AP Biology Unit 0: Foundations of Biology, Scientific Method, and Basic Chemistry

Vocabulary flashcards covering experimental design, statistical concepts, basic chemical bonding, the properties of water, and the pH scale as outlined in the Unit 0 study guide.

Independent Variable (IV)

The variable manipulated or changed by the researcher; always plotted on the $X$-axis of a graph.

Dependent Variable (DV)

The factor being measured or observed that responds to the IV; always plotted on the $Y$-axis of a graph.

Controlled Variables (Constants)

Factors kept identical across all groups to prevent confounding results.

Negative Control Group

A group not exposed to the experimental treatment; used as a baseline expected to show no effect.

Positive Control Group

A group exposed to a treatment with a known result; ensures the experimental setup works correctly.

Hypothesis

A testable, falsifiable statement predicting a relationship between variables.

Mean

The average value of a data set.

Standard Deviation (SD)

A measure of data dispersion; a low value indicates that data points are close to the mean.

Standard Error of the Mean (SEM)

Measures the precision of the sample mean estimate.

Error Bars

Visual markers on graphs where an overlap of $2SEM$ usually indicates no statistical significance, while no overlap suggests a significant difference.

CHNOPS

An acronym for the core elements required for life: Carbon ($C$), Hydrogen ($H$), Nitrogen ($N$), Oxygen ($O$), Phosphorus ($P$), and Sulfur ($S$).

Covalent Bonds

Bonds where atoms share electrons; can be polar (unequal sharing, like $H_2O$) or nonpolar (equal sharing, like $O_2$).

Ionic Bonds

The transfer of electrons from a metal to a non-metal, creating charged ions that attract each other.

Hydrogen Bonds

A weak attraction between a partially positive hydrogen atom in one polar molecule and a partially negative atom (usually $O$ or $N$) in another.

Polarity

A property of water where highly electronegative Oxygen pulls electrons closer, creating a partial negative charge while Hydrogens remain partially positive.

Cohesion

Water molecules sticking to each other via hydrogen bonding, creating high surface tension.

Adhesion

Water molecules sticking to other polar surfaces, which is crucial for capillary action in plant xylem.

High Specific Heat

Water's ability to absorb or release large amounts of heat with minimal temperature change, stabilizing environments.

Evaporative Cooling

The process where the hottest molecules leave as gas, lowering the surface temperature of the remaining liquid.

Density of Ice

Ice is less dense than liquid water because hydrogen bonds lock molecules into a crystalline lattice, protecting aquatic life below.

Universal Solvent

Water's ability to dissolve polar and ionic substances due to its capacity to form hydration shells.

pH Scale

A scale ranging from $0$ to $14$ that measures the concentration of hydrogen ions $[H^+]$ in a solution.

Acids

Substances with a pH ranging from $0$ to $6.9$, characterized by a high concentration of $[H^+]$.

Bases

Substances with a pH ranging from $7.1$ to $14$, characterized by low $[H^+]$ and high $[OH^-]$ concentrations.

Logarithmic Nature of pH

Each step on the pH scale represents a $10$-fold change in $[H^+]$ concentration (e.g., pH $3$ is $100$ times more acidic than pH $5$).