10.4 evidence of evolution key concept evidence of common ancestry among species comes from many...
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10.4 Evidence of Evolution
KEY CONCEPT Evidence of common ancestry among species comes from many sources.
10.4 Evidence of Evolution
Evidence for evolution in Darwin’s time came from several sources.
• Fossils provide evidence of evolution.• Fossils in older layers are more primitive than
those in the upper layers.• Extinct Fossils resemble modern
animals. This shows a common ancestry.
1. Fossils:
10.4 Evidence of Evolution
There are several types of fossils.
a) Permineralization occurs when minerals carried by water are deposited around a hard structure.
b) A natural cast forms when flowing water removes all of the original tissue, leaving an impression.
c) Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.
d) Preserved remains form when an entire organism becomes encased in material such as ice, ash,etc.
10.4 Evidence of Evolution
•Dating Fossils
10.4 Evidence of Evolution
– It compares the placementof fossils in layers of rock.
– Scientists infer the order inwhich species existed.
Relative dating estimates the time during which an organism lived.
10.4 Evidence of Evolution
Radiometric Dating
• Isotopes are unstable in their nuclei, so they decay• Isotopes have a known half life (rates of decay are known). • Half life = number of years it takes for half of the isotopes to
decay• 14C has a half life of 5700 years, and 14N is a decay product• Age determined by comparing ratio of 14C to 14N
– Wider ratio = older samples
Isotopes: atoms of the same element with differing neutrons
Ex: 12C and 14C12C = 6 protons + 6 neutrons14C = 6 protons + 8 neutrons
10.4 Evidence of Evolution
10.4 Evidence of Evolution
2. Geography• The study of geography provides evidence of evolution.
– island species most closely resemble nearest mainland species
– populations can show variation from one island to another
10.4 Evidence of Evolution
3. Embryology• Embryology provides evidence of evolution.
Larva
Adult barnacleAdult crab
– identical larvae, different adult body forms– similar embryos, diverse organisms– Shows common ancestry
10.4 Evidence of Evolution
4. Anatomy• 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.
10.4 Evidence of Evolution
Human hand
Bat wing
Mole foot
Fly wing
– Analogous structures are not evidence of a common ancestor.
• Homologous structures are different than Analogous Structures
– Analogous structures have a similar function.
10.4 Evidence of Evolution
• Vestigial structures are remnants of organs or structures that had a function in an early ancestor.
• Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs.
Structural patterns are clues to the history of a species.
10.4 Evidence of Evolution
Pythons have tiny femurs (leg bone)
10.4 Evidence of Evolution
5. Molecular and Genetic Evidence
• AKA Biochemical Evidence• Two closely-related organisms will have similar DNA, RNA,
and protein (amino acid) sequences.• This also gives evidence of a common ancestor.