Evolution Darwin’s Ideas Hardy-Weinberg Evidence for Evolution Speciation and Mechanisms Origins

Evidence Supporting Evolution 2006 Fossil Discovery of Early Tetrapod “Tiktaalik” “missing link” from sea to land animals Evidence Supporting Evolution

Evidence for Evolution Paleontology – fossils show change in a species over time Biogeography – Similar species are found in similar ecosystems around the world Morphology – Comparing structures Homologous structures – body parts with similar structure but possible different function. Shows common ancestry Analogous structures – similar structure develops in organisms that share a common ecosystem but not a common ancestry Biochemical or Molecular - Similarities in gene sequences, proteins, DNA

Fossils Preserved remains of living things Paleontology is the study of the fossil record Most organisms do not leave a fossil after death Explains the “missing links” Sedimentation Fossils As the organism decomposes the spaces will be filled with the minerals from the silt

The Archaeopteryx Fossil Forelimb has three functional fingers with grasping claws. Reptilian Features Lacks the reductions and fusions present in other birds. Breastbone is small and lacks a keel. True teeth set in sockets in the jaws. The hind-limb girdle is typical of dinosaurs, although modified. Long, bony tail. Avian Features Vertebrae are almost flat-faced. Impressions of feathers attached to the forelimb. Belly ribs. Incomplete fusion of the lower leg bones. Impressions of feathers attached to the tail. LEFT: Archaeopteryx lithographica Found in 1877 near Blumenberg, Germany

How old is that fossil? Relative Dating Absolute Dating Age of fossils based according to their location in strata Absolute Dating Age of fossils determined by analyzing the content of radioactive isotopes found in the fossil. Half-life: The length of time required for half of the radioactive elements to change into another stable element. Unaffected by temperature, light, pressure, etc. All radioactive isotopes have a dependable half life. Ex: C14 decays into N14

Relative Dating

Absolute Dating How radioactive “naturally occurring” elements get inside an organism: A.K.A – Radiometric dating

Homologous Structures Anatomical evidence Anatomical evidence 1. These structures are called… homologous 2. These structures are evidence for…. common ancestry 3. similar internal structure = similar development 4. different function = different environment & niche 5. close evolutionary r’ship!

Analogous structures Solving a similar problem with a similar solution Convergent evolution Don’t be fooled by their looks! same function different development & anatomy Those fins & tails & sleek bodies are analogous structures! convergent evolution - NOT common ancestor Those fins & tails & sleek bodies are analogous structures! Does this mean they have a recent common ancestor? Solving a similar problem with a similar solution

Comparative hemoglobin structure Molecular Homology The sequence in DNA & proteins is a molecular record of evolutionary relationships. Why compare DNA & proteins across species? 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 Comparative hemoglobin structure Molecular Record What are we comparing here? - comparing DNA (base sequence) & proteins (amino acid sequence) What assumption do we make about genes and relatedness?  the more closely related, the more DNA bases & amino acids you have in common have to compare genes for protein the organisms have in common… can’t compare genes for proteins you don’t have Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans

These are remnants of structures that were functional in ancestral species Vestigial organs Why would whales have pelvis & leg bones if they were always sea creatures? Remains of ancestral structures = mutations can occur without affecting survival & reproduction Evolutionary relationship snakes & whales — remains of pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone

Evolution evidence at the cellular level Domains: Archaea, Bacteria and Eukarya Elements conserved through all: DNA, RNA and many metabolic pathways. Eukaryotes – core features: Cytoskeleton Nucleus Membrane-bound organelles Linear chromosomes Endomembrane system