12/1/10 Riding the Con)nents Con)nental Shi1 & Spread of Biodiversity •  250 million years ago was a supercon)nent. •  Around 150 mya it began to break apart. •  Biogeography Vicariance •  Vicariance – Species become separated from each other when geographical barriers emerge. •  Mite Harvestman –  Currently Found on 5 con)nents –  Sarah Boyer •  Evolu)onary Tree from Mite Harvestman DNA –  The study of how biodiversity maps around the world. –  Two common paFerns: Vicariance & Dispersal Dispersal •  Dispersal-­‐Occurs when species themselves spread away from their place of origin •  Marsupials –  Originally evolved thousands of kilometers away –  Oldest fossils of marsupial-­‐like mammals 150 m.y. old from China –  Exhibit Vicariance & Dispersal Late Jurassic-­‐Early Cretaceous (150-­‐120 mya ago) Late-­‐Creataeous-­‐Paleogene (70-­‐55 mya) Palogene (40-­‐25 mya) Pliocene (3 mya) 1 12/1/10 Vicariance and Dispersal in a Nutshell… •  Allowance of Species to evolve into remarkable new forms •  Ancestors of Darwin’s Finches •  Hawaiian Geese •  Mauri)us island in Indian Ocean –  Dodo Bird –  DNA revealed close kinship with pigeons na)ve to Southeast Asia. The Pace of Evolu)on/Fits & Starts • 
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Bethany Schultz 1971 – one of the most influen)al studies –  published at the American Museum of Natural History –  Niles Eldredge & Stephen Jay Gould –  stasis in trilobites -­‐rows of columns in the eyes did not change for 6 million yrs! Punctuated Equilibria –  Stasis punctuated by rela)vely fast evolu)onary change •  Natural selec)on may adapt popula)ons to local condi)ons (but not much) –  Most change – when a small popula)on branched and became a new species. –  No fossils of the branching have been found! •  two reasons • 
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-­‐popula)ons were small -­‐evolved into new species quickly What you’ve learned •  Con)nental Shi1s millions of years ago allowed for spread of rich biodiversity •  Species spread through Vicariance and Dispersal •  Evolved into unique species inhabi)ng the structural geography of the current world. Life)me of a Species •  99% of all species that have ever existed have vanished from the planet. •  Mollusks leave some of the most complete fossil records of any animal. •  Study done in NZ that charted Mollusks for the past 43 million years; the study found that although species longevity varied the general conclusion was that the species only lasted a few million years. The earliest fossil species are 16 million years old; the last know are 1 million years old •  1600’s Dutch explorers arrived on Mauri)us; killed Dodo’s for food and sport; inadvertently introduced the first rats which ate the eggs of the Dodos; when adults and young were being killed there was no way for the Dodos to repopulate and they became ex)nct •  1900’s Loggers desecrated the Carolina Parakeets popula)on in the southeastern part of the US; cut down old-­‐growth forests where parakeets made their nests in hollow logs. •  Habitat loss can lead to habitat isola)on; habitat isola)on can lead to gene)c dri1ing which leads to muta)ons and slows the spread of helpful traits ; if an isolated popula)on is wiped out by something like fire or freeze it may not be able to recover 2 12/1/10 Cradles of Diversity •  David Jablonski-­‐ paleontologist at University of Chicago –  Analyzed fossil records of bivalves; where they were located, how large their range became; how long they endured; analyzed 3599 species from past 11 million years revealed a paFern: twice as many new genera of bivalves had emerged in the tropical oceans than in cooler waters-­‐ once they evolved in the tropics they expanded toward the poles, soon though the bivalves near the poles became ex)nct the others survived; argued that the tropics have lower ex)nc)on rate and a good environment for high number of bivalves, this lead to high biodiversity in the tropics. •  Bradford Hawkins-­‐ biologist at University Cal. Irvine –  