General Science · Practice test 6

Correct answer: have no true nucleus

Bacteria are prokaryotes: their DNA floats free in the cell rather than being enclosed in a nucleus. They do have genetic material and a membrane, and they reproduce by dividing.

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Correct answer: brief heavy storms followed by cooler, drier air

A cold front pushes under warmer air and shoves it sharply upward, which builds tall clouds and short violent storms. Once it passes, the colder drier air behind it takes over. The slow steady drizzle described in the second choice belongs to a warm front.

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Correct answer: spiral

Spiral galaxies, including the Milky Way, have a central bulge with arms of stars and gas spiraling outward. Elliptical galaxies instead have a smooth, rounded shape with no arms.

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Correct answer: photosynthesis converts light into stored energy

Chloroplasts contain chlorophyll and use light energy to build sugar from carbon dioxide and water. Animal cells lack chloroplasts entirely.

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Correct answer: rate at which the measured quantity is changing

The slope, or steepness, of a line graph shows how quickly the plotted quantity changes; a steep line means rapid change and a flat line means little or no change.

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Correct answer: similar chemical properties

A column, or group, gathers elements with the same number of outer electrons, and it is those electrons that decide how an element reacts. Sharing the same proton count would make them the same element.

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Correct answer: Chlorophyll

Chlorophyll absorbs red and blue light and reflects green, which is why plants look green, and it is the pigment that captures light energy for photosynthesis.

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Correct answer: atomic number

The modern periodic table orders elements by atomic number, the count of protons, which also happens to roughly track increasing atomic mass for most elements.

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Correct answer: small intestine

The small intestine is lined with millions of tiny projections that give it an enormous surface area for absorbing nutrients. The stomach mainly breaks food down, and the large intestine chiefly reclaims water.

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Correct answer: adrenal glands

The adrenal glands, sitting atop the kidneys, release adrenaline to quickly raise heart rate and blood flow to muscles, the body's fight-or-flight response.

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Correct answer: weathering

Weathering breaks rock apart in place; erosion is the transport of those pieces by water, wind, or ice; deposition is where they finally settle. The distinction between the first two is the one most often confused.

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Correct answer: Arteries

Arteries carry blood away and veins bring it back, a rule that holds regardless of whether the blood is carrying oxygen. Capillaries are the tiny vessels connecting the two.

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Correct answer: The inner core

From the surface inward the layers run crust, mantle, outer core, inner core. The inner core is mostly iron and, despite enormous heat, stays solid under the immense pressure.

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Correct answer: The liver

The liver makes bile, which helps break up fats. The gallbladder is the trap here: it stores and releases bile but does not produce it.

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Correct answer: metres

The metre is the SI base unit of length. Litres measure volume, grams measure mass, and seconds measure time.

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Correct answer: protons in the nucleus

The proton count defines which element an atom is, so it is the atomic number. Protons plus neutrons gives the mass number, which is the fourth choice and the usual confusion.

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Correct answer: neutrons

Isotopes share a proton count, which is what makes them the same element, but carry different numbers of neutrons and so different masses. Carbon-12 and carbon-14 are the familiar example.

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Correct answer: dependent variable

The dependent variable is what the experimenter measures, and it is expected to change in response to whatever the independent variable does.

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Correct answer: producers

Producers, mainly green plants and algae, build their own food from sunlight and so occupy the base of every food chain. Consumers must eat other organisms, and decomposers break down what is dead.

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Correct answer: recognize and attack specific pathogens

Lymphocytes, including B cells and T cells, identify particular invaders and mount a targeted immune response, including producing antibodies. Carrying oxygen is the job of red blood cells.

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Correct answer: the sound waves reaching you are compressed

As the source moves toward you each wave is emitted a little closer than the last, so the waves bunch up, the frequency rises, and the pitch sounds higher. This is the Doppler effect. Loudness changes too, but loudness is not pitch.

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Correct answer: Sedimentary

Sedimentary rock builds up in gentle layers that can bury remains without destroying them. Igneous rock forms from molten material and metamorphic rock from heat and pressure, both of which erase any fossil.

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Correct answer: 4

Carbohydrate and protein each supply about 4 calories per gram, well under the roughly 9 calories per gram that fat provides.

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Correct answer: watts

Power, the rate at which energy is used, is measured in watts. Volts measure electrical pressure, amperes measure current, and ohms measure resistance.

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Correct answer: testable

A hypothesis must make a prediction that an experiment could contradict. Being correct is not required and cannot be known in advance; a hypothesis proved wrong has still done its job.

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