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This 5 page Class Notes was uploaded by Jaime Jackson on Thursday April 7, 2016. The Class Notes belongs to BI 203-001 at Portland State University taught by Radhika Reddy in Winter 2016. Since its upload, it has received 22 views. For similar materials see in Biology at Portland State University.
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Date Created: 04/07/16
Thursday, April 7, y Chapter 15: Evolutionary Theory Objectives • Describe chemistry of the origins of life • Trace the history of life and relate to geologic phenomenon • Understand the tree of life Early Earth • Life began on a planet characterized by abundant volcanic activity, frequent electrical storms, repeated meteorite strikes, and an atmosphere that lacked oxygen gas The chemistry of the origin of life: Raw materials + Suitable environment + Energy sources • Matter: H O vapor and compounds released from volcanic eruptions, including N and 2 2 its oxides, 2O ,4CH ,3NH 2 H , a2d H S • Energy: Intense volcanic activity, lightning, and UV radiation Stanley Miller’s experiments showed that the abiotic synthesis of organic molecules is possible • Miller set up an airtight apparatus with gases circulating past an electrical discharge, to simulate conditions on the early Earth The chemistry of the origin of life: Raw materials + Suitable environment + Energy sources Chemical Physical Stage Abiotic synthesis of monomers: “simple” organic 1 Stage Formation of polymers: “complex” organic 2 Stage Packaging of polymers into 3 protobionts Stage Self- 4 Stage 3: Packaging of replication polymers into protobionts • What characteristics do cells and protobionts share? Structural organization Simple reproduction Simple metabolism Simple homeostasis Stage 4: Self replication • RNA may have served both as the first genetic material and as the first enzymes 1 Thursday, April 7, y The first genes may have been short strands of RNA that replicated without protein support RNA catalysts or ribozymes may have assisted in this process Ages of rocks and fossils mark geologic time • Radiometric dating: measures the decay of radioactive isotopes • A fossil’s age can be inferred from the ages of the rock layers above and below the strata in which the fossil is found • The fossil record documents the main events in the history of life Key events in life’s history • Prokaryotes lived alone on and transformed the atmosphere. • Photosynthesis by some prokaryotes produced oxygen that enriched the water and atmosphere of Earth. • Eukaryotes are about 1.8 billion years old. • The first multicellular plants and fungi began to colonize land about 500 million years ago. Adaptive radiations may follow the evolution of new adaptations, such as wings • Colonization of land and radiations of land plants were associated with many novel features waxy coat: prevents dehydration vascular tissue: allows water to be channels from root to plant Seeds: protects egg Flowers: allows long range reproduction Continental drift has played a major role in macroevolution • Continental drift: the slow, continuous movement of Earth’s crustal plates on the hot mantle • Important geologic processes occur at plate boundaries: Sliding plates are earthquake zones Colliding plates form mountains • Pangaea supercontinent formed 250 million years ago • Pangaea formation altered habitats and triggered the greatest mass extinction in Earth’s history Its breakup led to the modern arrangement of continents Australi’s marsupials became isolated when the continents separated, and placental mammals arose on other continents India’s collision with Eurasia 55 million years ago led to the formation of the Himalayas The effects of continental drift may imperil human life • Volcanoes and earthquakes result from the movements of crustal plates The boundaries of plates are hotspots of volcanic and earthquake activity An undersea earthquake caused the 2004 tsunami, when a fault in the Indian Ocean ruptured 2 Stage Self- Thursday, April 7, y The history of life on Earth reflects a steady background extinction rate with episodes of mass extinction • Over the last 600 million years, five mass extinctions have occurred in which 50% or more of the Earth’s species went extinct • Cretaceous extinction: 50% of marine species and many terrestrial lineages (including all dinosaurs except birds) 65 million years ago Likely cause was a large asteroid that struck the Earth, blocking light and disrupting the global climate A rebound in diversity follows mass extinctions as survivors become adapted to vacant ecological niches • Adaptive radiation: a group of organisms forms new species, whose adaptations allow them to fill new habitats or roles in their communities Mammals underwent a dramatic adaptive radiation after the extinction of nonavian dinosaurs 65 million years ago Phylogenies are based on homologies in fossils and living organisms • Phylogeny: the evolutionary history of a species or group of species which are based on Fossil record Homologous morphological traits, behaviors, and molecular sequences • Convergent evolution: Analogous similarities resulting from similar environments do not provide information about evolutionary relationships Systematics classifies organisms and determines their evolutionary relationship Taxonomists assign each species a binomial consisting of a genus and species name Genera are grouped into progressively larger categories. Each taxonomic unit is a taxon A phylogenetic tree is a hypothesis of evolutionary relationships within a group • Cladistics uses shared derived characters to group organisms into clades, including an ancestral species and all its descendents An inclusive clade is monophyletic Shared ancestral characters were present in ancestral groups • Shared characters are used to construct phylogenetic trees • Ingroup: taxa whose phylogeny is being investigated • Outgroup : taxon that diverged before the lineage leading to the members of the ingroup The phylogenetic tree of reptiles shows that crocodilians are the closest living relatives of birds • They share numerous features, including fourchambered hearts, singing to defend territories, and parental care of eggs within nests • These traits were likely present in the common ancestor of birds and crocodiles Molecular systematics compares nucleic acids or other molecules to infer relatedness of taxa 3 Thursday, April 7, y • Scientists have sequenced more than 100 billion bases of nucleotides from thousands of species The more recently two species have branched from a common ancestor, the more similar their DNA sequences should be The longer two species have been on separate evolutionary paths, the more their DNA should have diverged An organisms evolutionary history is encoded on its genome • DNA coding for important sequences (like rRNA genes) is useful for investigating relationships between taxa that diverged hundreds of millions of years ago • This comparison has shown that animals are more closely related to fungi than to plants Questions 1. What were the first organisms? A. Prokaryotes B. Eukaryotes C. Plants D. Animal 2. Which of the following is the correct order of the evolution/appearance of the organisms/processes? A. Prokaryotic cells, eukaryotic cells, photosynthesis, multicellular organisms, animals, land plants B. Prokaryotic cells, photosynthesis, eukaryotic cells, multicellular organisms, animals, land plants 3. What is the evolutionary significance of photosynthesis? A. Increased atmospheric water allowed for the evolution of complex organisms. B. Increased atmospheric hydrogen sulfide allowed for the evolution of complex organisms. C. Increased atmospheric carbon dioxide allowed for the evolution of complex organisms. D. Increased atmospheric oxygen allowed for the evolution of complex organisms. 4. Which of the following is an advantage of living on land? A. Less animal life, making it easier to avoid predators B. A faster rate of photosynthesis C. Access to more nutrients D. All of the above 5. Which adaptations allowed plants to succeed on land? A. Structures to protect sperm and eggs B. Waxy waterproof coatings C. Development of roots D. All of the above 6. Which of the following allowed for the adaptive radiation of mammals? A. The transition from nocturnal to diurnal (daytime) activity B. The development of feathers C. The extinction of the dinosaurs 4 Thursday, April 7, y D. The change from a fast metabolism to a slow metabolism 7. The evolutionary history of a group of organisms is called ____________. A. phylogeny B. parsimony C. taxonomy 5
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