GED Science Preparation Course Lessons 2026

Lesson 1: The GED Science test and how to approach it

The GED® test has four subjects: Math, Science, Social Studies and Reasoning Through Language Arts. You can take them together or one at a time. Create a free account on ged.com, then log in to schedule. Request any testing accommodation before you schedule.

The test at a glance

In a drag-and-drop question you move words or pictures into place, such as animals into a food web. In a hot spot question you click part of a picture or graph.

Scores

• 145–164: passing score.
• 165–174: College Ready. This may help you skip college placement testing.
• 175–200: College Ready + Credit. This may qualify you for up to 10 college credit hours.
• To earn your high school equivalency you need 145 or higher on all four subjects.

What the test covers

All questions connect to two focusing themes: Human Health and Living Systems and Energy and Related Systems. About half of the questions come in scenarios: one short text, graph, table or diagram followed by two or three questions. The rest stand alone.

The eight science practices

1. Comprehending scientific presentations: understand science texts, terms, graphs, tables and diagrams.
2. Investigation design: find hypotheses, variables and sources of error; judge or plan an experiment.
3. Reasoning from data: use evidence, draw conclusions and make predictions.
4. Evaluating conclusions with evidence: decide whether evidence supports or challenges a claim.
5. Working with findings: compare and combine results from different studies.
6. Expressing scientific information: show information in words, numbers, symbols or graphs.
7. Scientific theories: apply models, theories and formulas.
8. Probability and statistics: find the mean, median, mode and range, and work out probabilities.

A method for every question

1. Read the question first.
2. Read the title, labels and units of every table or graph.
3. Find the exact evidence that answers the question.
4. Cross out options the information does not support.
5. Check units and make sure you answered the question that was asked.

Themenquiz 1: The GED Science test and how to approach it

Lesson 2: Science practices – experiments, data and evidence

Experiments

• A hypothesis is a testable prediction or explanation, often written as "If …, then …."
• The independent variable is what the scientist changes on purpose.
• The dependent variable is what the scientist measures. It depends on the independent variable.
• Controlled variables are kept the same, so only one thing changes at a time.
• A control group gets no treatment. It gives a baseline to compare with.
• Repeated trials and larger samples reduce random error and make results more reliable.

Sources of error include inexact measuring tools, reading mistakes and conditions that were not kept the same.

Observations, inferences and theories

An observation is what you notice with your senses or tools ("the leaf is yellow"). An inference is an explanation based on observations ("the plant may need more water"). A scientific theory is a well-tested explanation supported by a large body of evidence. It is not just a guess.

Reading data

• Read the title, the labels and the units first.
• A trend is the general pattern: rising, falling or leveling off.
• To predict a value between two data points, follow the pattern. Predictions far outside the data are less certain.
• Correlation is not causation. Two things can rise together because a third factor causes both.

Evidence and conclusions

A conclusion should only say what the data show. Evidence supports a claim when it matches it. One reliable result that goes against a general claim challenges it. When studies disagree, compare their sample sizes, methods and conditions.

Statistics and probability

• Mean: add the values and divide by how many there are.
• Median: the middle value when the values are in order. With an even count, take the mean of the two middle values.
• Mode: the value that appears most often.
• Range: the largest value minus the smallest.
• Probability = number of wanted outcomes ÷ total number of possible outcomes. It can be written as a fraction, a decimal or a percent.

Metric units

Science uses metric units. Kilo- means 1,000 (1 kg = 1,000 g). Centi- means one hundredth (100 cm = 1 m). Milli- means one thousandth (1 L = 1,000 mL).

Themenquiz 2: Science practices: experiments, data and evidence

Lesson 3: Life science – the human body, health and cells

Cells

Cell theory says that all living things are made of cells, the cell is the basic unit of life, and new cells come from existing cells. The levels of organization are cell → tissue → organ → organ system → organism.

Mitosis makes two identical cells for growth and repair. Meiosis makes sex cells (eggs or sperm) with half the number of chromosomes. Human body cells have 46 chromosomes; human sex cells have 23.

Body systems working together

• Circulatory: the heart and blood vessels carry oxygen and nutrients to cells.
• Respiratory: the lungs take in oxygen and remove carbon dioxide.
• Digestive: breaks down food; most nutrients are absorbed in the small intestine.
• Nervous: the brain and nerves send signals.
• Muscular and skeletal: support and movement.
• Immune: fights pathogens.
• Excretory: the kidneys filter wastes from the blood.
• Endocrine: glands release hormones. Insulin from the pancreas lowers blood sugar.

