Evolution “Change over-time”

How does evolution happen?  Natural Selection: o Variation caused by mutation o Environmental pressure o Selection of certain inheritable traits o Adaptation over many generations

The Evidence for Evolution/ The evidence for a common ancestor  The Fossil Record  Anatomy & Embryology  Biological Molecules

The Fossil Record  Fossil – the remains or traces of an organism that died long ago  Fossils show that different organisms appeared at different times and places on Earth What do you know about fossils?

Rock Layers

Transitional Species  “Missing link” – link between characteristics in past and present species

Vestigial Structures  Have no apparent function, but that resemble structures their presumed ancestors had.  Examples: whales have pelvic bones, boa constrictors have hip and leg bones

Embryology & Anatomy  Anatomy – the study of body structures of organisms  Embryology – the study of how organisms develop

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Homologous Structures  Similar structures that occur in different species that were inherited from the most recent common ancestor  Example: forelimbs of vertebrates

Analogous Structures  Structures that have similar functions but do not come from the same ancestor.  Example: wings

Biological Molecules  Biologists can compare DNA, RNA, amino acid sequences, proteins, and other biological molecules from many different organisms  More similarities = more closely related Share a recent ancestor

DNA Comparisons Human Chimpanzee Mouse A CG T

Humans are…  45% similar to black cottonwood tree  60% similar to chickens  85-89% similar to mice  98-99% similar to chimpanzees  99.8% similar to each other

Gel Electrophoresis  A technique that uses an electrical field within a gel to separate DNA by their size and charge. ABCD