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How did life begin? Miller and Urey’s Experiment  Passed sparks through a mixture of hydrogen methane ammonia and water  This produced amino acids –

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Presentation on theme: "How did life begin? Miller and Urey’s Experiment  Passed sparks through a mixture of hydrogen methane ammonia and water  This produced amino acids –"— Presentation transcript:

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2 How did life begin? Miller and Urey’s Experiment  Passed sparks through a mixture of hydrogen methane ammonia and water  This produced amino acids – the building blocks of life

3 E N D O S Y M B T I H O E T O I R C Y

4 Theory of Life cont. Endosymbiotic theory  eukaryotic cells arose from living communities formed by prokaryotic organisms  Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles

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6 Lamark Theory of acquired characteristics  Lamark said organisms acquired traits by using their bodies in new ways  These new characteristics were passed to offspring  Lamark was totally wrong!

7 Geologists: Hutton and Lyell  Fundamentalists said that the earth was around 6000 years old  Hutton and Lyell argued that the earth is many millions of years old b/c  layers of rock take time to form  processes such as volcanoes and earthquakes shaped the earth and still occur today

8 Malthus  Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone

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10 Charles Darwin ( ) Sailed around the world

11 2. What did Darwin’s Travels reveal  The diversity of living species was far greater than anyone had previously known!!  These observations led him to develop the theory of evolution!!

12 3.How did tortoises and birds differ among the islands of the Galapagos? Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches

13 Galapagos Tortoises

14 Evolution is when organisms change over time. So, modern organisms descended from ancient ones

15 Evolution is a Theory – Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural worldEvolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science must be supported by facts, it can’t be based on supposition.A theory in science must be supported by facts, it can’t be based on supposition.

16 Darwin finally published his ideas in 1859  Only when other naturalists were developing the same theory that he had did Darwin finally publish his findings.

17 Artificial Selection  nature provides variation, humans select variations that are useful.  Example - a farmer breeds only his best livestock

18 Natural Selection  The traits that help an organism survive in a particular environment are “selected” in natural selection

19 What color genes are in the beetle gene pool?

20 What’s happening to the color genes in the beetle gene pool? Why is this happening?

21 Explain why we say green beetles have been selected against while brown beetles have been selected for?

22 Natural Selection and Species Fitness  Overtime, natural selection results in changes in the inherited characteristics of a population.   These changes increase a species fitness (survival rate) Bottom line: Those that are best adapted to their environment survive to reproduce. Those that are best adapted to their environment survive to reproduce.

23 Evidence of Evolution 1.Fossil Record 2.Geographic Distribution of Living Species 3.Homologous Body structures 4.Similarities in Embryology 5. Vestigial organs

24 Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

25 Primate Fossils AustralopithecusHomo erectusHomo sapien

26 Remember PANGEA?

27 Evidence of Evolution 2.Geographic Distribution of Living Species Similar animals in different locations were the product of different lines of descent

28 Evidence of Evolution Geographic Distribution of Living Species Analogous Structures are the result of are the result of convergent evolution convergent evolution -Similar animals in different locations exhibit analogous structures due to similar environmental pressures. Eg. North American flying squirrel and the Australian sugar glider

29 This means they are analogous structures.

30 Convergent evolution  Fish: aquatic vertebrates  Dolphins: aquatic mammals  similar adaptations to life in the sea  not closely related Those fins & tails & sleek bodies are analogous structures!

31 Evidence of Evolution Adaptive radiation leads to Homologous Body Structures thru divergent evolution  Structures that have different mature forms but develop from the same embryonic tissues e.g. Wing of bat, leg of turtle & human arm, are similar by de- scent not function. Turtle Alligator Bird

32 Convergent evolution  Fish: aquatic vertebrates  Dolphins: aquatic mammals  similar adaptations to life in the sea  not closely related Those fins & tails & sleek bodies are analogous structures!

33 Homologous Body Structures………… …………are the result of divergent evolution

34 13. Evidence of Evolution Similarities in Embryology  In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

35 Embryological development

36 Vestigial organs  Modern animals may have structures that serve little or no function  remnants of structures that were functional in ancestral species  evidence of change over time  some snakes & whales show remains of the pelvis & leg bones of walking ancestors  eyes on blind cave fish  human tail bone This is not LaMarck’s loss from “disuse”!

37 Vestigial Structures in snakes

38 Vestigial Structures in whales

39 Molecular record Millions of years ago Horse/ donkey Sheep/ goat Goat/cow Llama/ cow Pig/ cow Rabbit/ rodent Horse/cow Human/rodent Dog/ cow Human/ cow Human/kangaroo Nucleotide substitutions  Comparing DNA & protein structure  universal genetic code!  DNA & RNA  compare common genes  cytochrome C (respiration)  hemoglobin (gas exchange) Closely related species have sequences that are more similar than distantly related species  DNA & proteins are a molecular record of evolutionary relationships Closely related species have sequences that are more similar than distantly related species  DNA & proteins are a molecular record of evolutionary relationships Why compare these genes?

40 Comparative hemoglobin structure Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans LampreyFrogBird Dog MacaqueHuman Why does comparing amino acid sequence measure evolutionary relationships?

41 Descent with Modification  Each living species has descended with changes from other species over time

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43 Summary of Darwin’s Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors

44 Variation in Populations 2 processes can lead to this: Mutations - change in DNA sequence Gene Shuffling – from sexual reproduction

45 Gene Pool Combined genetic info. of all members Allele frequency is # of times alleles occur

46 Genetic Drift changes populations… Random change in allele frequency causes an allele to become common

47  Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population

48 Evolution of Populations Occurs when there is a change in relative frequency of alleles………. in other words – a change in the contents of the gene pool

49  Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)

50  Nonrandom mating aka artificial selection: inbreeding and assortive mating (both shift frequencies of different genotypes)

51  Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

52 Single-Gene vs. Polygenic Traits Single-Gene: 2 Distinct Phenotypes Polygenic: Many Phenotypes (EG: tongue rolling)

53 Natural Selection on Polygenic Traits  Shifts to middle range  Shifts to 2 extremes  Shifts to 1 extreme

54 Are you more closely related to a turtle or a frog?

55 Natural selection in action  Insecticide & drug resistance  insecticide didn’t kill all individuals  resistant survivors reproduce  resistance is inherited  insecticide becomes less & less effective


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