During exercise, muscles need more oxygen, so the heart beats faster and you breathe faster: systems working together.

Homeostasis

Homeostasis means keeping conditions inside the body stable. It works by negative feedback: a change triggers a response that reverses it. When you are too hot, you sweat; when you are too cold, you shiver. When blood sugar rises after a meal, insulin brings it back down.

Nutrition and energy

• Carbohydrates: the main source of energy (4 Calories per gram).
• Proteins: build and repair tissue (4 Calories per gram).
• Fats: store energy (9 Calories per gram).
• Vitamins, minerals, fiber and water keep the body working.

Cells get energy through cellular respiration: glucose + oxygen → carbon dioxide + water + energy. If you take in more Calories than you use, the body stores the extra, mostly as fat. If you take in fewer, it uses stored energy.

Disease

Pathogens are germs that cause infectious disease: bacteria, viruses, fungi and parasites. They spread through the air, by touch, in food or water, or through vectors such as mosquitoes. Handwashing, safe food handling and vaccines help prevent disease. A vaccine trains the immune system to recognize a pathogen. Antibiotics kill bacteria but do not work on viruses. Some diseases, such as diabetes, are not infectious.

Themenquiz 3: Life science: the human body, health and cells

Lesson 4: Life science – ecosystems, heredity and evolution

Energy in ecosystems

Producers such as plants make their own food by photosynthesis: carbon dioxide + water + light energy → glucose + oxygen. Consumers eat other living things: herbivores eat plants, carnivores eat animals and omnivores eat both. Decomposers such as bacteria and fungi break down dead matter and return nutrients to the soil.

In a food chain, each arrow points from the food to the eater, showing the direction energy flows. A food web is many connected food chains. In an energy pyramid, only about 10% of the energy at one level passes to the next; most is lost as heat. Energy flows through an ecosystem, but matter is recycled.

Populations and relationships

• Carrying capacity is the largest population an environment can support over time. Food, water and space are limiting factors.
• Predator and prey numbers rise and fall in cycles; predator numbers usually change after prey numbers.
• Mutualism: both species benefit (bees and flowers).
• Commensalism: one benefits and the other is not affected.
• Parasitism: one benefits and the other is harmed (a tick on a dog).
• Disruptions such as habitat loss or an invasive species (a species brought to a new area, often with no natural predators there) can cause populations to crash or species to go extinct.

Heredity

DNA is found in chromosomes. A gene is a section of DNA that codes for a trait. Each parent passes one version (allele) of each gene. A dominant allele (capital letter, A) shows when present; a recessive allele (small letter, a) shows only when there are two (aa). The genotype is the pair of letters; the phenotype is the trait you can observe.

This cross gives 1 AA : 2 Aa : 1 aa. So 3 out of 4 (75%) show the dominant trait and 1 out of 4 (25%) show the recessive trait. A cross of Aa × aa gives 2 Aa and 2 aa: a 50% chance of each phenotype.

A mutation is a change in DNA. It can be harmful, helpful or have no effect. In people and other animals, only mutations in sex cells can be passed to offspring.

Evolution

Natural selection: individuals vary, many traits are inherited, and more young are born than can survive. Those with helpful traits survive and reproduce more, so those traits become more common over generations. A helpful trait is an adaptation. When separated groups change until they can no longer breed together, a new species forms (speciation). A cladogram is a branching diagram of common ancestry: species that branch apart more recently are more closely related.

Themenquiz 4: Life science: ecosystems, heredity and evolution

Lesson 5: Physical science – energy, motion and matter

Energy

Kinetic energy is energy of motion. Potential energy is stored energy, as in a raised object, a stretched spring, food or a battery. Other forms include thermal, electrical, light, sound and nuclear energy. Energy cannot be created or destroyed; it only changes form. Some energy always becomes heat. A flashlight changes chemical energy into electrical energy, then light and heat.

• Conduction: heat moves by direct contact (a metal spoon in hot soup).
• Convection: heat moves with a flowing liquid or gas (warm air rising).
• Radiation: heat moves as electromagnetic waves and needs no matter (sunlight through space).
• Heat always flows from warmer to cooler.
• Exothermic reactions release heat (burning). Endothermic reactions absorb heat, so they feel cold (an instant cold pack).

