Evidence For Evolution Fossil Record Biogeography Homologous Structures Vestigial Structures Comparative Embryology Molecular Evidence Imperfections of Adaptations

Deposited last, newest fossils deposited first, oldest fossils Rocks formed by layers (sediments) settling on top are called sedimentary. Newest Layers Deposited last, newest fossils Oldest Layers deposited first, oldest fossils

Geologists can determine just how old each layer is Most of these layers are sedimentary rock. Geologists can determine just how old each layer is Fossils are within that time period

The Fossil Record of Horses Record shows size and shape progression Used to be as small as dogs!

Some fossils are simply older versions of insects much like those found on Earth today

The Fossil Record A story we piece together as we find new fossils Clearly, the fossil record tells us of times when life on Earth was very different than it is today The story tells us life has gradually become more complex. Fossil of cells that resemble modern cyanobacteria (3.5 billion years old) a very scary salamander

Biogeography The distribution of different organisms around the planet Biogeography Video (7:03)

What is similar between these different animals? These 3 organisms live in similar environments around the world (the US, Australia, and Argentina) What is similar between these different animals? jack rabbit (a lagamorph) kangaroo (a marsupial) patagonian hare (a rodent)

Homologous Structures Structures used for different purposes that indicate a common ancestry Why would appendages used for different purposes have the same underlying bone structure?

Vestigial Structures Structures that have no function in the organism The only explanation is that they are remnants of evolution Human Appendix Human Tail Bone Snake Spurs Whale Hips

Comparative Embryology Turtle Mouse Human Chick Pig Can you tell which is which? mouse, turtle, chick, pig, and human Why would all these very different organisms need to develop the same way?

Molecular Evidence Compare DNA sequences of different organisms to see how similar they are! % Similarity Between Species

Human DNA? 96% similar to chimpanzee 85% mouse 50% fruit flies Just as DNA shows you descended from your parents it also shows you descended from the grandparent of them all ~3.8 billion yrs ago

Imperfections of Adaptations The Panda’s Thumb Eats bamboo, not meat Developed thumb grasp bamboo Not a perfect solution, but it works!

Important Points To Remember About The Process of Evolution

Evolution acts on populations not individuals Individual organisms do not improve themselves Nature selects the best of the members of a population to survive and produce the next generation

Mutations may produce such unique features but selection enhances them Evolution does not produce new adaptations! It amplifies (increases) or diminishes (decreases) variations that are already present Mutations may produce such unique features but selection enhances them