Studied popula)on of 7520 birds; the birds that live close to the poles belong to younger lineages than the ones that live in the tropics; ice ages, retrea)ng glaciers, temperature swings; all raise the risk of ex)nc)on in the cooler regions of the world-­‐ tropics are a rela)vely stable climate, changes are gentle, makes it easy to survive; tropics have higher rate of new species, but also creates a lot of energy for new species to live side by side. Radia)ons (Con’t.) •  Situa)ons which result in adap)ve radia)on occur following mass ex)nc)ons, or when species move into new, unoccupied regions. •  Crea)on of new species is in)mately )ed to the ecological phenomena of niches •  These species become more diverse as they take advantage of their new opportuni)es. •  It takes some degree of geographical isola)on to become a new species. Radia)ons •  Evolu)onary paFern called adap)ve radia)on. •  One or a few species which diversify ("spread out") and generate mul)ple daughter species. Beavers •  Beavers (Castor canadensis) are semi-­‐aqua)c rodents. •  Allogenic Ecosystem Engineers. •  35 Million years ago, begin to exist in North America. •  15 million years ago, rapid specia)on. •  Now only 1 species, the Mountain Beaver exists. 3 12/1/10 What Happened? Why? •  The radia)on of burrowing beavers. •  Climate changes toward cooler, drier, and more open habitats. Cichlid Fishes •  Found in the Great Lakes of east Africa. •  Rise of new specia)on. •  The subsequent radia)on of adapted rodent species led to the ex)nc)on of burrowing beavers. Why did cichlids radiate in the 1st place? 4 12/1/10 Ligh)ng the Cambrian Fuse Adap)ve Radia)ons •  A burst of diversifica)on accompanied by drama)c morphological evolu)on –  Animal evolu)on from protozoans. 1.5 billion year old fossil records. –  Sponges 630 mya –  Some living groups 555mya (12 million years before Cambrian period) •  Cambrian Explosion Explosive period of animal evolu)on. Cambrian Explosion: Physiological Process •  Phylogeny of early animals illustrate animal evolu)on in leaps. –  Arthropods –  530 million year old rocks -­‐ small shell like fossils –  Rocks 20 million years younger-­‐
recognizable rela)ves of living arthropods, vertebrates… •  As an adap)ve radia)on, early evolu)on of animals unsurpassed. •  Diagram marks changes during Ediacaran and Cambrian periods. Disparity / What explains this remarkable radia)on? •  One way to gauge changes – •  Radia)on occurred when measure diversity over )me. Earth was going through drama)c physical changes. –  Not only way to measure diversity. –  Cold climate = glacier –  Less varia)on among 100 genera coverage of beetles than between single – 
Oceans devoid of free species of squid or single species of hummingbird. oxygen •  Morphological varia)on is •  Paul Hoffman known as Disparity. —  Rise of oxygen level •  Disparity of animals expanded evidence. rapidly during the Cambrian period before tapering off. 5 12/1/10 Gene)c Tool Kit •  If rise in oxygen opened door for animal, evolu)on what pushed the animals through? •  Set of genes that control development –  Gene)c Tool Kit –  Evolved in Ediacaran period. •  Gene)c tool kit gave early animals the sort of flexibility adap)ve radia)ons require. •  New Body plans allowed animals to organize themselves into new ecosystems the Earth had never seen before. Driven To Ex)nc)on Ex)nc)on Rates fluctuate over )me • Largest ex)nc)on was 252 million years ago: 55% of all genera went ex)nct (about 90% of all species) • Forests and Reefs drop out of fossil record, don’t reappear for 20 million years •  Most ex)nc)ons do not occur as part of mass ex)nc)ons (20%) Natural Selec)on did not converge on a single strategy for predators or prey •  Evolu)on of new predators changed the fitness landscape for early animals. •  Natural Selec)on favors new defenses. •  New ecosystem creates many different selec)on pressures. –  Creates trade-­‐offs with other pressures. •  Instead of single adap)ve peak animals now evolved on fitness landscape