GED Science Practice Test 2

Two findings seem to conflict: SS is harmful, but S stays common where malaria is common (14% and 11%) and is rare where malaria is rare (2% and 1%). The passage gives the key: people with AS are "much less likely to die from malaria."

Step by step:

1. Where malaria is common, AA people are more likely to die of malaria, and SS people are likely to die of sickle-cell disease.
2. AS people survive best, so they have more children.
3. Each AS parent passes the S allele to about half of their children, so the S allele stays in the population.
4. Where malaria is rare, AS has no advantage, so S is not kept common. That fits the table.

The correct answer is A: this is natural selection favoring the carriers (heterozygotes).

Tip: Natural selection acts on traits that already exist. An environment does not create the mutations it needs; it changes which individuals survive and reproduce.

The prediction is about what happens to S without malaria. The best support is data from places where malaria is rare.

Step by step:

1. Regions where malaria is common: Lowland Valley 14%, Coastal Plain 11%.
2. Regions where malaria is rare: Highland Plateau 2%, Mountain Town 1%.
3. So S is far less common where malaria is rare. If Lowland Valley lost its malaria, it would become more like those regions, and S would be expected to decline.
4. The other choices are true statements, but none of them compares regions with and without malaria.

The correct answer is B.

Tip: Evidence supports a claim only if it is about the same variable as the claim. Ask: "Does this fact actually connect the cause (malaria) to the effect (S frequency)?"

Newton's second law says F = m \times a. To find acceleration, divide both sides by the mass: a = \dfrac{F}{m}.

Step by step:

1. Force: F = 90 N. Mass: m = 0.45 kg.
2. a = \dfrac{90 \text{ N}}{0.45 \text{ kg}} = 200 \text{ m/s}^2
3. Check: 0.45 \times 200 = 90 ✓

The answer is A, 200 m/s².

Why the others are wrong: 40.5 comes from multiplying force by mass, 0.005 from dividing mass by force (upside down), and 89.55 from subtracting.

Tip: A light object pushed by a large force gets a large acceleration. If your answer is tiny, you probably divided the wrong way.

The passage says a wavy, uneven boundary "shows a time when rock at the surface was worn away by erosion before new layers were deposited on top of it."

Step by step:

1. Superposition: A, B and C were deposited first, in that order (oldest at the bottom).
2. The fault cuts A–C but stops at the wavy line, so faulting happened after C.
3. The wavy line means the top of the rock (including the top of C and the fault) was worn away by erosion.
4. Only after that was layer D deposited on the eroded surface.

The correct answer is C.

Tip: Erosion surfaces are "missing time" in the rock record. Rock that was once there was removed before the next layer was laid down.

A controlled variable is something kept the same for every group so that it cannot affect the results.

Step by step:

1. The passage says "Each flask held 100 mL of water at 35 °C." The water temperature was the same in every flask, so it is controlled.
2. The mass of sugar (0, 5, 10, 20 or 40 g) was changed on purpose. That is the independent variable.
3. The volume of gas in each balloon was measured as the result. That is the dependent variable.
4. The number of yeast cells at the end was never measured, so it is not one of the experiment's variables.

The correct answer is C, the temperature of the water.

Tip: Look for the words each, same and identical in an experiment description; they point to controlled variables.

Read the data first: gas rose from 5 mL (0 g) to a peak of 95 mL (20 g), then fell to 60 mL (40 g). The 40 g flask had the most sugar, so the yeast did not run out of food.

The passage gives the key idea: at a very high sugar concentration, "water tends to move out of yeast cells by osmosis."

Step by step:

1. At 40 g the sugar solution is very concentrated, so there is less free water outside the cells than inside.
2. Water moves out of the yeast cells, and the dried-out cells cannot carry out their life processes as fast.
3. Slower activity means less sugar broken down and less gas given off.
4. The yeast were still active (60 mL is far more than the 5 mL with no sugar), so they were slowed, not all killed.

The correct answer is B.

Tip: When a graph rises and then falls, look in the passage for a second factor that becomes important at high values.

Meiosis makes sex cells (sperm and eggs) with half the number of chromosomes of a body cell, so that when a sperm and an egg join, the offspring has the full number again.

Step by step:

1. Body cell: 78 chromosomes (39 pairs).
2. Meiosis halves the number: 78 \div 2 = 39.
3. Check with fertilization: sperm (39) + egg (39) = 78, the normal number for a puppy's body cells ✓

The correct answer is B, 39.

