4.2.2-.4 Causes of Extinction

4.1.1 BiodiversityBiodiversityThe amount of biological diversity per unit area.It includes: genetic, habitat and species diversity

Genetic DiversityIs the total number of genetic characteristics of a specific species.Habitat DiversityVariety of forests, deserts, grasslands, lakes, oceans, coral reefs, wetlands, and other biological communities, (niches per unit area).

Species DiversityIs the number of species or organisms per unit area found in different habitats of the planet.

State of US species.Projected Status of Biodiversity19982018

Critical and endangeredThreatenedStable or intactANTARCTICANORTHAMERICAEUROPEAFRICAASIASOUTHAMERICAAUSTRALIAPacificOceanAntarctic CirclePacificOceanTropic of CancerTropic of CapricornIndianOceanAtlanticOcean1509060E030W9012015006030N30S60Arctic CircleArctic CircleWhat are the relationships among ecosystem stability, diversity, succession and habitat ? How does diversity change during succession? How does habitat diversity influence species diversity and genetic diversity? How does ecosystem complexity, with its variety of nutrient and energy pathways, provide stability? How do human activities (agriculture, mining, logging, etc.) modify succession? What are the potential positive and negative results of human activities that simplify ecosystems? (monocrop agriculture)Why Should We Care About Biodiversity?Instrumental value: usefulness to us.

Intrinsic value:because they exist, Regardless of whetherthey are useful to us or not.GoodsFood, fuel, ecosystems, species, fiber, lumber, paper, 90% of todays food crops40% of all medicines (85% of antibiotics)

FoxgloveDigitalis purpurea, EuropeDigitalis for heart failure

Pacific yewTaxus brevifolia, Pacific NorthwestOvarian cancerEcological Services:Flow of materials, energy, and information in the biospherePhotosynthesisPollinationSoil formation and maintenanceNutrient recyclingModeration of weather extremesPurification of air and waterInformation:Genetic information: adaptation and evolutionGenetic information for genetic engineeringEducational and scientific informationOption:People would be willing to pay in advance to preserve the option of directly using a resource such as a tree, an elephant, a forest or a clean lake.Recreation:ExistenceAestheticProtect natural capital for future generations

Nonutilitarian:Hunting, fishing, swimming, scuba diving, water skiing, . . . . Eco-tourism4.1.2-.4 Natural Selection Evolution of mammalshttp://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Darwin and Evolution

Evolution are the changes in the gene pool of a population over time.Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully.Adaptation is an inherited characteristic that increases an organisms chance of survival.

IsabelaDarwin Wolf Pinta Marchena Genovesa FernandiaSantiagoBartolomRbidaPin zonSeymourBaltraSanta CruzSanta FeTortugaEspaolaSan CristobalFloreana

EQUATOR GalpagosIslands

Land IguanaMarine Iguana

FOUNDER SPECIESinsect and nectar eatersfruit and seed eatersKAUAI AKIALAOAAMAKIHIIIWIAPAPANEKONA FINCH extinctLAYSAN FINCHAKIAPOLAAUMAUI PARROTBILLBased on his observations, Darwin proposed that EVOLUTION occurs by NATURAL SELECTION.

Darwins PostulatesVariation within populations.Overproduction of offspring.Struggle for existence.Unequal survival and reproduction rates.http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Population of organismsLimited resources leads to a struggle for survival between offspring.Overproduction of offspringSurvivors reproduce more successfully.Mutations & Sexual reproduction produces variations among offspring.Population changes over time.Evolution of Mammals

Fig. 27.19d, p. 471

DISPERSAL OF HIGHLY EVOLVED PLACENTAL MAMMALSSouth AmericaExtinctions of many marsupials and early placental mammals About 5 million years ago, during the Pliocene

Nonvertebrate chordatesJawless fishesCartilaginous fishesBony fishesAmphibiansReptilesBirdsMammals

Fig. 27.19a, p. 471

North AmericaMONOTREMES, MARSUPIALS EVOLVE AND MIGRATE THROUGH PANGEASouth AmericaAntarcticaAustraliaIndiaAfricaEurasia About 150 million years ago, during the Jurassic

Spiny anteaterMONOTREMES

PlatypusKoalaMARSUPIALS

Tasmanian DevilFig. 27.19b, p. 471

PLACENTAL MAMMALS EVOLVE; ADAPTIVE RADIATIONS BEGINIsolation of the early monotremes, marsupials on this land massBetween 100 and 85 million years ago, during the CretaceousPLACENTAL MAMMALSWalruses

