Evidence for Evolution PDF

Evidence for Evolution The Fossil Record - Fossils are preserved ancient remains of dead organisms - The study of fossils is called paleontology - Sedimentary rocks contain fossils which reveal organisms that were alive during different time periods on Earth The Fossil Record - Foss...

Evidence for Evolution The Fossil Record - Fossils are preserved ancient remains of dead organisms - The study of fossils is called paleontology - Sedimentary rocks contain fossils which reveal organisms that were alive during different time periods on Earth The Fossil Record - Fossils form when the remains of a buried organism are gradually replaced by mineral deposits - Fossil formation is rare because when oxygen is present, bodies usually decompose too quickly to fossilize - Hard-bodied organisms are more likely to be preserved than soft-bodied organisms The Fossil Record - Organisms can also be preserved in amber (tree sap), volcanic ash, and ice formations  The Fossil Record - Cuvier noted that: - Fossils of more complex organisms are found in younger rock samples - Deeper and older rock samples contain fossils that are less similar to modern plant and animal life - Lyell noted that: - Geological change is slow and gradual rather than fast and catastrophic The Fossil Record - Fossils show intermediary links between groups of organisms that may share common characteristics - Archaeopteryx, lived 150 million years ago. Fossils reveal characteristics of both reptiles and birds. This suggests that birds evolved from reptiles (or dinosaurs). Biogeography - The study of the geographical distribution of organisms based on living species and fossils - Lemurs are endemic (unique - only found here) to Madagascar, a small island just off the coast of Africa. However, the fossil record shows lemurs once existed throughout Africa Biogeography - Organisms that are geographically close will have higher relatedness than organisms that are geographically separate, regardless of environment. - Darwin noted that: - Remote islands became populated by species that arrived by water or air. After species became established, many evolved into new species over time.  Anatomy - Bone structure and function may be examined as evidence of evolution Homologous Structures - Have similar developmental origin and similar number of bones, muscles, ligaments, tendons, and blood vessels  Anatomy Embryology - Similarities in the stages of embryonic development in animals also show evolutionary relationships through homologous features Anatomy Analogous Structures - Body parts of organisms that do not have common evolutionary origin but perform similar functions - Ex. bird wings vs. insect wings - Bird wings are supported by bones, insect wings are supported by chitin Anatomy Vestigial Structures - Structures that were functional in organisms ancestors but have no current function - EX. Pelvic bones perform no function in modern whales since they have no hind limbs. Their presence suggests that they have a terrestrial ancestor Competition - Nature favours certain individuals in a population over others - Competition must therefore exist between individuals of the same species Molecular Biology - Evolutionary relationships among species are reflected in their DNA - Relatedness can be determined by comparing DNA gene sequences - The more related two species are, the more similar their DNA is Phylogenetic tree of relatedness between vertebrates based on DNA comparisons Modern Theory of Evolution Darwin didn't know... - Darwin didn’t understand how exactly organism's inherited traits and how they move from one generation to the next Modern Genetics - We now know the source of variation - Mendel focused on how traits were passed from one generation to the next - Evolutionary change is now described as changes in allele frequencies (gene pool) - natural selection favours some alleles over others - Mutations have also contributed to genetic variation Pseudogenes Pseudogenes are vestigial genes that have undergone mutations and no longer serve a purpose Ex. Dolphins have 1000 olfactory receptor genes but only use 200 of them - They just don't need as many underwater Modern Paleontology - Enhanced evolutionary understanding due to: - Fossil discoveries (early humans, primitive whales, feathered dinosaurs) - Plate tectonics (movements of the Earth’s crust) Radiometric Dating - We can now determine the age of Earth and different rock layers - The amount of decay in radioisotopes can be examined and their half-life can be used to determine the ages of rocks Modern Synthesis - Modern evolutionary biology is supported by the most recent advances and discoveries in molecular genetics, geology, and paleontology - We can now explain complex adaptations and structures and explain the evolution of entirely new species