Presentation on theme: "Evolution and Biodiversity"— Presentation transcript:
1Evolution and Biodiversity Chapter 4Evolution and Biodiversity
2Chapter Overview Questions How do scientists account for the development of life on earth?What is biological evolution by natural selection, and how can it account for the current diversity of organisms on the earth?How can geologic processes, climate change and catastrophes affect biological evolution?
3Chapter Overview Questions (cont’d) What is an ecological niche, and how does it help a population adapt to changing environmental conditions?How do extinction of species and formation of new species affect biodiversity?
4Chapter Overview Questions (cont’d) What is the future of evolution, and what role should humans play in this future?How did we become such a powerful species in a short time?
6Core Case Study: Why Should We Care about the American Alligator? Hunters wiped out population to the point of near extinction.1967- classified as endangered1975- numbers had rebounded1977- reclassified as threatenedFigure 7-1
7Core Case Study: Why Should We Care about the American Alligator? Alligators have important ecological role.Alligators are a keystone species:Influence on ecosystem is much greater than their numbers would suggestFigure 7-1
8Core Case Study: American Alligator as Keystone Species Dig deep depressions (gator holes).Hold water during dry spells, serve as refuges for aquatic life.Build nesting mounds.provide nesting and feeding sites for birds.Keeps areas of open water free of vegetation (swimming paths)Keep gar populations in check
14Core Case Study Earth: The Just-Right, Adaptable Planet Distance from sunSpinsSize- molten mantle, retain atmosphereStratospheric Ozone(2 billion years)21% Oxygen(several hundred million years)Biodiversity & SustainabilityTempFigure 4-1
15Core Case Study Earth: The Just-Right, Adaptable Planet During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC.Figure 4-1
16Biological EvolutionThis has led to the variety of species we find on the earth today.Figure 4-2
17Recorded human history begins about 1/4 second before midnight Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnightRecorded human history begins about 1/4 second before midnightAge of mammalsAge of reptilesInsects and amphibians invade the landOrigin of life ( billion years ago)Figure 4.3Natural capital: greatly simplified overview of the biological evolution by natural selection of life on the earth, which was preceded by about 1 billion years of chemical evolution. Microorganisms (mostly bacteria) that lived in water dominated the early span of biological evolution on the earth, between about 3.7 billion and 1 billion years ago. Plants and animals evolved first in the seas. Fossil and recent DNA evidence suggests that plants began invading the land some 780 million years ago, and animals began living on land about 370 million years ago. Humans arrived on the scene only a very short time ago—equivalent to less than an eye blink of the earth’s roughly 3.7-billion-year history of biological evolution.First fossil record of animalsPlants begin invading landEvolution and expansion of lifeFig. 4-3, p. 84
18How Do We Know Which Organisms Lived in the Past? Our knowledge about past life comes fromfossilscores drilled out of buried iceanalysis of protein similaritiesDNA & RNA analysis.Figure 4-4
19EVOLUTION, NATURAL SELECTION, AND ADAPTATION Evolution in Seven Words:Genes Mutate, Individuals are Selected, Populations Evolve
20Natural selection acts on individuals, but evolution occurs in populations Three conditions are necessary for biological evolution:1. Genetic variability traits must be heritable3. trait must lead to differential reproduction.An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.
21EVOLUTION, NATURAL SELECTION, AND ADAPTATION Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.With positive selection pressure, advantageous traits help individuals to survive long enough to have and raise their young.With negative selection pressure, individuals die before they can reproduce.
22EVOLUTION, NATURAL SELECTION, AND ADAPTATION Advantageous traits originate from genetic variability.Genetic variability occurs through…mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.Exposure to mutagens: radioactivity, x rays, certain chemicalsRandom mistakes in DNA duplication, or during RNA transcription and translation.
23Limits on Adaptation through Natural Selection A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.
24Common Myths about Evolution through Natural Selection Yes: Biological evolution through natural selection is about the most descendants.No: (Misunderstandings)“Survival of the fittest” means “survival of the biggest, fastest, or strongest”.Organisms develop certain traits because they need them.Species evolve towards genetic perfection.
