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 Fossils form when the remai...

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