2. Darwin’s Idea Descent with modification  Descendants spread into different habitats  New habitats necessitated adaptation  This accounts for diversity of life Natural Selection  Individuals inherit characteristics well-suited to their environment  Those individuals leave more offspring than others  Those offspring are more likely to have well-suited characteristics  Problem: Blending theory of Inheritance

3. Fossil Record Most fossils found in sedimentary rock  Due to aquatic preservation, fossils remain largely intact and fossilize in layers Rock forms in layers, or strata  Often sand or silt is deposited on top of existing layer, compacting it into rock Fossil Record is formed due to the layering  Older rock is “lower” than younger rocks  Charles Lyell- Uniformitarianism Helps put the puzzle of life together  Fossils help show what organisms have as similarities or dissimilarities due to…..

4. Geographic Distribution Another way to understand the similarities Is to see how they are spread out around the globe Some animals in South American tropics share similarities with African desert animals rather than African tropical animals Australia is home to more marsupial animals than anywhere else in the world, and had relatively few placental animals.

5. Echidna

6. Duckbilled Platypus

7. Mammals-Marsupials

9. Structural Similarities Skeletal structures are very similar in parts of different animals.  Human, Feline, Whale, and Bat limbs are similar Homologous structures  structures that indicate common ancestry Vestigial structures  structures that have a major function in one organism, but less in another

11. Blind Mole Rat

12. ???Vestigial structure

14. Developmental Similarities  Developing embryos of different organisms appear similar during maturation.  Organisms start differentiating at different times, with more closely related organisms differentiating later in the process.  Distinctive differences occur later in the process

19. Molecular Biology  In the era of DNA, why don’t we just use the ultimate similarity of life and compare DNA sequences to see how closely organisms resemble one another?  The closer the DNA sequences, the closer related  The less the sequences match, the further relationship