General Science · Practice test 7

Correct answer: bone marrow

The soft marrow inside large bones produces both red and white blood cells. It is a good reminder that the skeleton is living tissue, not just a frame.

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Correct answer: Mitochondrion

The mitochondrion carries out respiration, turning sugar and oxygen into ATP, the energy currency the rest of the cell spends. Ribosomes build proteins and the nucleus stores DNA.

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Correct answer: the gravitational pull of the Moon

The Moon's gravity raises a bulge of water on the near side of Earth and another on the far side, and Earth's rotation carries coastlines through those bulges, giving roughly two high tides a day. The Sun contributes a smaller pull.

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Correct answer: bacteria but not viruses

Antibiotics attack structures and processes that only bacteria have, such as the bacterial cell wall. Viruses lack those structures, which is why antibiotics do nothing for a cold or the flu.

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Correct answer: condense into a liquid

Cooling a gas removes energy from its particles, slowing them until intermolecular forces pull them close enough together to form a liquid, the process of condensation.

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Correct answer: a synthesis reaction

In a synthesis reaction, reactants join to build one larger compound, the opposite of a decomposition reaction, in which a compound breaks apart into simpler substances.

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Correct answer: bending light rays inward to a focus

A converging, or convex, lens bends parallel light rays inward so they meet at a focal point, which is how a magnifying glass or camera lens forms an image.

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Correct answer: growth and the repair of tissue

Mitosis replaces worn-out cells and lets an organism grow, always producing identical copies. Meiosis is the specialized division reserved for making sex cells.

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Correct answer: synapse

At a synapse the electrical signal in one neuron triggers the release of chemical messengers that cross the tiny gap and trigger a new signal in the next neuron.

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Correct answer: phenotype

Phenotype is what you can actually see or measure; genotype is the underlying genetic makeup that produces it. Two organisms can share a phenotype while carrying different genotypes.

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Correct answer: alveoli

Alveoli are the tiny air sacs at the end of the airway, thin enough for oxygen and carbon dioxide to cross into and out of the blood. The trachea and bronchi are passages that carry air to them.

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Correct answer: exothermic

An exothermic reaction gives off energy as heat, as burning fuel does. An endothermic reaction instead absorbs heat from its surroundings, which is why some cold packs feel cold when activated.

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Correct answer: nucleus

The nucleus houses the chromosomes and acts as the cell's control center, sending out instructions for which proteins to build.

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Correct answer: basic

Values above 7 on the 0-to-14 pH scale are basic, or alkaline, while values below 7 are acidic; 10 sits well into the basic range.

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Correct answer: distance

Work is force times the distance moved in the direction of that force, so holding a weight still does no work no matter how tiring it feels. Dividing work by time gives power.

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Correct answer: speeding it up without being used up itself

A catalyst lowers the energy barrier so the reaction proceeds faster, and it emerges unchanged and reusable. It does not change how much product forms, only how quickly.

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Correct answer: a star

The Sun is an average yellow dwarf star, fusing hydrogen into helium in its core. A galaxy is a vast collection of stars, and our own is the Milky Way.

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Correct answer: About one tenth

Only about ten percent of the energy at each trophic level is stored in the next; the rest is spent on living or lost as heat. That loss is why food chains rarely run beyond four or five links.

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Correct answer: Big Bang theory

The Big Bang theory holds that the universe began expanding from an extremely hot, dense point roughly 13.8 billion years ago and has been expanding and cooling ever since.

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Correct answer: processes it is exposed to, such as heat, pressure, or weathering

The rock cycle shows that rock is not fixed: melting and cooling produces igneous rock, heat and pressure produce metamorphic rock, and weathering and compaction produce sedimentary rock, and any type can feed into any other.

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Correct answer: magma rises through weaknesses in the crust

Volcanoes typically form where molten rock finds a path up through the crust, often near plate boundaries where one plate sinks beneath another and melts.

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Correct answer: Two, genetically identical to the parent

Mitosis is ordinary cell division for growth and repair: one cell becomes two identical copies with the full chromosome count. Meiosis is the one that makes four cells with half the chromosomes, for reproduction.

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Correct answer: a long period of light, steady rain followed by warmer air

A warm front slides gently up and over the cooler air ahead of it, producing widespread layered clouds and steady light rain over a long stretch before milder air finally arrives.

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Correct answer: mouth

Saliva contains an enzyme that starts breaking starch into sugars as soon as food is chewed, well before it reaches the stomach.

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Correct answer: Vitamin D

Ultraviolet light triggers vitamin D synthesis in the skin, and vitamin D is needed to absorb calcium. A shortage weakens bone, causing rickets in children.

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