What the General Science Section Tests
The General Science (GS) section covers a broad range of science topics at a high school level. It has 16 questions on the CAT-ASVAB and 25 on the paper version, covering life science (biology), earth and space science, and physical science (chemistry and physics basics).
GS directly feeds into Air Force Electronic (E) composite, Army FA (Field Artillery), GM (General Maintenance), and ST (Skilled Technical) scores. If you want technical jobs in any branch, a strong GS score matters.
Life Science (Biology) — Roughly 35% of Questions
Cell Biology
- The cell is the basic unit of life.
- Nucleus — contains DNA, controls cell activity
- Mitochondria — "powerhouse of the cell," produces ATP (energy)
- Cell membrane — controls what enters/exits the cell
- Chromosomes — carry genetic information (humans have 46)
Body Systems
Know what each major system does:
- Circulatory system: heart, blood, blood vessels — transports oxygen, nutrients, and waste
- Respiratory system: lungs, airways — gas exchange (O₂ in, CO₂ out)
- Digestive system: breaks down food; starts in the mouth, ends at the large intestine
- Nervous system: brain, spinal cord, nerves — controls body functions and responses
- Endocrine system: glands produce hormones to regulate body processes
- Skeletal system: 206 bones in the adult human body; provides structure and protects organs
- Muscular system: voluntary (skeletal) and involuntary (cardiac, smooth) muscles
Genetics Basics
- DNA — stores genetic information. DNA → RNA → Protein
- Dominant vs. recessive traits — dominant trait expressed when at least one dominant allele present
- Chromosomes — humans have 23 pairs. Sex chromosomes: XX (female), XY (male)
Ecology
- Food chain: Producer → Primary consumer → Secondary consumer → Tertiary consumer
- Photosynthesis: Plants convert CO₂ + H₂O + sunlight → glucose + O₂
- Cellular respiration: Glucose + O₂ → CO₂ + H₂O + energy (ATP)
Earth and Space Science — Roughly 30% of Questions
Earth's Layers
- From inside out: inner core → outer core → mantle → crust
- The crust is the thinnest layer. The mantle is the thickest.
- Tectonic plates float on the mantle. Their movement causes earthquakes and volcanoes.
Rock Cycle
- Igneous — formed from cooled magma/lava (granite, basalt)
- Sedimentary — formed from compressed layers of sediment (sandstone, limestone)
- Metamorphic — formed when rock is changed by heat/pressure (marble, slate)
Weather and Atmosphere
- Layers of atmosphere: Troposphere → Stratosphere → Mesosphere → Thermosphere → Exosphere
- Weather occurs in the troposphere. The ozone layer is in the stratosphere.
- Cold front: cold air mass pushes warm — brings storms. Warm front: warm air slides over cold — gentle rain.
Space
- Planets in order from the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- Inner planets (rocky): Mercury, Venus, Earth, Mars
- Outer planets (gas giants): Jupiter, Saturn, Uranus, Neptune
- A light-year is a unit of distance, not time.
- The Moon orbits Earth; Earth orbits the Sun.
Physical Science — Roughly 35% of Questions
Matter
- States of matter: solid, liquid, gas, plasma
- Atoms make up elements. An atom has protons (positive) + neutrons (neutral) in the nucleus, and electrons (negative) in orbitals.
- Atomic number = number of protons. Atomic mass ≈ protons + neutrons.
- Compounds = two or more different elements chemically bonded (H₂O, CO₂)
- Mixtures = substances combined but not chemically bonded (saltwater, air)
Chemical Reactions
- Acids — pH below 7; donate H⁺ ions (HCl, vinegar)
- Bases — pH above 7; accept H⁺ ions (NaOH, baking soda)
- Neutral — pH = 7 (pure water)
- Acid + Base → Salt + Water (neutralization)
Motion and Forces
- Newton's First Law: An object in motion stays in motion unless acted on by a force (inertia).
- Newton's Second Law: F = ma (Force = mass × acceleration)
- Newton's Third Law: Every action has an equal and opposite reaction.
- Gravity: F = GMm/r². On Earth's surface, g ≈ 9.8 m/s².
How to Study GS Efficiently
GS covers a lot of ground, so prioritize:
- Memorize human body systems first. These generate the most questions and are straightforward to learn.
- Learn the physical science basics (atoms, pH, Newton's laws) — they come up consistently.
- Use mnemonics for order-of-things lists (planets, atmospheric layers, Earth's layers).
- Don't go deep on any single topic. GS tests breadth, not depth. One or two facts per topic is usually enough.
Take the General Science section drill to identify your weak areas and focus study time accordingly.