Independent book-reader practice

CLEP Natural Sciences Online Practice Test 1

120 questions · 90 minutes · five choices per question. Select the one best answer. After submission, review every missed or uncertain item; raw practice results are not official CLEP scaled scores.

Question 1 of 120

Which region of the human brain coordinates voluntary muscle movements and helps maintain balance?

Answer choices for question 1A. The corpus callosumB. The cerebrumC. The medulla oblongataD. The hypothalamusE. The cerebellum

Question 2 of 120

A 2 kg cart starts from rest and reaches a speed of 6 m/s in 3 s along a frictionless track. What is the net force acting on the cart?

Answer choices for question 2A. 2 NB. 4 NC. 12 ND. 18 NE. 6 N

Question 3 of 120

In a small population, the frequency of an allele shifts from one generation to the next purely by random chance rather than by any survival advantage. This mechanism of evolution is called

Answer choices for question 3A. natural selectionB. gene flowC. mutationD. adaptationE. genetic drift

Question 4 of 120

In a plant cell, which organelle captures light energy and carries out photosynthesis?

Answer choices for question 4A. MitochondrionB. RibosomeC. NucleusD. ChloroplastE. The vacuole

Question 5 of 120

A forest is destroyed by a wildfire, but the soil, along with many seeds and roots, survives beneath the surface. Over the following years grasses return first, then shrubs, and eventually the forest regrows. This gradual regrowth of a community on land where the soil already remains is best described as

Answer choices for question 5A. deforestationB. primary successionC. natural selectionD. eutrophicationE. secondary succession

Question 6 of 120

Why is the bond between oxygen and hydrogen in a water molecule classified as polar covalent?

Answer choices for question 6A. Electrons are transferred completely from hydrogen to oxygen.B. The two atoms have identical electronegativity and share electrons equally.C. Electrons are shared unequally, leaving oxygen slightly negative and hydrogen slightly positive.D. No electrons are shared between the atoms.E. Hydrogen bonds hold the oxygen and hydrogen together within the molecule.

Question 7 of 120

At a mid-ocean ridge, new oceanic crust is continually created. This occurs at a boundary where two tectonic plates

Answer choices for question 7A. collide, forcing one plate beneath the otherB. move apart as magma rises and solidifies between themC. slide horizontally past one anotherD. converge slowly without one plate descending beneath the otherE. press together and fold upward into a tall mountain range

Question 8 of 120

What is the primary function of the valves located between the chambers of the human heart?

Answer choices for question 8A. To produce new red blood cellsB. To exchange oxygen and carbon dioxide with the airC. To generate the heartbeat's electrical signalD. To prevent blood from flowing backwardE. To pump blood out to the entire body

Question 9 of 120

An atom of carbon-14 has an atomic number of 6 and a mass number of 14. How many neutrons are in its nucleus?

Answer choices for question 9A. 8B. 6C. 14D. 20E. 7

Question 10 of 120

A lunar eclipse takes place when

Answer choices for question 10A. the Moon passes between the Sun and Earth and casts a shadow on EarthB. the Moon is at first quarter and half of its lit side faces EarthC. the Moon enters the shadow cast by another planet in the solar systemD. the Moon reaches perigee and appears larger than usual from EarthE. Earth passes between the Sun and Moon and its shadow falls on the Moon

Question 11 of 120

Ignoring air resistance, a heavy bowling ball and a light tennis ball are released from the same height at the same instant. Which statement is correct?

Answer choices for question 11A. The bowling ball lands first because it is heavier.B. The bowling ball falls at a constant speed while the tennis ball speeds up.C. The tennis ball lands first because it is lighter.D. Neither ball accelerates as it falls.E. Both balls reach the ground at the same time.

Question 12 of 120

Two small spheres each carry a positive electric charge. When they are brought close together, they will

Answer choices for question 12A. attract each other stronglyB. share charge until both spheres become neutralC. exert no force on each otherD. merge into a single neutral sphereE. repel each other

Question 13 of 120

Sugars made during photosynthesis in a plant's leaves are transported to the roots and other tissues mainly through the

Answer choices for question 13A. phloemB. xylemC. stomataD. epidermisE. the cambium

Question 14 of 120

A few individuals from one population of beetles migrate into a neighboring population and breed with them, introducing alleles that were not present before. This process is called

Answer choices for question 14A. genetic driftB. mutationC. speciationD. natural selectionE. gene flow

Question 15 of 120

When a DNA molecule replicates, each resulting double helix is made of

Answer choices for question 15A. two newly synthesized strandsB. one original strand and one newly made strandC. two original strands with no new nucleotidesD. a strand of DNA paired with a strand of RNAE. a triple helix of one original strand and two new strands

Question 16 of 120

Two species of birds in the same forest feed on exactly the same insects and use the same nesting sites. Over time, one species tends to decline or shift its behavior. This outcome is best explained by

Answer choices for question 16A. predationB. mutualism between the two speciesC. commensalismD. decompositionE. competition for the same limited resources

Question 17 of 120

In a sealed container, 12 g of carbon reacts completely with 32 g of oxygen to form carbon dioxide, with nothing left over. What mass of carbon dioxide is produced?

