Zoology · Ch 6 — Evolution
Evidences for Biological Evolution
Evidences for Biological Evolution
Evolution is supported not by any single line of proof but by several independent kinds of evidence that all point the same direction. Paleontology — the study of prehistoric life through fossils — supplies the oldest and most direct physical record. Comparative anatomy compares internal body plans across living species to reveal shared or independently-evolved structures. Embryology compares how different animals develop from egg to adult, since early developmental stages often resemble one another far more than the corresponding adults do. Molecular biology compares the sequences of conserved genes and proteins across species. Each of these evidence categories is treated in its own subsection below, …
Molecular Evidences
Molecular evolution is the study of how the sequence composition of molecules such as DNA, RNA and proteins changes across generations, using the combined tools of evolutionary biology and population genetics. A key discovery underlying this field is that many proteins and other life-sustaining molecules are highly conserved across very distantly related species — meaning their sequences change only slowly over evolutionary time. This slow, roughly steady rate of change in a conserved molecule is referred to as a molecular clock, and it can be used to estimate how long ago two lineages diverged from a common ancestor: the more differences accumulated between two species' versions of the same molecule, the longer ago they are presumed to have split. Two molecules widely used to study evolutionary relationships in this way are cytochrome c (a protein central to the cellular respiratory pathway) and rRNA (ribosomal RNA, central to protein synthesis), both chosen becaus …