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1 Name ________________________ Date ______________ Pd _____ Evolution NotesName ________________________Date ______________Pd _____
2 The History of Life on Earth Earth has been home to living things for about 3.8 billion yearsFossils provide evidence of earlier lifeFossils – the remains of organisms preserved in the EarthTypes of Fossils:Hard body parts, such as boneMinerals replace parts of organismPrints made by organismsOriginal remains of entire organismFossilized BoneImprint FossilWoolly MammothInsect in Amber
3 History of Life Continued… Relative DatingAbsolute DatingThe age of fossils can be used to determine the history of life on EarthRelative Dating – by comparing one fossil with another fossil, it can be determined if one fossil was formed before or after anotherAbsolute Dating – by measuring radioactivity, the exact age of a fossil can be determined
4 History of Life Continued… Once the age of fossils is determined, the fossil record can be establishedFossil Record – the information about the fossils found in a particular locationThe fossil record can be used to determine when a species lived or died
5 The History of Life Continued… The fossil record indicates that more complex organisms developed on Earth over timeAt first, all living things lived in the oceansFirst came unicellular organisms (3.8 billion years ago)These are organisms made of a single cell.Over time, different types of unicellular organisms developed – bacteria, archaea, protists, etc.Then came multicellular organisms (1.2 billion years ago)These are organisms made of many cellsThen came life on land (500 million years ago)500 million years ago the first multicellular organisms moved from water to landFirst came plants, fungi, and insects, then came amphibians and reptiles, finally came birds and mammals
6 The History of Life Continued… Although organisms were constantly developing, Earth’s history also includes mass extinctionsMass Extinction – when huge numbers of species have died or become extinct in a very short timePermian Extinction (250 million years ago)In this extinction, 90% of the species living in the oceans became extinctOccurred when Earth’s land masses joined togetherCretaceous Extinction (65 million years ago)In this extinction, more than half of the species on Earth (including dinosaurs) became extinctThis was caused by a meteorite collision – the evidence of this is the Chicxulub Crater
8 Life Changes Over TimeBecause of the fossil record, in the past 200 years scientists have explored the idea of evolutionEvolution – the process through which species change over timeEvolution results from a change in DNA (a mutation)Jean Baptiste de Lamarck (early 1800s) – he was the first scientist to propose an idea of how life evolvedHe proposed that an organism can acquire a trait during its lifetime and pass that trait on to its offspringThis idea could not be supported by evidence so it was not accepted as scientific factJean Baptiste de LamarckLamarck’s Giraffes
9 Life Changes Over Time Continued… Charles Darwin – A British Naturalist who spent 5 years on the H.M.S. BeagleHe observed animals, especially on the Galapagos IslandsFor example, when observing finches, he saw a variety of beak shapes that were adapted to what they ate and where they livedCharles Darwin
10 Life Changes Over Time Continued… Darwin proposed the idea of evolution through the process of natural selectionNatural Selection – members of a species that are best suited to their environment survive and reproduce at a higher rate than other members of the speciesNatural selection occurs through the continuous cycle of genetic mutation and reproductionKey Principles of Natural Selection:OverproductionVariationAdaptationSelection
11 Natural Selection Overproduction: Variation: When a plant or animal reproduces, it usually makes more organisms than can surviveVariation:Within a species there are natural differences in traits caused by differences in DNAThese natural differences are passed from one generation to the nextSometimes there is a change in DNA, a mutation, that is also passed onVariationOverproduction
12 Natural Selection Continued… Adaptation:Sometimes a mutation occurs that makes an organism better able to survive than othersAdaptation – any inherited trait that gives an organism an advantage in its particular environmentSelection:Species with an adaptation are more likely to survive and reproduceThis adaptation becomes more common with each generationThe environment is selecting for this traitAdaptationSelection
13 EvolutionThrough the process of natural selection, new species develop from earlier speciesIn 1859, Darwin’s observations resulted in the publication of On the Origin of the Species, a book about evolution through natural selectionSpeciation: evolution of new species from an existing speciesMay occur when the environment changesIsolation is essential to speciationSpeciation of SalamandersIsolation:For a species to develop into two new species, two populations must be prevented from reproducing with each otherWhen separate, they each develop different mutations, which, over time, result in different species
14 Evidence for Evolution Observations provide evidence for theoriesIn order to understand the importance of Darwin’s work, it is important to understand the term scientific theoryScientific Theory:A statement based on fact and observationA theory that has been widely accepted is used to explain and predict natural phenomenaExamples of Scientific Theories:Theory of GravityThe Big Bang TheoryEvolution through Natural SelectionA scientific theory is NOT a guess or an opinion!!!
15 Evidence for Evolution Fossil evidence for the evolution of the horseFossil evidence supports evolutionGeographic evidence about fossils shows that two species with a common ancestor can develop differently in different locationsAncestor – an early form of an organism from which later forms descendScientists can determine modern plants and algae have a common ancestor in fossil algae
16 Evidence for Evolution Continued Biological evidence supports evolutionThe structure of living things:Vestigial organs – physical structures that were fully developed and functional in an earlier group of organisms but are reduced and unused in later speciesExample – hip and femur bones in whalesHomologous Structures – similar structures with different functions:Many different species share similar structures, but they are used differently by each speciesThis indicates a common ancestorExample – arms and wingsHomologous StructuresVestigial Organ
17 Evidence for Evolution Continued… Biological Evidence Continued…Development of living things:Similarities in development – scientists have seen that many organisms are very similar during early stages of development, when an embryoSimilarities in DevelopmentgeneticGenetic evidence supports evolutionScientists can tell how closely related organisms are by comparing their DNAExample – clock gene
18 CladogramsCladogram – a visual representation of the evolutionary relationship among species based on the evidence collectedShow how closely (or distantly) related two species areShow which species evolved before or after other speciesShow the similarities between more closely related species
19 Evolution of Humans Early humanlike species: Ardipithecus – one of the oldest hominid fossils foundAustralopithecus afarensis – Lucy – 3.5 million years old, 1 meter tallFossils are 500,000 to 6 million years oldEach species is more humanlike than the one beforeOver time, some hominids went extinct and others evolved. Eventually, the only one left was us, Homo sapiens.
20 Evolution of Humans Continued… Neanderthals and Cro Magnons lived at the same time as modern humans, but went extinctNeanderthals – Homo neanderthalensisLived 130,000 to 35,000 years agoLarger skulls with sloping foreheads, but shorter than modern humansCro Magnons - Homo sapiens sapiensLived 35,000 to 10,000 years agoTall with large and round skullsSkilled hunters and toolmakersModern humans:Modern humans are Homo sapiens (“wise human”)First fossil evidence of modern humans is about 100,000 years oldCro Magnon Skull
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