origin of life/evolution

Radiometric dating

A technique used to determine the age of rocks or fossils based on the known decay rates of radioactive isotopes.

Half-life

The amount of time required for half of a radioactive sample to undergo decay.

Homologous structures

Anatomical features in different organisms that share a common ancestral origin, regardless of whether their current functions differ.

Analogous structures

Anatomical features in different species that perform similar functions but arose independently through separate evolutionary paths.

Vestigial structures

Remnants of anatomical organs or structures that have lost most or all of their original function compared to ancestral species.

Comparative biochemistry

The study of similarities and differences in molecular components, such as DNA sequences and proteins, to determine evolutionary relationships.

Comparative embryology

The comparison of embryonic development across different species to establish evolutionary relatedness.

Cytochrome c

A highly conserved protein whose sequence variations across organisms are used to gauge evolutionary distance.

Plate tectonics

The geological theory explaining the large-scale movement of lithospheric plates driving continental drift.

Continental drift (Pangea)

The gradual movement of continents across the Earth's surface over time, starting from the single supercontinent Pangea.

Taxonomy

The scientific discipline concerned with naming, defining, and classifying organisms.

Binomial nomenclature

The formal system of naming species using a two-part scientific name consisting of the Genus and species.

Gradualism

The hypothesis that evolution proceeds primarily by the slow, steady accumulation of minor changes over long periods.

Acquired traits (Lamarck)

An obsolete evolutionary concept suggesting that modifications gained by an organism during its lifetime can be inherited by offspring.

Natural selection

The process by which individuals possessing advantageous heritable traits survive and reproduce at higher rates than others.

Descent with modification

The evolutionary principle that living species have descended, with cumulative changes, from ancestral species.

Stabilizing selection

A type of natural selection that favors intermediate variants by acting against extreme phenotypes.

Diversifying selection

A form of natural selection that favors individuals at both phenotypic extremes over intermediate types.

Directional selection

A mode of natural selection in which an extreme phenotype is favored over others, causing the phenotypic mean to shift over time.

Sexual selection

Selection driven by preferences for specific traits in mates, enhancing reproductive success rather than overall survival.

Artificial selection

The intentional selective breeding of organisms by humans to favor specific desired traits.

Industrial melanism

The evolutionary process where dark-colored forms of an organism become dominant in habitats darkened by industrial pollution.

Antibiotic resistance

The evolution of bacterial populations allowing them to survive exposure to chemical treatments designed to kill them.

Plasmids

Small, circular, double-stranded DNA molecules in bacteria that can carry genes for resistance and transfer between cells.

Sexual dimorphism

Systematic physical differences between males and females of the same species beyond their reproductive organs.

Polymorphism

The occurrence of two or more distinctly different morphs or alleles in a population's gene pool.

North-south cline

A continuous, geographic gradient of physical or genetic traits shifting incrementally along a latitudinal axis.

Outbreeding

The practice of mating individuals that are less closely related than average, which increases genetic diversity.

Independent assortment

The principle that alleles for different traits segregate independently of one another during gamete formation in meiosis.

Crossing over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I.

Random fertilization

The arbitrary combination of any single sperm with any single egg, multiplying genetic combinations in offspring.

Diploidy

The cellular condition of possessing two complete sets of chromosomes, allowing recessive alleles to remain masked in heterozygous states.

Heterozygote advantage

A phenomenon where individuals carrying two different alleles at a locus have a higher fitness than individuals with two identical alleles.

Frequency-dependent selection

An evolutionary mechanism where the fitness of a phenotype depends directly on how common it is in the population.

Search image

A cognitive template developed by predators for detecting the most abundant or visible prey type.

Evolutionary neutral traits

Phenotypic features that confer neither a selective advantage nor a disadvantage to an organism's survival and reproduction.

Genetic drift

Unpredictable fluctuations in allele frequencies from one generation to the next due to chance events, affecting smaller populations most significantly.

Gene flow

The transfer of genetic variation and alleles from one population to another through migration.

Mutations

Permanent alterations in the nucleotide sequence of an organism's genome, serving as the ultimate origin of new alleles.

Non-random mating

Occurs when individuals choose mates based on specific physical characteristics or genetic relationships, altering genotype frequencies.

Bottleneck effect

A severe reduction in population size caused by an environmental event, resulting in a drastically reduced and random allele pool.

Founder effect

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

Hardy-Weinberg equilibrium

A state in which allele and genotype frequencies remain constant across generations in the absence of evolutionary influences.

Species

Under the biological concept, a group of populations whose members can interbreed in nature and produce viable, fertile offspring.

Reproductive isolation

The existence of biological factors or barriers that impede members of two species from producing viable, fertile hybrids.

Prezygotic barrier

A mechanism that prevents mating or fertilization between species prior to the formation of a zygote.

Postzygotic barrier

A reproductive barrier that operates after fertilization, reducing the survival or fertility of hybrid offspring.

Speciation

The evolutionary process by which a single ancestral lineage splits into two or more distinct species.

Allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

Sympatric speciation

The emergence of a new species without physical or geographical separation from the parent population.

Polyploidy

A chromosomal alteration in which an organism possesses more than two complete sets of chromosomes, often causing instant speciation in plants.

Habitat isolation

A prezygotic barrier where two species encounter each other rarely because they occupy different ecological niches within the same area.

Behavioral isolation

A prezygotic barrier resulting from unique courtship rituals or communication signals that are unrecognized by other species.

Temporal isolation

A prezygotic barrier that occurs when species breed during different seasons, times of day, or years.

Divergent evolution

The process by which related species accumulate differences and evolve into distinct forms after adapting to different environments.

Convergent evolution

The independent evolution of similar functional or structural features in lineages that are not closely related.

Parallel evolution (co-evolution)

The process where two or more species reciprocally affect each other's evolution or independently develop similar traits along related lineages.

Adaptive radiation

The rapid diversification of a single ancestral species into multiple descendant species that fill diverse ecological niches.

Punctuated equilibrium

A model of evolution suggesting long periods of evolutionary stability (stasis) are abruptly interrupted by brief episodes of rapid speciation.

Theory of endosymbiosis

The evolutionary proposal that eukaryotic cell organelles, such as mitochondria and chloroplasts, originated from free-living prokaryotic organisms engulfed by host cells.