Here you will find short definitions of key terms in the debate over faith, evolution, and intelligent design.
a – b – c – d – e – f – g – h – i – j – k – l – m – n – o – p – q – r – s – t – u – v – w – x – y – z
adaptation: a feature of an organism that enables it to survive and reproduce in a specific environment.
amino acid: an organic compound that contains one or more amino groups and one or more acidic carboxyl groups; amino acids can be combined in chains (polymerized) to form peptides and proteins.
artificial selection: the process by which humans deliberately choose to breed only those organisms in a population that have desirable traits.
atheism: disbelief in God.
base pair: two nucleotides on opposite but complementary strands in a DNA molecule; because of their shapes, adenine (A) forms a base pair with thymine (T) and guanine (G) forms a form a base pair with cytosine (C).
body plan: the basic symmetry and architecture of an organism; the distinctive anatomical arrangement of fundamental structural elements such as the skeleton or shell; circulatory, respiratory and nervous systems; digestive tract; and appendages.
Cambrian Explosion: an event at the beginning of the Cambrian, lasting less than 10 million years, during which most of the major animal phyla first appear in the fossil record.
chance: the characteristic of being dissociated from any discernible pattern or direction, with more than one outcome being possible in given set of circumstances.
cell: the basic structural and functional unit of all living organisms, enclosed by a semipermeable plasma membrane.
chromosome: a thread-like structure in the nucleus of a eukaryotic cell; consists of a single compacted molecule of DNA and some proteins.
complexity: the improbability of assembling a structure, system, or molecule.
complex and specified information: a form of information found in a natural structure that is highly unlikely and conforms to an independent pattern.
convergent evolution: the appearance of similar characteristics in two or more taxa by independent lines of descent.
co-option: the use of an existing biological structure or feature for a new function; exaptation.
creationism: generally speaking, the view that life was created by a supernatural creator, typically based on an interpretation of a sacred text (such as the book of Genesis in the Bible); more specifically, in public discussions in America “creationism” is typically used as shorthand for young-earth creationism.
Darwinian evolution or Darwinism: the theory that all living things are descended from a common ancestor and modified by the unguided process of natural selection acting on random variations.
DNA: deoxyribonucleic acid; a molecule consisting of two long, intertwined chains of nucleotides that carry the information to specify the sequence of amino acids in proteins.
duplication mutation: the production of a copy of some segment of DNA during meiosis.
embryo: an early developmental stage of a multicellular organism.
evolution: of the many meanings of this word, three are most important: (1) change over time—the fact that most of the organisms alive today are different from organisms that existed in the past; (2) universal common descent—the hypothesis that all organisms are modified descendants of a single common ancestor in the distant past; (3) the mechanism of biological change—the hypothesis that an undirected process of natural selection acting on random mutations has been the principal cause of modification. The latter two meanings encapsulate the modern theory of evolution accepted by most scientists, sometimes known as “neo-Darwinism.”
extrapolation: a conjecture based on the assumption that a phenomenon or trend observed in the present can be extended into the past or future.
fitness cost: the decrease in an organism’s ability to survive and reproduce in other environments following a mutation that confers a selective advantage in one environment.
flagellum: a long whiplike appendage that provides some function (usually locomotion) in microorganisms.
fossil: the mineralized remains, impression, or trace of a once-living organism.
fossil succession: the specific order of fossils, from lower to higher, within geological strata.
function: the role that a biological structure or feature plays in survival, reproduction, or other activities of an organism.
functional information: nucleotide sequences of DNA and RNA that code for proteins with biological functions.
gene: a unit of heredity on a chromosome, usually understood as a DNA sequence that specifies a particular protein.
genetic information: the sequences of nucleotides in DNA and RNA that specify the sequences of amino acids in proteins.
genome: the total DNA of an organism.
gradualism: the Darwinian view that since all species have descended from other species by the ordinary process of reproduction, evolution has occurred in steps no larger than those that now distinguish parents and offspring.
heredity: the transmission of traits from parents to offspring.
historical science: an enterprise that observes and studies clues left by past events and uses what is known about present cause-and-effect relationships to reconstruct the history of those events; examples include geology, paleontology, archaeology and forensics.
homologous structure: a body part in two or more different species that is similar in structure and position but has a different function; for example, the forelimbs of bats, porpoises, and humans. After Darwin, “homologous” was redefined to mean “similar due to common ancestry.”
hopeful monster: a hypothetical organism that supposedly originates in a single generation from a “macromutation” with large-scale effects on anatomy.
Hox gene: one of a cluster of homeotic genes; the Hox genes of many animals (such as insects and mammals) are remarkably similar.
hypothesis: (1) an educated guess; (2) a tentative explanation; (3) a proposition to be tested by comparing it to evidence.
inference to the best explanation: a method of scientific reasoning that favors the hypothesis that would, if true, best explain the relevant evidence; hypotheses that qualify as “best” typically provide coherent and causally adequate explanations of the evidence or phenomenon in question.
irreducible complexity: the characteristic of a system of well-matched, mutually interacting parts performing a specific function, in which the removal of any one of the parts causes the system to effectively cease functioning.
intelligence: a type of cause, process, or principle that is able to act with will, forethought, and intentionality to find, select, adapt, and implement the means needed to effectively bring about ends (or achieve goals or realize purposes). (Definition adapted from The Design of Life.)
intelligent design: a scientific research program as well as a community of scientists, philosophers and other scholars who seek evidence of design in nature. The theory of intelligent design holds that certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection. Through the study and analysis of a system’s components, a design theorist is able to determine whether various natural structures are the product of chance, natural law, intelligent design, or some combination thereof.
