GED — All Questions

Which part of a plant cell captures light energy for photosynthesis?

• a.Cell wall
• b.Ribosome
• c.Nucleus
• d.Chloroplast✓

Chloroplasts contain chlorophyll, the pigment that absorbs sunlight to power photosynthesis. The nucleus stores genetic material, and ribosomes build proteins. Photosynthesis converts light energy into chemical energy stored in sugars.

What is the chemical formula for water?

• a.H2O✓
• b.O2
• c.CO2
• d.NaCl

Water is made of two hydrogen atoms and one oxygen atom, giving the formula H2O. CO2 is carbon dioxide and NaCl is table salt. Chemical formulas show the types and numbers of atoms in a molecule.

In a food chain, organisms that make their own food using sunlight are called—

• a.decomposers
• b.producers✓
• c.predators
• d.consumers

Producers, such as green plants, make their own food through photosynthesis and form the base of a food chain. Consumers eat other organisms, and decomposers break down dead matter. Energy flows from producers to consumers.

Which gas do humans need to breathe in to survive?

• a.Nitrogen
• b.Carbon dioxide
• c.Hydrogen
• d.Oxygen✓

Humans inhale oxygen, which cells use to release energy from food through respiration. We exhale carbon dioxide as a waste product. Although nitrogen is the most abundant gas in air, the body does not use it for respiration.

A scientist records that a substance boils at 100°C at sea level. Boiling point is an example of a—

• a.chemical formula
• b.chemical change
• c.living factor
• d.physical property✓

Boiling point is a physical property because it can be measured without changing the substance's identity. A chemical change would produce a new substance. Physical properties include color, density, and melting point.

Which of the following best describes the function of the heart?

• a.It produces digestive enzymes.
• b.It filters waste from the blood.
• c.It pumps blood around the body.✓
• d.It controls breathing rate.

The heart is a muscular pump, and circulating blood is the whole of its job: it moves oxygen and nutrients out to the tissues and carries waste away. Filtering waste from the blood is the kidneys' work. Producing digestive enzymes is done by the pancreas and the glands of the gut. And breathing rate is set by the brainstem, not by the heart, although the two adjust together during exercise.

What force pulls objects toward the center of the Earth?

• a.Gravity✓
• b.Friction
• c.Electricity
• d.Magnetism

Gravity is the force that attracts objects toward Earth's center, giving them weight. Friction resists motion between surfaces, and magnetism acts on certain metals. Gravity keeps us and objects on the ground.

A trait passed from parents to offspring through genes is called—

• a.an instinct
• b.a learned behavior
• c.an inherited trait✓
• d.an adaptation

Inherited traits, such as eye color, are passed genetically from parents to offspring. Learned behaviors are acquired through experience, not genes. Genes carry the instructions that determine inherited characteristics.

During the water cycle, what process turns liquid water into water vapor?

• a.Precipitation
• b.Condensation
• c.Evaporation✓
• d.Collection

Evaporation is the change of liquid water into vapor, usually driven by heat from the sun. Condensation is the reverse, forming clouds, and precipitation returns water as rain or snow. Evaporation moves water into the atmosphere.

Which of these is a renewable energy source?

• a.Natural gas
• b.Solar power✓
• c.Petroleum
• d.Coal

Solar power comes from sunlight, which is replenished continuously, making it renewable. Coal, natural gas, and petroleum are fossil fuels that take millions of years to form and can be used up. Renewable sources do not run out on a human timescale.

The smallest unit of life capable of carrying out all life processes is the—

• a.atom
• b.cell✓
• c.molecule
• d.organ

The cell is the basic structural and functional unit of all living things. Atoms and molecules are smaller but are not themselves alive. Organs are made of many cells working together.

A study finds that a group of plants given fertilizer grew taller than plants without it. In this experiment, fertilizer is the—

• a.conclusion
• b.control group
• c.independent variable✓
• d.dependent variable

The independent variable is the factor the scientist deliberately changes; here it is the fertilizer. The plant height that responds is the dependent variable. Well-designed experiments change only one variable at a time.

Which planet is closest to the Sun?

• a.Jupiter
• b.Venus
• c.Earth
• d.Mercury✓

Mercury is the innermost planet, orbiting nearer the Sun than any other. Venus is the second planet out and Earth the third, which is why both are common wrong picks. Jupiter is the fifth planet and far beyond all of them. Distance from the Sun drives a planet's temperature and the length of its year.

