2Core Case Study: Why Should We Care about the American Alligator? Largest reptile in North America1930s: Hunters and poachersImportance of gator holes and nesting mounds1967: endangered species1977: comeback, threatened species
104-2 Where Do Species Come From? Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations.Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).
11Biological Evolution by Natural Selection Explains How Life Changes over Time Charles DarwinAlfred Russel WallaceTree of Life
12Six Major Kingdoms of Species as a Result of Natural Selection
13ProkaryotesEukaryotesEubacteriaArchaebacteriaProtistsPlantsFungiAnimalsCenozoicFirst humansMesozoicExtinction of dinosaursPlantscolonize landPaleozoic500Origin ofmulticellularorganisms1,0001,500Oldesteukaryotic fossils2,000Millions of years agoAccumulation ofO2 in atmospherefrom photosyntheticcyanobacterium2,500PrecambrianFigure 4.3Overview of the evolution of life on the earth into six major kingdoms of species as a result of natural selection. For more details, see p. S46 in Supplement 7.3,0003,500Oldest prokaryoticfossils4,000Earth cool enoughfor crust to solidify4,500Origin of EarthFig. 4-3, p. 81
14The Fossil Record Tells Much of the Story of Evolution FossilsPhysical evidence of ancient organismsReveal what their internal structures looked likeFossil record is incomplete: why?
15Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era
16The Genetic Makeup of a Population Can Change Populations evolve by becoming genetically differentGenetic variationsFirst step in biological evolutionOccurs through mutations in reproductive cells
17Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring Natural selection: acts on individualsSecond step in biological evolutionAdaptation may lead to differential reproductionGenetic resistanceWhen environmental conditions change, populationsAdaptMigrateBecome extinct
19A group of bacteria, including genetically resistant ones, are exposed to an antibioticEventually the resistant strainreplaces the strain affected bythe antibioticThe genetically resistant bacteriastart multiplyingMost of the normal bacteria dieFigure 4.5Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria.Normal bacteriumResistant bacteriumFig. 4-5, p. 83
20A group of bacteria, including genetically resistant ones, are exposed to an antibioticNormal bacteriumResistant bacteriumEventually the resistant strainreplaces the strain affected bythe antibioticThe genetically resistant bacteriastart multiplyingMost of the normal bacteria dieFigure 4.5Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria.Stepped ArtFig. 4-5, p. 83
21Case Study: How Did Humans Become Such a Powerful Species? Three human adaptationsStrong opposable thumbsWalk uprightComplex brain
22Adaptation through Natural Selection Has Limits Genetic change must precede change in the environmental conditionsReproductive capacity
23Three Common Myths about Evolution through Natural Selection “Survival of the fittest” is not “survival of the strongest”Organisms do not develop traits out of need or wantNo grand plan of nature for perfect adaptation
314-3 How Do Geological Processes and Climate Change Affect Evolution? Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.
32Geologic Processes Affect Natural Selection Tectonic plates affect evolution and the location of life on earthLocation of continents and oceansSpecies physically move, or adapt, or form new species through natural selectionEarthquakesVolcanic eruptions
33Movement of the Earth’s Continents over Millions of Years
34225 million years ago 135 million years ago 65 million years ago PresentFigure 4.6Over 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 also in the rise of new species when 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 tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species?Fig. 4-6, p. 85
35225 million years ago 135 million years ago 65 million years ago PresentFigure 4.6Over 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 also in the rise of new species when 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 tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species?Stepped ArtFig. 4-6, p. 85
36Climate Change and Catastrophes Affect Natural Selection Ice ages followed by warming temperaturesCollisions between the earth and large asteroidsNew speciesExtinction
37Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years
38Northern Hemisphere Ice coverage 18,000years beforepresentNorthern HemisphereIce coverageModern day(August)LegendContinental iceSea iceLand above sea levelFigure 4.7Changes in ice coverage in the northern hemisphere during the past 18,000 years. Question: What are two characteristics of an animal and two characteristics of a plant that natural selection would have favored as these ice sheets (left) advanced? (Data from the National Oceanic and Atmospheric Administration)Fig. 4-7, p. 85
39Science Focus: Earth Is Just Right for Life to Thrive Certain temperature rangeDependence on waterRotation on its axisRevolution around the sunEnough gravitational mass
424-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity? Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.Concept 4-4B Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.