25New Species: Hybridization New species can arise through hybridization.Occurs when individuals to two distinct species crossbreed to produce a fertile offspring.The red wolf is thought to be a coyote/wolf hybrid
26New Species: Gene Swapping Some species (mostly microorganisms) can exchange genes without sexual reproduction.Horizontal gene transfer
28Why Should We Care About Biodiversity? Some consider it ethical to care about nature.Biodiversity provides us with:Natural Resources (food, water, wood, energy, and medicines)Natural Services (air and water purification, soil fertility, waste disposal, pest control)Aesthetic pleasure
29Biodiversity Loss and Species Extinction: Remember HIPPO H for habitat destruction and degradationI for invasive speciesP for pollutionP for human population growthO for overexploitation
30ECOLOGICAL NICHES AND ADAPTATION: Coastal Georgia Smooth cordgrass,Spartina alterniflora,Can grow in fresh water……but it doesn’t in the wild.Why not?
31ECOLOGICAL NICHES AND ADAPTATION Each species in an ecosystem has a specific role or way of life.Fundamental niche: the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use.Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.
32Species Diversity and Niche Structure: Different Species Playing Different Roles Biological communities differ in the types and numbers of species they contain and the ecological roles those species play.Species diversity has 2 components:species richness the number of different species the ecosystem containsspecies evenness the abundance of individuals within each of those species.
33Species Diversity and Niche Structure Niche structure: how many potential ecological niches occur, how they resemble or differ, and how the species occupying different niches interact.Geographic location: species diversity is highest in the tropics and declines as we move from the equator toward the poles.
34TYPES OF SPECIESNative, nonnative, indicator, keystone, and foundation species play different ecological roles in communities.Native: those that normally live and thrive in a particular community.Nonnative species a.k.a. invasive species: those that migrate, deliberately or accidentally introduced into a community.
35Indicator Species: Biological Smoke Alarms Species that serve as early warnings of damage to a community or an ecosystem.“Canary in a coal mine”Presence or absence of trout species because they are sensitive to temperature and oxygen levels.Birds- require a range of habitatLichens- stay in one place and absorb from the environmentAmphibians- vulnerable at any part of life cycle
36Case Study: Why are Amphibians Vanishing? Frogs serve as indicator species because different parts of their life cycles can be easily disturbed.Next
37Adult frog (3 years) Young frog Sperm Tadpole develops into frog SexualReproductionTadpoleFigure 7.3Typical life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting for food (frog legs), and nonnative predators and competitors.EggsFertilized eggdevelopmentEgg hatchesOrgan formationFig. 7-3, p. 147
38Case Study: Why are Amphibians Vanishing? Habitat loss and fragmentation.Prolonged drought.Increases in ultraviolet radiation.Parasites.Viral and Fungal diseases.Overhunting.Air OR water pollutionNatural immigration or deliberate introduction of nonnative predators and competitors.
39Keystone Species: Major Players Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it.Figures 7-4 and 7-5
40Foundation Species: Other Major Players Expansion of keystone species category.Foundation species can create and enhance the physical habitats to benefit other species in a community.Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize.Alligators making “gator holes”
41Generalist and Specialist Species: Broad and Narrow Niches Generalist species tolerate a wide range of conditions.Specialist species can only tolerate a narrow range of conditions. Exp: tiger salamander, giant pandaFigure 4-7
42Specialist species Generalist species with a narrow niche with a broad nicheNicheseparationNumber of individualsFigure 4.7Overlap of the niches of two different species: a specialist and a generalist. In the overlap area, the two species compete for one or more of the same resources. As a result, each species can occupy only a part of its fundamental niche; the part it occupies is its realized niche. Generalist species such as a raccoon have a broad niche (right), and specialist species such as the giant panda have a narrow niche (left).NichebreadthRegion ofniche overlapResource useFig. 4-7, p. 91
43SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors 350 million years old3,500 different speciesUltimate generalistCan eat almost anything.Can live and breed almost anywhere.Can withstand massive radiation.Figure 4-A
44Specialized Feeding Niches Resource partitioning reduces competition and allows sharing of limited resources.Figure 4-8
45Avocet sweeps bill through mud and surface water in search of small crustaceans,insects, and seedsRuddy turnstone searchesunder shells and pebblesfor small invertebratesHerring gull is atireless scavengerBrown pelican dives for fish,which it locates from the airDowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceansBlack skimmerseizes small fishat water surfaceLouisiana heron wades intowater to seize small fishFigure 4.8Natural capital: specialized feeding niches of various bird species in a coastal wetland. Such resource partitioning reduces competition and allows sharing of limited resources.Piping plover feedson insects and tinycrustaceans onsandy beachesOystercatcher feeds onclams, mussels, andother shellfish into whichit pries its narrow beakFlamingofeeds onminuteorganismsin mudScaup and otherdiving ducks feed on mollusks, crustaceans,and aquatic vegetationKnot (a sandpiper)picks up worms andsmall crustaceans leftby receding tide(Birds not drawn to scale)Fig. 4-8, pp
46Evolutionary Divergence: Darwin’s Finches Each species has a beak specialized to take advantage of certain types of food resource.Next
47Insect and nectar eaters Fruit and seed eatersInsect and nectar eatersGreater Koa-finchKuai AkialaoaAmakihiKona GrosbeakCrested HoneycreeperAkiapolaauFigure 4.9Natural capital: evolutionary divergence of honeycreepers into specialized ecological niches. Each species has a beak specialized to take advantage of certain types of food resources.Maui ParrotbillApapaneUnknown finch ancestorFig. 4-9, p. 91
48NATURAL SELECTION: DRIVEN BY GEOLOGIC PROCESSES, CLIMATE CHANGE, & CATASTROPHES The movement of solid tectonic plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones.The locations of continents and oceanic basins influence climate.The movement of continents have allowed species to move.