When wood burns, it turns to ash and gas. This is an example of a—

• a.chemical change✓
• b.reversible change
• c.physical change
• d.change of state

Burning is a chemical change because new substances, such as ash and gases, form and cannot easily be turned back into wood. Physical changes, like melting, do not create new substances. Chemical changes rearrange atoms into different compounds.

What do we call the variety of living organisms in an ecosystem?

• a.Community
• b.Climate
• c.Population
• d.Biodiversity✓

Biodiversity is the range of different species living in an area. A community is all the populations living together in that area — a related idea, but it names the assemblage rather than its variety. A population is a single species, so it cannot describe variety at all. And climate describes long-term weather patterns, not living things. High biodiversity tends to make an ecosystem more stable.

The process by which a species changes over many generations in response to its environment is called—

• a.condensation
• b.circulation
• c.digestion
• d.evolution✓

Evolution is the gradual change in inherited traits of a population over generations, often through natural selection. It explains how species adapt to their environments over long periods. Individuals do not evolve; populations do.

Which type of blood vessel carries blood away from the heart?

• a.Capillaries
• b.Nerves
• c.Veins
• d.Arteries✓

An artery is defined by direction: it carries blood away from the heart. Note that this is about direction and not oxygen — the pulmonary arteries carry oxygen-poor blood from the heart to the lungs, which is the exception that shows what the definition really rests on. Veins run the other way, returning blood to the heart. Capillaries are the fine vessels between the two where gases and nutrients are exchanged with the tissues. Nerves carry electrical signals and are not blood vessels at all.

A graph shows a town's average temperature rising steadily each decade. This trend best supports the idea of—

• a.climate change✓
• b.seasonal change
• c.daily weather
• d.an eclipse

A steady rise held across decades is a climate signal, because climate is precisely the long-run pattern rather than any single reading. Daily weather is the wrong timescale — it swings far more than this in a single afternoon. Seasonal change is also the wrong timescale, and it repeats each year instead of trending in one direction. And an eclipse is a brief astronomical event with no bearing on a decades-long temperature record.

Which of the following is a chemical property of a substance?

• a.Its density
• b.Its ability to rust✓
• c.Its hardness
• d.Its boiling point

Rusting is iron reacting with oxygen to form a new substance, so the ability to rust describes how the material behaves chemically. Density, hardness and boiling point can all be measured without turning the substance into anything else, which is exactly what makes them physical properties. The dividing line is whether observing the property destroys the original substance: weigh it, scratch it or boil it and you still have the same material, but rust it and you do not.

In the human body, which system is responsible for breaking down food into nutrients?

• a.Respiratory system
• b.Nervous system
• c.Digestive system✓
• d.Skeletal system

The digestive system breaks food down into nutrients the body can absorb and use. The respiratory system handles gas exchange, and the nervous system sends signals. Digestion begins in the mouth and continues through the stomach and intestines.

Which of these best explains why ice floats on water?

• a.Ice is less dense than water.✓
• b.Ice contains more salt than water.
• c.Ice has more mass than water.
• d.Ice is warmer than water.

Water is unusual: as it freezes its molecules lock into an open lattice that takes up more room than the liquid, so a given mass of ice occupies more volume and is therefore less dense. Anything less dense than the fluid around it floats. Ice does not contain more salt than the water it forms from — freezing tends to exclude salt. Having more mass is irrelevant without knowing volume, since density is mass per unit volume. And ice is colder than liquid water, not warmer.

Bacteria that break down dead plants and animals are known as—

• a.producers
• b.herbivores
• c.decomposers✓
• d.predators

Decomposers, including many bacteria and fungi, break down dead organisms and return nutrients to the soil. This recycling supports new plant growth. Without decomposers, dead matter and nutrients would accumulate unused.

A meteorologist predicts rain based on falling air pressure. Air pressure is measured with a—

• a.thermometer
• b.barometer✓
• c.telescope
• d.anemometer

A barometer measures air pressure, which helps forecast weather changes. A thermometer measures temperature and an anemometer measures wind speed. Falling air pressure often signals approaching storms.

Which statement correctly describes an atom?

