CLEP Natural Sciences key terms

The process by which individuals with traits better suited to their environment tend to survive and reproduce more, causing those traits to become more common in later generations.

The evolutionary formation of new and distinct species, often when populations become reproductively isolated and diverge genetically over many generations.

The evolutionary history and branching relationships among groups of organisms, typically represented as a tree showing common ancestry.

Similarity in structure or genes due to shared ancestry, such as the same bone arrangement in different vertebrate forelimbs, rather than similarity from convergent function.

Similarity in function or appearance between structures or features that evolved independently in unrelated lineages, such as wings of insects and birds.

A type of cell division that produces two daughter cells genetically identical to the parent cell, used for growth and replacement of body cells.

A reduction division that produces four haploid gametes from one diploid cell, involving two divisions and crossing over, which increases genetic variation.

One of two or more alternative versions of a gene at a given locus on a chromosome, which may produce different observable traits.

The specific combination of alleles an organism carries for a gene or set of genes, which together with environment influences its phenotype.

The observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment.

Adenosine triphosphate, the main energy-carrying molecule of cells; breaking its terminal phosphate bond releases energy that powers many cellular processes.

The first stage of cellular respiration, in which glucose is split into two pyruvate molecules in the cytoplasm, producing a small amount of ATP and NADH.

A series of reactions in the mitochondrial matrix that oxidizes acetyl groups from pyruvate, releasing carbon dioxide and producing NADH, FADH2, and ATP.

The process by which green plants, algae, and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen.

A group of individuals of the same species living in the same area at the same time and capable of interbreeding.

The maximum population size of a species that a given environment can sustain indefinitely given available food, habitat, water, and other resources.

An environmental resource or condition that restricts the growth, abundance, or distribution of a population when it is in short supply.

The proportion of all copies of a gene in a population that are a particular allele, used to measure genetic variation and evolutionary change.

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

A network of interconnected food chains in an ecosystem, showing which organisms eat which and how energy and matter flow among them.

An atom of the same element that has the same number of protons but a different number of neutrons, giving it a different atomic mass.

The number of protons in the nucleus of an atom, which uniquely identifies the chemical element and determines its position in the periodic table.

The total number of protons and neutrons in an atomic nucleus, which is approximately equal to the atom's atomic mass in atomic mass units.

The spontaneous breakdown of an unstable atomic nucleus, emitting particles or radiation and changing the nucleus into a different isotope or element.

The time required for half of the radioactive atoms in a sample to decay, a characteristic property of each radioactive isotope.

A chemical bond formed when two atoms share one or more pairs of electrons, typically between nonmetal atoms.

A chemical bond formed by the electrostatic attraction between oppositely charged ions, typically a metal cation and a nonmetal anion.

The amount of a substance that contains Avogadro's number (about 6.02 × 10^23) of particles, used to relate mass to numbers of atoms or molecules.

The mass of one mole of a substance, numerically equal to its formula mass in atomic mass units but expressed in grams per mole.

A logarithmic scale from 0 to 14 that measures the acidity or alkalinity of a solution as the negative logarithm of hydrogen ion concentration.

A substance that donates hydrogen ions (protons) to a solution, lowering its pH and reacting with bases to form salts.

A substance that accepts hydrogen ions or releases hydroxide ions in solution, raising pH and reacting with acids to form salts.

The principle that energy cannot be created or destroyed in an isolated system, only converted from one form to another.

The principle that the total entropy of an isolated system never decreases; heat flows spontaneously from hotter to colder objects, and energy conversions are never perfectly efficient.

A measure of the disorder or randomness of a system; it increases in spontaneous processes in isolated systems according to the second law of thermodynamics.

The change in observed frequency of a wave when the source, the observer, or both are moving relative to each other, causing a shift toward higher or lower pitch or color.

The increase in wavelength of light from a receding source, observed as a shift toward the red end of the spectrum and used to measure cosmic expansion.

The observation that distant galaxies recede from us at speeds proportional to their distance, implying that the universe is expanding.

The theory that Earth's lithosphere is divided into rigid plates that move over the asthenosphere, causing earthquakes, volcanoes, and mountain building at their boundaries.

The process in which one tectonic plate descends beneath another at a convergent boundary, often producing deep ocean trenches, volcanic arcs, and earthquakes.