Three Major Content Domains

Items from any of the three content domains of life science, physical science, and Earth and space science can pertain to one of these two themes, but content that falls outside the spheres of these themes do not appear on the GED® Science Test.

  • Human Health and Living Systems, the first focusing theme, pertains to material that is vital for the health and safety of all living things on the planet. Topics explored in this area of focus include the physical body and characteristics of humans and other living things. System of living organisms and related topics (e.g. diseases, evolution, and heredity) are also covered. This crosscutting concept also examines the mechanisms for how the human body works on chemical and physical levels. Within the domain of Earth and space science, topics are focused on how the environment affects living things and human society, as well as on how humans and other organisms affect the environment.
  • Energy and Related Systems, the second focusing theme, deals with a fundamental part of the universe. Topics in this area of focus cover sources of energy, transformations of energy, and uses of energy. Within the domain of life science, this theme is reflected in content exploring how energy flows through organisms and ecosystems. Similarly, the Earth’s geochemical systems are touched upon in Earth and space science. Topics related to how humans gain energy in their bodies and the results of the use of that energy are also relevant to this theme.

Content Knowledge Area 1: Life Science (40%)
Human Body and Health

  • Body systems and how they work together to perform a function
  • Homeostasis, feedback methods that maintain homeostasis, and effects of changes in the external environment on living things
  • Sources of nutrients and concepts in nutrition
  • Transmission of disease and pathogens, effects of disease or pathogens on populations, and disease prevention methods
  • Relationship between Life Functions and Energy Intake
  • Energy for life functions
  • Energy flows in ecologic networks (ecosystems)
  • Flow of energy in ecosystems, conservation of energy in an ecosystem, and sources of energy
  • Flow of matter in ecosystems and the effects of change in communities or environment on food webs
  • Carrying capacity, changes in carrying capacity based on changes in populations and environmental effects and limiting resources to necessary for growth
  • Symbiosis and predator/prey relationships
  • Disruption of ecosystems and extinction
  • Organization of Life (Structure and Function of Life)
  • Essential functions of life and cellular components that assist the functions of life
  • Cell theory, specialized cells and tissues, and cellular levels of organization
  • Mitosis and meiosis

Molecular Basis for Heredity

  • Central dogma of molecular biology, the mechanism of inheritance, and chromosomes
  • Genotypes, phenotypes, and the probability of traits in close relatives
  • New alleles, assortment of alleles, environmental altering of traits, and expression of traits


  • Common ancestry and cladograms
  • Selection and the requirements for selection
  • Adaptation, selection pressure, and speciation
  • Sources of nutrients and concepts in nutrition
  • Transmission of disease and pathogens, effects of disease or pathogens on population, and disease prevention methods

Content Knowledge Area 2: Physical Science (40%)
Conservation, Transformation, and Flow of Energy

  • Heat, temperature, the flow of heat results in work and the transfer of heat
  • Endothermic and exothermic reactions
  • Types of energy and transformations between types of energy
  • Sources of energy and the relationships between different sources
  • Types of waves, parts of waves, types of electromagnetic radiation, transfer of energy by waves, and the uses and dangers of electromagnetic radiation

Work, Motion, and Forces

  • Speed, velocity, acceleration, momentum, and collisions
  • Force, Newton’s laws, gravity, acceleration due to gravity, mass and weight
  • Work, simple machines, mechanical advantages, and power

Chemical Properties and Reactions Related to Living Systems

  • Structure of matter
  • Physical and chemical properties, changes of state, and density
  • Balancing chemical equations and different types of chemical equations, conservation of mass in balanced chemical equations and limiting reactants
  • Parts in solutions, general rules of solubility, saturation and the differences between weak and strong solutions

Content Knowledge Area 3: Earth & Space Science (20%)
Interactions between Earth’s Systems & Living Things

  • Interactions of matter between living and non-living things and the location, uses and dangers of fossil fuels
  • Natural hazards, their effects, and mitigation thereof
  • Extraction and use of natural resources, renewable vs. non-renewable resources, and sustainability

Earth & Its System Components and Interactions

  • Characteristics of the atmosphere, including its layers, gases, and their effects on the earth and its organisms, including climate change
  • Characteristics of the oceans and their effects on earth and organisms
  • Interactions between earth’s systems
  • Interior structure of the earth and its effects and major landforms of the earth

Structures and Organization of the Cosmos

  • Structures in the universe, the age and development of the universe, and the age and development of stars
  • Sun, planets, and moons, the motion of the earth and the interactions within the earth’s solar system
  • The age of the earth, including radiometrics, fossils, and landforms
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