car’s velocity was constant between 10 and 15 minutes. Which statement best describes the forces acting on the race car during this period?
A. The forces acting on the race car were balanced.
B. Gravity was the only force acting on the race car.
C. No forces were acting on the race car during this period.
D. The race car’s force was greater than the force of friction.
Use the chart and picture for Item 18:
Relationships Within an Ecosystem
18. The bee and flower shown in the picture are an example of which type of relationship?
A. commensalism
B. mutualism
C. parasitism
D. predation
Use the following passage and diagram for Item 19:
Centrifugation is the process of spinning a solution at high speed to separate the solution’s components by density. Centrifugation is often used to isolate the specific components of a blood sample for further analysis.
Centrifugation of a Blood Sample
19. According to the diagram, which component has the highest density?
A. plasma
B. whole blood
C. red blood cells
D. white blood cells
Use the diagram for Item 20:
20. Which statement describes a weakness in the model of a carbon atom?
A. The electrons are drawn smaller than the protons.
B. Protons and neutrons are shown in the atom’s nucleus.
C. The electrons are shown on fixed paths around the nucleus.
D. The numbers of protons, neutrons, and electrons are the same.
Use the passage for Item 21:
A 70% concentration of isopropyl alcohol is often used as a disinfectant for medical equipment such as thermometers and stethoscopes. The initial volume of 90% isopropyl alcohol needed to produce a batch of 70% isopropyl alcohol can be calculated using the following formula:
(90%)(initial volume) = (70%)(final volume)
21. How many milliliters of 90% isopropyl alcohol are needed to create 1 liter of 70% isopropyl alcohol?
A. 0.00129 mL
B. 0.78 mL
C. 1.29 mL
D. 780 mL
Use the chart and graph for Item 22:
Earth’s Atmosphere
22. The concentration of substances in a mixture can be expressed in multiple formats. Using the information in the table and graph, what percent of the atmosphere’s total volume is made up of hydrogen?
A. 0.00005%
B. 0.5%
C. 5.0%
D. 50.0%
Use the passage for Item 23:
Ocean currents are streams of water that flow in continuous, directed paths within the ocean. Currents moving through the upper 400 meters of the ocean are classified as surface currents. Currents that flow at greater depths are classified as deep water currents.
23. Which type(s) of currents can be better understood by studying the paths of global wind patterns?
A. surface currents
B. deep water currents
C. both surface and deep water currents
D. neither surface nor deep water currents
Use the passage for Item 24:
Work is done when a force applied to an object causes the object to move a distance. The amount of work done can be determined by multiplying the force applied by the distance moved (W = f × d).
24. Sliding a box up a ramp into the back of a moving van requires the same amount of work as lifting the box from the ground into the van. If the amount of work is the same, what benefit does using a ramp provide?
A. increasing the force required to move the box
B. decreasing the force required to move the box
C. decreasing the total distance moved by the box
D. increasing the total distance moved by the box
Use the diagram for Item 25:
The Electromagnetic Spectrum
25. Which type of radiation can have a wavelength larger than a human?
A. radio
B. microwave
C. visible light
D. gamma ray
Use the diagram for Item 26:
26. Sunscreen lotions and sprays are designed to provide a barrier against UVA and UVB rays only. What information in the diagram explains why sunscreens are not designed to protect against UVC rays?
A. UVC is extremely dangerous.
B. UVA and UVB cause skin cancer.
C. UVC is blocked by the ozone layer.
D. UVA and UVB have higher wavelengths.
27. Energy stored in chemical bonds is called chemical energy. Which of the following objects stores chemical energy?
A. lightbulb
B. solar panel
C. alkaline battery
D. electrical outlet
Use the diagram for Item 28:
Temperature Scales
28. Restaurant health and safety guidelines require poultry to be cooked to a minimum internal temperature of 165 degrees. On which temperature scale is this guideline based?
A. Kelvin
B. Celsius
C. Fahrenheit
D. none of these
Use the table for Item 29:
Chemical processes can be categorized as endothermic or exothermic. Examples of each type of process are listed in the following table.
29. Which generalization can be made based on the examples in the table?
A. A reaction that releases heat is endothermic.
B. A reaction that releases energy is exothermic.
C. Exothermic reactions have a net increase in energy.
D. Endothermic reactions neither absorb nor release heat.
Use the passage for Item 30:
The European woodwasp is an invasive species that is thought to have been accidentally introduced into the United States in a wood shipment in 2004. The European woodwasp feeds on pine trees. It can also carry a fungus that kills pine trees.