Answer choices for question 17A. 20 gB. 32 gC. 12 gD. 44 gE. 56 g

Question 18 of 120

The San Andreas Fault, where two plates grind horizontally past each other and produce frequent earthquakes, is an example of a

Answer choices for question 18A. divergent boundaryB. convergent boundaryC. transform boundaryD. hot spotE. a subduction zone

Question 19 of 120

When you touch a very hot surface, your hand pulls back before you consciously feel the pain. This rapid, involuntary response is a

Answer choices for question 19A. conditioned habit learned over many yearsB. reflex, coordinated mainly by the spinal cordC. voluntary action directed by the cerebrumD. hormonal response carried by the bloodE. a signal handled by the cerebellum to smooth out the motion

Question 20 of 120

In a pot of water heated on a stove, warm water rises while cooler water sinks, setting up a circulating current that transfers heat throughout the pot. This process is

Answer choices for question 20A. conductionB. radiationC. insulationD. convectionE. evaporation

Question 21 of 120

When you bend your arm at the elbow, the biceps contracts while the triceps relaxes; straightening the arm reverses the two. Muscles that operate in such opposing pairs are described as

Answer choices for question 21A. involuntary musclesB. cardiac musclesC. antagonistic musclesD. smooth musclesE. synergistic muscles

Question 22 of 120

In one common type of radioactive decay, a neutron in the nucleus changes into a proton and a fast-moving electron is emitted. This emitted electron is

Answer choices for question 22A. a positronB. an alpha particleC. a gamma rayD. a protonE. a beta particle

Question 23 of 120

A medium-mass star such as the Sun, after it uses up the hydrogen fuel in its core, will expand greatly and cool at its surface to become a

Answer choices for question 23A. white dwarfB. red giantC. neutron starD. black holeE. a supernova

Question 24 of 120

The streamlined bodies and fins of sharks (fish) and dolphins (mammals) look similar even though the two groups are only distantly related. These similar features are best described as

Answer choices for question 24A. homologous structures inherited from a streamlined recent common ancestorB. vestigial structures retained after an ancestral aquatic stageC. coevolved structures shaped by direct shark--dolphin interactionsD. analogous structures shaped independently by convergent evolutionE. acquired structures produced by repeated swimming during each animal's life

Question 25 of 120

The process in which a molecule of messenger RNA is built using one strand of DNA as a template is called

Answer choices for question 25A. translationB. replicationC. transcriptionD. respirationE. mutation

Question 26 of 120

A population grows rapidly at first, then slows and levels off as it approaches the maximum number its environment can support, tracing an S-shaped curve. This pattern is called

Answer choices for question 26A. logistic growthB. exponential growthC. zero population growth from the startD. random fluctuationE. linear growth

Question 27 of 120

In a chemical reaction, a sodium atom loses one electron to become a sodium ion, Na⁺. This change is best described as

Answer choices for question 27A. reduction, because reduction always means losing electronsB. oxidation, because oxidation is the loss of electronsC. oxidation, but only if oxygen gas is one of the reactantsD. reduction, because forming a positive ion reduces the atom's sizeE. neutralization, because forming an ion cancels out the atom's charge

Question 28 of 120

What is the main driving force that moves Earth's tectonic plates over geologic time?

Answer choices for question 28A. The rotation of Earth on its axisB. Tides caused by the Moon's gravityC. Winds in the upper atmosphereD. Convection currents in the hot, slowly flowing mantleE. The steady pull of the Sun's gravity on Earth's crust

Question 29 of 120

In the circulatory system, the exchange of oxygen, nutrients, and wastes between the blood and the body's tissues takes place mainly in the

Answer choices for question 29A. capillariesB. arteriesC. veinsD. aortaE. the venules

Question 30 of 120

Two identical cars are moving, but the second car travels twice as fast as the first. Compared with the first car, the faster car's kinetic energy is

Answer choices for question 30A. the sameB. twice as greatC. eight times as greatD. half as greatE. four times as great

Question 31 of 120

In the ABO blood group, the alleles I^A and I^B are each dominant to i. A person with the genotype I^A i will have blood type

Answer choices for question 31A. type OB. type A-negativeC. type ABD. type BE. type A

Question 32 of 120

Some whales have small hip and leg bones buried within their bodies that play no role in swimming. These structures are best interpreted as

Answer choices for question 32A. analogous structures shaped by convergent evolutionB. adaptations that improve the whale's swimmingC. homologous structures that evolved independently after whales entered the oceanD. new structures that are just beginning to grow into working legsE. vestigial structures inherited from four-legged ancestors