• a.It is the smallest unit of a compound.
• b.It is a particle found only in metals.
• c.It is the smallest living thing.
• d.It is the smallest unit of an element.✓

An atom is the smallest particle of an element that still has that element's properties. The smallest unit of a compound is a molecule, not an atom, which is the near-miss worth learning. Atoms are not confined to metals — every element, including the gases you are breathing, is made of them. And the smallest living thing is a cell, which is built from enormous numbers of atoms and is a different order of thing entirely.

The energy stored in food is a form of—

• a.chemical energy✓
• b.light energy
• c.sound energy
• d.kinetic energy

Food stores chemical energy in the bonds of its molecules, which the body releases during digestion and respiration. Kinetic energy is energy of motion. Cells convert this chemical energy into usable forms to power life processes.

Which action would most reduce the amount of waste sent to landfills?

• a.Sending yard waste to the landfill
• b.Recycling paper, glass, and plastic✓
• c.Buying products with extra packaging
• d.Using more disposable items

Recycling diverts paper, glass and plastic out of the waste stream and back into manufacturing, so the material never reaches the landfill at all. Sending yard waste there does the opposite: it is organic matter that could be composted, and it adds directly to landfill volume. Buying products with extra packaging increases waste before the item is even used. And using more disposable items replaces things that would have been reused, which raises the volume thrown away.

A scientist repeats an experiment several times and gets similar results. This repetition mainly helps to—

• a.change the independent variable
• b.make the results more reliable✓
• c.prove the hypothesis is a law
• d.eliminate the need for a control

Repeating an experiment and getting consistent results makes the findings more reliable and trustworthy. Repetition helps rule out chance errors. Reliable, reproducible data is a cornerstone of the scientific method.

Which cell structure releases the energy stored in food molecules?

• a.The cell membrane
• b.The vacuole
• c.The mitochondrion✓
• d.The ribosome

Mitochondria carry out cellular respiration, breaking down sugars in the presence of oxygen and capturing the released energy in a form the cell can spend. The cell membrane controls what crosses into and out of the cell. A vacuole is a storage compartment, largest in plant cells. And ribosomes assemble proteins, a job that consumes energy rather than supplying it.

The instructions a cell uses to build its proteins are carried by—

• a.glucose
• b.DNA✓
• c.cholesterol
• d.hemoglobin

DNA stores the sequence information that specifies each protein, which is why it is copied before a cell divides and passed to both daughter cells. Glucose is a fuel molecule and carries no information. Hemoglobin is itself a protein, one of the products rather than the instructions. And cholesterol is a lipid that helps form membranes.

How do the cells produced by meiosis differ from those produced by mitosis?

• a.They contain no genetic material at all
• b.They carry twice the number of chromosomes
• c.They are unable to divide ever again
• d.They carry half the number of chromosomes✓

Meiosis halves the chromosome number to make sex cells, so that fertilization restores the full set rather than doubling it each generation. Doubling is exactly what meiosis prevents. The cells are not dead ends, since a fertilized egg divides many times. And they certainly contain genetic material; half a set is still a set.

An allele is described as dominant when it—

• a.shows in the trait even with one copy present✓
• b.appears only when two copies are present
• c.is found more often in a population
• d.changes into a different allele over time

A dominant allele expresses itself in the observable trait whenever it is present, so a single copy is enough to mask a recessive partner. Needing two copies is the definition of recessive, which is the contrast being drawn. Dominance says nothing about how common an allele is; rare alleles can be dominant. And alleles do not convert into one another, though mutation can create new ones.

Two parents are each heterozygous for a trait, carrying one dominant and one recessive allele. What fraction of their offspring is expected to show the recessive trait?

• a.One in four✓
• b.One in two
• c.None at all
• d.Three in four

A Punnett square for this cross gives one homozygous dominant, two heterozygous and one homozygous recessive, so a quarter of the offspring are expected to show the recessive form. One in two would be the result of crossing a heterozygote with a homozygous recessive parent. Three in four is the fraction expected to show the dominant trait. And a recessive trait can certainly appear, since both parents carry the allele without showing it.

The difference between an organism's genotype and its phenotype is that the phenotype is—

• a.the trait that can actually be observed✓
• b.the number of chromosomes in its cells
• c.the species to which it belongs
• d.the set of alleles it happens to carry

Phenotype names what shows: the height, the color, the enzyme activity you can measure. The alleles themselves are the genotype, the underlying combination that the phenotype partly reflects. Chromosome number is a feature of the karyotype rather than either term. And species membership is a classification, not an individual's expressed trait.

