Evolution

Evolution The theory of evolution is the theory of change in a population over time. Recall that a scientific theory is a well-tested framework, or explanation of facts and laws. The following is a collection of evidence supporting the theory of evolution.

Evidence for Evolution Fossils - trace of long-dead organism - can tell us what kind of organisms existed at various times in Earth’s history, where they lived, their behavior, and extinctions. - record is incomplete (has “missing links”)

Evidence for Evolution In 2006, scientists found the “missing link” between fish and amphibians. Tiktaalik has strong bony fins, which could have helped it walk on land.

How to date a fossil: Relative dating- can tell if a fossil is older or younger than another fossil Absolute dating- uses radioactive molecules in the body (like C-14) to estimate the age of the fossil in years Ex. Half-life of C-14 is 5730 yrs 16 g  8 g  4 g  2 g 5730 yrs 5730 yrs 5730 yrs

Relative vs. Absolute Dating

Evidence for Evolution 2. Adaptations – anything that allows an organism to survive better in its environment - Ex.: thorns, claws, mimicry (resembles harmful organism), camouflage (blending in with environment)

Evidence for Evolution 3. Anatomical structures - Some very different organisms have very similar bone structure (analogous & homologous features) - Also, some organisms have structures with no present-day use (called vestigial structures) that suggests their ancestors might have used them. Ex.: appendix The legs of a skink are vestigial structures.

Homologous Body Structures Body Structures that have the same internal structure, BUT, provide different functions for the different organisms. Thus, may indicate these organisms came from a common ancestor.

Analogous Body Structures Analogous Structures - pertain to the various structures in different species having the same appearance, structure, or function but have evolved separately, thus do not originate from a common ancestor.

Vestigial Body Structures Vestigial Structures are structures (either internal or external) that have no present day use. This is a type of evidence that gives clues about the activities, appearance, or ancestry of an organism. * This is why a surgeon can remove your appendix without causing any harm!

Geographic Distribution of Living Species Different Animals On Different Continents But Similar Adaptations To Shared Environments

Similarities In Early Development Embryonic Structures Of Different Species Show Significant Similarities Embryo – early stages of vertebrate development

Similarities In Embryonic Development Evidence for Evolution - Comparative Embryology Similarities In Embryonic Development

Human Fetus – 5 weeks

Chicken Turtle Rat

Evidence for Evolution 4. Biochemistry similarities - Comparison of DNA/RNA/proteins from different organisms shows how closely they are related.

Similarities in DNA Sequence