Question 33 of 120

During intense exercise, muscle cells run short of oxygen but must keep making ATP through glycolysis. To regenerate the NAD⁺ that glycolysis requires, these cells convert pyruvate into

Answer choices for question 33A. lactateB. ethanol and carbon dioxideC. glucoseD. acetyl-CoA that enters the Krebs cycleE. oxygen and water

Question 34 of 120

Sea otters keep sea urchin populations in check; where otters are removed, urchins multiply and destroy entire kelp forests. A species whose effect on its community is far larger than its numbers suggest is called a

Answer choices for question 34A. producerB. invasive speciesC. keystone speciesD. decomposerE. an indicator species

Question 35 of 120

When a hydrocarbon fuel such as methane (CH₄) burns completely in oxygen, the main products are

Answer choices for question 35A. hydrogen gas and solid carbonB. water onlyC. nitrogen and oxygenD. carbon dioxide and waterE. carbon monoxide only

Question 36 of 120

Limestone that is buried deep underground and subjected to intense heat and pressure without melting changes into marble. Marble is therefore classified as

Answer choices for question 36A. a sedimentary rockB. a metamorphic rockC. an igneous rockD. a type of magmaE. a single mineral rather than a rock

Question 37 of 120

A moving railroad car couples with an identical stationary car, and the two move off together. Ignoring friction, the total momentum of the two coupled cars just after the collision is

Answer choices for question 37A. equal to the moving car's momentum immediately before the collisionB. zero because the stationary car initially had no momentumC. twice the moving car's momentum immediately before the collisionD. greater than the initial momentum by an unknown amountE. half the moving car's momentum immediately before the collision

Question 38 of 120

Several light bulbs in a house are wired in parallel. When one bulb is unscrewed and removed from its socket, the other bulbs keep glowing. This happens because a parallel circuit

Answer choices for question 38A. connects every bulb along one single path, so the current passes through them one after anotherB. stores enough charge in its wires to keep the other bulbs litC. gives each bulb its own separate branch, so removing one bulb leaves the other branches completeD. boosts the voltage across the remaining bulbs whenever one is removedE. redistributes the source voltage from the open branch to the neighboring branches

Question 39 of 120

Cystic fibrosis is caused by a recessive allele. If two carriers, each heterozygous (Cc), have children, what is the probability that any given child will have cystic fibrosis?

Answer choices for question 39A. 0B. 1/4C. 1/2D. 3/4E. 1

Question 40 of 120

In a nuclear reactor, a uranium-235 nucleus absorbs a neutron and splits, releasing energy along with two or three additional neutrons that can strike other uranium nuclei and cause them to split as well. This self-sustaining sequence is called a

Answer choices for question 40A. fusion reactionB. radioactive decay seriesC. combustion reactionD. chain reactionE. a nuclear meltdown

Question 41 of 120

The observation that nearly all distant galaxies are moving away from us, with more distant galaxies receding faster, is a key piece of evidence for

Answer choices for question 41A. a universe that stays the same size foreverB. a universe that is steadily contractingC. the Big Bang theory of an expanding universeD. the idea that Earth sits at the center of the universeE. random local galaxy motions within an otherwise nonexpanding universe

Question 42 of 120

Between meals, when blood glucose drops, the pancreas releases a hormone that signals the liver to release stored glucose, raising blood sugar back toward normal. This hormone is

Answer choices for question 42A. glucagonB. insulinC. adrenaline released only during exerciseD. estrogenE. thyroxine

Question 43 of 120

A person pushes a box with a steady force of 20 N and moves it 5 m in the direction of the force. How much work is done on the box?

Answer choices for question 43A. 4 JB. 25 JC. 0 JD. 100 JE. 15 J

Question 44 of 120

After an antibiotic is used widely, a bacterial population comes to be dominated by resistant strains. This change is best explained by

Answer choices for question 44A. a temporary physiological adjustment made by each exposed bacteriumB. natural selection favoring the resistant individuals that survive and reproduceC. the antibiotic creating brand-new resistance genes in every cellD. all bacteria inheriting resistance gained through repeated useE. The original bacteria were all killed and resistant ones later arrived from another location.

Question 45 of 120

During meiosis, homologous chromosomes exchange corresponding segments, increasing genetic variation among the resulting cells. This exchange is called

Answer choices for question 45A. mitosisB. replicationC. crossing overD. binary fissionE. nondisjunction

Question 46 of 120

A biome characterized by permanently frozen subsoil (permafrost), very cold temperatures, and low-growing vegetation with no trees is the

Answer choices for question 46A. tundraB. tropical rainforestC. desertD. temperate grasslandE. the taiga (boreal forest)

Question 47 of 120

Magnesium forms Mg²⁺ ions and nitrogen forms N^3- ions. What is the correct formula for the neutral ionic compound magnesium nitride?

