Life Science

ASVAB Armed Services Vocational Aptitude Battery

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1 Introduction

About the ASVAB AFQT Score and Military Eligibility Line Scores and Military Jobs (MOS) How to Use This Guide

2 Verbal Domain (WK + PC)

Word Knowledge Basics Word Knowledge Practice Paragraph Comprehension Basics Paragraph Comprehension Practice

3 Mathematics Domain (AR + MK)

Number Operations Word Problems Algebra Geometry Test Strategies

4 Science & Technical Domain (GS + EI + MC)

Life Science Physical Science Electronics Fundamentals Mechanical Principles Applied Science Questions

5 Technical Skills Domain (AI + SI + AO)

Automotive Basics Automotive Systems Shop Tools and Practices Shop Safety and Materials Assembling Objects

Life Science

Key Takeaways Explain This Topic AI

Cells are the basic unit of life—know the difference between prokaryotic (no nucleus) and eukaryotic (nucleus) cells.

The human body has 11 organ systems; focus on circulatory, respiratory, digestive, and nervous systems for the ASVAB.

Ecology covers how organisms interact with their environment—understand food chains, ecosystems, and energy flow.

Genetics basics include DNA, genes, chromosomes, and inheritance patterns (dominant vs. recessive traits).

Life science questions make up roughly 50% of the General Science subtest.

Last updated: January 2026

Quick Answer: Life science questions on the ASVAB cover biology basics including cell structure (prokaryotic vs. eukaryotic), human body systems (11 total), ecology (food chains, ecosystems), and genetics (DNA, inheritance). Expect roughly 8 of the 16 General Science questions to cover life sciences.

Cell Biology

All living things are made of cells—the basic unit of life. The ASVAB tests your understanding of cell structure and function.

Types of Cells

• Cell Type Characteristics Examples
• Prokaryotic No nucleus, no membrane-bound organelles, simpler structure Bacteria, archaea
• Eukaryotic Has nucleus, membrane-bound organelles, more complex Plants, animals, fungi
• Key Cell Organelles

• Organelle Function Memory Tip
• Nucleus Contains DNA, controls cell "Brain" of the cell
• Mitochondria Produces energy (ATP) "Powerhouse" of the cell
• Ribosomes Makes proteins "Protein factories"
• Cell Membrane Controls what enters/exits "Gatekeeper"
• Chloroplasts Photosynthesis (plants only) "Solar panels"
• Cytoplasm Gel-like fluid holding organelles "Cell jelly"
• Vacuole Storage (large in plants) "Storage tank"
• Cell Processes

• Process What Happens Formula/Result
• Mitosis Cell division (creates identical cells) 1 cell → 2 identical cells
• Meiosis Sex cell division (reduces chromosomes by half) 1 cell → 4 gametes
• Photosynthesis Plants convert sunlight to food CO₂ + H₂O + Light → Glucose + O₂
• Cellular Respiration Cells convert glucose to energy Glucose + O₂ → CO₂ + H₂O + ATP
• Human Body Systems

The human body has 11 major organ systems. Focus on these key systems for the ASVAB:

• System Main Organs Primary Function
• Circulatory Heart, blood vessels, blood Transports oxygen, nutrients, hormones
• Respiratory Lungs, trachea, bronchi Gas exchange (O₂ in, CO₂ out)
• Digestive Stomach, intestines, liver Breaks down food, absorbs nutrients
• Nervous Brain, spinal cord, nerves Controls body, processes information
• Muscular Skeletal, smooth, cardiac muscles Movement and support
• Skeletal Bones, joints, cartilage Support, protection, movement
• Immune White blood cells, lymph nodes Fights infection and disease
• Endocrine Glands (thyroid, pituitary) Produces hormones
• Excretory Kidneys, bladder, skin Removes waste products
• Reproductive Sex organs Produces offspring
• Integumentary Skin, hair, nails Protection, temperature regulation
• Circulatory System Details

• Component Function Key Fact
• Heart Pumps blood 4 chambers (2 atria, 2 ventricles)
• Arteries Carry blood away from heart Usually carry oxygenated blood
• Veins Carry blood to heart Usually carry deoxygenated blood
• Capillaries Exchange site Smallest blood vessels
• Red Blood Cells Carry oxygen Contain hemoglobin
• White Blood Cells Fight infection Part of immune system
• Platelets Blood clotting Prevent bleeding
• Respiratory System Details
• The path of air: Nose/Mouth → Trachea → Bronchi → Bronchioles → Alveoli
• Alveoli : Tiny air sacs where gas exchange occurs
• Diaphragm : Muscle that controls breathing
• Inhalation: Diaphragm contracts, lungs expand
• Exhalation: Diaphragm relaxes, lungs compress
• Ecology

Ecology studies how organisms interact with each other and their environment.

• Levels of Organization
• From smallest to largest: Individual → Population → Community → Ecosystem → Biome → Biosphere

• Level Definition Example
• Population Same species in an area All deer in a forest
• Community All species in an area Deer, wolves, trees in a forest
• Ecosystem Community + physical environment Forest with soil, water, climate
• Biome Large region with similar climate Temperate forest, desert, tundra
• Biosphere All life on Earth Every ecosystem combined
• Food Chains and Webs

• Level Role Example
• Producers Make their own food (photosynthesis) Plants, algae
• Primary Consumers Eat producers (herbivores) Rabbits, deer
• Secondary Consumers Eat primary consumers (carnivores) Foxes, snakes
• Tertiary Consumers Top predators Eagles, wolves
• Decomposers Break down dead matter Bacteria, fungi

Energy Rule : Only about 10% of energy transfers between each level. This is why food chains rarely have more than 4-5 levels.

Ecological Relationships

• Relationship Description Example
• Mutualism Both species benefit Bees and flowers
• Commensalism One benefits, other unaffected Barnacles on whales
• Parasitism One benefits, one harmed Ticks on dogs
• Predation One kills and eats another Lion eating zebra
• Competition Both compete for same resources Two species of finches
• Genetics

Genetics is the study of heredity—how traits are passed from parents to offspring.

Key Terms

• Term Definition
• DNA Molecule that carries genetic information
• Gene Section of DNA that codes for a trait
• Chromosome Structure made of DNA and proteins
• Allele Different versions of a gene
• Genotype Genetic makeup (letters: AA, Aa, aa)
• Phenotype Physical expression of genes (what you see)
• Inheritance Patterns

• Term Meaning Result
• Dominant Expressed when one copy present Written as capital letter (A)
• Recessive Only expressed when two copies present Written as lowercase (a)
• Homozygous Two identical alleles AA or aa
• Heterozygous Two different alleles Aa
• Punnett Square Example

For a cross between Aa × Aa (both parents heterozygous):

• A a
• A AA Aa
• a Aa aa
• Results: 25% AA, 50% Aa, 25% aa (3:1 phenotype ratio for dominant trait)