AP Biology Outline 2026-2027 (Chapters 1-4)

Comprehensive practice flashcards covering AP Biology Chapters 1-4 based on lecture notes.

What is biology defined as in Chapter 1?

Biology is the scientific study of life.

What is reductionism in the context of biological systems?

An approach that reduces complex systems to simpler components that are more manageable to study.

What are emergent properties?

New properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases.

What is systems biology?

The exploration of the network of interactions that underlie the emergent properties of a system.

What distinguishes a eukaryotic cell from a prokaryotic cell?

A eukaryotic cell contains membrane-enclosed organelles and stores DNA in its nucleus, whereas a prokaryotic cell is smaller and lacks these features.

Why is the cell considered the smallest unit of biological organization?

Because it can perform all actions needed for life.

What is the full hierarchy of biological organization listed from largest to smallest level?

Biosphere, Ecosystems, Communities, Populations, Organism, Organs, Tissues, Cells, Organelles, Molecules.

What are genes?

Units of inheritance contained within DNA that make up genetic code.

How is genetic information transferred from the nucleus to ribosomes for protein synthesis?

mRNA carries a copy of the genetic information from the nucleus to the ribosomes.

What is gene expression?

The entire process by which the information in a gene directs the production of a cellular product.

What is a genome?

The entire library of genetic instructions that an organism inherits.

How does genomics differ from traditional genetic research?

Genomics studies whole sets of genes and one or more species, rather than investigating a single gene at a time.

What is a proteome?

The entire set of proteins expressed by a given cell, tissue, or organism.

What is bioinformatics?

The use of computational tools to store, organize, and analyze the huge volume of biological data that results from high-throughput methods.

How does energy flow through an ecosystem?

Energy flows through an ecosystem as light and exits as heat.

What are decomposers and what is their role in an ecosystem?

Typically bacteria and fungi that break down waste products, organic debris, and bodies of dead organisms so materials can be recycled by plants.

What is climate change defined as in the outline?

A directional change to the global climate that lasts for three decades or more.

According to the notes, how much have human activities increased global average temperatures since 1900?

By $1\,^{\circ}\text{C}$.

Approximately how many species of organisms have biologists identified and named?

Biologists have identified and named about $1.8 \times 10^6$ species.

What are the three domains used to classify all living organisms?

Bacteria, Archaea, and Eukarya.

What are the three kingdoms of multicellular eukaryotes in Domain Eukarya?

Kingdom Plantae, Kingdom Fungi, and Kingdom Animalia.

What defines the nutritional mode of members in Kingdom Fungi?

They absorb nutrients from outside their bodies.

What primary mechanism did Charles Darwin propose for biological evolution?

Natural Selection, where the natural environment selects for certain traits among naturally occurring variant traits in a population.

What is inductive reasoning?

A type of logic that forms important general conclusions based on collecting and analyzing specific observations.

What is deductive reasoning?

Logic that flows from general premises to specific predicted results.

What is the independent variable in a scientific experiment?

The variable that is intentionally manipulated by the experimenter.

What is the dependent variable in a scientific experiment?

The factor that is measured and predicted to change in response to the independent variable.

What is a controlled experiment?

An experiment designed to compare a control group (unmanipulated) to an experimental group (manipulated).

What is matter?

Anything that takes up space and has mass.

What is an element?

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

What is a compound?

A substance that contains two or more different elements combined in a fixed ratio.

What percentage of the 92 natural elements are classified as essential elements?

About $20\%$ to $25\%$.

How many essential elements are required by humans compared to plants?

Humans require $25$ essential elements, while plants require $17$.

What three subatomic particles make up an atom?

Protons, neutrons, and electrons.

What is the approximate mass of a proton or neutron in grams and Daltons?

Approximately $1.7 \times 10^{-24}\,g$, which equals about $1\text{ Dalton}$ (or amu).

What does the atomic number of an element indicate?

The number of protons (and electrons in a neutral atom) in an element.

How is the mass number of an atom calculated?

It is the total sum of protons and neutrons in the nucleus of an atom.

In the chemical representation of Phosphorus, what does the number 15 indicate?

The atomic number of Phosphorus.

What are isotopes?

Different atomic forms of the same element that have the same number of protons but a different number of neutrons.

What defines a radioactive isotope?

An isotope in which the nucleus decays spontaneously, giving off subatomic particles and energy.

What is potential energy?

Energy that matter possesses due to its location or structure.

What happens when an electron absorbs energy?

It moves to an electron shell further away from the nucleus.

What are valence electrons?

The electrons located in the outermost electron shell of an atom.

What is a covalent bond?

The sharing of a pair of valence electrons by two atoms.