Answer choices for question 47A. MgNB. Mg₂N₃C. Mg₃ND. Mg₃N₂E. Mg₂N₂

Question 48 of 120

A student compares an unknown mineral, W, with two reference minerals. A scratch counts only when it leaves a permanent groove.
Test Result
W drawn across calcite (hardness 3) Calcite is scratched
W drawn across fluorite (hardness 4) Fluorite is not scratched
Fluorite drawn across W W is scratched
Which conclusion is best supported by the results?

Test	Result
W drawn across calcite (hardness 3)	Calcite is scratched
W drawn across fluorite (hardness 4)	Fluorite is not scratched
Fluorite drawn across W	W is scratched

Answer choices for question 48A. W is softer than both calcite and fluorite.B. W is harder than calcite but softer than fluorite.C. W has the same hardness as calcite because it scratched calcite.D. W is harder than fluorite because fluorite scratched it.E. The relative hardness of W cannot be inferred from scratch tests.

Question 49 of 120

In pea plants, a tall heterozygous plant (Tt) is crossed with another tall heterozygous plant (Tt). What is the probability that a given offspring is homozygous dominant (TT)?

Answer choices for question 49A. 3/4B. 1/2C. 1/4D. 0E. 1/3

Question 50 of 120

On a sunny day at the beach, the sand becomes much hotter than the ocean water even though both receive the same sunlight. This happens mainly because water has a

Answer choices for question 50A. lower thermal conductivity, so energy cannot enter it as quicklyB. lower specific heat than sandC. lower latent heat, so less energy is involved in phase changesD. higher thermal conductivity, so absorbed energy spreads through it fasterE. higher specific heat, so it takes more energy to raise its temperature

Question 51 of 120

The microscopic functional unit of the kidney, where blood is filtered and urine begins to form, is the

Answer choices for question 51A. alveolusB. neuronC. villusD. the hepatocyteE. nephron

Question 52 of 120

In the core of the Sun, hydrogen nuclei combine to form helium, releasing a great deal of energy. This type of nuclear reaction is called

Answer choices for question 52A. fissionB. ionizationC. radioactive decayD. combustionE. fusion

Question 53 of 120

Our Sun is one of several hundred billion stars that belong to a large, spiral-shaped system of stars, gas, and dust called the

Answer choices for question 53A. solar systemB. universeC. Milky Way galaxyD. Big DipperE. the Andromeda galaxy

Question 54 of 120

Modern biologists divide all living things into three large groups called domains. These three domains are

Answer choices for question 54A. Bacteria, Archaea, and EukaryaB. Plants, Animals, and FungiC. Prokaryotes, Protists, and VirusesD. Vertebrates, Invertebrates, and MicrobesE. Monera, Protista, and Fungi

Question 55 of 120

Most human enzymes work fastest near body temperature and slow or stop when the temperature climbs too high. The main reason very high temperatures stop an enzyme is that they

Answer choices for question 55A. increase molecular motion until every collision produces a reactionB. disrupt the enzyme's shape so the active site binds poorlyC. convert the enzyme into a product of the reaction it catalyzesD. strengthen the active site until substrate can no longer leaveE. create additional active sites that compete for the same substrate

Question 56 of 120

Fertilizer runoff adds excess nutrients to a lake, causing algae to grow explosively; when the algae die and decay, dissolved oxygen is used up and fish die off. This process is called

Answer choices for question 56A. ecological successionB. desertificationC. biomagnificationD. eutrophicationE. acid rain

Question 57 of 120

Which property is characteristic of an acidic solution?

Answer choices for question 57A. It feels slippery and tastes bitter.B. It turns red litmus paper blue.C. It tastes sour and turns blue litmus paper red.D. It has a pH greater than 7.E. It reacts with metals to release chlorine gas.

Question 58 of 120

An underground layer of permeable rock or sediment that stores and transmits groundwater, supplying water to wells, is called

Answer choices for question 58A. an aquiferB. a glacierC. surface runoffD. impermeable bedrockE. a watershed

Question 59 of 120

Hemophilia is an X-linked recessive disorder. A carrier mother (X^H X^h) has children with an unaffected father (X^H Y). Which of their children can be affected by hemophilia?

Answer choices for question 59A. daughters who inherit their father's unaffected X chromosomeB. sons who inherit the X^h allele from their motherC. daughters who inherit one X^h allele from their motherD. sons who inherit their father's Y chromosome without a maternal XE. sons who inherit an X^h allele from their father

Question 60 of 120

Two motors each lift the same load to the same height, but the first motor does it in half the time the second motor takes. Compared with the second motor, the first motor develops

Answer choices for question 60A. less powerB. the same powerC. no powerD. more powerE. half as much power

Question 61 of 120

A singer produces a higher-pitched note. Compared with a lower-pitched note, the sound wave of the higher note has a

Answer choices for question 61A. higher frequencyB. larger amplitudeC. slower speed in the same airD. longer wavelengthE. a greater loudness than the lower note

Question 62 of 120

Which blood cells are the body's main defenders against invading bacteria and viruses?

