Transcript Slide 1
Natural selection, could have produced very Simple cells through a sequence of four main stages: 1. 2. 3. 4. The abiotic (nonliving) synthesis of small organic molecules, such as amino acids and nucleotides. The joining of these small molecules into macromolecules, including proteins and nucleic acid. The packaging of these molecules into “protobionts,” droplets with membranes that maintained an internal chemistry different from that of their surroundings. The origin of self-replicating molecules that eventually made inheritance possible. Earths atmosphere was a reducing (electronadding) environment , in which compounds could have formed from simple molecules. In 1953, Stanley Miller and Harold Urey, of the University of Chicago, tested the OparinHaldane Hypothesis. They created lab conditions comparable to those that scientists at the time thought existed on early earth. Their apparatus yielded a variety of amino acids found in organisms today, along with other organic compounds. Self-Replicating RNA The first genetic material may have been short pieces of RNA capable of guiding polypeptide synthesis and self-replication. Early protobionts containing such RNA would have been more effective at using resources and would have increased in number through natural selection. Protobionts are collections of abiotically produced molecules surrounded by a membrane-like structure. 25.2 The Fossil Record -Richest Source of Fossils Sedimentary rock Amber -Fossil Record Includes Great changes in dominating organisms Organisms very different from today's Organisms that where once common but now extinct How existing organisms came to be -Fossil Record is Substantial and significant An incomplete chronicle of evolutionary change Biased in favor of species that existed for a long time Limited Still being filled with new discoveries How Fossils & Rocks are Dated -Radiometric Dating Most common technique Based on decay of radioactive isotopes Method works for fossils up to 75,000 years old -Rate of Decay Expressed as a half-life -Half-life Time required for 50% of parent isotopes to decay -Old Fossils Sediments in rock around them help the dating process Magnetism of rocks contributes too Origin of New Groups of Organisms By dating fossils we are able to see how today's animals got to how they are today Chapter 25.3 Archean and Proterozoic eons Phanerozoic eon - Eras and you Stromatolites -Prokaryotes -Eukaroytes and Endosymbiosis How life is possible Archean Eon and O Iron oxide Oxygen revolution -Devastating results -Cyanobacteria Cellular respiration Photosynthesis 2 Eukaryotes Multi-cellular life Cambrian explosion -Predation -Adaption Land colonization Humans “time-on-the-clock” Continental Drift-The slow movement of the continental plates across Earth’s surface. Consequences • • • • Alters the habitats in which organisms live. Pangea (All land)- ocean basins became deeper, which lowered sea level and drained coastal seas. Pangea destroyed a considerable amount of the marine species habitat. Climate change northward and southward. Promotes • • Allopatric speciation on a grand scale. Help explain puzzles about the geographic distribution of extinct organisms. Mass extinction- Period of time when global environmental changes lead to the elimination of a large number of species throughout Earth. Red represents extinction rate of marine animal families. Blue represents overall increase in the # of marine animal families. The Big Five •The Permian and the Cretaceous Permian- Boundary between Paleozoic and Mesozoic eras Consequences Can reduce a thriving and complex ecological community to a pale shadow of its former self. Cretaceous- Boundary between the Mesozoic and Cenozoic eras. Adaptive Radiation- period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles, or niches, in their communities. Worldwide Regional Evolutionary Effects of Developmental Genes Heterochrony -An evolutionary change in the rate or timing of developmental events. *An organisms shape depends in part on the relative growth rates of different body parts during development. -If reproductive-organ development accelerates compared to other organs, the sexually mature stage of the species may retain body features that were juvenile in an ancestral species – Paedomorphosis. This salamander is sexually mature, but has maintained its gills and other larval features. Changes in Spatial Pattern Hox genes -Prompts cells to develop into structures appropriate for a particular location *The evolution of vertebrates from invertebrate animals may have been influenced by alterations in Hox genes and the genes that regulate them. *How they are expressed can have a big impact on morphology. *A change in the location of the Hox gene correlates with the conversion of different body parts. The Evolution of Development A change in the nucleotide sequence of a gene may affect its function wherever the gene is expressed. Changes in the regulation of gene expression can be limited to a single cell type. A change in the regulation of a developmental gene may have fewer harmful side effects than a change to the sequence of the gene. Changes in the form of organisms often may be caused by mutations that affect the regulation of developmental genes-not their sequence.