LUCA: Last Universal Common Ancestor; the most recent organism from which, in theory, all subsequent organisms have descended.
macroevolution: the origin of new large-scale features such as organs or body plans.
maladapted: poorly suited to survive and reproduce in a given environment.
materialism: the view that all that exists are matter and energy and the blind physical forces that govern them.
materialistic (or naturalistic) evolution: the belief that the development of life was the product of a blind, undirected process of matter and energy and that God played no role in guiding that process.
microevolution: small-scale changes within existing species or gene pools.
mitochondria: organelles in eukaryotic cells that convert food into a form of energy usable by the cell.
molecular homology: similarity of the nucleotide sequences of DNA or RNA molecules, or the amino acid sequences of proteins.
molecular machines: microscopic assemblages of biological molecules (such as proteins) that move and perform key cellular functions.
mutant: an organism with a new trait resulting from a mutation.
mutation: alteration of an organism’s DNA due to random, chance mistakes during replication or damage from external agents such as chemicals or radiation.
naturalism: the view that nature (usually defined as matter and energy) is all that exists.
natural selection: the undirected process in which organisms better adapted to their environment survive and reproduce at a higher rate than those less adapted, with the result that the survivors’ characteristics are more prevalent in subsequent generations.
necessity: characteristic of an event in which there were no other logically or physically possible outcomes.
neo-Darwinism: the modern version of Darwinian evolutionary theory, according to which (1) all living things are descended from one universal common ancestor; and (2) the primary engine for evolutionary innovation is a blind and unguided process of natural selection acting on random mutations in DNA.
nucleic acid: a molecule consisting of joined nucleotides that can carry biological information; for example, DNA and RNA.
nucleotide: the fundamental structural unit of a nucleic acid (DNA or RNA); consists of a nitrogen-carrying base (purine or pyrimidine), a sugar molecule, and a phosphate group.
old-earth creationism: the belief that the earth was created by God billions of years ago and that the “days” in Genesis represent ages/long periods of time; an effort to interpret the Biblical account of creation in the book of Genesis and apply it to science.
organ: a group of tissues that form a distinct structure and perform a specific function, such as a heart or lung.
paleontology: the scientific study of fossils and their use to reconstruct the history of life.
phylogeny: the evolutionary history of a group of organisms.
prebiotic: prior to the existence of biological life.
protein: a large polypeptide that performs a biological function.
protoplasm: the substance inside a living cell, once thought to be simple, but now known to be a complex network of biomolecules, microscopic structures, and molecular machines; includes the cytoplasm and (in eukaryotes) the nucleus.
punctuated equilibrium: a characteristic of the fossil record in which new species appear suddenly (punctuation), then persist unchanged (stasis) until they disappear (extinction); named by Stephen Jay Gould and Niles Eldredge and attributed by them to allopatric speciation.
random variation: minor differences among the individual organisms in a population.
RNA: ribonucleic acid; a molecule consisting of the nucleotides adenine, guanine, cytosine, and uracil (instead of thymine); involved in converting DNA sequences into amino acid sequences during protein synthesis in living cells.
scientism: the view that scientific inquiry is the only valid way of obtaining knowledge.
scientific materialism: the view that materialism is true and science is capable of justifying or confirming it. (Definition taken from The Design of Life.)
speciation: the origin of a new species from an existing one.
species: the taxonomic rank below genus; there are many definitions of this word, all of which are controversial to some extent, but the most common definition used for sexually reproducing organisms is “a group of interbreeding organisms that is reproductively isolated from other such groups.”
stasis: the persistence of a particular species without discernible change through geological strata.
teleology: the study of end-directed processes, especially in nature or history. (Definition taken from The Design of Life.)
theism: belief in God (or gods).
theistic evolution: the effort to reconcile Darwin’s theory of unguided evolution with belief in God.
transcription: the process by which mRNA is synthesized using DNA as a template.
transitional form: an organism that has features consistent with the Darwinian hypothesis that it is intermediate between a supposed ancestor and supposed descendant.
translation: the process by which protein is synthesized by a ribosome using mRNA as a template.
Tree of Life: Darwin’s metaphor for the history of life, which portrays all living things (the tips of the branches) as modified descendants of a single common ancestor (the root or trunk).
universal common ancestry: the hypothesis that all species are biological descendants of a single common ancestor, and that all life can be portrayed as a tree with a single root.
vestigial features: features that apparently serve no function in an organism and are allegedly holdovers from an evolutionary past. (Definition taken from The Design of Life.)
variation: one or more differences among individual organisms in the same species.
young-earth creationism: the belief that the earth was created by God 6,000-10,000 years ago and that the “days” in Genesis represent literal 24-hour days; an effort to interpret the Biblical account of creation in the book of Genesis and apply it to science.