49225 million years ago 135 million years ago 65 million years ago Figure 4.5Geological processes and biological evolution. Over millions of years the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species as land areas split apart and promote the rise of new species when once isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s huge plates separated and eventually resulted in today’s locations of the continents (bottom right).65 million years agoPresentFig. 4-5, p. 88
50Climate Change and Natural Selection Changes in climate throughout the earth’s history have shifted where plants and animals can live.Next
51Northern Hemisphere Ice coverage 18,000years before presentNorthern HemisphereIce coverageModern day(August)Note:Modern sea ice coveragerepresentssummer monthsLegendContinental iceFigure 4.6Changes in ice coverage in the northern hemisphere during the past 18,000 years. (Data from the National Oceanic and Atmospheric Administration)Sea iceLand above sea levelFig. 4-6, p. 89
52SPECIATION, EXTINCTION, AND BIODIVERSITY Speciation: A new species can arise when member of a population become isolated for a long period of time.Due to natural selection over time, the genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.
53Catastrophes and Natural Selection Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.
54Geographic Isolation… …can lead to reproductive isolation, which leads to divergence of gene pools and speciation.Figure 4-10
55matches snow for camouflage. Adapted to cold through heavier fur,short ears, short legs,short nose. White furmatches snow for camouflage.Arctic FoxNorthernpopulationEarly foxPopulationSpreadsnorthwardand southwardand separatesDifferent environmentalconditions lead to different selective pressures and evolution into two different species.Adapted to heat through lightweightfur and long ears, legs, and nose, which give off more heat.SouthernPopulationFigure 4.10Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation.Gray FoxFig. 4-10, p. 92
56Extinction: Lights Out Extinction occurs when the population cannot adapt to changing environmental conditions.The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate.Figure 4-11
57Categorizing Extinction Rates Biologists estimate that 99.9% of all the species that ever existed are now extinct.Background extinction- a certain number of species disappearing at a slow rate due to changes of local environmental conditionsEstimate: 1-5 species per million per yearMass depletion- rates of extinction above background level but not high enough to be considered a mass extinction.Mass extinction- a significant rise in extinction rate above background level.
