analogous structure
a structure in one organism that is similar to that of another organism due to convergent evolution and not shared common ancestry
Cambrian explosion
a biologic event during the Cambrian period when many lineages of organisms first appeared
clade
a taxonomic group that includes an ancestor and all of its descendants
common ancestor
an earlier organism that, through evolution, gives rise to new species that are related
convergent evolution
process by which two species acquire similar features due to similar selection pressures and not shared ancestry
endosymbiotic theory
the idea that eukaryotic cells and their organelles evolved from early cells engulfing prokaryotes
extinction
loss of all members of a particular group
fossil record
all the fossilized artifacts taken in the context of their placement within Earth's geological strata
gene pool
the total set of genes of all individuals in a population
homologous structures
structures that are similar due to inheritance from a common ancestor
macroevolution
evolutionary change at or above the species level
mass extinction
the loss of many species because of global environmental conditions
microevolution
a change in allele frequencies within a population from one generation to the next
phylogenetic tree
a diagram that shows the history of evolutionary relationships among two or more groups of organisms
phylogeny
the evolutionary history of groups of organisms
primordial soup theory
the idea that life began in one of the ancient oceans or another body of water because of the chemical combination in the atmosphere and the influx of energy to make molecules that support life
protocell
a self-organizing, spherical collection of lipids proposed as the origin of living cells
radiometric dating
the scientific process of using the half-life of radioactive elements to establish the absolute age of a fossil
speciation
the process through which a species evolves into two or more new species
stasis
a pattern in which a species in the fossil record shows minimal change over time