30. The introduction of the European woodwasp is most likely to disrupt pine forest ecosystems in which way?
A. increased competition among consumers
B. loss of habitat for tree-dwelling organisms
C. water contamination by decaying pine trees
D. disease transmission to other insect species
Use the diagram for Item 31:
31. Which of the following members of the ecosystem would be considered a secondary consumer?
A. mice because they feed on a producer
B. rabbits because they have two food sources
C. grasshoppers because they have two predators
D. birds because they feed on a primary consumer
Use the diagram for Item 32:
32. What percentage of the energy available at the producer level is transferred all the way to the tertiary consumer level?
A. 0%
B. 0.1%
C. 10%
D. 25%
Use the passage for Item 33:
A genetic carrier is an individual who has one copy of the gene for a recessive genetic disease and one healthy gene. Since two copies of the disease gene are required to produce the disease, a carrier does not have the disease but can pass on the gene to children.
33. After undergoing genetic screening, a pregnant woman learns that she is a carrier for two genetic diseases: cystic fibrosis and spinal muscular atrophy. Her husband is not a carrier for either disease. What is the probability that the couple’s child will be a carrier for at least one of the two diseases?
A. 0%
B. 50%
C. 75%
D. 100%
Use the passage and the diagram for Item 34:
Mitosis is the process of dividing a cell’s nuclear material to produce two identical daughter cells. During mitosis, the cell contains two copies, or pairs, of each chromosome. These chromosome pairs line up and then separate, so that each new daughter cell will receive one complete set of chromosomes. The diagram shows the major stages of mitosis.
34. According to the diagram, chromosome pairs separate during which stage of mitosis?
A. prophase
B. anaphase
C. telophase
D. metaphase
35. Essential functions of life are those functions that must be carried out by all living things. Which function is not essential to all life?
A. growth
B. metabolism
C. reproduction
D. thermoregulation
36. If the longest day of the year in New York, USA, occurs on June 21, when does the shortest day of the year occur in Perth, Australia?
A. March 21
B. June 21
C. September 21
D. December 21
37. The equation for photosynthesis is shown below.
6CO2 + 6H2O + Energy → C6H12O6 + 6O2
Which of these correctly identifies the products in the equation?
A. glucose, oxygen
B. carbon dioxide, water
C. oxygen, carbon dioxide
D. oxygen, water, glucose
38. A driver applies the brakes of a car to exert a constant force. Which type of velocity-time graph would describe the car’s acceleration?
A. Straight line graph with a slope of zero
B. Exponential line that curves downward with a generally negative slope
C. Straight line graph with a negative slope
D. Exponential line that curves upward with a generally positive slope
39. While conducting an examination of a patient, an optometrist applies drops to the patient’s eyes. The drops cause the pupils to enlarge. Which part of the eye is affected by the drops?
A. lens
B. iris
C. retina
D. cornea
40. During labor, a baby’s head puts pressure on the opening of the uterus. Pressure receptors in the uterus send signals to the brain, which releases the hormone oxytocin. Oxytocin stimulates uterine smooth muscle contractions, which cause the baby to exert more pressure on the uterine opening. Which BEST describes this physiological situation?
A. This is a negative feedback mechanism leading to homeostasis.
B. This is a negative feedback mechanism leading to extremes.
C. This is a positive feedback mechanism leading to homeostasis.
D. This is a positive feedback mechanism leading to extremes.
THIS IS THE END OF THE SCIENCE PRETEST.
Answers and Explanations
1. Correct answer: D. According to the table, stars with surface temperatures between 11,000 and 25,000 K appear blue-white. Range is calculated as the difference between the highest and lowest temperature. For blue-white stars, this would be 25,000 K to 11,000 K, for a range of 14,000 K.
2. Correct answer: G. The temperature range for a Class G star is 5000 K to 6000 K. The surface temperature of the sun is within this range.
3. Correct answer: C. Dairy products like yogurt are rich in calcium. Blood calcium levels are more likely to rise after eating calcium-rich foods, causing the thyroid gland to release more calcitonin.
4. Bones make up the skeletal system. The intestines are part of the digestive system. The kidneys are part of the excretory system. The thyroid and parathyroid glands and the hormones they produce are part of the endocrine system.
