Movement of particles from low to high concentration areas.
Requires energy, usually from ATP or electrical charge differences across cell membranes.
Adenosine Triphosphate (ATP)
A molecule that provides energy for cellular reactions.
Releases energy when a phosphate group is removed from one of its high-energy bonds.
Adhesion
The property of water molecules to stick to other surfaces.
Agriculture
Artificial cultivation of food, fiber, and other goods.
Involves systematic growing and harvesting of organisms.
Allele
A version of a gene resulting from variations in nucleotide sequence.
Allele Frequency
How often an allele appears in a population; its relative frequency.
Analogous Structure
A physical structure in different species with similar function but different form and inheritance.
Aquatic
Describes an organism associated with a water environment.
Atom
The smallest unit of an element retaining the element's chemical and physical properties.
Biochemical Conversion
Changing organic matter into other chemical forms, like fuels.
Bioenergetics
The study of energy flow (energy transformations) into and within living systems.
Biogeochemical Cycles
Movement of abiotic factors between living and nonliving components within ecosystems.
Also known as nutrient cycles (e.g., water, carbon, oxygen, and nitrogen cycles).
Biological Macromolecules
Biomacromolecules that interact with biological systems and their environments.
Biology
The scientific study of life.
Biome
A large area with distinct plant and animal groups adapted to that environment.
Biosphere
The zone of life on Earth; the sum total of all ecosystems.
Biotechnology
Procedures using biological systems or living organisms to develop or modify products or processes for specific uses.
Commonly associated with genetic engineering.
Biotic
Describes a living or once-living organism in an ecosystem.
Carbohydrate
A macromolecule containing carbon, hydrogen, and oxygen in a 1:2:1 ratio.
Serves as a major energy source for living organisms (e.g., sugars, starches, cellulose).
Carrier (Transport) Proteins
Proteins embedded in the plasma membrane for moving ions, small molecules, and macromolecules into and out of cells.
Also known as transport proteins.
Catalyst
A substance that speeds up a chemical reaction without being changed by the reaction.
Cell
The basic unit of structure and function for all living organisms.
Common components: genetic material, cytoplasm, and a cell membrane.
Eukaryotic cells contain specialized organelles.
Cell Cycle
The series of events leading to cell division and duplication.
Main phases: interphase, nuclear division, and cytokinesis.
Cellular Respiration
A complex set of chemical reactions where potential chemical energy in "food" molecules is released.
Partially captured in the bonds of adenosine triphosphate (ATP) molecules.
Chloroplast
An organelle in plant cells and eukaryotic photosynthetic organisms where photosynthesis occurs.
Chromosomal Mutation
A change in the structure of a chromosome (e.g., deletion, duplication, inversion, and translocation).
Deletion: Loss of a chromosome segment containing genes.
Duplication: A chromosome segment is duplicated.
Inversion: A chromosome segment breaks off and reattaches in reverse order.
Translocation: A chromosome segment breaks off and attaches to a nonhomologous chromosome.
Chromosomes
A single piece of coiled DNA and associated proteins.
Linear in eukaryotic cells and circular in prokaryotic cells.
Contains genes that encode traits; each species has a characteristic number.
Cloning
A process of copying a cell, cell product, or organism from an original source.
DNA Cloning: Transfer of a DNA fragment to a self-replicating genetic element (e.g., bacterial plasmid).
Reproductive Cloning: Transfer of genetic material from a donor cell nucleus to an egg cell (nucleus removed) to create an embryo and an exact genetic copy of the donor organism.
Therapeutic Cloning: Taking undifferentiated embryonic cells (stem cells) for medical research.
Co-dominance
A pattern of inheritance where the phenotypic effect of two alleles in a heterozygous genotype fully and equally express each phenotype; not expressed in any other genotypic combination.
Cohesion
Intermolecular attraction between like molecules.
Surface tension results from the cohesive properties of water.
Community (Ecological)
Different populations of organisms interacting in a shared environment.
Competition
When individuals or groups compete for resources like territory, mates, water, and food.
Concentration
The amount or proportion of a substance when combined with another.
Concentration Gradient
The graduated difference in solute concentration per unit distance through a solution.
Consumer (Ecological)
An organism that obtains energy by feeding on other organisms or their remains.
