3Today’s Objective (learning goal) To identify how fossils are used as evidence in changes within a species.
4Section 14.1 Summary – pages 369-379 Clues to the PastAbout 95 percent of the species that have existed are extinct—they no longer live on Earth.The oldest rocks that have been found on Earth formed about 3.9 billion years ago.Among other techniques, scientists study fossils to learn about ancient species.Section 14.1 Summary – pages
5Section 14.1 Summary – pages 369-379 Fossils are evidence of organisms that lived long ago that are preserved in Earth’s rocks.TYPES OF FOSSILSFossils TypesFormationA trace fossil is any indirect evidenceTrace fossilsleft by an animal and may include afootprint, a trail, or a burrow.When minerals in rocks fill a spaceCastsleft by a decayed organism, they makea replica, or cast, of the organism.A mold forms when an organism isMoldsburied in sediment and then decays,leaving an empty space.Petrified fossilsPetrified-minerals sometimes penetrateand replace the hard parts of an organismAmber-PreservedorAt times, an entire organism wasquickly trapped in ice or tree sap thatfrozen fossilshardened into amber.Section 14.1 Summary – pages
6Section 14.1 Summary – pages 369-379 Paleontologists, scientists who study ancient life, are like detectives who use fossils to understand events that happened long ago.They use fossils to determine the kinds of organisms that lived during the past and sometimes to learn about their behavior.Section 14.1 Summary – pages
7Section 14.1 Summary – pages 369-379 Paleontologists also study fossils to gain knowledge about ancient climate and geography.By studying the condition, position, and location of rocks and fossils, geologists and paleontologists can make deductions about the geography of past environments.For example, if they find a fossil of a plant that resembles a present day plant that can only survive in mild weather, they can infer that the conditions were mild when that plant was living as well.Section 14.1 Summary – pages
8Section 14.1 Summary – pages 369-379 For fossils to form, organisms usually have to be buried in mud, sand, or clay soon after they die.Fossils are not usually found in other types of rock because of the ways those rocks form.For example, the conditions under which metamorphic rocks form often destroy any fossils that were in the original sedimentary rock.Most fossils are found in sedimentary rocks These rocks form at relatively low temperatures and pressures that may prevent damage to the organism.Section 14.1 Summary – pages
9Section 14.1 Summary – pages 369-379 Few organisms become fossilized because, without burial, bacteria and fungi immediately decompose their dead bodies.Occasionally, however, organisms do become fossils in a process that usually takes many years.Section 14.1 Summary – pages
10Section 14.1 Summary – pages 369-379 A Protoceratops drinking at a river falls into the water and drownsSediments from upstream rapidly cover the body, slowing its decomposition. Minerals from the sediments seep into the body.Over time, additional layers of sediment compress the sediments around the body, forming rock. Minerals eventually replace all the body’s bone material.Earth movements or erosion may expose the fossil millions of years after it formed.Section 14.1 Summary – pages
11Section 14.1 Summary – pages 369-379 Scientists use a variety of methods to determine the age of fossils.One method is a technique called relative dating.If the rock layers have not been disturbed, the layers at the surface must be younger than the deeper layers.Section 14.1 Summary – pages
12Section 14.1 Summary – pages 369-379 Thus, the fossils in the top layer must also be younger than those in deeper layers.Using this principle, scientists can determine relative age and the order of appearance of the species that are preserved as fossils in the layers.Section 14.1 Summary – pages
13Section 14.1 Summary – pages 369-379 To find the specific ages of rocks, scientists use radiometric dating techniques utilizing the radioactive isotopes in rocks.Radioactive isotopes are atoms that are unstable and break down, or decay, over time, giving off radiation.Section 14.1 Summary – pages
14Section 14.1 Summary – pages 369-379 Because every radioactive isotope has a characteristic decay rate, scientists use the rate of decay as a type of clock.The half-life of an isotope is the time it takes for half of the isotope in a sample to decayA radioactive isotope forms a new isotope after it decays.Section 14.1 Summary – pages
15If you can know the amount of an unstable isotope that was in a sample And you know the rate at which that isotope decaysAnd you can measure the amount of that isotope presently in the sampleYou can figure out how old the sample is
16Animals that eat the plants get 14C from the plants they eat 14C is used to date organic samples like wood, hair, shells, and other plant and animal productsAtmospheric 14C is incorporated into organic molecules by plants during photosynthesisAnimals that eat the plants get 14C from the plants they eatBlack dots represent carbon, grey dots carbon14
17Section 14.1 Summary – pages 369-379 Scientists use carbon-14 to date fossils less than years old.Carbon-14 (14C) is an isotope of carbon, that has 6 protons and 8 neutrons14C decays to 14N at a constant rateEvery 5,730 years half the 14C in a sample will emit a beta particle (electron) and decay to 14NThus 5,730 years is called the half life of 14CSection 14.1 Summary – pages
18For example, if the half-life of 14C (Carbon 14) is 5,730 years and a sample today has 1,000 14C atomsafter 5,730 years C atoms will remain
27Section 14.1 Summary – pages 369-379 Scientists use potassium-40, a radioactive isotope that decays to argon-40, to date rocks containing potassium bearing minerals.Based on chemical analysis, chemists have determined that potassium-40 decays to half its original amount in 1.3 million years.Section 14.1 Summary – pages
28Section 14.1 Summary – pages 369-379 Scientists always analyze many samples of a rock using as many methods as possible to obtain consistent values for the rock’s age.Errors can occur if the rock has been heated, causing some of the radioactive isotopes to be lost or gained.Section 14.1 Summary – pages
29Section 14.1 Summary – pages 369-379 The fossil record indicates that there were several episodes of mass extinction that fall between time divisions.A mass extinction is an event that occurs when many organisms disappear from the fossil record almost at once.Section 14.1 Summary – pages
31PhylogeneticsThe study of evolutionary relationships among groups of organisms (species, populations), which are discovered through:Molecular sequencing data – DNA sequencing and protein synthesisMorphological data matrices – homologous structures, analogous structures, and embryonic development
34Homologous Structures Scientists Noticed Animals With Backbones Had Similar Bone StructureSame Structures Different FunctionArms, Wings, Legs, FlippersLimb Bones Develop In Similar PatternsHelp Scientist Group Animals
41Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species, usually a result of diffusion of the same species to different and isolated environments that blocks the gene flow among the distinct populations. This allows differentiation of characteristics through genetic drift and natural selection.
