Chapter 3 of 431% of exam

Science

Science is the most heavily weighted section of the ATI TEAS 7, reflecting how much foundational science nursing requires. It emphasizes human anatomy and physiology, along with life science (biology), physical science (chemistry and physics basics), and scientific reasoning. This chapter surveys the major body systems and how they work together, the structure and function of cells, the fundamentals of genetics and chemistry, and the logic of the scientific method. A strong grasp of how the body maintains balance, or homeostasis, ties these topics together and prepares you for clinical study.

Anatomy and Physiology: Body Systems

Anatomy and physiology dominate the science section. You must know the major organ systems, their primary organs, and how they cooperate to keep the body functioning and balanced.

Match systems to their functions
The circulatory system transports oxygen and nutrients, the respiratory system exchanges gases, the urinary system filters waste, and the skeletal system provides support and protection.
Know the heart and blood vessels
Arteries carry blood away from the heart and veins return it; the left ventricle pumps oxygenated blood to the entire body while the right ventricle sends blood to the lungs.
Understand the nervous system layout
The central nervous system is the brain and spinal cord; the peripheral nervous system is the nerves branching out. Neurons receive signals through dendrites and send them along the axon.
Recognize how systems maintain homeostasis
The nervous and endocrine systems work together to keep internal conditions stable, using hormones such as insulin from the pancreas to regulate blood glucose.

Cells and Cellular Processes

The cell is the basic unit of life, and its organelles carry out specialized jobs. Understanding cellular structure and transport explains how tissues, organs, and whole organisms operate.

Identify key organelles
The nucleus stores DNA, mitochondria produce ATP energy through cellular respiration, ribosomes build proteins, and the cell membrane controls what enters and exits.
Follow the levels of organization
Life is organized from smallest to largest as cells, tissues, organs, organ systems, and organisms. Cells combine to form tissues, which build organs.
Distinguish passive and active transport
Osmosis and diffusion move substances without energy, from high to low concentration (water moves toward higher solute in osmosis). Active transport requires energy to move against a gradient.
Understand enzymes
Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy, without being used up in the process.

Genetics and Reproduction

Genetics explains how traits pass from parents to offspring through chromosomes and alleles. These principles underlie inherited conditions that nurses encounter in patient care.

Know human chromosome numbers
A typical human body (somatic) cell has 46 chromosomes in 23 pairs, while gametes (egg and sperm) carry 23 chromosomes each.
Distinguish dominant and recessive alleles
A dominant allele is expressed with only one copy, while a recessive allele is expressed only when two copies are present.
Use genotype and phenotype correctly
Genotype is the genetic makeup (the alleles present), while phenotype is the observable trait that results from that genotype.
Understand cell division basics
Mitosis produces two identical body cells for growth and repair, while meiosis produces gametes with half the chromosome number for reproduction.

Basic Chemistry and Physical Science

Chemistry underlies physiology, from the pH of blood to the bonds that hold molecules together. A working knowledge of atoms, bonds, and reactions supports understanding of body chemistry.

Know the parts of an atom
Protons carry a positive charge and neutrons are neutral, both in the nucleus, while electrons carry a negative charge and orbit the nucleus. An ion has gained or lost electrons.
Distinguish ionic and covalent bonds
Ionic bonds form when electrons transfer between atoms, creating charged ions; covalent bonds form when atoms share electrons.
Use the pH scale
The pH scale runs from 0 to 14; 7 is neutral, below 7 is acidic, and above 7 is basic. Pure water has a pH of 7.
Tell physical from chemical changes
A physical change (melting, cutting, boiling) alters form but not composition, while a chemical change (rusting, burning) forms a new substance.

Scientific Reasoning and the Scientific Method

Science questions also test how knowledge is produced. You must understand experimental design, variables, and how to draw valid conclusions from data.

Form a testable hypothesis
A hypothesis is a testable prediction proposed before an experiment, which data can support or refute. It is not a proven fact or a final conclusion.
Identify variables
The independent variable is deliberately changed by the researcher, the dependent variable is measured in response, and constants are kept the same.
Use a control group
A control group receives no experimental treatment and provides a baseline for comparison, helping isolate the effect of the independent variable.
Measure with correct units
Mass is measured in grams, length in meters, volume in liters, and force in newtons. Choosing the right unit is essential for valid, comparable data.
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Last updated: July 2026

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