2I. Origins of Life How do we know? Chemical analysis: chemists have conducted lab experiments to show how simple organic compounds could have been created.Radioactive dating: radiocarbon, radiometric dating with radioactive rocks and fossils
3H2O CH4 CO2 N2 Electrode NH3 H2 Electrical sparks simulating lighting Water vaporN2CO2ElectrodeNH3H2Electrical sparkssimulating lightingprovide energy tosynthesize organiccompoundsCondenserCold waterCooled watercontaining organiccompoundsH2OSample forchemicalanalysisFig. 5.3, p. 104
4Life evolved in two phases over the course of 4.7-4.8 billion years Chemical evolution of organic molecules and polymersBiological evolution from single celled prokaryotic bacteria to multi-cellular eukaryotic organisms
5Chemical EvolutionFormation of the Earth’s Crust: 4.6 to 4.7 billion years ago a cloud of cosmic dust condensed into planet earth which soon turned molten due to radioactive decay and meteorite impacts. As cooling took place a thin crust developed.Formation of the earth’s seas: volcanic eruptions and comet impacts brought water vapor that rained down on earth to create the sea
6Chemical Evolution (cont.) Small organic molecules form in the seas: from eroded minerals from rocks4.4 billion years ago the first atmosphere was formed. The main components were believed to be: CO2, N2,H2O , CH4, NH3, H2S, HCL, no oxygenThis mixture is often to as: The primordial stew
7Chemical Evolution (cont.) Large organic molecules form in the seas: energy from lightening, heat from volcanoes, and UV light and the chemicals in the atmosphere combined to form the first large organic molecules such as amino acids and carbs.Another theory is that these large molecules formed in hydrothermal vents.First protocells form in the seas: these new compounds washed into the seas and sat for millions of years to form the first DNA and protocells
9Biological Evolution3.5 to 3.8 billion years ago, well below the surface of the sea away from harmful UV radiation the first prokaryotic cells formed: PROKARYOTIC2.3 to 2.5 billion years ago the first cyanobacteria appear and they: photosynthesizebillion years ago oxygen: formed from cyanobacteria1.2 billion years ago we see the first eukaryotic cells arrive, which could reproduce sexually and produce a wide variety of organismsmillion years ago we see: the first land plants and animalsHow do we know what organisms were around:Fossil recordRadiometric dating of rocks near the fossils
10Modern humans (Homo sapiens) appear about 2 seconds before midnight Age of mammalsRecorded human history begins 1/4 second before midnightAge of reptilesInsects and amphibians invade the landOrigin of life (3.6–3.8 billion years ago)Plants invade the landFossils become abundantFossils present but rareEvolution and expansion of lifeFig. 5.4, p. 105
11EvolutionHeritable changes in a population’s genetic make-up through successive generationsAn overwhelming majority of biologists believe that this is the best explanation for the changes that have occurred over the last 3.7 billion years and also for why life on earth today is so diverse.The theory of evolution is based on the idea that all species descended from other species
122nd Generation1st generationGG, Gg = green beetlegg = brown beetleEvolution= shift in gene frequency in a population
13Macroevolutionlong term, large scale evolutionary changes among a group or species. One species leads to the appearance of many other species.
14Genetic persistence:The inheritance of DNA molecules from the origin of the first cells through all subsequent lines of descent which is the basis of the unity of life
15Genetic divergenceLong term changes in lineage’s of species, which are the basis of the diversity of life
16Genetic lossesThe steady background extinction or relatively abrupt catastrophic loss of lineage
17Microevolution: the small genetic changes that a population experiences How does microevolution work?
18It is the development of genetic variability in a population A population’s gene pool is the sum total of all genes possessed by the individuals of the population’s species
19Microevolution is a change in the species gene pool over time
20Members of a population have different molecular forms of the same gene called alleles. Sexual reproduction leads to a shuffling of alleles. As a result each individual has a different combination of alleles. This is called genetic variability
21Microevolution works through a combination of four processes: every Mutation, natural selection, gene flow, genetic drift
22Mutation:The source for all new alleles (genes) is mutations, which are random changes in the structure of DNA molecules in a cell.Adaptation: any genetically controlled trait that helps an organism survive and reproduce under a given set of environmental conditionsEvery so often a mutation is beneficial and the result is a new genetic trait that will ensure the survival of offspring betterMutations are rare
23Natural SelectionDifferential reproduction: because of random shuffling or recombination of genes, certain individuals may by chance have one or more beneficial adaptations that allow them to survive under various environmental conditions. As a result they are more likely to reproduce than individuals that do not have such adaptations.