5. Short-answer Reponse:
3-Point Response
• A clear and well-developed explanation of how a low-calcium diet affects the feedback mechanism for blood calcium regulation
• A clear and well-developed explanation of how chronically unbalanced blood calcium levels could contribute to the development of osteoporosis
• Complete support from the passage and diagram
Sample Paper
A diet low in calcium limits the supply of calcium available to the body, causing the body to spend a disproportionate amount of time in the part of the regulatory pathway that works to raise blood calcium levels. In this part of the pathway, low blood calcium signals the parathyroid gland to release PTH. PTH then stimulates calcium levels in the blood to increase by causing the release of calcium from bones, reabsorption in the kidneys, and increased uptake from food in the intestines. When the ability to uptake calcium in the intestines is limited by a low-calcium diet, the body has to rely more heavily on the bones as a source of calcium. Over time, releasing more calcium from the bones than is being deposited can lead to a decrease in bone mineral density and the development of osteoporosis.
2-Point Response
• An adequate or partially articulated explanation of how a low-calcium diet affects the feedback mechanism for blood calcium regulation
• An adequate or partially articulated explanation of how chronically unbalanced blood calcium levels could contribute to the development of osteoporosis
• Partial support from the passage and/or diagram
Sample Paper
If blood calcium levels are always low, the body will always be trying to raise calcium levels. One way to raise blood calcium is to remove calcium from bones. Removing calcium can be harmful to bones and could eventually cause osteoporosis.
1-Point Response
• A minimal or implied explanation of how a low-calcium diet affects the feedback mechanism for blood calcium regulation
• A minimal or implied explanation of how chronically unbalanced blood calcium levels could contribute to the development of osteoporosis
• Minimal or implied support from the passage and/or diagram
Sample Paper
The body will not have enough calcium. The body will have to take calcium from bones. Bones with less calcium could get osteoporosis.
0-Point Response
• No explanation of how a low-calcium diet affects the feedback mechanism for blood calcium regulation
• No explanation of how chronically unbalanced blood calcium levels could contribute to the development of osteoporosis
• No support from the passage or diagram
6. Correct answer: B. Homologous structures in different species are inherited from the same ancestral species. Species that share a common ancestor will have similarities in their DNA, which stores the genetic code. The species’ similar genetic codes produce the homologous structures.
7. Correct answer: A. The bones in the cat forelimb look most similar in shape and size to the bones in the human arm. This suggests that the common ancestor of the human and cat lived more recently than the ancestor humans share with the other species in the diagram.
8. Short-answer response:
3-Point Response
• A clear and well-developed explanation of how natural selection leads to adaptation in forelimbs
• Well-developed examples from the given diagram identifying structural features that support the forelimb’s unique function in specific species
• Complete support from the passage and diagram
Sample Paper
The process of natural selection allows species to become better adapted to survive in their environment over time. Though the forelimb structures of the species in the diagram originated from the same ancestor, each species’ structures have been modified over time in response to the species’ unique environments. The forelimb of the whale has reduced humerus, radius, and ulna bones, and elongated second and third phalanges. These adaptations allow the whale’s fin to cut through water to support the function of swimming. The forelimbs of the bat and bird have a reduced humerus and carpals and specialized phalanges. These adaptations allow the species’ wings to fan out to support the function of flying.
2-Point Response
• An adequate or partially articulated explanation of how natural selection leads to adaptation in forelimbs
• Partial examples from the given diagram identifying structural features that support the forelimb’s unique function in specific species
• Partial support from the passage and/or diagram
Sample Paper
Species that have a common ancestor can live in different environments. The species’ forelimb structures change over time so each species can survive in its own environment. The whale’s forelimb structure is adapted for swimming. The bat’s and bird’s forelimb structure is adapted for flying.
1-Point Response
• A minimal or implied explanation of how natural selection leads to adaptation in forelimbs
• One or incomplete examples from the given diagram identifying structural features that support the forelimb’s unique function in specific species
• Minimal or implied support from the passage and/or diagram
Sample Paper
Different species need to be able to do different things, so their forelimbs have to be a little different. Whales swim with fins. Bats and birds fly with wings.
0-Point Response
• No explanation of how natural selection leads to adaptation in forelimbs
• No examples from the given diagram identifying structural features that support the forelimb’s unique function in specific species
• No support from the passage and/or diagram
9. Correct answer: 6 and 6. In a chemical equation, the coefficient (number) in front of each substance identifies the number of molecules. According to the photosynthesis equation, 6 molecules of CO2 (carbon dioxide) and 6 molecules of H2O (water) are used to produce 1 molecule of C6H12O6 (glucose) and 6 molecules of O2 (oxygen).