Natural selection acts on a population when—

• a.the environment stays exactly the same across generations
• b.organisms decide which traits to pass on
• c.every individual remakes itself to suit the habitat it lives in
• d.individuals with certain traits leave more offspring✓

Selection works through differential reproduction: heritable traits that help their bearers survive and breed become more common in later generations. Individuals do not remake themselves to fit their surroundings; the variation is already present and is sorted. A wholly unchanging environment gives selection less to act on rather than more. And no organism chooses what it transmits.

The similar bone arrangement in a human arm, a whale flipper and a bat wing is evidence that these animals—

• a.use their limbs for the same task
• b.share a common ancestor✓
• c.belong to the same living species
• d.live in the same kind of habitat

The same underlying skeletal plan put to very different uses is what biologists call a homologous structure, and shared ancestry is the explanation for the shared plan. The three animals live in quite different habitats, which is part of the point. Their limbs do entirely different jobs, so function cannot explain the resemblance. And they are unmistakably separate species.

A bacterial population survives repeated treatment with the same antibiotic and becomes harder to kill. This is best explained as—

• a.the antibiotic itself growing weaker with repeated use
• b.selection of resistant individuals already present✓
• c.bacteria gradually learning how to avoid the medicine
• d.patients becoming immune to the drug

Chance variation means a few bacteria can survive the drug, and when the rest are killed those few multiply, so resistance spreads through the population. Bacteria have no capacity to learn anything. The chemical itself does not weaken; the population changes. And it is the bacteria, not the patient, that become resistant, which is why the distinction matters clinically.

The role of an enzyme in a cell is to—

• a.carry oxygen in the blood
• b.speed up a chemical reaction✓
• c.store genetic information
• d.form the wall of the cell

Enzymes are catalysts: they lower the energy needed for a specific reaction so it proceeds fast enough to sustain life, and they emerge unchanged to do it again. Genetic information is stored in DNA. Oxygen transport is the work of hemoglobin. And cell walls are built from carbohydrates such as cellulose in plants.

Sweating when body temperature rises is an example of—

• a.metabolism
• b.photosynthesis
• c.homeostasis✓
• d.reproduction

Homeostasis is the maintenance of steady internal conditions, and evaporating water off the skin is one of the body's ways of pushing temperature back toward its set point. Metabolism is the sum of chemical reactions in the body, which generates the heat rather than regulating it. Reproduction produces new organisms. And photosynthesis occurs in plants and some microbes, not in people.

In the human lungs, oxygen passes into the blood across the walls of—

• a.the diaphragm
• b.the alveoli✓
• c.the trachea
• d.the bronchi

The alveoli are the tiny sacs at the ends of the airways, thin-walled and richly supplied with capillaries, and gas exchange happens there. The trachea and the bronchi are conducting tubes that carry air toward them without exchanging much of anything. And the diaphragm is the muscle whose contraction draws air in.

Most absorption of nutrients from digested food takes place in—

• a.the large intestine
• b.the esophagus
• c.the small intestine✓
• d.the stomach

The small intestine is lined with folds and tiny projections that give it an enormous surface area, and it is where the products of digestion cross into the blood. The stomach mainly stores food and begins protein digestion with acid and enzymes. The esophagus only transports food downward. And the large intestine chiefly reclaims water and salts from what is left.

Signals travel through the human nervous system along—

• a.tendons
• b.alveoli
• c.neurons✓
• d.platelets

A neuron is the cell built for the job, receiving a signal at one end and passing it along its fiber to the next cell. Tendons are connective tissue joining muscle to bone. Platelets are blood cell fragments involved in clotting. And alveoli are air sacs in the lungs.

A vaccine protects against a disease by—

• a.prompting the immune system to prepare defenses✓
• b.blocking the germ from entering the body
• c.killing the germ once the first symptoms have appeared
• d.replacing the gene that causes the illness in a patient

A vaccine presents the immune system with a harmless version or piece of a pathogen so that antibodies and memory cells are ready before a real exposure. Killing germs after symptoms begin is what a treatment such as an antibiotic attempts. Gene replacement is gene therapy, a different technology for different diseases. And a vaccine does not form a barrier; the germ can still enter and is then met by a prepared defense.