Answer choices for question 62A. Red blood cellsB. PlateletsC. White blood cellsD. Plasma proteins that carry oxygenE. Stem cells circulating in the bloodstream

Question 63 of 120

Oceanic islands often have unique species found nowhere else, and species on neighboring islands resemble one another more closely than species on distant islands. This geographic pattern is evidence for

Answer choices for question 63A. separate origins for each island population with no shared ancestryB. evolution, as isolated populations diverge from common ancestorsC. convergent evolution alone, with no role for isolation or common ancestryD. continuous gene flow that prevents neighboring island populations from divergingE. direct environmental modification of individuals that is inherited by their offspring

Question 64 of 120

The first stage of cellular respiration, which splits a glucose molecule into two molecules of pyruvate in the cytoplasm, is

Answer choices for question 64A. the Krebs cycleB. the electron transport chainC. fermentationD. glycolysisE. the Calvin cycle

Question 65 of 120

In a food chain, grass is eaten by a grasshopper, which is then eaten by a bird. The grasshopper occupies the role of a

Answer choices for question 65A. primary consumerB. producerC. secondary consumerD. decomposerE. a tertiary consumer

Question 66 of 120

Atoms tend to form chemical bonds mainly in order to

Answer choices for question 66A. increase their number of protonsB. become radioactiveC. achieve a stable, filled outer shell of electronsD. place their valence electrons in higher-energy orbitalsE. gain additional neutrons in the nucleus

Question 67 of 120

Warm ocean currents such as the Gulf Stream affect the climate of nearby coasts mainly by

Answer choices for question 67A. drawing heat out of coastal air as the tropical water moves polewardB. increasing coastal cloud reflectivity enough to offset the transported heatC. preventing seasonal winds from crossing the coastlineD. carrying heat that warms the air over coastal regionsE. warming the seawater while transferring little energy to the air above it

Question 68 of 120

When a blood vessel is cut, which blood component is chiefly responsible for forming a clot to stop the bleeding?

Answer choices for question 68A. Red blood cellsB. PlateletsC. White blood cellsD. HemoglobinE. Antibodies dissolved in the plasma

Question 69 of 120

A laboratory measures the decay of an isotope in a sealed sample.
Elapsed time (years) Isotope remaining (mg)
0 80
2,600 40
5,200 20
7,800 10
A second sample originally contained 80 mg of this isotope and now contains 5 mg. If the decay rate is unchanged, about how old is the second sample?

Elapsed time (years)	Isotope remaining (mg)
0	80
2,600	40
5,200	20
7,800	10

Answer choices for question 69A. 10,400 yearsB. 2,600 yearsC. 5,200 yearsD. 7,800 yearsE. 20,800 years

Question 70 of 120

A small, icy body that develops a long, glowing tail of gas and dust when it travels close to the Sun is best described as a(n)

Answer choices for question 70A. meteoriteB. asteroidC. a meteorD. planetE. comet

Question 71 of 120

At constant pressure, what happens to the volume of a fixed amount of gas as its temperature increases?

Answer choices for question 71A. The volume decreases as its absolute temperature increases.B. The volume stays the same because the amount of gas is fixed.C. The volume increases only if the pressure also increases.D. The volume decreases because faster particles occupy less effective space.E. The volume increases in proportion to its absolute temperature.

Question 72 of 120

In flowering plants, the transfer of pollen from an anther to a stigma is called

Answer choices for question 72A. fertilizationB. germinationC. photosynthesisD. dispersalE. pollination

Question 73 of 120

According to the endosymbiotic theory, the mitochondria and chloroplasts of eukaryotic cells originated as

Answer choices for question 73A. free-living prokaryotes that were engulfed by an early host cell and survived inside itB. pieces of the host cell's own nucleus that broke awayC. viruses that infected only animal cellsD. mineral crystals that formed in the early oceanE. inward folds of the host cell's own outer membrane that pinched off

Question 74 of 120

In cells, which molecule stores and quickly delivers energy for most cellular processes by breaking a high-energy phosphate bond?

Answer choices for question 74A. DNAB. Glucose stored in the nucleusC. ATPD. CelluloseE. Starch stored in the mitochondria

Question 75 of 120

Why does higher biodiversity generally make an ecosystem more stable and better able to recover from disturbances?

Answer choices for question 75A. More species make each population independent of environmental conditions.B. Overlapping ecological roles can preserve functions when one species declines.C. More consumer species reduce the ecosystem's dependence on primary producers.D. Greater species richness prevents organisms from competing for shared resources.E. One dominant species can regulate the responses of every other population.

Question 76 of 120

How many atoms in total are present in one formula unit of aluminum sulfate, Al₂(SO₄)₃?