Crossing-over
Exchange of genetic material between homologous chromosomes during anaphase I of meiosis.
Contributes to genetic variability in gametes and offspring.
Cytokinesis
The final phase of a cell cycle, resulting in cytoplasm division.
Decomposer
An organism that obtains nutrients from dead and decaying organic matter.
Allows nutrients to be accessible to other organisms.
Deoxyribonucleic Acid (DNA)
A biological macromolecule encoding genetic information for living organisms.
Capable of self-replication and RNA synthesis.
Diffusion
Movement of particles from high to low concentration areas; a result of kinetic molecular energy.
DNA Replication
The process in which DNA makes a duplicate copy of itself.
Dominant Inheritance
A pattern of inheritance where the phenotypic effect of one allele is completely expressed within a homozygous and heterozygous genotype.
Ecology
The study of relationships between organisms and their interactions with the environment.
Ecosystem
A system composed of organisms and nonliving components of an environment.
Embryology
The branch of zoology studying the early development of living things.
Endemic Species
A species found in its originating location and restricted to that geographic area.
Endocytosis
A process where a cell engulfs extracellular material through an inward folding of its plasma membrane.
Endoplasmic Reticulum (ER)
An organelle with folded membranes and sacs.
Responsible for production, processing, and transportation of materials inside and outside a eukaryotic cell.
Rough ER: Has surface ribosomes, synthesizes proteins for export.
Smooth ER: No ribosomes, synthesizes lipids and steroids, transports synthesized macromolecules.
Endosymbiosis
A theory that early eukaryotic cells formed from simpler prokaryotes.
Energy Pyramid
A model illustrating biomass productivity at multiple trophic levels in an ecosystem.
Energy Transformation
Energy changing from one form to another; some energy is lost to the environment.
Environment
The total surroundings of an organism or group of organisms.
Enzyme
A protein that increases the rate of a chemical reaction without being changed by the reaction; an organic catalyst.
Eukaryote
An organism composed of one or more cells with a membrane-bound nucleus, specialized organelles, and mitotic nuclear division.
Evolution
New species develop from preexisting species (macroevolution).
A change in allele frequencies in a population over generations (microevolution).
Exocytosis
A process where a cell releases substances to the extracellular environment by fusing a vesicular membrane with the plasma membrane.
Extinction
Describes a species with no known living individuals.
Extracellular
Located outside a cell.
Facilitated Diffusion
Transporting substances across a plasma membrane with the concentration gradient, aided by carrier proteins; does not require energy.
Food Chain
A simplified path illustrating the passing of potential chemical energy (food) from one organism to another.
Food Web
A complex arrangement of interrelated food chains illustrating energy flow between interdependent organisms.
Forensics
The science of tests and techniques used during crime investigations.
Fossils
Preserved remains or traces of organisms that once lived on Earth.
Founder Effect
A decrease in genetic variation caused by the formation of a new population by a small number of individuals from a larger population.
Frame-shift Mutation
The addition (insertion mutation) or removal (deletion mutation) of one or more nucleotides not divisible by three.
Results in a completely different amino acid sequence.
The earlier in the sequence the changes occur, the more altered the protein will be.
Freezing Point
The temperature at which a liquid changes to a solid.
Gamete
A specialized cell (egg or sperm) used in sexual reproduction containing half the normal number of chromosomes of a somatic cell.
Gene
A sequence of nucleotides in a DNA segment providing a blueprint for a hereditary trait.
Gene Expression
The process of a nucleotide sequence of a gene being used to make a functional product such as protein or RNA.
Gene Recombination
A natural process of breaking and joining a nucleic acid molecule to a different molecule; a result of crossing-over.
Gene Splicing
A type of gene recombination where DNA is intentionally broken and recombined using laboratory techniques.
Gene Therapy
The intentional insertion, alteration, or deletion of genes within an individual's cells and tissues for treating a disease.
Genetic Drift
A change in the allele frequency of a population as a result of chance events rather than natural selection.
Genetic Engineering
A technology that manipulates or alters the genetic material of a cell, resulting in desirable functions or outcomes that would not occur naturally.
Genetically Modified Organism
An organism whose genetic material has been altered through genetic engineering.
Genetics
The scientific study of inheritance.
Genotype
The genetic composition of an organism.
