Biological Science: Life, Water, and Carbon Foundations

Vocabulary flashcards reviewing core principles of biology, atomic structure, water chemistry, thermodynamics, chemical evolution, and scientific methodology from Chapters 1 and 2.

Chemical Evolution

The leading explanation for the origin of life on Earth, proposing that inputs of energy led to the formation of increasingly complex carbon-containing substances, culminating in a self-replicating molecule.

Atomic Number

The characteristic number of protons found in the nucleus of any atom of a given element.

Mass Number

The sum of the number of protons and neutrons present in an atom's nucleus.

Dalton (Da)

A unit of mass equal to the mass of one proton or one neutron ($1\,\text{Da}$).

Isotope

Any of the different forms of an element containing the same number of protons but a different number of neutrons, resulting in different atomic masses.

Valence Shell

The outermost electron shell of an atom.

Valence Electrons

Electrons located in the outermost (valence) shell of an atom.

Valence

The number of unpaired valence electrons in an atom's outer shell, which determines the number of covalent bonds the atom can form.

Electronegativity

The relative strength with which an atom pulls shared electrons toward its nucleus in a chemical bond.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between two atoms with similar electronegativities.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between atoms with different electronegativities, producing partial charges ($\delta^-$ and $\delta^+$).

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Hydrogen Bond

A weak electrical interaction between a partial positive charge on a hydrogen atom and a partial negative charge on another electronegative atom.

Hydrophilic

Referring to polar or charged molecules ("water-loving") that readily interact with and dissolve in water.

Hydrophobic

Referring to nonpolar and uncharged molecules ("water-fearing") that do not readily dissolve in water.

Cohesion

The attraction between like molecules, such as hydrogen bonding among adjacent water molecules.

Adhesion

The attraction between unlike molecules, such as water molecules adhering to a polar or charged solid surface.

Surface Tension

The cohesive force resulting from attraction between molecules at the surface of a liquid, causing the surface to resist forces that increase its area.

Specific Heat

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

Heat of Vaporization

The amount of energy required to change $1\,\text{g}$ of a liquid substance into a gas.

Acid

A substance that gives up protons ($\text{H}^+$) during chemical reactions, raising the hydronium ion ($\text{H}_3\text{O}^+$) concentration of a solution.

Base

A substance that acquires protons ($\text{H}^+$) during chemical reactions, lowering the hydronium ion ($\text{H}_3\text{O}^+$) concentration of a solution.

Mole

A standard unit equal to $6.022 \times 10^{23}$ chemical entities.

Molarity (M)

The concentration of a substance in solution, expressed as the number of moles of solute present per liter of solution.

pH

A logarithmic measure expressing the concentration of protons in a solution, defined as $\text{pH} = -\log[\text{H}_3\text{O}^+]$.

Buffer

A substance or mixture (such as a weak acid and its conjugate base) that minimizes changes in solution pH by accepting or donating protons.

Endothermic Reaction

A chemical reaction or physical process that must absorb thermal energy from its surroundings to proceed.

Exothermic Reaction

A chemical reaction or physical process that releases thermal energy to its surroundings.

Potential Energy

Stored energy derived from an object's position or the configuration of shared electrons in covalent bonds.

Kinetic Energy

The energy of motion, including the kinetic energy of molecular movement (thermal energy).

First Law of Thermodynamics

The principle stating that energy is conserved; it cannot be created or destroyed, only transferred or transformed.

Entropy

A quantitative measure of the amount of disorder or randomness in a physical system.

Second Law of Thermodynamics

The principle stating that total entropy in isolated physical and chemical processes always increases over time.

Miller's Spark-Discharge Experiment

A landmark 1953 experiment demonstrating that complex organic compounds (such as amino acids) can form spontaneously from simple gases exposed to heat and electrical discharges.

Functional Group

A specific combination of reactive atoms attached to a carbon skeleton that dictates the chemical behavior and properties of organic molecules.

Monomer

A small molecular subunit that can covalently bind with other similar subunits to form a polymer.

Polymer

A large molecule composed of numerous monomer subunits bonded together via polymerization.

Condensation Reaction

A chemical reaction (also called a dehydration reaction) in which monomers polymerize and form a covalent bond, resulting in the loss of a water molecule.

Hydrolysis

A chemical reaction in which a covalent bond linking monomers within a polymer is cleaved by the addition of a water molecule.

Cell Theory

The core biological theory stating that all organisms are made up of cells and that all cells come from pre-existing cells.

Spontaneous Generation

The disproved hypothesis asserting that living organisms can arise spontaneously from non-living matter under certain conditions.

Pasteur's Swan-Necked Flask Experiment

An experimental test disproving spontaneous generation by demonstrating that sterilized broth inside a swan-necked flask remains sterile unless pre-existing cells enter from the air.

Chromosome Theory of Inheritance

The principle proposed by Sutton and Boveri stating that genetic or hereditary information is encoded in genes located on chromosomes.

Central Dogma

The fundamental framework describing the direction of genetic information flow in cells: DNA codes for RNA, which codes for proteins.

Adenosine Triphosphate (ATP)

The primary cellular currency used by organisms to store and transfer chemical energy needed for metabolic activity.

Evolution

A change in the heritable characteristics of a population over time.

Natural Selection

The process driving evolution in which individuals with certain heritable traits produce more surviving offspring in a given environment than individuals lacking those traits.

Fitness

The relative ability of an individual organism to survive and produce surviving offspring in a specific environment.

Adaptation

A heritable trait that increases an individual's evolutionary fitness in a particular environment.

Phylogeny

The evolutionary history and genealogical relationships among a group of organisms or species.

Phylogenetic Tree

A diagram depicting estimated evolutionary relationships and genealogical lineages among species based on shared genetic sequence data.

Eukaryote

An organism whose cells contain a membrane-bound nucleus.

Prokaryote

A unicellular organism belonging to Bacteria or Archaea that lacks a membrane-bound nucleus.

Taxonomy

The scientific discipline concerned with naming, describing, and classifying biological organisms into structured groups (taxa).

Domain

The taxonomic rank created by Carl Woese that categorizes cellular life into three primary taxa: Bacteria, Archaea, and Eukarya.

Null Hypothesis

A statement specifying what should be observed in an experiment if the hypothesis being tested is incorrect or if the variable has no effect.

Pedometer Hypothesis

The hypothesis proposed by Wittlinger and colleagues stating that desert ants calculate their distance from the nest by keeping track of stride number and stride length.