ASVAB

System	KeyStructuresandFunctions
Skeletal	206bonesthatprovidesupport protection movement mineralstorage andbloodcellproduction Jointsare , , , , .
	immovable(skullsutures) slightlymovable(vertebrae) orfreelymovable(knee elbow) , , ,
Muscular	Skeletalmuscleisvoluntaryandstriated;smoothmuscleisinvoluntaryandlinesorgans;cardiacmuscleis
	involuntary striated andfoundonlyintheheart Musclesworkinantagonisticpairs suchasthebicepsand , , . ,
	triceps
Circulatory	The four-chambered heart pumps blood carrying oxygen nutrients hormones and waste Arteries carry , , , .
	bloodawayfromtheheart veinscarrybloodtowardit andcapillariesexchangematerialswithtissues , ,
Respiratory	Exchangesgases Gasexchangeoccursbydiffusioninthealveoli;thediaphragmandintercostalmuscles .
	controlbreathing
Digestive	Breaksfoodintonutrientsbymechanicalandchemical(enzyme)digestion Thesmallintestineabsorbsmost .
	nutrients Accessoryorgans:salivaryglands liver gallbladder pancreas . , , ,
Nervous	Centralnervoussystem(brainandspinalcord)andperipheralnervoussystem(nerves) Neuronstransmit .
	electricalimpulses;neurotransmitterscarrysignalsacrosssynapses
Endocrine	Glandsthatreleasehormones:pituitary(mastergland) thyroid(metabolism) adrenals(stressresponse) , , ,
	pancreas(bloodsugar) gonads(reproduction) ,
Immune	Innateimmunityprovidesnonspecificbarriers(skin mucus);adaptiveimmunityuseslymphocytes Bcells , .
	produceantibodies;Tcellsdestroyinfectedcells Vaccinesbuildimmunitywithoutcausingdisease .
Excretory	Kidneys filter blood and produce urine; nephrons are the functional units . Urine flows kidneys → ureters →
	bladder urethra →
Reproductive	Testesproducespermandtestosterone;ovariesproduceeggs estrogen andprogesterone Fertilization , , .
	usuallyoccursinthefallopiantube

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Oxygen-poor blood returns

Blood picks up oxygen

through veins

Pumped to the lungs

Pumped out to the body

System	Pathway
Respiratory	Nose/mouth pharynx larynx trachea bronchi bronchioles alveoli → → → → → →
Digestive	Mouth esophagus stomach small intestine large intestine rectum → → → → →
Urinary	Kidneys ureters bladder urethra → → →

Blood contains red blood cells (carry oxygen on hemoglobin), white blood cells (fight infection), platelets (clotting), and plasma (the liquid portion). Blood types A, B, AB, and O are based on antigens on the red blood cells, and the Rh factor is either positive or negative.

Ecology studies how organisms interact with one another and with their environment. The levels of organization build from the individual upward.

Population					Community					Ecosystem					Biosphere
Allmembersofonespecies					Allthepopulationsinan					Acommunityplusits					AlltheecosystemsonEarth
inanarea					area					nonlivingfactors

Energy flows through ecosystems in food chains and food webs. Producers (autotrophs) make their own food by photosynthesis. Consumers (heterotrophs) eat other organisms: herbivores eat plants, carnivores eat animals, and omnivores eat both. Decomposers break down dead matter. Only about 10% of the energy at one trophic level passes to the next (the 10% rule).

about 0.1% of the energy

about 1%

about 10%

100% of the energy captured from sunlight

Biogeochemical cycles recycle matter. The water cycle involves evaporation, condensation, precipitation, and runoff. The carbon cycle moves carbon through the atmosphere, living things, and the Earth. The nitrogen cycle converts atmospheric nitrogen into usable forms through nitrogen fixation. Biomes are major ecological communities: terrestrial biomes include tundra, taiga, temperate forest, tropical rainforest, grassland, and desert; aquatic biomes include freshwater and marine ecosystems.

Geology

Plate tectonics explains Earth's surface features. Tectonic plates ride on the asthenosphere, moved by convection currents in the mantle. At divergent boundaries, plates separate, forming rifts and mid-ocean ridges. At convergent boundaries, plates collide, forming mountains, trenches, and volcanoes. At transform boundaries, plates slide past each other, causing earthquakes.

