AP Biology Unit 1 (Topics 1-7)

Scientific Method

A step-by-step process used by scientists to investigate questions, gather evidence, and draw conclusions based on experiments and observations.

Null Hypothesis

A testable explanation stating that there is no effect or difference between two groups of data and that observations are the result of chance.

Alternative Hypothesis

A testable explanation stating that there is a relationship, effect, or difference between two groups of data and that observations are due to a nonrandom cause.

Negative Control Group

A group not exposed to any treatment or exposed to a treatment known to have no effect.

Positive Control Group

A group exposed to a treatment known to have an effect.

Experimental Group

The group that receives the experimental treatment or independent variable.

Independent Variable

The one factor changed between groups; the manipulated variable; graphed on the x-axis.

Dependent Variable

The factor measured and affected by the independent variable; graphed on the y-axis.

Constant (Controlled Variable)

A factor kept consistent for all groups, ensuring that only the independent variable affects the outcome.

Statistics

Methods used to collect, process, or interpret quantitative data; help us understand important information.

Descriptive Statistics

Methods used to summarize or describe observations or samples; include measures of central tendency and variability.

Inferential Statistics

Methods that use observations to make estimates or predictions and generalize from a sample to a wider population; include SEM, confidence intervals, and hypothesis tests.

Central Tendencies

Measures in descriptive statistics, including mean, median, and mode, that describe the center of a dataset.

Mean

The average of a dataset; sensitive to outliers.

Median

The middle number in an ordered set of data points.

Mode

The value that appears most often; useful for categorical data.

Variability

The degree to which data are spread out in a dataset; helps provide a more complete summary of a distribution.

Range

The difference between the largest and smallest values in a dataset.

Standard Deviation

A measure of how much the values in a dataset typically deviate from the mean; measures the spread of data.

Standard Error

A measure used to assess how accurately a sample mean estimates the population mean.

Chi-Square

A form of statistical analysis used to compare observed counts or frequencies with expected counts or frequencies.

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down into other substances by chemical reactions.

Electronegativity

The measure of an atom’s ability to attract electrons toward itself.

Atomic Number

The number of protons in an element.

Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element.

Octet Rule

Atoms tend to gain, lose, or share electrons to complete their valence shells and become stable.

Chemical Bond

An attraction between two atoms resulting from the sharing or transferring of valence electrons.

Compound

A substance consisting of two or more different elements combined in a fixed ratio.

Covalent Bond

A bond formed when two atoms share electrons, usually between two nonmetals.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between two atoms, as in O₂.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between atoms, as in water.

Ionic Bond

The attraction between oppositely charged ions; usually formed when a metal transfers electrons to a nonmetal.

Adhesion

The attraction between different substances, such as water and other polar or charged molecules.

Cohesion

The attraction between molecules of the same substance, such as water molecules attracting one another.

Capillary Action

The upward movement of water caused by cohesion, adhesion, and surface tension; occurs when adhesion to a surface helps pull water upward.

Solvent

The dissolving agent in a solution.

Solution

A homogeneous mixture of two or more substances.

Solute

The substance that is dissolved in a solution.

pH

A measure of how acidic or basic (alkaline) a solution is.

Acid

A substance that increases the concentration of hydrogen ions (H⁺) when dissolved in water.

Base

A substance that accepts H⁺ or releases hydroxide ions (OH⁻).

Buffer

A solution that resists changes in pH when an acid or base is added.

Functional Groups

Chemical groups attached to a carbon skeleton that participate in chemical reactions.

Organic Chemistry

The study of compounds containing covalently bonded carbon.

Organic Compounds

Compounds that contain carbon and hydrogen.

Hydrocarbons

Organic molecules consisting only of carbon and hydrogen; provide the basic framework for more complex organic molecules.

Macromolecule

A very large molecule, commonly formed by joining smaller organic molecules together.

Dehydration Reaction

A reaction that covalently bonds two monomers by removing water; a hydroxyl group from one monomer and hydrogen from another combine to form released water.

Hydrolysis

A reaction that breaks a covalent bond in a polymer by adding water; a hydrogen attaches to one monomer and a hydroxyl group attaches to the other.

Polymers

Chain-like macromolecules made of similar or identical repeating units covalently bonded together.

Monomers

The repeating molecular units that make up polymers.

Disaccharide

A carbohydrate formed when two monosaccharides are joined by a covalent bond.

Starch

A polymer of glucose monomers that allows plants to store excess glucose.

Monomer

A single molecular unit that can be joined with others to form a polymer.

Cellulose

A structural polysaccharide that forms the tough material of plant cell walls.

Polymer

A chain-like macromolecule made of similar or identical repeating units.

Monosaccharide

A simple sugar whose molecular formula is generally a multiple of CH₂O.

Polysaccharide

A polymer containing many sugar monomers joined through dehydration reactions.

Glycogen

A highly branched polymer of glucose stored mainly in animal liver and muscle cells.

Glycosidic Linkage

A covalent bond that joins one carbohydrate molecule to another.

Lipid

A diverse class of mostly nonpolar and hydrophobic molecules that do not form true polymers.

Fat

A type of lipid composed of glycerol and fatty acids that functions in energy storage, insulation, and other cellular processes.

Fatty Acid

A long hydrocarbon chain with a carboxyl group at one end.

Phospholipid

A major component of cell membranes that forms a bilayer in water, with hydrophobic tails and hydrophilic heads.

Antiparallel

The arrangement of two DNA strands that run parallel to each other but in opposite 5′-to-3′ directions.

DNA

Deoxyribonucleic acid; consists of two polynucleotide strands forming a double helix, with antiparallel strands held together by hydrogen bonds between complementary bases.

RNA

Ribonucleic acid; usually a single-stranded polynucleotide that can vary in shape because of base pairing.

Nucleotide

The building block of a nucleic acid, containing a nitrogenous base, a five-carbon sugar, and one or more phosphate groups.

Nucleic Acid

A polymer made of nucleotide monomers that stores, transmits, and helps express hereditary information.

Gene

A specific DNA sequence that contains hereditary information and usually codes for a functional product.

Pyrimidine

A nitrogenous base with one six-membered ring.

Purine

A nitrogenous base with one six-membered ring bonded to one five-membered ring.

Primary Protein Structure

The linear sequence of amino acids determined by a gene; influences the protein’s secondary and tertiary structures.

Secondary Protein Structure

Coils and folds produced by hydrogen bonding within the polypeptide backbone.

Tertiary Protein Structure

The overall three-dimensional folding of one polypeptide caused by interactions between amino acid side chains, including hydrophobic and ionic interactions, hydrogen bonds, and disulfide bridges.

Quaternary Protein Structure

The association of two or more polypeptide chains; found only in some proteins.

Protein

A molecule consisting of one or more polypeptides folded into a specific three-dimensional shape; proteins contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

Amino Acid

An organic molecule containing an amino group, a carboxyl group, and a variable side chain; 20 common amino acids are used to build proteins.

Hydroxyl Chemical Formula

-OH

Carbonyl Chemical Formula

C=O

Carboxyl Chemical Formula

-COOH