24Natural selection does not create favorable genes; instead it favors some individuals over others by acting on genes already in the gene pool.Natural selection occurs when the combined effects of adaptation and differential reproduction result in a particular beneficial gene becoming more common in succeeding generations
25Three types of Natural Selection: Directional: it pays to be different: changing environmental conditions cause gene frequencies to shift so that individuals with traits at one end of the normal range become more common than midrange species
26Directional Natural Selection Snail colorationbest adaptedto conditionsAverageNew averagePreviousaverageNaturalselectionNumber of individualsNumber of individualsAverage shiftsColoration of snailsColoration of snailsProportion of light-coloredsnails in population increasesFig. 5.6a, p. 110
27Stabilizing: it pays to be average: in a stable environment species that have abnormal genes have no advantage and tend to be eliminated.
28Stabilizing Natural Selection Light snailseliminatedDark snailseliminatedNaturalselectionSnails withextremecoloration areeliminatedNumber of individualsNumber of individualsColoration of snailsColoration of snailsAverage remains the same,but the number of individuals withintermediate coloration increasesFig. 5.6b, p. 110
29Diversifying: it doesn’t pay to be normal: when environmental conditions favor individuals at both extremes of the genetic spectrum and sharply reduce the number of mid-range individuals.
30Diversifying Natural Selection Intermediate-colored snailsare selected againstSnails with light and darkcolors dominateNaturalselectionLightcolorationis favoredDarkcolorationis favoredNumber of individualsNumber of individualsColoration of snailsColoration of snailsNumber of individualswith light and dark colorationincreases, and the number withintermediate coloration decreasesFig. 5.6c, p. 110
32Genetic drift:involves change in a genetic composition of a population by chance and is important in small populations
33Co evolutionWhen populations of two different species interact over a long time, changes in the gene pool of one species can lead to changes in the gene pool of the other species. For example:
34An Example of evolution by natural selection: The peppered moths of EnglandDuring the industrial revolution.
35Coevolution gone awry Coevolution Coevolution can occur between animals that have a symbiotic relationship as well those who have a predator prey relationshipCoevolution gone awry
36Ecological Niches and Adaptation Ecological niche: the species way of life or the functional role of the species in an ecosystem. For example:a. types of resources usedb. range of tolerancec. how it interacts with components of the ecosystemd. its role in flow of energy and matter cycling
37Fundamental vs realized niche Fundamental niche vs. realize niche: Your fundamental niche is all the possible conditions that you can live under. Your realized niche is how you are actually living. For example: you may be capable being a star, but competition keeps you from getting the job
38Niche separation Number of individuals Generalist species with a broad nicheGeneralist specieswith a narrow nicheNichebreadthRegion ofniche overlapResource useFig. 5.7, p. 111
39Generalist species vs. Specialist species Generalist: have very broad niches and eat a variety of foods and can live in a variety of places under differing conditions. For example cockroachSpecialist: narrow niche, may only be able to live in one type of habitat or eat only one type of food. For example: panda bearIs it better to be a generalist or a specialist?
40SpeciationTwo species arise from one species in response to changes in environmental conditions.The mechanism for speciation occurs in two phasesGeographic isolation: occurs when two populations of a species becomes physically separated for long periodsReproductive isolation: occurs as mutation and natural selection occur independently in two separated populations of the same species. Eventually, the changes are so great that two groups will no longer interbreed.