Answer choices for question 76A. 9B. 12C. 14D. 17E. 20

Question 77 of 120

A cold front forms where

Answer choices for question 77A. cold, dense air advances beneath warm air and forces the warm air upwardB. warm air advances gradually over retreating cold air along a shallow slopeC. two air masses meet but neither advances enough to displace the otherD. two air masses rotate around a low-pressure center without meetingE. warm air is lifted from the ground between two converging cold fronts

Question 78 of 120

According to Einstein's special theory of relativity, a clock moving at a speed close to the speed of light, as observed by a stationary observer, will

Answer choices for question 78A. run faster than the observer's own clockB. run slower only because its light signals take longer to arriveC. run slower than the observer's own clockD. run at exactly the same rate as the observer's clockE. run slower only while it is accelerating, then match the observer's clock

Question 79 of 120

After fertilization, the single-celled zygote undergoes a series of rapid mitotic divisions that increase the number of cells without much overall growth in size. These early divisions are called

Answer choices for question 79A. meiosisB. fertilizationC. metamorphosisD. cleavageE. differentiation

Question 80 of 120

During childbirth, contractions of the uterus push the baby against the cervix, which triggers still stronger contractions until birth occurs. This self-amplifying loop is an example of

Answer choices for question 80A. negative feedbackB. positive feedbackC. a purely random eventD. an inherited reflex active at all timesE. homeostasis that keeps the mother's body conditions constant

Question 81 of 120

In an atom, electrons are arranged in regions around the nucleus that correspond to different amounts of energy. These regions are called

Answer choices for question 81A. energy levels (shells)B. protonsC. nucleiD. isotopesE. neutrons

Question 82 of 120

Which is the largest planet in our solar system?

Answer choices for question 82A. EarthB. SaturnC. JupiterD. MarsE. Neptune

Question 83 of 120

A car travels down a straight, level highway at a constant velocity. What can you conclude about the forces acting on it?

Answer choices for question 83A. No forces are acting on the car at all.B. The forces are balanced, so the net force is zero.C. There is a large net force in the direction of motion.D. The forward driving force is larger than the resistive forces.E. A small forward force is needed to keep the car moving at steady speed.

Question 84 of 120

In a string of older holiday lights wired in series, if a single bulb burns out the entire string goes dark. This happens because a series circuit

Answer choices for question 84A. provides many separate paths for the currentB. lets current continue through the wire even when the circuit is openC. places each bulb directly across the source on an independent branchD. provides only one path, so a break anywhere stops the current everywhereE. diverts current around the failed bulb through a second shared path

Question 85 of 120

A certain orchid stores its nectar at the bottom of an unusually long, narrow spur, and it is pollinated only by a single moth species whose feeding tube is just long enough to reach that nectar. Over time, changes in the flower's spur and the moth's feeding tube appear to have driven each other. This reciprocal evolutionary influence between two interacting species is best described as

Answer choices for question 85A. convergent evolutionB. artificial selectionC. coevolutionD. genetic driftE. adaptive radiation

Question 86 of 120

During which part of the cell cycle does a cell copy its DNA in preparation for dividing?

Answer choices for question 86A. InterphaseB. Mitosis (the M phase)C. CytokinesisD. Only after the cell has already dividedE. During prophase, as the chromosomes condense

Question 87 of 120

In a food web, if a disease sharply reduces the population of a primary consumer, the most likely immediate effect is that

Answer choices for question 87A. producer populations may decline while predator populations increaseB. producer populations may increase while predator populations decreaseC. producer and predator populations may both increase immediatelyD. decomposer populations must decline because less sunlight enters the webE. energy transfer to every higher trophic level must remain unchanged

Question 88 of 120

In the reaction Zn + 2 HCl → ZnCl₂ + H₂, zinc takes the place of hydrogen in the compound. This reaction is best classified as a

Answer choices for question 88A. synthesis reactionB. decomposition reactionC. double-replacement reactionD. single-replacement reactionE. a combustion reaction

Question 89 of 120

Warm air can hold more water vapor than cold air. As a mass of humid air cools in the evening, water may condense onto surfaces as dew once the air reaches its

Answer choices for question 89A. boiling pointB. freezing pointC. dew pointD. melting pointE. flash point

Question 90 of 120

Which endocrine gland is often called the ``master gland'' because its hormones regulate the activity of several other endocrine glands?

Answer choices for question 90A. The thymus glandB. The thyroid glandC. The pancreasD. The adrenal glandE. The pituitary gland

Question 91 of 120

A runner completes one full lap of 400 m around a track in 50 s, finishing exactly where she started. Her average speed for the lap is

Answer choices for question 91A. 0 m/sB. 0.125 m/sC. 20 m/sD. 450 m/sE. 8 m/s

Question 92 of 120

A guinea pig heterozygous for two independently assorting traits (AaBb) is crossed with a guinea pig recessive for both traits (aabb). What fraction of the offspring is expected to have genotype aabb?