If sperm had 78, the puppy would have 156 chromosomes, double the normal number, and the number would keep doubling every generation.

Tip: Mitosis keeps the chromosome number the same (body growth and repair); meiosis halves it (sex cells).

Two findings must be reconciled: work input (800 J) is larger than the useful output (600 J). The law of conservation of energy says energy is never destroyed, so the missing 200 J must have gone somewhere else.

Step by step:

1. The passage says the movers slide the crate up the ramp. Sliding surfaces rub, which causes friction.
2. Friction converts kinetic (motion) energy into thermal energy: the crate bottom and ramp surface warm slightly, and a little energy becomes sound.
3. Energy check: 600 \text{ J (raised crate)} + 200 \text{ J (heat and sound from friction)} = 800 \text{ J} ✓

The correct answer is D.

Tip: Whenever a machine's output is less than its input, the "lost" energy has usually been transformed into heat by friction. It is not destroyed.

The passage says a planet "makes one transit each time it completes one orbit." So the time between two neighboring dips from the same planet is one orbit.

Step by step:

1. Find the dips labeled b: they are at days 4, 14, 24 and 34.
2. Time between neighboring b dips: 14 - 4 = 10, 24 - 14 = 10, 34 - 24 = 10 days.
3. The spacing is always 10 days, so one orbit takes 10 days.

The correct answer is B, 10 days.

4 days is just the time of the first dip, 1 is the drop in brightness (100% − 99% = 1%), and 24 days is the spacing of the c dips (days 8 and 32), which belongs to planet c.

Tip: For anything that repeats, the period is the spacing between repeats, not the position of the first one.

To test whether a trait is inherited, you need to compare parents with their offspring while keeping other causes, such as diet, the same.

Step by step:

1. The question gives two possible causes of beak depth: genes (inheritance) and food.
2. Choice C raises chicks on the same food, so diet is controlled.
3. If chicks of deep-beaked parents still grow deep beaks, and chicks of shallow-beaked parents grow shallow ones, the difference must come from the parents, which means the trait is inherited.
4. The other studies never compare parents with offspring, so they cannot show inheritance.

The correct answer is C.

Tip: A good test changes or compares only the variable in question (here, parentage) and controls the alternative explanation (here, diet).

Calculate each momentum with p = m \times v.

Step by step:

1. Car: p = 1{,}200 \text{ kg} \times 15 \text{ m/s} = 18{,}000 \text{ kg}\cdot\text{m/s}
2. Bus: p = 9{,}000 \text{ kg} \times 2.0 \text{ m/s} = 18{,}000 \text{ kg}\cdot\text{m/s}
3. The two values are the same.

The correct answer is C: they have equal momentum, 18,000 kg·m/s each.

The car is faster and the bus is heavier, and here the two effects balance exactly. Choices A and B each look at only one factor. Choice D is wrong because the momentum formula uses only mass and velocity, not force.

Tip: When a formula multiplies two quantities, a big value of one can be balanced by a small value of the other. Always calculate before you compare.

The two trials seem to disagree: Trial A lost mass, but Trial B did not. The difference between them is whether the bottle was open or sealed.

Step by step:

1. Trial A (open): 260.0 - 257.4 = 2.6 g lost.
2. Trial B (sealed): 260.0 g before and 260.0 g after, with no change, even though the same reaction happened (it fizzed the same way).
3. The equation shows one product is carbon dioxide gas (CO₂). In the open bottle, the gas escaped into the air, so the scale no longer counted it. In the sealed bottle, the gas was trapped and still weighed.
4. So the mass was not destroyed; it left the bottle as gas. This agrees with the law of conservation of mass.

The correct answer is B.

Tip: If mass seems to disappear (or appear) in a reaction, check whether a gas could have escaped (or entered). A closed system always keeps the same total mass.

Read the temperature columns: in both trials the temperature fell from 21.0 °C to 18.5 °C, a drop of 2.5 °C.

Step by step:

1. The mixture got colder even though nothing cooled it.
2. That means the reaction absorbed thermal energy from the liquid and its surroundings.
3. A reaction that absorbs energy is endothermic. (A reaction that releases energy and warms its surroundings is exothermic.)

The correct answer is A.

Choice D is a common trap: reactions do not "release cold." Cold is simply less thermal energy, and a temperature drop means energy was taken in. Choice B confuses giving off a gas with giving off heat.