43How Do New Species Evolve? Geographic isolationReproductive isolation
44Geographic Isolation Can Lead to Reproductive Isolation
45Arctic Fox Northern population Gray Fox Southern population Adapted to coldthrough heavier fur,short ears, short legs,and short nose. Whitefur matches snow forcamouflage.NorthernpopulationSpreads northand southand separatesDifferent environmentalconditions lead to differentselective pressures and evolutioninto two different species.Early foxpopulationGray FoxAdapted to heatthrough lightweightfur and long ears,legs, and nose, which give off more heat.SouthernpopulationFigure 4.8Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation.Fig. 4-8, p. 87
46Extinction is Forever Extinction Endemic species Particularly vulnerable
554-5 What Is Species Diversity and Why Is It Important? Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of ecosystems.
56Species Diversity: Variety, Abundance of Species in a Particular Place Species richnessSpecies evennessDiversity varies with geographical locationMost species-rich communitiesTropical rain forestsCoral reefsOcean bottom zoneLarge tropical lakes
57Variations in Species Richness and Species Evenness
58Science Focus: Species Richness on Islands Species equilibrium model, theory of island biogeographyRate of new species immigrating should balance with the rate of species extinctionIsland size and distance from the mainland need to be considered
59Species-Rich Ecosystems Tend to Be Productive and Sustainable Species richness seems to increase productivity and stability or sustainabilityHow much species richness is needed is debatable
604-6 What Roles Do Species Play in Ecosystems? Concept 4-6A Each species plays a specific ecological role called its niche.Concept 4-6B Any given species may play one or more of five important roles—native, nonnative, indicator, keystone, or foundation roles—in a particular ecosystem.
61Each Species Plays a Unique Role in Its Ecosystem Ecological niche, nichePattern of livingGeneralist speciesBroad nicheSpecialist speciesNarrow niche
62Specialist Species and Generalist Species Niches
63Niche separation Niche breadth Specialist specieswith a narrow nicheGeneralist specieswith a broad nicheNicheseparationNumber of individualsFigure 4.11Specialist species such as the giant panda have a narrow niche (left) and generalist species such as a raccoon have a broad niche (right).NichebreadthRegion ofniche overlapResource useFig. 4-11, p. 91
64Case Study: Cockroaches: Nature’s Ultimate Survivors GeneralistsHigh reproductive ratesGiant panda and tiger salamandersSpecialistsLow reproductive rates
66Specialized Feeding Niches of Various Bird Species in a Coastal Wetland
67surface water in search of small crustaceans, insects, and seeds Ruddy turnstonesearches undershells and pebblesfor smallinvertebratesDowitcher probesdeeply into mud insearch of snails,marine worms, andsmall crustaceansBlack skimmerseizes small fishat water surfaceBrown pelican divesfor fish, which itlocates from the airHerring gullis a tirelessscavengerAvocet sweeps billthrough mud andsurface water in searchof small crustaceans,insects, and seedsFlamingo feeds on minute organisms in mudScaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetationLouisiana heron wades into water to seize small fishOystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beakKnot (sandpiper)picks up wormsand small crustaceansleft by receding tidePiping plover feeds on insects and tinycrustaceans on sandy beachesFigure 4.13Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources.Fig. 4-13, p. 93
68Niches Can Be Occupied by Native and Nonnative Species Nonnative species; invasive, alien, or exotic speciesMay spread rapidlyNot all are villains
69Indicator Species Serve as Biological Smoke Alarms Can monitor environmental qualityTroutBirdsButterfliesFrogs
70Case Study: Why Are Amphibians Vanishing? (1) Habitat loss and fragmentationProlonged droughtPollutionIncrease in UV radiationParasitesViral and fungal diseasesClimate changeOverhuntingNonnative predators and competitors
71Case Study: Why Are Amphibians Vanishing? (2) Importance of amphibiansSensitive biological indicators of environmental changesAdult amphibiansImportant ecological roles in biological communitiesGenetic storehouse of pharmaceutical products waiting to be discovered
73Adult frog (3 years) Tadpole develops into frog Young frogSpermTadpole developsinto frogSexualreproductionTadpoleFigure 4.14Life 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 by humans, and nonnative predators and competitors.EggsFertilized eggdevelopmentEgg hatchesOrgan formationFig. 4-14, p. 94
74Keystone, Foundation Species Determine Structure, Function of Their Ecosystems Keystone speciesPollinatorsTop predatorFoundation speciesCreate or enhance their habitats, which benefit othersElephantsBeavers
75Case Study: Why Should We Protect Sharks? Keystone speciesEat dead and dying fish in the oceanStrong immune systemsWounds do not get infectedAlmost never get cancerCould help humans if we understood their immune system