erup)ng with a rugged expanse of hills. Payne and Finnegan •  Two paleontologists from Stanford •  Surveyed 227,229 fossils of marine invertebrates from about 520 million years ago to 20 million years ago •  Results Show: larger geographical range: =>longer survival, decreased ex)nc)on odds Smaller geographical range: =>increased chance of genus ex)nc)on 6 12/1/10 Shannon Peters •  Paleontologist from University of Wisconsin •  fossils of the Paleozoic Fauna are found in carbonate rocks •  Fossils of the Modern Fauna are found in silicoclas)c rocks •  Over the past 540 million years, •  carbonate rocks became rare, while silicoclas)c rocks became common. When Life Nearly Died Out Mass Ex)nc)ons vs. Background Ex)nc)ons Do Mass ex)nc)ons have the same cause as Background ex)nc)ons? •  To find out researchers looked at rocks –  They are filled with fossils from Climate Change •  Planet’s changing climate is influencing ex)nc)on rates •  Geologists es)mate temps from an)quity using oxygen 18 •  High levels = warm climate •  Peter Mayhew: warmer= less diversity, cooler= more diversity Permian-­‐Triassic Ex)nc)on •  Volcano erup)ons?  Harsh cocktail of gases in atmosphere/stratosphere  Warmer climate  Warmer oceans  Bacteria make toxic gases Before, During, A1er –  Contain uranium to date rocks Permian-­‐Triassic Ex)nc)on Rock findings indicate that it happened in 2 pulses: •  1st was 260 million years ago •  2nd was 252 million years ago  Other gases destroy ozone layer  Muta)ons Asteroid Caused Permian-­‐Triassic Mass Ex)nc)on ≈250myo 7 12/1/10 Walter Alvarez collected stones from 66myo •  Found High concentra)ons of iridium •  Proposed cause of the cretaceous ex)nc)on: Iridium rich asteroid struck earth in Mexico Large Carnivores Ruled the Land Pterosaurs ruled the sky Then a Cataclysmic Event Happened… Ex)nc)ons and Evolu)on Gigan)c volcanic erup)ons Giant asteroid at Chicxulub in at Deccan Traps? Mexico's Yucatan peninsula? Marine Rep)les Vanished Cretaceous Ex)nc)on Pliosaur ea)ng a Mosasaur Ammonites are squid ancestors Two-­‐thirds of Life Was Gone! •  A1er each mass ex)nc)on, once the ecosystems finally recovered they were fundamentally different. •  As old biodiversity is wiped out it makes way for evolu)on of new radia)ons by wiping out predators or clearing out ecological niches. 8 12/1/10 The Great Die-­‐Off Julia Moritz, John Moreno, Gloria Ayala and Aubrey Pickerell •  Bird Popula)ons declining 100 )mes faster than before. •  Trend indicated a mass ex)nc)on not seen in 66 MY Industrial Revolu)on Greenhouse gases and Global Warming Ocean Acidity Habitat Loss •  The habitat of a living organism, plant, animal, or microbe, is a place, or a set of environmental condi)ons, where the organism lives. • 
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•  The fragmenta)on of habitats causes an eventual loss of species from all • 
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Urbaniza)on Agricultural Prac)ces Forest Destruc)on Alterna)ve Medicine Industry Grazing Mining Non-­‐na)ve species introduc)on Pollu)on Fire suppression Recrea)on Effects of Habitat Loss •  Rain forests are currently the most seriously impacted ecosystem . Because they contain 50% or more of the world's species. •  In the last two centuries, nearly all of the prairie grassland in the United States has disappeared. •  Had much to do with the disappearance of many species of marine life. 9 12/1/10 Mass Ex)nc)ons •  A sharp decrease in the diversity & abundance of life. •  They occur when the rate of ex)nc)on increases w/ respect to the rate of specia)on. •  On 5 occasions there have been mass ex)nc)ons. •  Periods of high ex)nc)on rates coincide with major environmental changes including: -­‐ Volcano erup)ons -­‐ Asteroid Impacts -­‐ Global Warming Mass Ex)nc)ons (Con’t.) •  Mass ex)nc)ons have some)mes accelerated the evolu)on of life on Earth. •  Dominance of par)cular ecological niches passes from one group of organisms to another. •  So humans are agents of a new pulse of ex)nc)ons. 10