Tip: Endo = energy goes in (surroundings get colder). Exo = energy goes out (surroundings get warmer).

Read both columns and look at the changes in each 30-minute period.

Step by step:

1. Temperature rises: 0–30 min: +1.1 °C; 30–60 min: +0.4 °C; 60–90 min: +0.1 °C. The rise gets smaller each time.
2. Sweat rate rises at the same time: 0.2 → 1.0 → 1.4 → 1.5 L/h.
3. As the body heats up, it sweats more; the extra evaporation removes heat, so the temperature levels off near 38.6 °C.
4. A response that works against a change and brings the body back toward balance is negative feedback, a key part of homeostasis.

The correct answer is C.

Tip: Negative feedback reduces a change (sweating when hot, shivering when cold). Positive feedback makes a change bigger and is much rarer in the body.

The passage says the burner "supplies energy at a steady rate." That means the energy added during a stage is proportional to how long the stage lasts.

Step by step:

1. Melting (flat at 0 °C): from 1 to 9 minutes, so 9 - 1 = 8 minutes.
2. Warming the liquid from 0 °C to 100 °C: from 9 to 19 minutes, so 19 - 9 = 10 minutes.
3. 10 minutes > 8 minutes, so warming the liquid water took more energy than melting the ice.
4. A flat line does not mean no energy was used. The burner was on the whole time; during melting, its energy went into changing the state instead of raising the temperature.

The correct answer is B.

Tip: With a steady energy source, time is a stand-in for energy. Compare stage lengths along the x-axis, not the size of the temperature change.

A half-life is the time it takes for half of a radioactive substance to decay. After each half-life, the amount left is cut in half.

Step by step:

1. Start: 100% of the original carbon-14.
2. After 1 half-life: 50%.
3. After 2 half-lives: 25%. So 2 half-lives have passed.
4. Time: 2 \times 5{,}730 = 11{,}460 years.

The correct answer is B, 11,460 years.

5,730 years would leave 50%, and 17,190 years (3 half-lives) would leave 12.5%. Multiplying 5,730 by 25% (1,432.5) treats decay as a straight percentage, which is not how half-life works.

Tip: Make a quick halving table (100 → 50 → 25 → 12.5 …) and count the steps.

The coach's claim is about a change caused by training. Only a study that follows the same people before and after training can test that.

Step by step:

1. Study 1 shows marathon runners have more slow-twitch fibers (80%) than untrained adults (50%) or sprinters (25%). But it measures different people once. It shows a correlation, not a cause. People born with more slow-twitch fibers may simply be the ones who succeed at marathons.
2. Study 2 actually trained people for six months. Their slow-twitch percentage barely changed (49% → 51%), which the researchers judged "too small to be meaningful."
3. Study 2 did find a real change: mitochondria rose by about 40%. Training improved the fibers' ability to use oxygen without changing their type.
4. So the evidence does not support the coach's claim.

The correct answer is A.

Tip: A comparison of different groups at one time shows a correlation. To show that X causes a change, look for a study that changes X and tracks the same individuals.

The 10% rule: at each step up a food chain, only about one-tenth of the energy is passed on. The rest is used for life processes or lost as heat.

Step by step:

1. Grass: 50,000 kcal.
2. Grasshoppers: 50{,}000 \times 0.10 = 5{,}000 kcal.
3. Frogs: 5{,}000 \times 0.10 = 500 kcal.
4. Snakes: 500 \times 0.10 = 50 kcal.

There are three steps from grass to snakes, so the answer is C, 50 kcal.

500 kcal is the energy that reaches the frogs (stopping one step early), and 5,000 kcal reaches the grasshoppers.

Tip: Count arrows, not organisms. Four organisms in a chain means three transfers, so multiply by 0.10 three times.

Follow the chain of cause and effect in the passage: eruption → sulfur dioxide droplets → less sunlight reaches the surface → cooler temperatures (about 0.5 °C) for about a year.

Step by step:

1. Plants need sunlight and warmth to grow. Less sunlight and cooler weather can shorten the growing season.
2. So the most likely effect is cooler, shorter growing seasons and lower harvests in some farming regions.
3. Choices B and D say the opposite of the passage (more sunlight, warmer temperatures).
4. Choice C is not connected: nothing in the passage mentions sea level, and a cooling would not raise it.

The correct answer is A.

Tip: For Earth-systems questions, trace each step: what changed in the atmosphere, how that changed sunlight or temperature, and how that change reaches living things.