Why are antibiotics ineffective against a viral illness such as influenza?

• a.Antibiotics act on features that viruses lack✓
• b.Antibiotics only work on animal cells
• c.Viruses are too small for any medicine
• d.Viruses reproduce faster than any drug acts

Antibiotics attack structures and processes specific to bacteria, such as the bacterial cell wall or bacterial ribosomes, and a virus has neither, which is why the drug has nothing to act on. Size is not the obstacle; antiviral medicines do exist. Antibiotics are not aimed at animal cells at all, which is what makes them safe to take. And speed of reproduction is not the reason the drug fails.

In photosynthesis, a plant uses carbon dioxide, water and light energy to produce—

• a.sugar and oxygen✓
• b.starch and hydrogen
• c.protein and nitrogen
• d.carbon dioxide and water

Photosynthesis builds a sugar from carbon dioxide and water and releases oxygen as a by-product, which is the source of nearly all the oxygen in the air. Protein synthesis requires nitrogen taken up separately as nitrate and is a different process. Plants do store starch, but it is made later from sugar, and hydrogen gas is not released. And carbon dioxide and water are the inputs, not the products.

Cellular respiration in human cells consumes glucose and oxygen and releases—

• a.sugar, oxygen and stored light energy
• b.nitrogen, water and heat only
• c.protein, salt and electrical charge
• d.carbon dioxide, water and usable energy✓

Respiration is the reverse direction from photosynthesis: the carbon in glucose leaves as carbon dioxide, the hydrogen ends up in water, and the energy released is captured for the cell's work with some lost as heat. Producing sugar and oxygen is what photosynthesis does. Protein and salt are not products of this reaction. And nitrogen plays no part in it.

In an energy pyramid for an ecosystem, the amount of energy available at each higher level—

• a.stays about the same
• b.doubles at every step
• c.decreases sharply✓
• d.increases sharply

Most of the energy an organism takes in is spent staying alive and lost as heat, so only a small fraction passes to whatever eats it, which is why food chains are short and top predators are few. Energy cannot increase as it moves up, since nothing is added. Staying constant would violate that same loss. And doubling is the opposite of what happens.

Decomposers such as fungi and bacteria are important to an ecosystem because they—

• a.control the size of predator groups
• b.add oxygen to the atmosphere
• c.return nutrients to the soil✓
• d.produce food from sunlight

Decomposers break down dead tissue and waste, releasing nitrogen, phosphorus and other elements in forms that plants can take up again, which is what keeps the nutrient cycle turning. Making food from sunlight is the producers' role. Predator numbers are regulated by prey supply and competition. And oxygen is added by photosynthesis, while decomposition generally consumes it.

The carrying capacity of a habitat is—

• a.the total area the habitat covers
• b.the number of different species it currently holds
• c.the rate at which its population grows each year
• d.the largest population it can support over time✓

Carrying capacity is set by the limiting resources — food, water, space, nesting sites — and a population that overshoots it falls back. The number of species present is richness, a measure of variety rather than of a ceiling. Growth rate describes how fast a population changes, not where it levels off. And area alone says nothing about how much life the ground can support.

A graph shows a rabbit population falling steeply one year. What is the most likely effect on the fox population that preys on those rabbits?

• a.It falls in the following period✓
• b.It rises immediately and then levels
• c.It is unaffected by the change
• d.It rises in the following period

Predators depend on their prey for food, so fewer rabbits means fewer foxes surviving and breeding, and the fox decline lags the rabbit decline by a season or more. A rise would require more food, not less. Being unaffected would mean the foxes had another equally good food source, which the question does not offer. And an immediate rise gets the direction and the timing both wrong.

An introduced species often spreads rapidly in its new range because—

• a.it reproduces more slowly than natives
• b.the new habitat has no resources for natives
• c.it needs fewer nutrients than any native
• d.local predators and diseases do not control it✓

A species arriving without the predators, parasites and diseases that held it in check at home can multiply faster than native competitors, which is what makes some introductions invasive. Slow reproduction would hinder the spread rather than help it. Lower nutrient needs may sometimes help but is not the general reason. And the habitat plainly does have resources, which is why natives were living there.