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1/28/2014 HOW LONG DID ALL THIS TAKE? EVIDENCE FOR EVOLUTION 1. The Fossil Record TIMELINE “THEORY” OF PANGAEA Key events in evolutionary history of life on Earth 3.5–4.0 bya: life originated 2.7 bya: free O2 = photosynthetic bacteria 2 bya: first eukaryotes FIRST EUKARYOTES ~2 bya Development of internal membranes create internal micro-environments advantage: specialization = increase efficiency natural selection infolding of the plasma membrane plasma membrane nuclear endoplasmic envelope reticulum (ER) nucleus 1ST ENDOSYMBIOSIS Evolution of eukaryotes origin of mitochondria (own DNA) engulfed aerobic bacteria, but did not digest them mutually beneficial relationship natural selection internal membrane system aerobic bacterium mitochondrion DNA cell wall Prokaryotic cell Prokaryotic ancestor of eukaryotic cells plasma membrane Endosymbiosis Eukaryotic cell Ancestral eukaryotic cell Eukaryotic cell with mitochondrion 1 1/28/2014 2ND ENDOSYMBIOSIS Evolution of eukaryotes origin of chloroplasts engulfed photosynthetic bacteria, but did not digest them mutually beneficial relationship Eukaryotic cell with mitochondrion THEORY OF ENDOSYMBIOSIS Evidence natural selection photosynthetic bacterium chloroplast Endosymbiosis structural mitochondria & chloroplasts resemble bacterial structure genetic mitochondria & chloroplasts have their own circular DNA, like bacteria functional mitochondria & chloroplasts move freely within the cell mitochondria & chloroplasts reproduce independently from the cell Lynn Margulis mitochondrion Eukaryotic cell with chloroplast & mitochondrion CAMBRIAN EXPLOSION When you think “fossil,” what comes to mind? Oh,I know… Fossil – any part or trace of a once-living organism Diversification of Animals within 10–20 million years most of the major phyla of animals appear in fossil record Many types… 543 mya Trace fossils include burrows, tracks, even fossilized poop! Amber • Amber is fossilized tree sap. It often traps pollen, insects and other small animals. Insects trapped in amber. Fossil burrows Dinosaur tracks Dinosaur & Fish Poop 2 1/28/2014 Petrified Wood • Molds/Castings When wood is buried in ash or sandy sediments, silica can form within the wood structure, eventually replacing the organic material. Molds and castings form when the hard shell or exoskeleton of an organism is buried in sediment. • The sediment hardens around the body, then the body dissolves or decomposes, leaving a void or mold. • The mold can fill with minerals to form a cast in the shape of the mold. • Casting of a fossil trilobite These petrified logs are found at Petrified Forest National Park in Arizona. Imprint Fossils Frozen Organisms In some places, animals and plants get trapped in snow and are preserved for thousands of years. This obviously happens only in cold mountainous and polar areas. • • • When plants and animals fall in fine sediments, their bodies can sometimes leave an imprint that shows up when the resulting rock layers are split apart. Above - Otzi, the famous “Ice Man” found frozen in the Italian Alps Clockwise from left - The imprints of feathers can be seen in the Archaeopteryx fossil. A dragonfly imprint in the same fine sediment bed. The delicate imprint of an extinct fern’s frond. Left - Dima, a baby mammoth found preserved in the Siberian permafrost by Russian miners. Fossil Bones • • Bones and teeth of vertebrates are resistant enough to remain intact when the rest of the body has decayed. Dinosaur skeletons are among the most spectacular fossils ever found. A 12,000 year old mammoth skeleton INDEX FOSSILS Sue, the largest, most complete T. rex fossil ever found. It resides at the Field Museum in Chicago. 3 1/28/2014 DATING FOSSILS 3. 