Introductory Biology: Evolutionary Principles, Biochemistry, Cell Structure, and Membrane Dynamics

Vocabulary practice flashcards covering fundamental concepts in introductory biology, evolutionary theory, biological chemistry, macromolecular structure, cell architecture, and membrane dynamics.

Life

An imperfect replicating system that evolves by natural selection.

Emergent Properties

New properties that arise with each step upward in the hierarchy of biological organization owing to the arrangement and interactions of parts as complexity increases.

Reductionism

The approach of zooming in on the levels of biological hierarchy and studying parts separately to make complex systems easier to understand.

Systems Biology

An approach that explores biological systems by analyzing the complex interactions among their parts, often utilizing computer modeling and mathematics.

Inductive Reasoning

A type of logic in which general conclusions are derived from a large number of specific observations.

Deductive Reasoning

A type of logic that flows from the general to the specific, using "if… then" logic.

Adaptive Radiation

A process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, especially when environmental changes create new resources, challenges, or niches.

Artificial Selection

The modification of species by humans through the selective breeding of individuals that possess desired, heritable traits.

Relative Fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals in the population.

Vestigial Structures

Remnants of features that served important functions in an organism's ancestors but are no longer functional in the present-day species.

Homologous Structures

Anatomical features in different species that share an underlying framework inherited from a common ancestor, but have adapted to perform different functions.

Convergent Evolution

The independent evolution of similar features in evolutionary lineages that do not share a recent common ancestor, driven by natural selection in similar environments.

Directional Selection

Natural selection that shifts the overall makeup of a population by favoring individuals at one extreme of a phenotypic distribution.

Disruptive Selection

Natural selection that favors individuals at both extremes of a phenotypic distribution over individuals with intermediate phenotypes.

Stabilizing Selection

Natural selection that eliminates extreme phenotypic variants from a population and preserves intermediate phenotypes.

Intrasexual Selection

A direct competition among individuals of one sex (often males) for mates of the opposite sex.

Intersexual Selection

A form of sexual selection, commonly referred to as mate choice, in which individuals of one sex (usually females) are choosy in selecting their mates.

Frequency-Dependent Selection

A form of balancing selection in which the fitness of a particular phenotype depends on how common it is in the population.

Heterozygote Advantage

Greater reproductive fitness of heterozygous individuals compared to homozygous individuals of either genotype, which preserves two or more alleles at that locus.

Protocells

Abiotically produced, membrane-bound spherical droplets that maintain an internal chemical environment distinct from their surroundings.

Radiometric Dating

A method for determining the absolute age of rocks and fossils based on the characteristic half-life of radioactive decay of parent isotopes into daughter isotopes.

Electronegativity

The attraction of a particular atom for the shared electrons within a covalent bond.

Polar Covalent Bond

A covalent bond formed between atoms differing in electronegativity, resulting in unequal electron sharing and partial charges ($\delta^+$ and $\delta^-$).

Cohesion

The linking together of like molecules, such as water molecules binding to one another through hydrogen bonds.

Adhesion

The clinging of one substance to a different substance, such as water molecules adhering to plant cell walls through hydrogen bonding.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, caused by cohesive hydrogen bonding at the liquid-air interface.

Specific Heat Capacity

The amount of heat that must be absorbed or lost for $1\,\text{g}$ of a substance to change its temperature by $1^\circ\text{C}$.

Buffer

A substance that minimizes changes in the concentrations of $\text{H}^+$ and $\text{OH}^-$ in a solution by accepting or donating hydrogen ions.

Structural Isomers

Compounds that have the same molecular formula but differ in the covalent arrangements of their carbon skeletons (such as straight versus branched chains).

Cis-Trans Isomers

Molecules that possess identical covalent partners but differ in spatial arrangements around an inflexible double bond.

Enantiomers

Isomers that are non-superimposable mirror images of each other due to the presence of an asymmetric carbon atom.

Dehydration Reaction

A chemical reaction in which two molecules covalently bond to each other with the simultaneous removal of a water molecule ($\text{H}_2\text{O}$).

Hydrolysis

A chemical reaction that breaks bonds between monomers in a polymer through the addition of a water molecule ($\text{H}_2\text{O}$).

Glycosidic Linkage

A covalent bond formed between two monosaccharides by a dehydration reaction.

Chitin

A structural polysaccharide composed of $N$-acetylglucosamine monomers linked by $\beta$ bonds, found in fungal cell walls and arthropod exoskeletons.

Amphipathic Molecule

A molecule possessing both a hydrophilic (water-loving, polar) region and a hydrophobic (water-repelling, nonpolar) region.

Primary Structure

The linear sequence of amino acids in a polypeptide chain, determined by genetic information.