58Effects of Humans on Biodiversity The scientific consensus is that human activities are decreasing the earth’s biodiversity.Figure 4-13
59Silurian Permian Jurassic Cambrian Ordovician Devonian Devonian TerrestrialorganismsSilurianPermianJurassicCambrianOrdovicianDevonianDevonianCretaceousPre-cambrianMarineorganismsCarboniferousNumber of familiesTertiaryQuaternaryFigure 4.13Natural capital: changes in the earth’s biodiversity over geological time. The biological diversity of life on land and in the oceans has increased dramatically over the last 3.5 billion years, especially during the past 250 million years. During the last 1.8 million years this increase has leveled off.Millions of years agoFig. 4-13, p. 94
60Species and families experiencing mass extinction Bar width represents relativenumber of living speciesMillions ofyears agoEraPeriodExtinctionCurrent extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.QuaternaryTodayCenozoicTertiaryExtinction65Cretaceous: up to 80% of rulingreptiles (dinosaurs); many marinespecies including manyforaminiferans and mollusks.CretaceousMesozoicJurassicExtinctionTriassic: 35% of animal families, including many reptiles and marine mollusks.180TriassicExtinctionPermian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.250PermianCarboniferousExtinction345Figure 4.12Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities.Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.DevonianPaleozoicSilurianOrdovicianExtinction500Ordovician: 50% of animal families, including many trilobites.CambrianFig. 4-12, p. 93
61GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding.We have used genetic engineering to transfer genes from one species to another (gene splicing)Takes half the time and costs less than crossbreeding.Figure 4-15
62Genetic Engineering: Genetically Modified Organisms (GMO) GMOs use recombinant DNAgenes or portions of genes from different organisms.Figure 4-14
63Case Study: Species Diversity on Islands MacArthur and Wilson proposed the species equilibrium model a.k.a. theory of island biogeography in the 1960’s.Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on:Island sizeDistance to nearest mainland
64THE FUTURE OF EVOLUTION Biologists are learning to rebuild organisms from their cell components and to clone organisms.Cloning has lead to high miscarriage rates, rapid aging, organ defects.Genetic engineering can help improve human condition, but results are not always predictable.Currently: We do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism.
65BiopharmingBiopharming is when humans use genetically engineered organisms for the production of consumables such asDrugsChemicalsHuman body partsWhich one of these have we not yet mastered?
66Controversy Over Genetic Engineering There are a number of privacy, ethical, legal and environmental issues.Should genetic engineering and development be regulated?What are the long-term environmental consequences?
67Case Study: How Did We Become Such a Powerful Species so Quickly? Compared to other species, we lack:strength, speed, agility.weapons (claws, fangs), protection (shell).poor hearing and vision.We have thrived as a species because of our:opposable thumbsability to walk uprightcomplex brains (problem solving).
68Ch 4 Final ThoughtsMicroevolution- Traits changing in a species (e.g.color, fur type, etc.)Industrial Melanismin pepper moths:Macroevolution- The development of new species
69Ch 4 Final ThoughtsGradualism- species change slowly over time at a steady rate of change (Darwin was wrong about this)Punctuated Equilibrium- Long periods of stability punctuated by peiods of rapid change, initiated by changes in the environment (evolutionary biologist Stephen Jay Gould)# of speciesTime# of speciesTime
70Ch 4 Final ThoughtsNatural Selection happens to individuals, and leads to differential reproduction (think about the wooly worms lab)Evolution happens to a population over time, and is ultimately understood as changes in gene frequencies within that population.Leads to microevolution in the short termLeads to macroevolution in the long term
71Genetic Engineering: Genetically Modified Organisms (GMO) GMOs use recombinant DNAgenes or portions of genes from different organisms.Figure 4-14
72Identify and remove portion of DNA with Phase 1Make Modified GeneE. coliGeneticallymodifiedplasmidInsert modifiedplasmid into E. coliCellExtractPlasmidExtract DNAPlasmidGene ofinterestDNAIdentify and remove portion of DNA withdesired traitRemove plasmidfrom DNA of E. coliInsert extracted(step 2) into plasmid(step 3)Identify and extract gene with desired traitGrow in tissueculture tomake copiesFigure 4.14Genetic engineering: steps in genetically modifying a plant.Fig. 4-14, p. 95
73Transfer plasmid copies to a carrier agrobacterium Phase 2Make Transgenic CellA. tumefaciens(agrobacterium)Foreign DNAE. ColiHost DNAPlant cellNucleusTransfer plasmid copies to a carrier agrobacteriumAgrobacterium inserts foreign DNA into plant cell to yield transgenic cellFigure 4.14Genetic engineering: steps in genetically modifying a plant.Transfer plasmid to surface of microscopic metal particleUse gene gun to injectDNA into plant cellFig. 4-14, p. 95
74Grow Genetically Engineered Plant Phase 3Grow Genetically Engineered PlantTransgenic cellfrom Phase 2Cell division oftransgenic cellsCulture cellsto form plantletsFigure 4.14Genetic engineering: steps in genetically modifying a plant.Transfer to soilTransgenic plantswith new traitsFig. 4-14, p. 95
75Grow Genetically Engineered Plant Transgenic cellfrom Phase 2Phase 3Grow Genetically Engineered PlantCell division oftransgenic cellsCulture cellsto form plantletsTransfer to soilTransgenic plantswith new traitsStepped ArtFig. 4-14, p. 95