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Alicia Walker Lecture – April 18, 2012Zoology 101 – McIntyre – History of Life - 18 Apr 2012Learning guidelines: • Read assigned chapters • Ask questions! • Use notes handouts – they are the skeletons upon which you construct your understanding • Think, and then write notes • Are there any further questions? – Ask in class – Talk to me before/after class – Ask your TA in discussion – Email me: always use subject line Zoology 101… Levels of biological organization: We will be focusing on the levels fromOrganism to BiosphereEcology: study of species interactions with each other and the environmentEvolution: study of processes that give rise to diversity of life by changinggene frequencies throughout timeThe ecological theater & the evolutionary play Ecological theater - set (the environment); cast (the species present)Evolutionary play – plot (unfolds in real time); ending (uncertain, but norewind, we know the ending at the present moment) and the details areimportantG. Evelyn Hutchinson came up with these termsCourse goals: Alter perspective of environment Origins of life: Primordial Soup Hypothesis: During the 1920s, Russian chemist A.I. Oparin and British scientist J.B.S. Haldane independently hypothesized that Earth’s early atmosphere was a reducing (electron-adding) environment, in which organic compounds could have formed from simpler molecules. The energy for this organic synthesis could have come from lightning and intenseAlicia Walker Lecture – April 18, 2012UV radiation. Haldane suggested that the early oceans were a solution of organic molecules, a “primitive soup” from which life arose. Stanley Miller and Harold Urey (1953) at the University of Chicago tested the Oparin-Haldane hypothesis. STEP 1-3 (Miller-Urey); STEP 4 is still a mysterySTEP 1: “Primordial Soup” of inorganic molecules + energy – amino acidsSTEP 2: Amino acids + catalyst (energy + chemistry) – complex moleculesSTEP 3: Complex molecules + catalyst (clay) – organized vesiclesSTEP 4: Organized vesicle – LIFE (metabolism & reproduction)Theory vs. Experimental Evidence: - Theory – an explanation that is broader in scope than a hypothesis, generates new hypotheses, and is supported by a large body of evidence- Experimental evidence – fossil record, DNA evidenceFossil record: 1. Amazing2. Incomplete 3. Biased- 3.5 billion years ago (3,500 mya) –fossilized stromatolite- 1.5 billion years – 1st eukaryotes(Tappania, single-celled)- 1 billion multicellular eukaryotes- Timeline is not on a linear scale- 565 mya – bodied eukaryotes- 400 million years ago (mya) – 1stvertebrates (early fish)- 375 mya – amphibiansAlicia Walker Lecture – April 18, 2012Special examples: Conservation Biology: windmills &biomass removal; windmills influence of birds (migration patterns & insectivore community)The Oxygen Revolution- When oxygenic photosynthesis firstevolved, the free O2 it producedprobably dissolved in the surroundingwater until it reached a high enoughconcentration to react with dissolvediron. This would have caused the ironto precipitate as iron oxide, whichaccumulated as sediments.- Once all the iron had precipitated, additional O2 dissolved in the water until the seas and lakes became saturated with O2. O2 finally began to “gas out” of the water and enter the atmosphere. This change left its mark in the rusting of iron-rich terrestrial rocks, a process that began about 2.7 billion years ago. - The amount of atmospheric O2 increased gradually from 2.7 to 2.3 billion years ago, but then shot up relatively between 1% and 10% of its present level. - Prokaryotes photosynthesis – iron uptake of O2 Oceanic O2 – atmospheric O2 (run out of iron in the ocean, O2 diffuses into atmosphere)Cambrian explosion - Fossils of several animal groups – sponges, cnidarians (sea anemones and their relatives), and molluscs – appear in even older rocks dating from the late Proterozoic- The fossils of large pre-Cambrian animals reveal little predation. Instead, these animals appear to have been grazers (feeding on algae), suspension feeders, or scavenger, not hunters- In a relatively short period of time (10 million years), predators over 1 m in length emerged that had claws and other features for capturing prey; simultaneously , new defensive adaptations, such as sharp spines and heavy body armor, appeared in their preyAlicia Walker Lecture – April 18, 2012- Some DNA analyses suggest that most animal phyla originated and began to diverge from one another as early as 700 million to 1 billion years ago- (535-525mya) 570-530 mya, entirely marine- Diversification of invert body plans (hard and soft)Phylogenetic tree:- Branching structure - Nested relationships- Age of lineage- Most extant animal lineages originate during Cambrian explosionMass extinctions: large numbers of speciesbecome extinct throughout Earth- Five mass extinctions are documentedin the fossil record over the past 500million years. In each mass extinction,50% or more of Earth’s marine speciesbecame extinct.- BIG FIVE DATES: 444mya, 359mya,251mya, 200mya, and 65.5mya- I.e. the decimation of hard-bodied animals that lived in shallow seas- The Permian and the Cretaceous mass extinctions received the most attentionPermian: Defines the boundary between the Paleozoic and Mesozoic eras (251 mya), claimed about 96% of marine animals species and drastically altered life in the ocean. There was a loss of 8 of 27 insect orders. The Permian extinction occurred at the time of enormous volcano eruptions in what is now SiberiaArmored exoskeleton; branched appendages 5 bulging eyes proboscis with claws; they are extinct (long gone) and now nothing looks like themNotochord with muscles; no segments or appendagesAlicia Walker Lecture – April 18, 2012- Volcanism – lava/ash + CO2 – ocean warming (by 6°-10°F) – ocean anoxia + H2S gas – ozone holes – marine & terrestrial effects- Loss of 50% of marine invertebrate families, loss of 96% of marine species Cretaceous: Occurred about 65.5 mya and marks the boundary between the Mesozoic and Cenozoic eras. This event extinguished more than half of all marine species, and eliminated many families of terrestrial plants and animals, including all dinosaurs (except birds). One clue to a possible cause of the Cretaceous mass extinction is a thin layer of clay enriched in iridium that separates sediments from the Mesozoic and Cenozoic eras. Iridium


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UW-Madison BIOLOGY 101 - History of Life

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