10. Correct answer: D. In a chemical equation, reactants are to the left of the arrow and products are to the right. The products of photosynthesis are glucose and oxygen, and are shown on the right side of the photosynthesis equation. Glucose and oxygen are also the reactants for respiration, and are shown on the left side of the respiration equation.
11. California has a high incidence of earthquakes. Constructing buildings with steel-plate walls is a precaution used in areas with frequent earthquakes. Florida has a high incidence of hurricanes. Dikes, or levees, are walls built as a precaution against storm surge in areas with frequent hurricanes. Oklahoma has a high incidence of tornadoes. Constructing underground shelters is a precaution used in areas with frequent tornadoes.
12. Correct answer: D. Earthquakes occur most frequently along the boundaries of tectonic plates. When the pressure built up at a plate boundary becomes too great, energy is released in the form of an earthquake. According to the earthquake map, Washington has a high incidence of earthquakes, indicating that it lies near a plate boundary.
13. Correct answer: photosynthesis. Plants and other photosynthetic organisms absorb carbon dioxide from the atmosphere to use as a reactant in photosynthesis. According to the diagram, photosynthesis removes 110 gigatons of carbon from the atmosphere, far more than any other process in the diagram.
14. Correct answer: D. Fossil fuels are fuels derived from the fossil remains of dead organisms. Coal, oil, and natural gas are all fossil fuels. The diagram shows coal deposits storing 2000 GT of carbon, and oil and gas deposits storing 300 GT, for a total of 2300 GT of carbon stored in fossil fuel deposits
15. Correct answer: The graph should be marked where the line crosses the x-axis at 30 minutes. Above the x-axis, velocity is positive, indicating that the race car is moving forward. Below the x-axis, velocity is negative, indicating that the race car is moving in reverse. The race car changes direction when the graph crosses the x-axis.
16. Correct answer: B.
The units of velocity used in the graph are meters per minute (m/min). The units of time are minutes (min). Acceleration is calculated as change in velocity (m/min) divided by time (min), which results in units of m/min/min, or (m/min2).
17. Correct answer: A. According to the equation for Newton’s Second Law (f = ma), when an object’s acceleration is zero, the total net force acting on the object must also be zero. A total net force of zero means that all forces acting on the race car are balanced.
18. Correct answer: B. In mutualism, both species receive a benefit from engaging in the relationship. In this case, the bee receives a food source (nectar) from the flower. The flower receives assistance with reproduction as the bee transfers the flower’s pollen to the next flower it lands on.
19. Correct answer: C. A substance’s density describes how tightly packed the substance’s molecules are. When a solution is separated into its components, the component with the highest density will sink to the bottom and the component with the lowest density will remain at the top. In the diagram, red blood cells are at the bottom of the test tube, indicating that they have the highest density.
20. Correct answer: C. When part of a model does not exactly mirror the behavior of a natural phenomenon, the discrepancy is termed a weakness. Within an atom, electrons do orbit the nucleus, but not along fixed paths as shown in the diagram. Instead, electrons travel more randomly around the nucleus within electron clouds.
21. Correct answer: D. The initial volume of 90% isopropyl alcohol needed can be calculated by inserting 1 L into the formula and then solving: initial volume = (70% × 1 L)/(90%) = 0.78 L. Because there are 1000 mL in a liter, the number of milliliters needed can be calculated by multiplying 0.78 L × 1000 = 780 mL.
22. Correct answer: A. The table identifies the atmospheric concentration of hydrogen to be 0.5 PPM. As shown in the pie graph, the concentration in percent volume can be determined by dividing the concentration in PPM by 10,000. Therefore, 0.5 PPM ÷ 10,000 = 0.00005% hydrogen concentration in the atmosphere.
23. Correct answer: A. As wind moves along the ocean’s surface, the gas particles in the air drag the water particles on the ocean’s surface in the same direction. This causes global wind patterns and surface ocean currents to travel along the same paths.
24. Correct answer: B. A ramp is a simple machine that reduces the amount of force required to move an object by increasing the total distance over which the object is moved. Increasing the distance allows the same amount of work to be done, but with less force.
25. Correct answer: A. The distance between consecutive peaks of a wave identifies its wavelength. As indicated on the diagram, an average radio wave has a wavelength that is larger than a human. Radio waves have the longest average wavelength (103 meters) on the electromagnetic spectrum.