42Convergent evolution is the process by which unrelated or distantly related organisms evolve similar body forms, coloration, organs, and adaptations.
43Adaptive radiation is the evolution of an animal or plant group into a wide variety of types adapted to specialized modes of life.
46Puncuated Equilibrium A hypothesis in evolutionary biology which proposes that most species will exhibit little net evolutionary change for most of their geological history, remaining in an extended state called stasis. When significant evolutionary change occurs, the hypothesis proposes that it is generally restricted to rare and geologically rapid events of branching speciation (the evolutionary process by which new biological species arise) called cladogenesis. Cladogenesis is the process by which a species (organisms that breed and produce offspring that are also fertile) splits into two distinct species, rather than one species gradually transforming into another.
51The term coevolution is used to describe cases where two (or more) species reciprocally affect each other’s evolution.Coevolution is likely to happen when different species have close ecological interactions with one another. These ecological relationships include:1. Predator/prey and parasite/host2. Competitive species3. Mutualistic species
52Genetic drift -random fluctuations in the numbers of allele differences in a population *Takes place when the occurrence of alleles, increases and decreases by chance over time.*Typically occurs in small populations, where infrequently occurring alleles face a greater chance of being lost*Will continue until the involved allele is either lost by a population or until it is the only allele present in a population at a particular location*Can cause a new population to be genetically distinct from its original population, which has led to the hypothesis that genetic drift plays a role in the evolution of new species.
54Gene flow (also known as gene migration) is the transfer of alleles or genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies (the proportion of members carrying a particular variant of a gene).Immigration may also result in the addition of new genetic variants to the established gene pool of a particular species or population.
55Mutations - when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. Mutation causes a high rate of natural selection in a changing environment.Natural Selection the gradual process by which biological traits become either more or less common in a population as a function of the effect of inherited traits on the reproductive success of organisms interacting with their environment
57Stabilizing Selection, extreme varieties from both ends of the frequency distribution are eliminated. The frequency distribution looks exactly as it did in the generation before
58Directional Selection - individuals at one end of the distribution of beak sizes do especially well, and so the frequency distribution of the trait in the subsequent generation is shifted from where it was in the parental generation
59Diversifying (disruptive) Selection - both extremes are favored at the expense of intermediate varieties. This is uncommon, but of theoretical interest because it suggests a mechanism for species formation without geographic isolation
60Evolution By Natural Selection The Struggle for ExistenceSurvival of the FittestDescent with Modification
61The Struggle for Existence Malthus’ InfluenceHigh Birth Rates & Limited Resources Would Force Life & Death CompetitionEach Species Struggles For:FoodLiving SpaceResources
62Survival of the Fittest FitnessAbility of an Individual To Survive &ReproduceAdaptationInherited Characteristic That Increases an Organisms Chance for Survival
63Survival of the Fittest Adaptations Can Be:PhysicalSpeed, Camouflage, Claws, Quills, etc.BehavioralSolitary, Herds, Packs, Activity, etc.
64Survival of the Fittest Fitness Is Central To The Process Of EvolutionIndividuals With Low FitnessDieProduce Few OffspringSurvival of the FittestAKA Natural Selection
65Survival of the Fittest Key ConceptOver Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment
66Natural Selection Cannot Be Seen Directly It Can Only Be Observed As Changes In A Population Over Many Successive GenerationsRadiationFossil Record
69Population Growth Thomas Malthus, 1798 Economist Observed Babies Being Born Faster Than People Were DyingPopulation vs. Food Supply
70Population Growth Key Concept Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For EveryoneFamine, PestilencePolitical Instability, WarDeath Rate Will Increase To Balance Population & Food Supply
71Population GrowthDarwin Realized Malthus’s Principles Were Visible In Nature.Plants & Animals Produce Far More Offspring Than Can Be Supported.Most DieIf They Didn’t – Earth Would Be Overrun
72Natural Variation & Artificial Selection Abandoned The Idea That Species Were Perfect & UnchangingObserved Significant Variation in All Species ObservedObserved Farmers Use Variation To Improve Crops & Livestock (Selective Breeding)
73Natural Variation & Artificial Selection Differences Among Individuals Of A SpeciesArtificial SelectionSelective Breeding To Enhance Desired Traits Among Stock or Crops
74Natural Variation & Artificial Selection Key ConceptIn Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful
77Evidence of Evolution Key Concept Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In:The Fossil RecordThe Geographical Distribution of Living SpeciesHomologous Structures of Living OrganismsSimilarities In Early Development
78Geographic Distribution of Living Species Different Animals On Different Continents But Similar Adaptations To Shared Environments
79Darwin's TheoryIndividual Organisms In Nature Differ From One Another. Some Of This Variation Is InheritedOrganisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do Not Reproduce
80Darwin's TheoryBecause More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited ResourcesBecause Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence
81Darwin's TheoryIndividuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring.Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species
82Darwin's TheorySpecies Alive Today Have Descended With Modifications From Species That Lived In The PastAll Organisms On Earth Are United Into A Single Tree Of Life By Common Descent