Answer choices for question 92A. 1B. 3/4C. 1/2D. 1/8E. 1/4

Question 93 of 120

On a cladogram (a branching evolutionary tree), two species joined by the most recent branch point are interpreted as

Answer choices for question 93A. sharing every derived trait shown elsewhere on the diagramB. being closest together on the printed page, regardless of branch pointsC. sharing a more recent common ancestor than species on more distant branchesD. occupying the same habitat and ecological nicheE. descended one directly from the other along a single unbranched line

Question 94 of 120

Which feature is found in eukaryotic cells but not in prokaryotic cells?

Answer choices for question 94A. A membrane-bound nucleusB. A cell membraneC. RibosomesD. Genetic material of some kindE. Cytoplasm that fills the inside of the cell

Question 95 of 120

The process by which plants release water vapor into the atmosphere through tiny pores in their leaves, adding water to the water cycle, is called

Answer choices for question 95A. condensationB. precipitationC. runoffD. transpirationE. infiltration

Question 96 of 120

Which of the following is a physical change rather than a chemical change?

Answer choices for question 96A. Wood burning to ashB. Water boiling into steamC. Iron rustingD. Baking soda reacting with vinegar to fizzE. Milk turning sour as it spoils

Question 97 of 120

Along the western coast of South America, an oceanic plate sinks beneath a continental plate, producing a deep ocean trench and a chain of volcanoes. This activity occurs at a

Answer choices for question 97A. convergent boundary where dense oceanic lithosphere subductsB. divergent boundary where new oceanic lithosphere formsC. transform boundary where plates slide horizontally pastD. passive continental margin far from an active boundaryE. intraplate hot spot above a relatively stationary mantle plume

Question 98 of 120

Which of the following is a primary function of a plant's roots?

Answer choices for question 98A. Carrying out most of the plant's photosynthesisB. Producing pollen for reproductionC. Anchoring the plant and absorbing water and minerals from the soilD. Releasing seeds into the windE. Producing the colorful petals that attract pollinators

Question 99 of 120

A neutral chlorine atom gains one electron. As a result, it becomes

Answer choices for question 99A. a positive ion (cation)B. a negative ion (anion)C. a different elementD. an isotope of chlorineE. an atom that stays electrically neutral

Question 100 of 120

According to Kepler's first law of planetary motion, the orbit of a planet around the Sun is

Answer choices for question 100A. a perfect circle with the Sun at the centerB. a straight lineC. a square pathD. an ellipse with the Sun at one focusE. an inward spiral that slowly draws the planet toward the Sun

Question 101 of 120

Which statement correctly distinguishes heat from temperature?

Answer choices for question 101A. Temperature is energy transferred between objects, while heat measures average particle motion.B. Temperature measures total particle energy, while heat measures average particle motion.C. Temperature reflects average particle kinetic energy, while heat is energy transferred because of a temperature difference.D. Temperature is measured in joules, while heat is measured in degrees Celsius.E. Temperature measures stored thermal energy, while heat measures how hot an object feels.

Question 102 of 120

In humans, a child's biological sex is determined by which sex chromosome is carried in the

Answer choices for question 102A. sperm, which may carry either an X or a Y chromosomeB. egg, which may carry either an X or a Y chromosomeC. egg, whose X chromosome determines sex according to which ovary released itD. sperm, which always carries an X chromosomeE. the temperature at which the embryo develops in the womb

Question 103 of 120

Which group of organisms appeared earliest in the history of life on Earth?

Answer choices for question 103A. Flowering plantsB. MammalsC. DinosaursD. Single-celled prokaryotesE. Backboned fish

Question 104 of 120

In the genetic code, a sequence of three nucleotide bases on a molecule of messenger RNA that specifies one amino acid is called a

Answer choices for question 104A. geneB. codonC. chromosomeD. ribosomeE. an anticodon

Question 105 of 120

In many predator-prey relationships, a rise in the prey population is typically followed by

Answer choices for question 105A. an immediate and permanent extinction of the predatorsB. a decline in predators because abundant prey reduce selection pressure on themC. a rise in the predator population, which then drives the prey back downD. the prey animals turning into predatorsE. a permanent rise in both the predator and prey populations together

Question 106 of 120

Compared with most molecular (covalent) compounds, ionic compounds such as table salt tend to have

Answer choices for question 106A. high melting points and the ability to conduct electricity when dissolved or meltedB. very low melting points and no ability to conduct electricityC. high solubility mainly in nonpolar liquids rather than in waterD. a gaseous state at room temperatureE. a soft, waxy texture that melts easily in the hand

Question 107 of 120

Layers of sand, mud, and shell fragments settle on the floor of a lake and, over long periods, are buried, compacted, and cemented into solid rock that sometimes preserves the remains of organisms as fossils. This rock is

Answer choices for question 107A. igneous rock, which forms when molten rock cools and hardensB. sedimentary rock, which forms as layers of sediment are compacted and cementedC. metamorphic rock, which forms when existing rock is changed by heat and pressureD. a mineral rather than a rockE. coal, which forms only from the compressed remains of ancient plants

Question 108 of 120

When you inhale, which muscle contracts and flattens to increase the volume of the chest cavity and draw air into the lungs?

