FTCE Biology 6-12 flashcards

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

Control group

In a controlled experiment, the group that does not receive the treatment being tested; it provides a baseline for comparison so the effect of the independent variable can be isolated.

Independent variable

The factor a researcher deliberately manipulates or selects in an experiment; its effect on the measured dependent variable is what the study is designed to test.

Scientific theory

A broad, well-supported explanation of natural phenomena built from many independent lines of evidence and repeatedly tested; unlike a hypothesis, it is not a tentative guess.

Chi-square test

A statistical test comparing observed counts with expected counts to judge whether a difference is due to chance; used for categorical frequency data rather than continuous measurements.

Osmosis

Net movement of water across a selectively permeable membrane from higher water potential (lower solute concentration) to lower water potential; it is passive and requires no ATP.

Enzyme

A protein catalyst that speeds a reaction by lowering activation energy; it is not consumed, and its active site is specific to particular substrate molecules.

Endosymbiotic theory

Explains mitochondria and chloroplasts as descendants of engulfed prokaryotes; evidence includes their own circular DNA, double membranes, and bacteria-like 70S ribosomes.

ATP

Adenosine triphosphate, the cell's main energy-transfer molecule; hydrolysis of its terminal phosphate bond releases energy for endergonic reactions, transport, and movement.

Semiconservative replication

DNA replication in which each new double helix retains one original strand and one newly synthesized strand; confirmed by the Meselson-Stahl density-gradient experiment.

Active transport

Movement of solutes across a membrane against their concentration gradient using energy, usually ATP; the sodium-potassium pump moves three Na⁺ out and two K⁺ in.

Fluid mosaic model

Model describing the plasma membrane as a phospholipid bilayer with proteins drifting laterally; hydrophobic tails face inward, and cholesterol modulates fluidity and permeability.

Law of segregation

Mendel's principle that the two alleles of a gene separate during meiosis so each gamete carries one; allele pairs are restored at fertilization.

Testcross

Cross of an individual showing a dominant phenotype with a homozygous recessive partner to determine whether the unknown genotype is homozygous dominant or heterozygous.

Incomplete dominance

Condition in which the heterozygote shows an intermediate phenotype, as when red and white flowers produce pink offspring; neither allele is fully expressed, unlike codominance.

Hardy-Weinberg equilibrium

Allele and genotype frequencies remain constant across generations when mutation, migration, selection, and drift are absent and mating is random, with p² + 2pq + q² = 1.

Genetic drift

Random change in allele frequencies due to chance sampling, strongest in small populations; shown by bottleneck and founder effects and unrelated to fitness.

Homologous structures

Body parts inherited from a common ancestor that may differ in function, such as the forelimbs of humans, whales, and bats; evidence of common descent.

Allopatric speciation

Formation of new species after a geographic barrier divides a population; separated groups accumulate genetic differences until reproductive isolation prevents interbreeding.

Binomial nomenclature

Two-part scientific name consisting of a capitalized genus and a lowercase species epithet, both italicized, as in Homo sapiens; it gives each species one universally recognized name.

Three-domain system

Classification of life into Bacteria, Archaea, and Eukarya based on ribosomal RNA and cell features; archaea lack peptidoglycan and have distinctive membrane lipids.

Virus

Acellular obligate intracellular parasite made of a protein capsid surrounding DNA or RNA; it reproduces only inside a host cell and belongs to no biological kingdom.

Fungi

Heterotrophic eukaryotes with chitin cell walls that absorb nutrients after extracellular digestion; includes molds, yeasts, and mushrooms, functioning mainly as decomposers and mutualists.

Alternation of generations

Plant life cycle alternating a multicellular haploid gametophyte that produces gametes with a multicellular diploid sporophyte that produces spores by meiosis.

Carrying capacity

The maximum population size an environment can sustain indefinitely; logistic growth levels off at this value as density-dependent limits such as food and space intensify.

Ten percent rule

About 10% of the energy at one trophic level transfers to the next; the remainder is lost as heat and metabolism, so food chains rarely exceed four or five levels.

Keystone species

A species whose effect on community structure greatly exceeds its abundance; its removal triggers cascading changes, as when sea otters limit sea urchin grazing.

Primary succession

Colonization of bare substrate that lacks soil, such as lava flows or glacial till, beginning with lichens and mosses that help create soil.

Competitive exclusion principle

Two species cannot occupy the same niche indefinitely in one habitat; the better competitor excludes the other unless resource partitioning separates their niches.

Negative feedback

Homeostatic mechanism in which a deviation from the set point triggers a response that reverses it, as when insulin lowers elevated blood glucose.

Action potential

Brief, all-or-none reversal of membrane voltage when threshold is reached; sodium channels open during depolarization and potassium channels restore the resting potential.

Neurotransmitter

Chemical released from a presynaptic axon terminal into a synapse that binds receptors on the postsynaptic cell, exciting or inhibiting it; removed by reuptake or enzymes.

Imprinting

Innate learning confined to a critical period in which a young animal attaches to the first moving object it encounters, as ducklings follow a mother figure.