Bio 105 1st Edition Lecture 24Past Lecture (3/16) Eras of the EarthPrecambrian – origin of life, photosynthesis, Eukaryotic cells.Paleozoic – “old life”Mesozoic – “middle life” age of reptiles, dinosaurs. Mammals were small.Cenozoic – “recent life” our era, period of human existence (geological significance)Keystone moments- Emergence of…life, photosynthesis , eukaryotic cells.- Mass extinction (5 of them)- Human emergence Extinction – 99.8% of special from earliest part of time have already gone extinct, without human impact on them. 1. Relative dating – dating fossils2. Radiometric dating – proved date for fossils. “Clock in the rock” and use radioactive isotopes. Radioactive carbon 14 decays at a known rate. Time passed the accurately found by comparing quantities of parents atoms and daughter atoms. Carbon is only one among a wide array of techniques. Carbon is used for dating young materials. Mass Extinction- Catastrophic events (or series of events) that radically change the course of evolution.- Characteristic:o Severe ecosystem collapse o Dominant species, disappearo Comprehensive Marine, freshwater, and terrestrial. Evident in plants and animals. - Recovery 5-20 million years you will have new species that replace lost ones. **EXTINCTION IS FOREVER**Post-extinction communities are dramatically different. It’s a period of opportunity for new species to evolve, part of the driving force of evolution. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Historical Mass extinctions (5)K-T- ended 240 million years ago, ended Mesozoic – age of reptiles P-T – (mother of all extinctions) Ended 64 million years ago, ended Paleozoic era.- Massive volcano activity – Siberian Trapso Materials in stratosphere that causes cooling. o Ozone depletion, a lot of UV radiation. - Tectonic activity – plates under Earth were shifting- Loss of shallow marine shorelines (95% of marine species disappear)- Loss of 70% of vertebrates on land. Huge percent of plants and insects.Pangaea – super continent Panthalassa – global ocean Generally there’s not just one cause of mass extinction.- All includeo Climate changeo Coral reef loss What happens after Mass Extinction?- Adaptive radiation – emergence of numerous species from a common ancestor as a result of new opportunities and problems. Triassic period –turtles mammals, and dinosaurs.Jurassic period – birds evolveCretaceous period – non-birds die out (animals and plants) Cretaceous extinction = dinosaur dooms day. 60-68% of species on Earth disappear. Current Lecture (23)Alvarez Team (Luis Alvarez and Walter Alvarez) - June 6, 1980 discovered that asteroid hit the Earth that resulted in the K-T extinction. It was discovered in India.- The Alvarez Hypothesis – increase Ir (Iridium) abundance found at K-T sites.- 1990 – site was discovered of K-T (Chicxulub Crater)- After there was a prolonged dark period.- Acid rain (sulfuric acid) / acids in the oceans- Wild fired from heat - First cooling, then warming.- Intense volcanic activity in India.Mammals evolved at the same time as Dinosaurs, but mammals lasted because they could go into hibernation. Dinosaurs were terminated after K-T.Significance of Mass Extinction- They are global catastrophes that casted a few million years (at least)- Drives a new era of speciation (eventually, not right away)- Radically change the course of evolution.Adaptive radiation - is a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches.Cenozoic Era - Diversification of mammals drastically increases.- Human emergence (Africa)o Began about 2 million years ago, but modern humans evolved in the last 200,000years. o Humans have been present for only .0001% of history of life. o Common ancestors – 5.5 million years ago.o Humans aren’t (more evolved) than other living