Secondary Structure

Regions of repetitive coiling ($\alpha$ helices) or folding ($\beta$ pleated sheets) within a polypeptide, stabilized by hydrogen bonds along the polypeptide backbone.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide, stabilized by interactions among amino acid side chains (R groups).

Quaternary Structure

The aggregate structural shape resulting from the association of two or more individual polypeptide subunits.

Phosphodiester Linkage

The covalent bond linking the phosphate group on the $5'$ carbon of one nucleotide sugar to the hydroxyl group on the $3'$ carbon of an adjacent nucleotide sugar.

Polymerase Chain Reaction (PCR)

A molecular biology technique used to generate thousands to millions of copies of a specific DNA sequence through repetitive cycles of denaturation, primer annealing, and extension.

Endomembrane Theory

The evolutionary model proposing that the eukaryotic nucleus and endomembrane system arose from invaginations of the plasma membrane in an ancestral prokaryote.

Endosymbiont Theory

The evolutionary model stating that mitochondria and chloroplasts originated as independent prokaryotic cells that were engulfed by an ancestral eukaryotic host cell.

Nuclear Lamina

A netlike array of intermediate protein filaments lining the inner surface of the nuclear envelope that mechanically maintains the shape of the nucleus.

Rough Endoplasmic Reticulum

A portion of the endomembrane network studded with ribosomes, specialized for the synthesis of secretory proteins, glycoproteins, and phospholipids.

Smooth Endoplasmic Reticulum

A portion of the endomembrane network lacking ribosomes, specialized for lipid synthesis, carbohydrate metabolism, drug detoxification, and calcium ion storage.

Golgi Apparatus

An organelle composed of stacks of flattened membranous sacs (cisternae) that receives, modifies, refines, sorts, and ships cellular products.

Phagocytosis

A type of endocytosis where large particulate substances or organisms are engulfed by a cell and packaged into a food vacuole that fuses with a lysosome.

Autophagy

A lysosomal recycling pathway in which damaged cellular organelles or cytoplasmic components are enveloped and hydrolyzed to salvage monomers.

Peroxisome

A single-membrane metabolic compartment containing enzymes that transfer hydrogen atoms to oxygen to produce hydrogen peroxide ($\text{H}_2\text{O}_2$), which is subsequently degraded to water.

Microtubules

Hollow rods composed of $\alpha$- and $\beta$-tubulin dimers measuring about $25\,\text{nm}$ in diameter, which resist compression, support cell shape, and facilitate chromosome and vesicle movement.

Microfilaments

Solid rods measuring about $7\,\text{nm}$ in diameter built from twisted actin chains, which bear tension, support cell shape, and enable amoeboid movement and muscle contraction.

Intermediate Filaments

Fibrous proteins with diameters between $8\,\text{nm}$ and $12\,\text{nm}$ (such as keratins) specialized for bearing tension, anchoring organelles, and forming the nuclear lamina in animal cells.

Tight Junctions

Intercellular junctions that stitch together plasma membranes of adjacent animal cells, forming a continuous barrier that prevents extracellular fluid from leaking across a cell layer.

Desmosomes

Fastening intercellular anchoring junctions that attach adjacent animal cells into strong sheets, anchored into the cytoplasm by intermediate filaments.

Gap Junctions

Specialized intercellular communicating junctions in animal tissues that provide cytoplasmic channels between adjacent cells for direct exchange of ions and small signaling molecules.

Plasmodesmata

Cytoplasm-lined membrane channels perforating plant cell walls that connect adjacent plant cells and allow free passage of water, small solutes, and certain macromolecules.

Fluid Mosaic Model

The model of cell membrane structure depicting the membrane as a mosaic of protein molecules drifting laterally within a fluid bilayer of phospholipids.

Osmolarity

The total concentration of all solute particles in a solution, expressed in osmoles of solute per liter of solution ($\text{Osm/L}$).

Tonicity

The ability of an extracellular solution to cause a cell to gain or lose water, dependent on the concentration of non-penetrating solutes relative to inside the cell.

Plasmolysis

A phenomenon in walled cells exposed to a hypertonic environment where water exits the cell, causing the protoplast to shrivel and pull away from the cell wall.

Facilitated Diffusion

The spontaneous passage of molecules or ions down their electrochemical gradient across a biological membrane via specific transmembrane transport proteins without energy expenditure.

Active Transport

The movement of a substance across a biological membrane against its concentration or electrochemical gradient, mediated by specific carrier transport proteins and requiring metabolic energy ($\text{ATP}$).

Electrogenic Pump

An active transport protein that generates a voltage across a membrane by causing a net transfer of electric charge.

Electrochemical Gradient

The combined driving force governing ion movement across a membrane, comprising both a chemical force (the ion concentration gradient) and an electrical force (the membrane potential).

Cotransport

A mechanism in which the downhill diffusion of one substance along its electrochemical gradient drives the active, uphill transport of another substance against its concentration gradient.