Answer choices for question 108A. The heartB. The bicepsC. The stomachD. The diaphragmE. The esophagus

Question 109 of 120

A car moving forward stops abruptly, and a passenger who is not wearing a seat belt lurches toward the windshield. This forward motion of the passenger is best explained by the passenger's

Answer choices for question 109A. inertia, the tendency of a moving body to keep moving in a straight lineB. sudden gain in mass as the car stopsC. weight increasing while the car slowsD. being shoved forward by a force from the seatE. a forward force created by the sudden braking of the car

Question 110 of 120

A magnetized compass needle is free to rotate. No matter where the compass is placed on Earth's surface, the needle settles pointing roughly north-south. The best explanation is that the needle

Answer choices for question 110A. aligns with the direction of Earth's rotational motion at that locationB. aligns with the gravitational field directed toward Earth's centerC. aligns with a magnetic field produced by nearby surface waterD. aligns with the direction of incoming radiation from the SunE. aligns with the local direction of Earth's planetary magnetic field

Question 111 of 120

For a recessive genetic trait to appear in a person, that person must inherit

Answer choices for question 111A. only one copy of the recessive alleleB. one recessive allele located only on the X chromosomeC. the allele on the Y chromosome onlyD. one dominant allele from each parentE. two copies of the recessive allele, one from each parent

Question 112 of 120

An unknown atom is found to have 11 protons in its nucleus. Based on this information, the atom must be

Answer choices for question 112A. carbon, no matter how many neutrons it hasB. identifiable only from its number of neutronsC. an isotope of sodium only if it also has 11 neutronsD. neon, since 11 is near neon on the periodic tableE. sodium, because the number of protons identifies the element

Question 113 of 120

We always see the same face of the Moon from Earth because the Moon

Answer choices for question 113A. rotates once each day while orbiting Earth once each monthB. does not rotate on its axis while it completes each orbitC. rotates once on its axis during each complete orbit of EarthD. rotates once on its axis during each complete orbit of the SunE. rotates many times on its axis during each orbit of Earth

Question 114 of 120

On the Galapagos Islands, related finch species have differently shaped beaks, each suited to the specific foods available on its island. This diversity of beak shapes is best explained by

Answer choices for question 114A. natural selection adapting each population to its local food sourceB. food directly reshaping each bird's beak and the acquired shape being inheritedC. gene flow continually making the island populations genetically identicalD. beaks changing shape through frequent use within a single bird's lifetimeE. genetic drift alone consistently matching each population's beak to its food

Question 115 of 120

Which statement correctly describes a key outcome of meiosis?

Answer choices for question 115A. It produces two diploid cells that are used mainly for growth and repair.B. It produces four varied haploid cells that can function in sexual reproduction.C. It produces four identical diploid cells with twice the parental chromosome number.D. It produces two haploid cells without recombination or independent assortment.E. It produces one diploid cell that retains the parental chromosome number.

Question 116 of 120

The burning of fossil fuels by humans affects the carbon cycle mainly by

Answer choices for question 116A. removing carbon dioxide from the atmosphereB. converting carbon dioxide into oxygenC. having no measurable effect on atmospheric gasesD. releasing large amounts of carbon dioxide into the atmosphereE. locking carbon away as solid deposits deep underground

Question 117 of 120

A solution with a pH of 4 is how many times more acidic, in hydrogen-ion concentration, than a solution with a pH of 6?

Answer choices for question 117A. 2 timesB. 4 timesC. 100 timesD. the sameE. 1,000 times

Question 118 of 120

Scientists locate the epicenter of an earthquake by analyzing the arrival times of

Answer choices for question 118A. seismic waves recorded at multiple seismograph stationsB. ocean tides at nearby beachesC. changes in the phases of the MoonD. cloud patterns in the atmosphereE. the strength of the aftershocks felt in the following days

Question 119 of 120

A rocket lifts off by burning fuel and pushing exhaust gases downward out of its engines. The rocket moves upward because

Answer choices for question 119A. exhaust striking the ground produces an upward force that follows the rocketB. lower air pressure above the rocket pulls it upward through the atmosphereC. heating the exhaust reduces its density enough to make the entire rocket buoyantD. downward momentum given to exhaust produces an equal and opposite force on the rocketE. fuel combustion removes enough rocket mass that gravity no longer acts on it

Question 120 of 120

In pea plants, purple flowers (P) are dominant to white flowers (p). If a homozygous purple plant (PP) is crossed with a white plant (pp), what will the offspring look like?

Answer choices for question 120A. Half purple and half whiteB. All purpleC. All whiteD. Three purple to one whiteE. All plants with pink flowers, a blend of the two colors