Golgi Apparatus
An organelle in eukaryotic cells responsible for processing proteins for release by the cell.
Gradualism
A proposed explanation that new species arise from slight modifications (mutations and phenotypic changes) over many generations.
Habitat
An area providing an organism with its basic survival needs.
Homeostasis
The regulatory process where an organism regulates its internal environment.
Homeostatic Mechanism
A regulatory mechanism maintaining a state of equilibrium (e.g., thermoregulation, water regulation, and oxygen regulation).
Homologous Structure
A physical characteristic in different organisms that is similar because it was inherited from a common ancestor.
Hypothesis
A scientifically testable explanation for an observed phenomenon.
Impermeable
Not permitting the passage of a substance or substances.
Incomplete Dominance
A pattern of inheritance where two alleles are neither dominant nor recessive.
Offspring have a phenotype blending the parental traits.
Inheritance
The process of genetic material being passed from parents to offspring.
Interphase
The longest-lasting phase of the cell cycle.
The cell performs most of its functions, such as preparing for nuclear division and cytokinesis.
Intracellular
Located inside a cell.
Isolating Mechanisms
Features preventing mating or breeding between two different species.
Temporal Isolation: Individuals active at different times.
Ecological Isolation: Individuals mate only in their specific habitat.
Behavioral Isolation: No sexual cues between species representatives.
Mechanical Isolation: No sperm transfer during attempted mating.
Gametic Incompatibility: Sperm transfer without fertilization.
Four factors preventing hybrid viability if matin occurs:
Zygotic Mortality: Fertilization but no zygote.
Hybrid Inviability: Embryo is not viable.
Hybrid Sterility: Resulting adult is sterile.
Hybrid Breakdown: First generation is viable, but future generations are not.
Law (Scientific)
Generalizes a body of observations; no exceptions have been found.
Explains things but does not describe them; serves as the basis of scientific principles.
Limiting Factor
A chemical or physical factor limiting the existence, growth, abundance, or distribution of an organism or population.
Lipids
Organic compounds composed mostly of carbon and hydrogen, including a smaller amount of oxygen.
Insoluble in water, serve as stored energy, and are a component of cell membranes.
Macromolecule
A polymer with high molecular mass.
Four main groups: carbohydrates, lipids, proteins, and nucleic acids.
Mechanism (Scientific)
Combination of components and processes serving a common function.
Meiosis
A two-phase nuclear division resulting in gametes with half the normal number of chromosomes.
Migration (Genetics)
The permanent movement of genes into or out of a population, changing allele frequencies.
Mitochondrion
A membrane-bound organelle in most eukaryotic cells; site of cellular respiration.
Mitosis
A nuclear division producing two somatic cells with the same genetic complement as the original cell.
Molecule
The smallest particle retaining chemical and physical properties, composed of two or more atoms.
Monomer
A molecule reacting with other molecules to form a polymer.
Each biological macromolecule has characteristic monomers.
Multicellular
Made up of more than one cell.
Multiple Alleles
More than two forms of a gene controlling trait expression.
Mutation
A permanent transmissible change of genetic material (e.g., chromosomal mutations and gene mutations).
Natural Selection
Organisms with inherited traits are better able to survive and reproduce compared to others of their species.
Nondisjunction
Sister chromatids fail to separate during and after mitosis or meiosis.
Nonnative Species
A species normally living outside a distribution range, introduced through human activity; also known as introduced, invasive, alien, nonindigenous, or exotic.
Nucleic Acid
A biological macromolecule (DNA or RNA) composed of C, H, N, O, and P carrying genetic information.
Nucleus
A membrane-bound organelle in eukaryotic cells that maintains the integrity of genetic material, controlling cellular activities.
Organ
An anatomical unit composed of tissues serving a common function.
Organ System
An anatomical system composed of a group of organs working together.
Organelle
A subunit within a cell with a specialized function.
Organic Molecule
A carbon-containing molecule that is a part of or produced by living systems.
Organism
A form of life; an animal, plant, fungus, protist, or bacterium.
Osmosis
Movement of water through permeable membranes from an area of higher water concentration (dilute) to an area of lower concentration (concentrated).
Passive Transport
Transportation of materials across a plasma membrane without using energy.
pH
Measure of acidity or alkalinity of an aqueous solution, scaling from 1 (acidic) to 14 (alkaline), with 7 being neutral.
