Natural Selection
This term defines an organism's ability to survive and produce fertile offspring.
Fitness.
These remains or traces of organisms from the past provide structural evidence of how species have changed over time.
Fossils
On a phylogenetic tree, this feature represents the most recent common ancestor of two or more lineages.
Node.
Speciation occurring within the same geographic area.
Sympatric speciation.
Vestigial structures, such as the human appendix or whale hip bones, provide evidence for this, indicating a structure had a function in an ancestor but not in the modern species.
Evolution/common ancestry.
These are structural similarities, like the wings of a bird and a butterfly, that result from similar environmental pressures rather than shared ancestry.
Analogous structures.
Principle choosing the tree with the fewest evolutionary events.
maximum parsimony.
This type of speciation occurs when a population is divided by a geographic barrier, such as a canyon or river.
Allopatric speciation.
This mechanism of evolution occurs when a small group becomes isolated, leading to an allele frequency that is different from the original, larger population.
The Founder effect.
Non-functional structural remnants that were functional in ancestors.
Vestigial structures.
A group containing an ancestor and all decendants.
Clade
Sudden population reduction causing severe loss of genetic diversity.
Bottleneck effect.
This type of evidence, often using BLAST, compares amino acid sequences in proteins like cytochrome c to determine how closely related species are.
Molecular homology.
Universal molecular code proving all life shares an ancestor.
The genetic code
A tree branch point indicating unresolved evolutionary relationships..
Polytomy
This prezygotic barrier occurs when two species mate at different times of the year.
Temporal isolation.
Antibiotic resistance in bacteria is a direct example of this type of selection, which favors one extreme phenotype over another in a changing environment.
Directional Selection.
Shared, highly conserved genes used to determine species relatedness.
Homologous genes.
Convergent evolution.
Postzygotic barrier where hybrid offspring are completely sterile.
Reduced hybrid fertility.