BatManateeArctic Fox

Beaver NORTH AMERICAMuskratCapybaraSOUTH AMERICACoypuBeaver MuskratBeaver andMuskratCoypu CapybaraCoypu andCapybaraFig. 27.19c, p. 471

North AmericaADAPTIVE RADIATIONS OF MORE EVOLVED PLACENTAL MAMMALSSouth AmericaAntarcticaAfricaEurasiaContinued isolation of early monotremes and marsupialsExtinctions of mammals About 20 million years ago, during the Miocene

Fig. 20.10, p. 319

RACCOONRED PANDAGIANT PANDADIVERGENCE approximately 40 million years agoDIVERGENCE 15-20 million years agoSPECTACLED BEARSLOTH BEARSUN BEARBLACK BEARPOLAR BEARBROWN BEARWhat is a Species?A group of potentially or actually interbreeding populations, with a common gene pool, which are reproductively isolated from other groups

The problem with the species definitionThe species concept is a human construct used to make sense of the natural world. While extraordinarily helpful in understanding life, it fails to capture the full complex reality of continually evolving populations of organisms.Sibling SpeciesSpecies that cant interbreed, but have no significant differences in appearance.

Very different appearance that can interbreed?!

Two tigons (male to the left, female to the right)

A Liger-Lion/Tiger

A "boblynx" -- a hybrid of bobcat and lynx;

A "zonkey" -- a hybrid of zebra and donkey;

The "Toast of Botswana", -- a hybrid of a female goat to a male sheep;

A "cama" -- a hybrid of camel and llama;A "yakalo" - a hybrid of buffalo or bison and yak;A "cattalo" (or "beefalo") -- a cross of a bison with a domestic cattle;A "coywolf" -- a hybrid of coyote and wolf; A "wholphin" -- a hybrid of a bottlenose dolphin mother and a false killer whale father. Same situation like with the "pumapard" (parents belong to different genera).

Some intraspecies hybrids (both genders fertile):

A "wig" -- a cross of a wild and a domestic pig;An unnamed cross of a Siberian and a Manchurian tiger. tulips

4.2.2-.4 Causes of ExtinctionEXTINCT is FOREVER!!

Non-human causes of extinction:Volcanic eventsOcean temperature changeSea level changesMeteoritesGlaciationsGlobal climate changeCompetition/predation

Human causes of extinction/loss of biodiversity - HIPPOHabitat destruction and fragmentationIntroduced speciesPollutionPopulation Over consumption

Rates of Extinction: = number of species becoming extinct per unit time.Rates of extinction are very difficult to estimate, because we don't even know within an order of magnitude how many species there are. Fossil records can reveal the average "lifetimes" of species, or how long different classes of plants and animals generally exist on the earth before going extinct.From this information, scientists can determine a "background" rate of extinction, or the natural rate of extinction without human intervention.Because of human intervention the Earth's species are dying out at an alarming rate, up to 1,000 times faster than their natural rate of extinction. By carefully examining fossil records and ecosystem destruction, some scientists estimate that as many as 137 species disappear from the Earth EACH DAY, which adds up to an astounding 50,000 species disappearing every year.

The Earth has experienced 5 MASS EXTINCTIONSMammals average species lifespan 1 million years. With ~ 5,000 mammalian species the background extinction rate = 1 every 200 years. In the past 400 years, though, 89 extinctions have been recorded, almost 45 times the natural rate. Over 50 of those extinctions have occurred in the past century, Rate = 100 times the background rate!!

Extinction Rates over geological time

Middle Cambrian age (about 540 million years ago) The locality is special because of the soft-bodied preservation of a wide diversity of fossil invertebrate animals. Period of great speciation.Characteristics of vulnerable speciesSmall population size - island species.Small population size - species with limited habitats.Extremely specialized species.Species with low reproductive potential.Species that require large territories.Species with limited dispersal ability.Vulnerable species - continuedMigratory species.Species that are economically valuable or hunted for sportPredators.Species that are vulnerable to pollution.Species that are incompatible with civilization.RainforestTropical rainforests contain at least half of the Earth's species. Most species have evolved to inhabit very specialized niches in their environment.When humans disrupt that environment, many species cannot survive. Because species depend on each other in a complicated web of relationships, changing just one part of that web harms the entire ecosystem.This breakdown of rainforest ecosystems will likely lead to the disappearance of up to 10% of the world's species within the next 25 years. Rainforest continuedThe human species depends on the rainforest's millions of life forms for its own existence - The genetic diversity found within the rainforests provides invaluable additions to the gene pool which help maintain and improve domestic crops. Without a diversity of strains, crops become overly homogenous and vulnerable to mass blight. Many medicines that we regularly use come from rainforest species.