OAE Biology key terms

A cyclical process of observing, asking questions, forming testable hypotheses, designing controlled experiments, analyzing data, and revising explanations based on evidence rather than authority or intuition.

A proposed, testable explanation for an observation that generates specific predictions; it must be falsifiable, meaning some possible result would count as evidence against it.

A study in which all variables except the one being tested are held constant, and subjects are compared against a control group receiving no treatment or a placebo.

The factor deliberately manipulated or selected by the researcher in an experiment, whose effect on the measured outcome is being investigated.

The outcome measured in an experiment; its value is expected to respond to changes in the independent variable and is recorded as data.

Evaluation of a scientist's manuscript by independent experts in the same field before publication, intended to catch methodological flaws, unsupported claims, and errors in interpretation.

A broad, well-tested explanation supported by large bodies of converging evidence, such as evolution or cell theory; it is not a guess and can still be revised.

A polar molecule whose hydrogen bonds create high cohesion, adhesion, specific heat, and heat of vaporization, making it the solvent and temperature buffer of living systems.

A weak attraction between a partially positive hydrogen atom and a partially negative atom such as oxygen or nitrogen; collectively these bonds stabilize water, proteins, and nucleic acids.

Describing substances that associate readily with water because they are polar or charged; hydrophilic heads of phospholipids face the watery interior and exterior of cells.

Describing nonpolar substances that repel water and cluster together in aqueous environments; hydrophobic tails form the interior of cell membranes.

A protein (or occasionally RNA) catalyst that speeds a biochemical reaction by lowering its activation energy without being consumed, and is usually specific to one substrate.

The minimum energy input required to start a chemical reaction; enzymes reduce it so reactions proceed at temperatures compatible with life.

Loss of a protein's functional three-dimensional shape caused by heat, extreme pH, or chemicals, which disrupts hydrogen bonds and other weak interactions in the structure.

The two-layered sheet of phospholipids forming the core of cell membranes, with hydrophilic heads outward and hydrophobic tails inward, creating a selectively permeable barrier.

Net movement of particles from an area of higher concentration to lower concentration, driven by random molecular motion and requiring no energy input.

Diffusion of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to lower water potential.

Movement of substances across a membrane against their concentration gradient using carrier proteins and energy, typically from ATP hydrolysis.

Adenosine triphosphate, the universal energy currency of cells; hydrolysis of its terminal phosphate bond releases energy that powers endergonic reactions and transport.

The set of catabolic pathways, including glycolysis, the Krebs cycle, and oxidative phosphorylation, that harvest energy from organic molecules to produce ATP, releasing carbon dioxide and water.

The light-driven process in chloroplasts that converts carbon dioxide and water into glucose and oxygen, using pigments such as chlorophyll to capture light energy.

A plant-cell organelle containing thylakoid membranes and chlorophyll where the light reactions and the Calvin cycle of photosynthesis occur.

An organelle bounded by a double membrane whose inner folds host the electron transport chain and ATP synthesis, making it the main site of aerobic ATP production.

Division of a eukaryotic nucleus producing two genetically identical daughter cells, used for growth, repair, and asexual reproduction; it includes prophase, metaphase, anaphase, and telophase.

Two successive nuclear divisions that halve chromosome number and generate genetically varied gametes through independent assortment and crossing over.

One of the alternative forms of a gene at a given locus, such as the dominant or recessive version that determines a particular trait's expression.

The specific combination of alleles an organism carries for a gene or set of genes, which interacts with the environment to produce observable traits.

The observable characteristics of an organism, resulting from the interaction of its genotype with environmental influences during development.

Exchange of corresponding chromosome segments between homologous chromosomes during prophase I of meiosis, producing recombinant chromatids and increasing genetic variation.

Semiconservative copying of a DNA molecule in which each strand serves as a template for a new complementary strand, using enzymes such as helicase and DNA polymerase.

The process of transcription of DNA into messenger RNA followed by translation of that RNA into a polypeptide chain at the ribosome according to the genetic code.

A heritable change in the nucleotide sequence of DNA, arising from copying errors or mutagens; it is the ultimate source of new alleles in a population.

Differential survival and reproduction of individuals whose heritable traits better suit their environment, causing those traits to increase in frequency over generations.

Change in the heritable characteristics of a population over generations, driven by mutation, natural selection, genetic drift, and gene flow.

The science of naming, describing, and classifying organisms into hierarchical groups, from domain and kingdom down to genus and species, based on shared characteristics and ancestry.

The two-part scientific naming system in which each species receives a capitalized genus name and a lowercase specific epithet, both italicized or underlined.

The evolutionary history and branching relationships among organisms or lineages, commonly represented by a tree diagram built from shared derived traits or molecular data.

An organism whose cells lack a membrane-bound nucleus and organelles, comprising the domains Bacteria and Archaea and typically having circular DNA and small ribosomes.

An organism whose cells contain a nucleus enclosing the chromosomes and membrane-bound organelles such as mitochondria and chloroplasts.

The maximum population size of a species that a given environment can sustain indefinitely, set by limiting resources such as food, water, and space.

Change in the number of individuals in a population over time; exponential growth occurs with unlimited resources, while logistic growth slows as carrying capacity is approached.

Any resource or condition that restricts the growth, abundance, or distribution of a population, such as nutrients, light, predators, or disease.

A network of interconnected feeding relationships in an ecosystem, showing how energy and matter pass from producers through multiple consumers and decomposers.

A feeding position in an ecosystem, such as producer, primary consumer, or secondary consumer, defined by the number of energy-transfer steps from the sun.

A diagram showing that only about ten percent of energy at one trophic level is incorporated into the next, so higher levels support fewer organisms.

The movement of elements such as carbon, nitrogen, and phosphorus among living organisms, the atmosphere, soil, and water through biological and geological processes.

The variety of life at genetic, species, and ecosystem levels; it supports ecosystem stability and resilience and is threatened by habitat loss and invasive species.

The study of ethical questions raised by biological research and technology, including informed consent, genetic testing, gene editing, and animal experimentation.

Direct manipulation of an organism's DNA using techniques such as recombinant DNA, gene cloning, or CRISPR editing to introduce or alter traits.

The ability to understand scientific concepts, evaluate evidence and sources, and apply scientific reasoning to personal and public decisions.