Phenotype
The observable expression of a genotype.
Photosynthesis
A process in which solar radiation is chemically captured and resulting in potential chemical energy in the bonds of carbohydrate molecules.
Plasma Membrane
A phospholipid and protein molecule bilayer that encapsulates a cell and controls the movement of materials in and out.
Plastids
A group of membrane-bound organelles in photosynthetic organisms that are responsible for synthesis and storage of food.
Point Mutation
A single-base substitution causing the replacement of a single-base nucleotide with another.
Silent Mutation: No change in amino acid.
Missense Mutation: Different amino acid.
Nonsense Mutation: Insertion of a stop codon.
Polygenic Trait
A trait controlled by two or more genes at different loci on different chromosomes.
Population
A group of individuals of the same species living in a specific geographical area and reproducing.
Population Dynamics
The study of short- and long-term changes in the number of individuals for a given population, as affected by birth, death, immigration, and emigration.
Principle (Scientific)
A concept based on scientific laws and axioms where general agreement is present.
Producer (Ecological)
An organism that uses a primary energy source to conduct photosynthesis or chemosynthesis.
Prokaryote
A single-celled organism lacking a membrane-bound nucleus and specialized organelles.
Protein
A macromolecule containing carbon, hydrogen, oxygen, and nitrogen.
Performs structural and regulatory functions for cells.
Protein Synthesis
The process in which amino acids are arranged in a linear sequence through transcription of DNA to RNA and translation of RNA to a polypeptide chain.
Pumps (Ion or Molecular)
Molecular mechanisms transporting ions or molecules across a cellular membrane using an energy source (e.g., glucose, sodium (Na+), calcium (Ca+), and potassium (K+)).
Punctuated Equilibrium
A proposed explanation that species are generally stable over long periods, with occasional rapid changes.
Recessive Inheritance
The phenotypic effect of one allele is only expressed within a homozygous genotype; not expressed in a heterozygous condition with a dominant allele.
Ribosome
A cellular structure composed of RNA and proteins that is the site of protein synthesis.
Science
Evidence-based knowledge gained through observation and experimentation related to the natural world and technology.
Selective Breeding
The process of breeding organisms resulting in offspring with desired genetic traits.
Semiconservative Replication
The DNA molecule uncoils and separates into two strands.
Each original strand becomes a template on which a new strand is constructed, resulting in two DNA molecules identical to the original.
Sex-linked Trait
A trait associated with a gene carried by either the male or female parent (e.g., color blindness and sickle-cell anemia).
Speciation
A process caused by genetic isolation, creating a new genetically distinct species.
Species
The lowest taxonomic level of biological classification, consisting of organisms capable of reproduction that results in fertile offspring.
Specific Heat
The measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval.
Succession
A series of predictable and orderly changes within an ecosystem over time.
Symbiotic Relationship
A relationship between two organisms.
Mutualism: Both organisms benefit.
Parasitism: One organism benefits, and the other is harmed.
Commensalism: One organism benefits, and the other is neither harmed nor benefits.
System
A set of interacting or interdependent components forming an integrated whole.
Open System: Able to interact with its environment.
Closed System: Isolated from its environment.
Temperature
Measure of the average kinetic energy of particles in matter; determines the rate and extent to which chemical reactions can occur in living systems.
Measured in degrees Celsius (^{\circ}C) or Fahrenheit (^{\circ}F).
Terrestrial
Describes an organism associated with a land environment.
Theory (Scientific)
Explanation of observable phenomena based on empirical data and scientific laws.
Provides a system of assumptions, principles, and rules to analyze, predict, or explain the nature or behavior of phenomena.
Tissue
An anatomical unit composed of cells organized to perform a similar function.
Transcription
The process of synthesizing a strand of messenger RNA (mRNA) using DNA as a template.
Translation
The process of decoding mRNA on a ribosome to produce a sequence of amino acids for protein synthesis.
Translocation
A segment of a chromosome breaks off and attaches to another chromosome.
Trophic Level
The position of an organism in relation to energy and nutrient flow through an ecosystem (e.g., producer, consumer, and decomposer).
Unicellular
Made up of a single cell.
Vestigial Structure
A physical characteristic in organisms that appears to have lost its original function.