41Different environmental conditions lead to different Adapted to coldthrough heavierfur, short ears,short legs, shortnose. White furmatches snowfor camouflage.NorthernpopulationArctic FoxSpreadsnorthwardandsouthwardseparatesDifferent environmentalconditions lead to differentselective pressures and evolutioninto two different species.Early foxpopulationAdapted to heatthrough lightweightfur and long ears,legs, and nose, whichgive off more heat.SouthernpopulationGray FoxFig. 5.8, p. 113
42Convergent evolution: Two separate species will evolve separately to create animals with similar characteristics. Species that have similar niches tend to evolve similar sets of traits in response similar environmental conditions. For example:
43Divergent evolution: speciation creates separate species
44ExtinctionWhen environmental changes occur species either evolve or cease to exist and their genetic material is permanently lost.Extinction patterns have been caused by large-scale movements of the continents and gradual climate changes like those from meteors and volcanoes.All species inevitably disappearBackground extinction is the low rate that species constantly disappear. It is the normal level. Approx.3 species per yearMass extinction: an abrupt rise in extinction rates above the background rate. It is catastrophic, global and often results in 25% to 70% loss of speciesThere are have been five previous mass extinctions and we are currently in the six mass extinction, which is being caused by humans.
45Speciation minus extinction equals biodiversity Although extinction is a natural process, humans have sped up the process and we have lost a lot of genetic materialThis mass extinction is different from previous extinctions in the following ways:1. First time it has ever been caused by one species2. This is the fastest it has every happened3. Adaptive Radiation will be slow after because we are destroying habitats
46Bar width represents relative number of living species EraPeriodMillions ofyears agoBar width represents relativenumber of living speciesSpecies and families experiencingmass extinctionExtinctionCurrent extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.QuaternaryTodayTertiaryCenozoicExtinction65Cretaceous: up to 80% of rulingreptiles (dinosaurs); many marinespecies including manyforaminiferans and mollusks.CretaceousJurassicMesozoicExtinction180Triassic: 35% of animal families, includingmany reptiles and marine mollusks.TriassicExtinction250Permian: 90% of animal families, includingover 95% of marine species; many trees,amphibians, most bryozoans andbrachiopods, all trilobites.PermianCarboniferousExtinction345Devonian: 30% of animal families,including agnathan and placodermfishes and many trilobites.DevonianPaleozoicSilurianOrdovicianExtinction500Ordovician: 50% of animal families,including many trilobitesCambrianFig. 5.10, p. 115
47Adaptive RadiationAdaptive radiation: an extinction of one species is an opportunity for another species and after a mass extinction there is a period in which numerous new species can evolveSpeciation and extinction affects biodiversity:
49How does Macroevolution occur? A. Macroevolution is concerned with how evolution takes place above the level of species and over long periods of time and shows how small changes can lead to the eventual creation of many different species, genera and families.B. Gradualist model: theory that says macro evolutionary change occurs over many millions of yearsC. Punctuated Equilibrium: opposing theory that says there are long periods of relatively punctuated with brief periods of very rapid changes.D. In reality it is probably a combination of both
50Common Misconceptions about Evolution “Survival of the fittest” is often misinterpreted as “survival of the strongest”. In biological terms fitness is a measure of reproductive success and the ones with the most descendants are the fittest. Natural selection is not "tooth and claw” competition.“Humans evolved from apes”, this is not true. Apes and humans have a common ancestor from which both are descended.Nature has a grand plan in which species become progressively more perfect, natural selection is random and there is no goal of perfection.
511) Before 5 mya: In Africa, our ancestral lineage and the chimpanzee lineage split. 2) Before 4 mya: The hominid Australopithecus anamensis walked around what is now Kenya on its hind legs.3) >3 mya: Australopithecus afarensis (“Lucy”) lived in Africa.4) 2.5 mya: Some hominids made tools by chipping stones to form a cutting edge. There were perhaps four or more species of hominid living in Africa.5) 2 mya: The first members of the Homo clade, with their relatively large brains, lived in Africa6) 1.5 mya: Hand axes were used. Also, hominids had spread out of Africa and into much of Asia and Europe. These hominids included the ancestors of Neanderthals (Homo neanderthalensis) in Europe and Homo erectus in Asia.7) 100,000 years ago: Human brains reached more or less the current range of sizes. Early Homo sapiens lived in Africa. At the same time, Homo neanderthalensis and Homo erectus lived in other parts of the Old World.8) 50,000 years ago: Human cultures produced cave paintings and body adornment, and constructed elaborate burials. Also, some groups of modern humans extended their range beyond Africa.9) 25,000 years ago: Other Homo species had gone extinct, leaving only modern humans, Homo sapiens, spread throughout the Old