Praxis Biology 5236 flashcards

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

Independent variable

The factor that an investigator deliberately manipulates or varies across treatment groups so that its effect on the measured outcome can be evaluated.

Control group

The group in an experiment that receives no treatment or an inactive placebo, providing a baseline against which the treated group is compared.

Accuracy vs. precision

Accuracy is how close a measurement is to the true value; precision is how closely repeated measurements agree with one another.

Standard deviation

A statistic describing the typical spread of data around the mean; small values indicate measurements cluster tightly, while large values indicate wide scatter.

Falsifiable hypothesis

A testable, specific statement predicting a relationship between variables that could be shown false by observation or experiment.

Cell theory

The principle that all living organisms are composed of cells, that cells arise only from pre-existing cells, and that the cell is the basic unit of life.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Active transport

Movement of solutes across a membrane against their concentration gradient using carrier proteins and energy, usually supplied by ATP hydrolysis.

ATP

Adenosine triphosphate, the universal energy currency of cells; hydrolysis of its terminal phosphate bond releases energy that drives endergonic cellular reactions.

Codon

A sequence of three mRNA nucleotides that specifies one amino acid or a stop signal during translation at the ribosome.

Meiosis

A two-division reductional process producing four haploid cells from one diploid cell, generating variation through crossing over and independent assortment.

Allele

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

Hardy-Weinberg equilibrium

A null model in which allele and genotype frequencies stay constant across generations in a large, randomly mating population with no mutation, migration, or selection.

Incomplete dominance

A pattern in which the heterozygote shows an intermediate phenotype between the two homozygotes, as when red and white flowers produce pink offspring.

Genetic drift

Random fluctuation of allele frequencies between generations, most pronounced in small populations, which can fix or eliminate alleles independently of natural selection.

Gene flow

Movement of alleles between populations through migration and interbreeding, which tends to reduce genetic differences among those populations over time.

Reproductive isolation

The condition in which populations can no longer interbreed to produce fertile offspring, the critical step in the formation of separate species.

Binomial nomenclature

The two-part naming system in which each species receives a capitalized genus name and a lowercase specific epithet, both italicized.

Domain Archaea

A group of prokaryotes distinct from bacteria in membrane lipids and cell wall composition, often inhabiting extreme environments such as hot springs and salt lakes.

Endosymbiotic theory

The explanation that mitochondria and chloroplasts originated from free-living bacteria engulfed by a host cell, supported by their own circular DNA and ribosomes.

Virus

An acellular infectious agent consisting of nucleic acid enclosed in a protein capsid, which reproduces only inside a living host cell.

Chitin

A tough polysaccharide that forms the cell walls of fungi and the exoskeletons of arthropods such as insects and crustaceans.

Carrying capacity

The maximum population size of a species that a given environment can sustain indefinitely, symbolized K in the logistic growth equation.

Keystone species

A species whose influence on community structure is disproportionately large relative to its abundance, so its removal triggers cascading changes.

Primary succession

Community development on newly exposed substrate lacking soil, such as bare rock or lava flows, beginning with pioneer species like lichens.

Competitive exclusion

The principle that two species competing for identical resources cannot coexist indefinitely; the superior competitor excludes the other or forces niche divergence.

Trophic level

A feeding position in a food chain, such as producer, primary consumer, or secondary consumer, through which energy passes with roughly ten percent efficiency.

Informed consent

The ethical requirement that research participants freely agree to take part after understanding the purpose, risks, and alternatives, without coercion.

Peer review

Pre-publication evaluation of a study by independent experts who judge its methods, analysis, and interpretation before it appears in a scientific journal.

Antibiotic resistance

The inherited ability of bacteria to survive antibiotic exposure, arising through mutation or gene transfer and spread by natural selection under drug pressure.

Bioethics

The study of ethical issues arising from biology and medicine, commonly organized around the principles of autonomy, beneficence, nonmaleficence, and justice.

Risk assessment

A structured evaluation weighing the probability and severity of harm from a technology against its expected benefits before policy or regulatory decisions are made.