BIOL 250 REVIEW WEEK 15 LESSON 40 LEARNING OBJECTIVES 1 Understand how mass extinctions are determined and know the causes and consequences of some exemplars 2 Learn about the factors that contribute to so called background extinctions 3 Delve into the causes for the current extinction crisis and challenges for the near future TAXONOMIC DIVERSITY MARINE ANIMALS What is the general pattern for taxonomic diversity over time Increase besides major drops due to mass extinction events Note marine animals have great fossil record hard shelled buried in sediments DIFFERENTIAL PATTERNS OF DIVERSIFICATIO PLANTS GROUPS N ACROSS Do the same land plant clades remain dominant through evolutionary history No pointed to as evidence of competition driving patterns of extinction DIFFERENT INCREASES IN TAXONOMIC DIVERSITY AMONG GROUPS When might we expect changes in taxonomic diversity to be coupled between groups A C Benton 1990 B Labandiera Sepkoski 1993 COEVOLUTION BETWEEN PLANTS AND INSECTS DRIVES DIVERSIFICATION SISTER GROUP ANALYSIS Why is it useful to compare sister clades what factors does this control for LECTURE POINT The number of animal families preserved in the fossil record has increased dramatically since the Cambrian period suggesting that the diversity of life has increased as well Which of the following factors could contribute to this pattern multiple answers could be correct The evolution of new groups of organisms such 1 as flowering plants have opened up novel ecological niches for other species such as insects to utilize 2 Diverse body plans appeared in the Cambrian allowing diverse animal forms to evolve The evolution of land plants and terrestrial 3 animals generated many novel niches that new species eventually filled 4 older geological formations 5 Mass extinctions eliminated as many as 95 of animal species at five different times in the history Fossils are more likely to be preserved from EXTINCTION RATES THROUGH EARTH S HISTORY End Permian K Pg What are the different causes of background extinctions versus mass extinction events Specifically what is thought to have caused the end Permian and K Pg mass extinction events Raup Sepkoski 1982 MASS EXTINCTIONS END PERMIAN EXTINCTION 100 my for diversity to completely recover Cause EL NI O AND END PERMIAN EXTINCTION Suggest El Ni o switch lines up better with extinctions Yadong Sun et al 2024 AGE OF THE DINOSAURS ABRUPT ENDING AT K PG BOUNDARY K PG BOUNDARY K PG BOUNDARY LAYER CHARACTERISTICS Iridium rare element in earth crust more common in meteorites Microtektities Shocked quartz altered minerals formed by high temps and collisions ASTEROID IMPACT Mammals were diverse before K Pg mass extinction Transformation and diversification in early mammal evolution Zhe Xi Luo Nature 450 1011 1019 13 December 2007 BACKGROUND EXTINCTION RATES THROUGH EARTH S HISTORY What pattern does this figure show for the rate of background extinction over the Phanerozoic Lecture Point What factors contribute to background extinctions Raup Sepkoski 1982 EXTINCTION RATES FOR PERIODS IN AND NOT IN MASS EXTINCTIONS BY GEOGRAPHIC RANGE What pattern do we see for non mass extinction periods background versus mass extinction periods for effect of range size Values above one indicate larger ranges have lower rates of extinction Payne et al 2007 PNAS GLOBAL PHYLOGENETIC ENDEMISM PATTERNS Red line phylogenetic endemism by latitude What pattern does this figure show for phylogenetic endemism with latitude Murali et al 2022 Sci Adv THE CURRENT MASS EXTINCTION Does it reflect levels of extinction seen in extinction events in the fossil record Consider the relative lengths of time EXTINCTION OF PLEISTOCENE MEGAFAUNA Piliou 1991 Stellar s sea cow Thylacine GREATLY INCREASED RATES OF VERTEBRATE EXTINCTION POST 1500S When do we see increases from baseline levels of extinction for the different taxa Gerardo Ceballos Ehrlich 2023 PNAS ARE WE IN A SIXTH MASS THE ANTHROPOCENE EXTINCTION What factors drive current extinctions INVASIVE SPECIES NEW AND EMERGING DISEASES Chytrid fungus Harlequin frogs 40 of species extinct Golden toad extinct 1989 Habitat loss Human impacts 2009 total ecosyste on impact ms 1993 2009 change in impact Venter et al 2016 Nat Com HUMAN INDUCED ATMOSPHERIC CHANGE CAN SPECIES MOVE OR ADAPT AS CLIMATE CHANGES CO2 levels measured at Vostok Antarctica blue Law Dome East Antarctica purple and Mauna Loa Hawaii red