Biology 1001 Spring 2008 (B. Fall), Class notes, topic #4—Evidence for evolution
complete the reading assignment in your text (Freeman, Biological Science, 2
ed.): pp. 22-23,
496-503, 561-563, 639-640.
Appreciate the diversity of evidence that has persuaded virtually all biologists of the fact of
Learn some techniques scientists use to determine both relative and absolute ages of fossils.
Describe some general patterns in the fossil record and conditions that can lead to fossilization.
Distinguish homologous from analogous structures.
Understand some basic patterns of biogeography that are explained by evolution.
Evidence for evolution
is provided by a wide variety of sources: fossils; comparative anatomy and
embryology (structural and developmental homologies); biogeography (patterns of geographic
distribution of organisms); phylogenetic patterns; plant and animal breeding (artificial selection);
and, more recently, comparative biochemistry (molecular homologies). These sources provide
overwhelming evidence that species change over time, and that species are descended, with
modification, from ancestral ones, creating hierarchical patterns of relatedness.
are remains or other evidence of past life, and include unaltered remains, mineralized
remains, casts and molds, and trace fossils (e.g., footprints, tracks, feces).
Three general kinds of rocks include: sedimentary, igneous, metamorphic.
(e.g., limestone, shale) form from layers of sediments (deposited by water, wind) and may
contain fossils; igneous rocks form from molten material (e.g., granite, volcanic ash), and may be
useful for radiometric dating of strata and associated fossils.
of a particular organism is a
event. Steps include burial after death;
fossilization after burial; discovery after fossilization. The fossil record is very biased (non-
random), and some groups are much better
represented as fossils than others. Those most likely
to become fossils include: organisms with hard parts; inhabit aquatic habitats where they are
more likely to be rapidly buried by sediments; belong to large population; lived more recently.
dating methods involve establishing chronological relationships (older/younger)—
younger sediments lie above older ones (the principle of
) unless subsequently
are distinctive fossils used to correlate sedimentary layers of similar
age in different regions. The geologic timetable (eras, periods, epochs; see Fig. 26.9 in text)
originated in the early 1800s and was based on characteristic fossil components of strata
(layers) and relative time.