IgneousRock					SedimentaryRock					MetamorphicRock
Formedwhenmagmaorlavacoolsand					Formedfromcompressedand					Formedwhenexistingrockischanged
hardens					cementedsediments					byheatandpressure

The rock cycle describes how rocks change from one type to another. Minerals are naturally occurring, inorganic solids with a definite chemical composition and crystal structure, identified by hardness (the Mohs scale, 1 to 10), luster, color, streak, cleavage, and fracture.

Weathering breaks rocks down, either physically (frost wedging, abrasion) or chemically (oxidation, carbonation). Erosion carries the weathered material away by water, wind, ice, or gravity, and deposition occurs when it settles.

Earthquakes are sudden releases of energy along faults. P-waves (primary) are the fastest and compressional, S-waves (secondary) are shear waves, and surface waves are the slowest and most destructive. The Richter scale measures magnitude; the Mercalli scale measures intensity. Volcanoes form where magma reaches the surface: shield volcanoes have gentle slopes and fluid lava, composite volcanoes are steep with explosive eruptions, and cinder cones are small and steep.

Oceanography

Oceans cover about 71% of Earth's surface, and seawater contains about 3.5% dissolved salts, mostly sodium chloride. Ocean layers include the warm, mixed surface zone, the thermocline (where temperature drops rapidly), and the cold, dense deep zone. Surface currents are driven by wind and bent by the Coriolis effect; deep currents are driven by differences in temperature and salinity (thermohaline circulation). Tides are caused by the gravitational pull of the Moon and Sun: spring tides (greatest range) occur when the Sun and Moon align, and neap tides (smallest range) occur when they are at right angles.

Meteorology

Layersoftheatmosphere(Lowesttohighest)

Layer	TemperatureWithAltitude	KeyFeature
Troposphere	Decreases	Whereweatheroccurs
Stratosphere	Increases	Containstheozonelayer
Mesosphere	Decreases	Coldestlayer;meteorsburnuphere
Thermosphere	Increases	Aurorasoccurhere
Exosphere	—	Transitiontospace

Weather is short-term atmospheric conditions; climate is the long-term pattern. Air pressure decreases with altitude, and wind flows from high pressure to low pressure. The Coriolis effect deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Air masses are large bodies of air with uniform temperature and humidity, and fronts are the boundaries between them. Cold fronts bring rapid changes and thunderstorms, warm fronts bring gradual changes and steady precipitation, and stationary fronts stall and bring prolonged precipitation. Relative humidity compares the water vapor in the air with the maximum it could hold, and the dew point is the temperature at which condensation begins. Clouds form when rising air cools to saturation.

Cumulus					Stratus					Cirrus					Nimbus
Puffy;fairweather					Layered;overcast					Wispy;highaltitude					Rain-producing

Severe weather includes thunderstorms (convective storms with lightning), tornadoes (rotating columns of air), and hurricanes (large rotating storms that form over warm ocean water).

Astronomy

The solar system formed about 4.6 billion years ago from a nebula. The Sun holds 99.8% of the solar system's mass, and nuclear fusion in its core converts hydrogen into helium, releasing energy. The eight planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Earth rotates on its axis once every 24 hours, causing day and night, and revolves around the Sun once every 365.25 days. Its 23.5° axial tilt causes the seasons. The Moon orbits Earth about every 27.3 days, and its phases result from the changing angle of sunlight we see reflected from it.

Stars form from collapsing nebulae; fusion begins when the core reaches about 10 million degrees. The Hertzsprung- Russell diagram classifies stars by temperature and luminosity. Main-sequence stars fuse hydrogen, red giants expand after their hydrogen runs low, white dwarfs are the remnants of low-mass stars, and supernovae are the explosive deaths of massive stars, leaving neutron stars or black holes. The Milky Way is a spiral galaxy of 100 to 400 billion stars. The redshift of distant galaxies shows that the universe is expanding, and the Big Bang theory holds that it began about 13.8 billion years ago from an extremely hot, dense state.

Chemistry