4. No absolute age; only older/younger WHAT IT TELLS US… 2. Relative Dating –compare fossil placement with fossils in other layers of rock 1. Radioactive Dating – measuring the amount of remaining radioactive isotopes in a sample Absolute age Half-Life – length of time required for HALF the radioactive atoms to decay Ex. Carbon-14 begins to decay when an organism dies (HL = 5730 yrs). The remaining amt is compared to the amt of Carbon-12 to determine the age. HALF-LIFE OF A PENNY LAB Plants and animals change Environments change Immense time span Extinction is the fate of a species WHAT IS AN ADAPTATION? Any variation that increases an organisms chance of survival in an environment EVIDENCE FOR EVOLUTION 2. Comparative Anatomy & Embryology 4 1/28/2014 CONTRIVANCE HOMOLOGOUS STRUCTURES A structure that is used for something other than its original use. Structures in different organisms that have shared evolutionary history, i.e. have a common ancestor Similar genes Anatomical evidence Homologous structures spines ANALOGOUS STRUCTURES Structures that are similar in function, but do not share evolutionary history leaves Parts evolved from different structures Ex. insect and bat wings succulent leaves needles tendrils colored leaves 5 1/28/2014 Analogous structures VESTIGIAL STRUCTURES A body structure that has no use in a present day organism, but was probably useful to an ancestor Ex. Appendix, tail bone, wisdom teeth Convergent Don’t be fooled by evolution their looks! Those & tails Does fins this mean & sleek they bodies have a are recent common ancestor? analogous structures ! Dewclaw All ball pythons have anal spurs, the vestigial remains of hind legs lost during evolution of lizard to snake Solving a similar problem with a similar solution FOSSIL WHALE LEGS Vestigial organs Whales are thought to have evolved from 4legged land animals that lived over 50 million years ago. Paleontologists expected to find whale ancestors that showed reduced and vestigial legs by looking in sediments that were between 50 and 30 million years old. Sure enough, they did. Some examples of this transition are shown below. Ambulocetus Pakicetus Basilosaurus 49 million years ago 42 million years ago 40 million years ago COCCYX IN HUMANS & APES Humans and other hominiod apes evolved from primates that had an external tail. In our hominoid ancestor, it was reduced to a small coccyx or tailbone that is not visible on the outside of the body. The coccyx or tailbone is visible in the chimp pelvis on the left and the human pelvis on the right. 6 1/28/2014 EMBRYOLOGY Embryo’s of many animals w/backbones look very similar Same groups of embryonic cells develop in the same order, and in similar patterns Cat Dolphin Among some species of snakes, early embryos have hind limb-buds that quickly disappear as the embryo develops. What does this suggest about snakes? Chicken Pig Mouse Human COMPARATIVE DNA/PROTEIN SEQUENCES Protein comparison looks at the order of amino acids that make up a protein. The fewer the differences, the more closely related the animals. EVIDENCE FOR EVOLUTION 3. Molecular Biology Human Macaque Dog Bird Frog Lamprey The sequence in DNA proteins Why &compare is a &molecular DNA proteins record of evolutionary across species? relationships. Comparative hemoglobin structure 8 0 32 45 67 125 CLADOGRAM A cladogram is a branching diagram that shows evolutionary relationships among organisms Branches in the cladogram show a new characteristic (a derived character) appeared that was not present in older organisms 10 20 30 40 50 60 70 80 90 100 110 120 compare Number of amino acid differences between common genes hemoglobin (146 aa) of vertebrate species and that of humans cytochrome C (respiration) hemoglobin (gas exchange) 7 1/28/2014 Building “family” trees SIMILARITIES IN DNA ancestral species Can be used to help determine classification and evolutionary relationships A gene in an Similar Genes Changes in DNA Species that share a more distant common ancestor should have more genetic differences 2 mutations new new mutation mutation mutation Species A EXAMPLES: CLOSE RELATIVES Gorilla Human Species B new Species C EXAMPLE: DISTANT RELATIVE Chimpanzees are humans’ closest living relative – in other words, we share a more recent ancestor with them than any other living species. Our genes are 98.2% identical. The humans and chimps last shared an ancestor with the gorillas at an earlier time. Human and chimp DNA is 97.7% identical to a gorilla’s. Human, chimp, and gorilla genes are 96.3% identical to orangutan genes. Orangutan 2 mutations Chimpanzee Half of the genes in a yeast are also found in humans. Experiments have shown that mutant yeast can be fixed by inserting the human version of a gene to replace their defective gene. Both humans and yeast have a gene for the myosin protein, which in humans enables muscles to contract and in yeast enables cell parts to move. Yeast Primates 8