What is electronegativity?

The attraction of a particular atom for the electrons of a covalent bond.

What is the difference between a nonpolar covalent bond and a polar covalent bond?

In a nonpolar covalent bond, electrons are shared equally due to equal electronegativity; in a polar covalent bond, electrons are shared unequally because one atom is more electronegative.

How is an ionic bond formed between two atoms?

Two atoms differ so much in electronegativity that the more electronegative atom strips an electron completely away from its partner, forming ions.

What are cations and anions?

A cation is a positively charged ion, and an anion is a negatively charged ion.

What are van der Waals interactions?

Weak, temporary interactions that occur only when atoms and molecules are very close together due to transient asymmetric electron distribution.

What is chemical equilibrium?

The point at which forward and reverse chemical reactions offset one another exactly, causing reactant and product concentrations to stabilize at a fixed ratio.

What is cohesion in water molecules?

The hydrogen bonding that holds substance molecules together, causing water to cling to itself.

What is adhesion?

The clinging of one substance to another substance.

What is surface tension?

A measure of how difficult it is to stretch or break the surface of a liquid.

What is a calorie defined as?

The amount of heat required to raise the temperature of $1\,g$ of water by $1\,^{\circ}\text{C}$.

What is specific heat?

The amount of heat a substance must absorb or lose for $1\,g$ of that substance to change its temperature by $1\,^{\circ}\text{C}$.

How does evaporative cooling occur?

As a liquid evaporates, the surface remaining behind cools because the hottest molecules with the greatest kinetic energy leave as a gas.

What is molarity?

The number of moles of solute per liter of solution.

How is an acid defined?

A substance that increases the hydrogen ion ($\text{H}^+$) concentration of a solution.

How is a base defined?

A substance that reduces the hydrogen ion ($\text{H}^+$) concentration of a solution.

What pH range defines acidic versus basic solutions?

Solutions with a pH less than $7$ are acidic, whereas solutions with a pH greater than $7$ are basic.

What is a buffer?

A substance that minimizes changes in the concentrations of $\text{H}^+$ and $\text{OH}^-$ in a solution.

What are hydrocarbons?

Organic molecules consisting entirely of carbon and hydrogen.

What are structural isomers?

Compounds that differ in the covalent arrangements of their constituent atoms.

What are cis-trans isomers?

Isomers in which carbons have covalent bonds to the same atoms, but differ in spatial arrangements due to the inflexibility of double bonds.

What are enantiomers?

Isomers that are mirror images of each other and differ due to the presence of an asymmetric carbon.

What occurs during a dehydration reaction?

Two monomers are covalently bonded to each other with the loss of a water molecule.

What occurs during hydrolysis?

Polymers are broken down into monomers through the addition of a water molecule.

What type of bond joins two monosaccharides together to form a disaccharide?

A glycosidic linkage formed by a dehydration reaction.

What is glycogen and how is it used by animals?

Glycogen is a polymer of glucose stored by animals that releases glucose when energy demand increases.

What is cellulose and where is it found?

A structural carbohydrate that forms a major component of the tough enclosing cell walls of plant cells.

What is the main structural difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no double bonds and max hydrogen; unsaturated fatty acids contain one or more double bonds with fewer hydrogen atoms.

What is the structure of a phospholipid?

A glycerol attached to two fatty acids and a negatively charged phosphate group.

What is a steroid and what is a primary animal example?

A lipid characterized by a carbon skeleton consisting of four fused rings; cholesterol is a common animal cell membrane component and precursor.

What are the four levels of protein structure?

Primary (amino acid sequence), Secondary (folds/coils from backbone hydrogen bonds), Tertiary (3D shape from side chain interactions), and Quaternary (aggregation of multiple polypeptide subunits).

What is denaturation in proteins?

A process where a protein loses its structure and functional ability due to alterations in pH, salt concentration, temperature, or other environmental factors.

What are the main structural differences between DNA and RNA?

DNA contains deoxyribose sugar, thymine, and forms a double helix; RNA contains ribose sugar, uracil, and is typically single-stranded.

What are the primary functions of mRNA, tRNA, and rRNA?

mRNA encodes proteins, tRNA carries amino acids to the ribosome, and rRNA forms the ribosome structure.

What is cell fractionation?

A technique where broken-up cells are spun in a centrifuge to separate specific cellular components for functional study.

What structural elements comprise a chloroplast?

Outer and inner membranes, thylakoids stacked into grana, stroma fluid, and lumen.

What are the three types of cell junctions found in animal tissues?

Tight junctions (impermeable seals), Desmosomes (anchoring rivets), and Gap junctions (communicating intercellular channels).