GACE Biology (710) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Hypothesis vs. theory

A hypothesis is a testable, falsifiable prediction about a relationship; a theory is a broad, well-supported explanatory framework that generates further hypotheses and predictions.

Independent and dependent variables

The independent variable is manipulated by the researcher; the dependent variable is measured as the outcome and is expected to depend on the independent variable.

Reliability versus validity

Reliability is the consistency of repeated measurements; validity is whether the measurement reflects the intended construct. An instrument can be reliable yet invalid.

Peer review and replication

Peer review screens studies for methodological soundness before publication, while replication by independent researchers provides stronger evidence that results are genuine and generalizable.

Endosymbiotic theory

Mitochondria and chloroplasts originated from engulfed bacteria, evidenced by their double membranes, circular DNA, and 70S ribosomes resembling prokaryotic cells.

Enzyme Km and Vmax

Km is the substrate concentration giving half-maximal velocity and is inversely related to enzyme affinity; Vmax is the maximum rate reached at saturating substrate concentration.

Competitive versus noncompetitive inhibition

A competitive inhibitor binds the active site and raises apparent Km without changing Vmax; a noncompetitive inhibitor binds elsewhere and lowers Vmax.

Fluid mosaic model

The plasma membrane is a phospholipid bilayer studded with proteins and cholesterol, with components free to move laterally, giving it fluidity and selective permeability.

Calvin cycle

The light-independent reactions in the stroma use ATP and NADPH from the light reactions to fix carbon dioxide into sugar, catalyzed by the enzyme rubisco.

Mendel's law of segregation

During meiosis, the two alleles of a gene separate so each gamete receives only one allele, restoring the pair at fertilization and producing predictable offspring ratios.

Semiconservative replication

Each new DNA molecule retains one original strand and one newly synthesized strand, with DNA polymerase adding nucleotides in the 5' to 3' direction.

Frameshift mutation

An insertion or deletion of nucleotides not divisible by three shifts the reading frame, altering all downstream codons and usually producing a nonfunctional protein.

X-linked recessive inheritance

Males are hemizygous for X-linked genes, so a single recessive allele on their X chromosome causes the trait, making affected males more common than affected females.

Hardy-Weinberg equilibrium

Allele and genotype frequencies stay constant across generations only with no mutation, no migration, random mating, large population size, and no natural selection.

Polymerase chain reaction

PCR amplifies DNA through repeated cycles of heat denaturation, primer annealing, and extension by a thermostable polymerase, doubling the target each cycle.

Natural selection

Heritable variation plus differential reproductive success under environmental pressure changes allele frequencies across generations, producing adaptation to local conditions.

Homologous versus analogous structures

Homologous structures share common ancestry though functions may differ; analogous structures perform similar functions but evolved independently, indicating convergent evolution.

Allopatric speciation

A geographic barrier physically separates populations, blocking gene flow; accumulated genetic differences and reproductive isolation eventually produce distinct species.

Genetic drift

Random changes in allele frequencies due to chance, strongest in small populations; bottleneck and founder effects sharply reduce genetic diversity.

Three domains of life

Bacteria, Archaea, and Eukarya; Archaea resemble bacteria in form but differ biochemically, and molecular comparisons support this classification over five kingdoms.

Ten percent rule

Only about ten percent of energy at one trophic level transfers to the next, the rest lost as heat and metabolism, limiting food chains to four or five links.

Logistic population growth

Growth slows as population size approaches carrying capacity K because resources become limiting, producing an S-shaped curve with zero growth at K.

Density-dependent factors

Limiting factors such as competition, predation, and disease whose effect intensifies as population density rises, helping regulate population size near carrying capacity.

Primary versus secondary succession

Primary succession begins on bare substrate without soil, starting with pioneer species; secondary succession follows disturbance where soil and seeds remain.

Negative feedback

A regulatory mechanism in which a detected deviation triggers a response that reverses it, returning the internal variable toward its set point and maintaining homeostasis.

Sliding filament model

Calcium binds troponin, exposing actin binding sites; myosin heads form cross-bridges and pull actin filaments, shortening the sarcomere and contracting the muscle.

Xylem versus phloem

Xylem transports water and dissolved minerals upward from roots via transpiration pull; phloem transports sugars bidirectionally under pressure flow.

Nephron reabsorption

The proximal tubule reabsorbs most filtered water, glucose, and ions; the loop of Henle and collecting duct concentrate urine under ADH control.

Action potential phases

Depolarization results from sodium ion influx through channels; repolarization follows potassium ion efflux, transmitting an electrical signal along the neuron.

Serial dilution

Repeated transfers each multiply the prior concentration by the dilution factor, so a 1:10 series reaches one-thousandth after three successive steps.

Beer-Lambert law

Absorbance is proportional to solute concentration and path length, allowing spectrophotometry to quantify dissolved substances of known molar absorptivity.

Negative versus positive controls

A negative control lacks the active treatment and detects contamination or false positives; a positive control contains a known active agent and confirms the assay works.