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Evidence for evolution in Darwin’s time came from several (four) sources. 1. Fossils provide evidence of evolution. Fossils in older layers are more primitive (older) than those in the upper layers. By comparing fossils from older rocks with fossils from younger layers, one could see life on Earth has changed over time.
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KEY CONCEPTEvidence of common ancestry among species comes from
many sources. Evidence for evolution in Darwins time came from
several (four) sources.
1. Fossils provide evidence of evolution. Fossils in older layers
are more primitive (older) than those in the upper layers. By
comparing fossils from older rocks with fossils from younger
layers, one could see life on Earth has changed over time. 2. The
study of biogeography provides evidence of evolution
2. The study of biogeography provides evidence of evolution. It
studies the distribution of organisms around the world. island
species most closely resemble nearest mainland species populations
can show variation from one island to another - similar embryos,
diverse organisms
3. Embryology provides evidence of evolution. Embryology is the
study of ontogeny (the process of development of an embryo). -
similar embryos, diverse organisms Larva Adult barnacle Adult crab
Fig. Although adult crabs and barnacles look and behave very
differently, they can look identical as larvae. This suggested to
Darwin that they share a common ancestor. Comparative embryology 4.
The study of anatomy provides evidence of evolution.
Homologous structures are similar in structure but different in
function. Homologous structures are evidence of a common ancestor.
Human hand Bat wing Mole foot Fig. Notice that each of these
homologous structures uses the same bones in relation to each
other. What body part of a dolphin is homologous to the structures
shown above? Homologous structures The study of anatomy provides
evidence of evolution.
Analogous structures have a similar function. Human hand Bat wing
Mole foot Fly wing Analogous structures are not evidence of a
common ancestor. Fig. Analogous structures evolved separately and
are not evidence of a common ancestor. A bats wing has bones
whereas insect wings do not. Structural patterns are clues to the
history of a species.
Vestigial structures are remnants of organs or structures that had
a function in an early ancestor. Ostrich wings are examples of
vestigial structures. Their wings are used for balance but not to
fly. Vestigial structures Many modern whale species have vestigial
pelvic and leg bones. They also have vestigial nerves for the sense
of smell, and small muscles devoted to external ears that no longer
exist. Other vestigial structures: Human appendix Wisdom teeth
Blind cave organisms Snake legs