Presentation on theme: "The Theory of Evolution"— Presentation transcript:
1 The Theory of Evolution Chapter 15The Theory of Evolution
2 & Evidence for Evolution 15-1 Natural Selection& Evidence for EvolutionThe idea that life evolves was firstProposed by Lucretius 1900 years ago!
3 His idea was not fully considered until The middle of the 1800’s. In 1859, the English naturalistCharles Darwin published convincingEvidence that species evolve, andHe proposed a reasonable mechanismExplaining how evolution occurs.
4 Like all scientific theories, the theory Of evolution has developed overDecades of experimental data.Today almost all scientists acceptThat evolution is the basis for theDiversity of life on Earth.
5 The theory of evolution has 4 parts: Variation exists with the genes ofEvery population of species(the results of mutation)2) In a particular environment, someIndividuals of a population or speciesAre better suited to survive andHave more offspring than others.
6 3) Over time, the traits that make Certain individuals of a population Able to survive and reproduceTend to spread in that population.4) There is clear proof from fossilsAnd many other sources that livingSpecies evolved from organismsThat are extinct.
7 Naturalist for the naval voyage of The HMS Beagle. In 1831, Darwin became theNaturalist for the naval voyage ofThe HMS Beagle.The purpose of the voyage was toSurvey the coast of South America.
8 During his voyage on the Beagle, Darwin found evidence that challenged The traditional belief that speciesAre unchanging.As Darwin visited the many placesOn his voyage, he saw things thatSeemed as if they could only beExplained by a process ofgradual change.
9 On the Galapagos Islands, Darwin Discovered different varieties of Finches that had different beaks.The birds looked similar, but hadEvolved beaks that suited theEnvironment where they ate.
11 When Darwin returned from his Voyage, he continued his lifelong Study of plants, animals, and geology.He didn’t report his findings called“evolution” until much later.
12 After reading an essay by Thomas Malthus, Darwin made a key association,Individuals that have physical orBehavioral traits that better suitTheir environmental are more likelyTo survive and reproduce than thoseThat do not have such traits.
13 Darwin called this process by which Populations change in response To their environment, natural selection.The changing of a species that resultsIn its being better suited to itsEnvironment is called adaptation.
14 In 1859, Darwin finally wrote down His ideas of evolution and natural Selection in a book called“On the Origin of Species byMeans of Natural Selection”Many people were deeply disturbed byIt, including the church because itHints that humans may have evolved from apes.
15 Darwin’s ideas have been updated… Natural selection causes changeWithin population.Such as, broccoli, cauliflower,Brussels sprouts, and cabbage allCome from the same plant!
16 In other words, natural selection Causes the frequency of certain Alleles in a population to increaseOr decrease over time.Isolation leads to species formation.
17 Isolation is the condition in which 2 populations of the same species Cannon breed with one another.This happens all the time, and is whyThere are many different types ofSquirrels, and is the reason thatDarwin saw different types ofThe same bird!
19 Extinction leads to species replacement. Over long periods of time, events suchAs climate changes and naturalDisasters result in some speciesBecoming extinct, which meansThat they disappear permanently.
21 Fossils provide an objective record Of evolution. A fossil is the preserved orMineralized remains or imprintOf an organism that lived long ago.
22 Today Darwin’s theory is almost Universally accepted, based on a Large body of supporting evidence,Most scientists agree on theFollowing 3 points…1) Earth is about 4.5 billion years old.2) Organisms have inhabited Earth forMost of its history.3) All organisms living today evolvedFrom earlier, simpler life-forms.
23 Although the fossil record will never Be complete, it presents strong Evidence that evolution hasTaken place.Paleontologists, scientists that studyFossils, can determine that age ofFossils fairly accurately by usingRadiometric dating.
24 Biological molecules contain a record Of evolution. A common ancestor is a speciesFrom which 2 or more speciesHave diverged.A phylogenetic tree shows howorganisms are relatedthrough evolution.
25 Anatomy and development Suggest common ancestry. Comparisons of the anatomy ofDifferent types of organisms oftenReveal basic similarities inBody structures.
26 For example, sometimes bones (or other structures) are present In an organism but are reduced inSize and either have no use orHave a less important function.Such structures are considered to beEvidence of an organism’sEvolutionary past.
27 These structures are called Vestigial structures.
28 Does evolution occur in spurts? The model of evolution in whichGradual change over a long period ofTime leads to species formationIs called gradualism.The model of evolution in which periodsOf rapid change in species is separatedBy periods of no change is calledPunctuated equilibrium.
29 Darwin wrote: “Can we doubt… that Individuals having any advantage, However slight, over others, wouldHave the best chance of survivingAnd of procreating their kind?”
30 There are 5 main elements to Natural Selection… 1) All species have genetic variation.2) The environment presents manyDifferent challenges to an individual’sAbility to reproduce.
31 3) Organisms tend to produce more Offspring than their environment Can support; thus, individuals of aSpecies often compete withOne another to survive.4) Individuals within a population thatAre better able to cope with theChallenges of their environment tendTo leave more offspring than thoseLess suited to the environment.
32 5) The traits of the individuals Best suited to a particular Environment tend to increaseIn a population over time.
34 The key lesson scientists have learned About evolution is that the Environment dictates the directionAnd amount of change.A well studied example of naturalSelection in action isIndustrial melanism.
35 Industrial melanism is the darkening Of populations of organisms over Time in response to industrial pollution.The best known case is theEuropean Peppered Moth.
36 The formation of new species Begins with small changes. The accumulation of differencesBetween groups is called divergence.Biologists call the process by whichNew species form speciation.
37 Overtime, populations of the same Species that differ genetically Because of adaptations to differentLiving conditions become whatBiologists call ecological races.Eventually races may become soDifferent that they can no longerInterbreed successfully, biologistsThen consider them a new species.
38 What keeps a new species separate? Reproductive isolation is the inabilityOf formerly interbreeding groupsTo mate or produce fertile offspring.This may happen due to geographicalReasons, or environmental reasons.