26. Correct answer: C. According to the diagram, UVA and UVB rays from the sun can both penetrate the ozone layer, but UVC cannot. Developing a sunscreen product that protects against UVC rays is unnecessary because UVC rays do not reach Earth.
27. Correct answer: C. An alkaline battery contains stored chemical energy in the form of two chemicals (zinc and magnesium dioxide). When a battery is placed in an electrical circuit, the two chemicals react, breaking chemical bonds to produce electrical energy.
28. Correct answer: C. Poultry is considered properly cooked when it reaches an internal temperature of 165 degrees Fahrenheit. According to the diagram, 165°F falls between the highest air temperature recorded in the United States and the boiling point of water. 165°F is considered hot enough to kill harmful bacteria that may be present in poultry.
29. Correct answer: B. The processes in the exothermic column all release energy into the environment, usually in the form of heat. A candle flame produces heat. Burning sugar produces a net release of energy. Making ice cubes and condensing water vapor both require the temperature of water to decrease, which occurs by the release of heat into the environment.
30. Correct answer: B. As the fungus carried by the European woodwasp kills pine trees, tree-dwelling organisms such as birds and squirrels will lose their homes. This habitat loss will disrupt the forest ecosystem because tree-dwelling species will be forced into greater competition for space or migration to another ecosystem.
31. Correct answer: D. A secondary consumer feeds on a primary consumer, which feeds on producers. In the food web shown, birds feed on grasshoppers, which feed on grasses and grains. The grasses and grains are producers, the grasshoppers are primary consumers, and the birds are secondary consumers.
32. Correct answer: B. In an ecosystem, approximately 10% of the energy available at any trophic level is passed up to the organisms in the next trophic level. In this energy pyramid, primary consumers receive 10% (1000 kcal) of the producers’ 10,000 kcal. Secondary consumers receive 10% of the primary consumers’ 1000 kcal, or 1% of the producers’ 10,000 kcal. Tertiary consumers receive 10% of the secondary consumers’ 100 kcal, or 0.1% of the producers’ 10,000 kcal.
33. Correct answer: C. The father passes on only healthy genes to the child. The mother could have passed on 4 different gene combinations to her child, as shown in the following diagram. The 3 gene combinations highlighted in gray include at least one diseased gene, meaning the child has a ¾, or 75%, chance of being a carrier for at least one disease.
34. Correct answer: B. Chromosome pairs separate during anaphase. This is illustrated in the third row of the diagram, in which the x-shaped chromosomes appear to be pulled apart and toward opposite sides of the cell.
35. Correct answer: D. Thermoregulation is the ability to maintain a stable body temperature even in a fluctuating environment. Though many organisms, like humans, can thermoregulate, others cannot. Lizards, for example, must absorb heat from the environment. Since all living things are not able to do it, thermoregulation is not an essential function of life.
36. Correct answer: B. Seasons in opposing hemispheres are due to the tilt of the Earth’s axis and the proximity of the hemisphere to the sun. In summer, the Northern Hemisphere is tilted toward the sun, so New York has its longest day on the summer solstice, in this case June 21. On the same June 21, the Southern Hemisphere is tilted away from the sun, so Perth, Australia, has its shortest day.
37. Correct answer: A. Glucose and oxygen are products of the photosynthesis reaction.
38. Correct answer: C. The car is decelerating at a constant force, so the velocity is decreasing at a constant rate. Therefore, the velocity-time graph describing this situation would be a straight line with a negative slope.
39. Correct answer: B. The iris contains the muscles that contract and relax to regulate the size of the pupil. When the iris contracts, the pupil gets smaller. Conversely, when the iris relaxes, the pupil enlarges. The drops cause the iris to relax, thereby enlarging the pupil.
40. Correct answer: D. The stimulus (pressure) leads to hormone secretion that evokes a response (muscle contraction) that furthers the increased stimulus (more pressure). This is a positive feedback mechanism leading to extremes and is stopped only when the baby is delivered and the pressure is finished.
Evaluation Chart
Check the Answers and Explanations section of the Science Pretest to see which answers you got correct and which ones you missed. For each question that you missed, find the item number in the chart below. Check the column on the left to see the test content area for that item. If you missed questions in a particular content area, you need to pay particular attention to that area as you study for the GED® test. The pages of this book that cover that content area are listed in the column on the right.
