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Charles Darwin (1809-1882) Sailed around the world 1831-1836.

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Presentation on theme: "Charles Darwin (1809-1882) Sailed around the world 1831-1836."— Presentation transcript:


2 Charles Darwin (1809-1882) Sailed around the world 1831-1836

3 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!!

4 How did tortoises and birds differ among the islands of the Galapagos? Each island had its own type of tortoises and birds that were clearly different from other islands

5 Galapagos Turtles

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

7 Evolution is a Theory – Just like Gravity! Evolution is a well supported explanation of phenomena that have occurred in the natural world A theory in science is a well tested hypothesis, not just a guess BUT an explanation to an observation

8 Theories Theories have been tested many times by many scientists, A theory BEST explains a certain observation People have tried to refute Charles Darwin’s theory of evolution, but so far have been unsuccessful, therefore it remains

9 Who influenced Darwin’s ideas? 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

10 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!

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


13 Darwin finally published his ideas in 1859 Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.

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

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




19 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)


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

22 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

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

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 Relative vs. Absolute Dating

26 Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossils Drawbacks – provides no info about age in years

27 Absolute dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain Drawbacks - part of the fossil is destroyed during the test

28 Carbon-14 Dating

29 Fossil Formation SG

30 Primate Fossils AustralopithecusHomo erectusHomo sapien

31 Primate Brain Capacity

32 Primate Bone structure

33 Human Relatives

34 Australopithecus afarensis

35 Homo habilis = handy human 1.5 to 2 mya Homo erectus 1.6 mya bipedal

36 Neanderthals 35,000 to 100,000 ya Cro-Magnon 35,000 to 40,000 ya

37 Modern Homo sapien (fully modern fossils 100,000 ya)

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


40 Evidence of Evolution Homologous Body Structures –Structures that have different mature forms but develop from the same embryonic tissues e.g. Wing of bat, human arm, leg of turtle Turtle Alligator Bird

41 Homologous Body Structures

42 Vestigial Organs –traces of homologous organs in other species –Organ that serves no useful function e.g. Appendix

43 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.

44 Embryological development



47 Natural Selection Acts on PHENOTYPE not genotype Only the Phenotype of an organism determines if the organism survives

48 Natural Selection The allele for long tongue (L) is dominant over the short tongue allele (l). Lizards that have long tongues have a better shot of surviving because the are better at catching dinner (flies). Of the lizards listed below, which have a better shot of surviving? LL, Ll, ll

49 Natural Selection The allele for long tongue (L) is dominant over the short tongue allele (l). Lizards that have long tongues have a better shot of surviving because the are better at catching dinner (flies). Of the lizards listed below, which have a better shot of surviving? LL, Ll, ll BOTH LL and Ll have long tongues, so natural selection acts on the phenotype NOT the genotypes

50 Natural Selection Each finch is best adapted to feed itself in the environment that they lived in. Does it matter if they are homozygous or heterozygous for the trait?

51 Recessive Lethal Alleles An allele that is lethal will cause a death in an individual if homozygous for the allele Example: Tay-Sachs Disease, is an autosomal recessive genetic disorderautosomal recessivegenetic disorder Tay-Sachs disease is caused by a genetic mutation on the HEXA gene on chromosome 15 mutationHEXA chromosome 15

52 Recessive lethal diseases Recessive lethal diseases are not very common, even though an organism with a lethal homozygous disorder will die before reproducing the lethal allele remains in the gene pool… Why?

53 How do you Get Tay-Sach’s disease?

54 “Carriers” A “carrier” of a disease is a heterozygous individual. The individual expresses the non-lethal normal allele BUT still carries a copy of the lethal allele. Two heterozygous individuals have a ¼ chance of getting a homozygous recessive individual, try the cross.


56 Mutations Can be beneficial because the create genetic variety Can be harmful because they can lead to an abnormal protein production ARE random

57 As the environment changes, so must the traits that are best fit for it How does change occur? –Mutations –Crossing Over during Prophase I of meiosis –Sexual Reproduction The greater the genetic variety of a population the better the chances of that population surviving change

58 When the Earth changes too quickly When the environment changes quickly, organisms might not survive and may go extinct because they may no longer be fit for the “new” environment Having a diversity of organisms gives the species a better chance of some of its organisms surviving Some examples…

59 Antibiotic resistant bacteria

60 Pesticide Resistance

61 Dinosaur extinction

62 Mass Extinction

63 Global Warming, are we heading towards another mass extinction?

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