Renewable energy sources are replaced naturally: solar, wind, water, geothermal and biomass. Nonrenewable sources run out: coal, oil, natural gas and uranium. Waves carry energy. Sound needs matter to travel through. Electromagnetic waves, from low to high energy: radio, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Higher frequency means shorter wavelength and more energy.

Motion and forces

• Newton's first law (inertia): an object keeps its motion unless a force acts on it.
• Second law: force = mass × acceleration. A bigger force gives more acceleration; more mass gives less.
• Third law: every action has an equal and opposite reaction. A rocket pushes gas down, and the gas pushes the rocket up.
• Momentum is conserved in collisions: the total before equals the total after.
• Gravity pulls all masses toward each other. Your mass is the same everywhere, but your weight (the pull of gravity) is less on the Moon.
• Simple machines (lever, pulley, ramp, wheel and axle, wedge, screw) let you use less force over a longer distance, but they do not reduce the work done.

Matter

Matter is made of atoms. An atom has a nucleus of protons (positive) and neutrons (no charge), with electrons (negative) around it. The number of protons is the atomic number. An element has one kind of atom; a compound has two or more elements joined together.

Matter can be solid, liquid or gas. Melting, freezing, evaporation, condensation and dissolving are physical changes: no new substance forms. In a chemical change a new substance forms; signs include gas bubbles, a color change, light or heat, and a solid forming in a liquid. Objects less dense than a liquid float in it; water's density is 1 g/mL.

In a chemical equation, reactants → products. Mass is conserved, so a balanced equation has the same number of each kind of atom on both sides. To count atoms, multiply the big number in front by the small number after the symbol: 2H₂O has 2 × 2 = 4 hydrogen atoms. The limiting reactant runs out first and decides how much product forms. In a solution, a solute (salt) dissolves in a solvent (water). Most solids dissolve better in warmer water.

Themenquiz 5: Physical science: energy, motion and matter

Lesson 6: Earth and space science

Cycles and resources

In the water cycle, water evaporates, condenses into clouds, falls as precipitation and runs off or soaks into the ground. In the carbon cycle, plants take in carbon dioxide during photosynthesis; respiration, decay and burning release it. Fossil fuels (coal, oil and natural gas) formed from ancient living things over millions of years. They are nonrenewable, and burning them adds carbon dioxide to the air. Using resources sustainably (conserving and recycling) makes them last.

Atmosphere, climate and oceans

Weather is the condition of the air over hours or days; climate is the average pattern over many years. Weather happens in the lowest layer of the atmosphere, the troposphere. The ozone layer in the stratosphere absorbs much of the Sun's ultraviolet light. In the greenhouse effect, gases such as carbon dioxide, methane and water vapor trap heat near Earth's surface. More of these gases traps more heat, which leads to climate change. Oceans cover most of Earth's surface, absorb heat and carbon dioxide, and move heat in currents.

Earth's interior and plates

From the outside in, Earth has a crust, a mantle, a liquid outer core and a solid inner core. The crust is broken into plates that move slowly over the mantle.

• Divergent boundary: plates move apart; new crust forms, as at mid-ocean ridges.
• Convergent boundary: plates push together, forming mountains, volcanoes and deep trenches.
• Transform boundary: plates slide past each other, causing earthquakes.
• Igneous rock forms when melted rock cools; sedimentary rock forms from pressed layers of sediment; metamorphic rock forms under heat and pressure.

Natural hazards include earthquakes, volcanoes, hurricanes, floods and droughts. Warning systems, strong building codes, levees and evacuation plans reduce the harm.

Space

• The universe holds billions of galaxies. Our Sun is a star in the Milky Way.
• Stars form in clouds of gas and dust. A Sun-like star becomes a red giant, then a white dwarf. A very massive star explodes as a supernova, leaving a neutron star or black hole.
• Earth rotates once a day and revolves around the Sun once a year. Seasons happen because Earth's axis is tilted.
• Tides are caused mainly by the Moon's gravity.
• In a solar eclipse the Moon is between the Sun and Earth. In a lunar eclipse Earth is between the Sun and the Moon.

Earth's history

Earth is about 4.5 billion years old. By the law of superposition, in undisturbed rock layers the lowest layer is the oldest. Fossils show past life and environments. Radiometric dating gives an age in years using half-life: the time it takes for half of a radioactive substance to decay.

Themenquiz 6: Earth and space science