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17–1The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different.

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Presentation on theme: "17–1The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different."— Presentation transcript:

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2 17–1The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different groups of organisms have changed over time

3 17–1The Fossil Record B.How Fossils Form Most fossils form in sedimentary rock. It is formed when exposure to rain, heat, wind and cold breaks down clay As layers of sediment build up over time, dead organisms may also sink to the bottom and become buried Conditions are right, the remains may be kept intact

4 17–1The Fossil Record C. Interpreting Fossil Evidence 1. Relative Dating- the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock (estimate age of fossils) 2. Radioactive Dating- scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains

5 17–1The Fossil Record D.Geologic Time Scale 1.Eras 2.Periods

6 Relative Dating Can determine Is performed by Drawbacks Absolute Dating Comparing Relative and Absolute Dating of Fossils Section 17-1 Compare/Contrast Table Go to Section: Imprecision and limitations of age data Difficulty of radio assay laboratory methods Comparing depth of a fossils source stratum to the position of a reference fossil or rock Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen Age of fossil with respect to another rock or fossil (that is, older or younger) Age of a fossil in years

7 Figure 17-2 Formation of a Fossil Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied. Section 17-1 Go to Section:

8 Figure 17-5 Geologic Time Scale EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quarternary Tertiary Cretaceous Jurassic Triassic Vendian650–544 Section 17-1 Go to Section:

9 EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quarternary Tertiary Cretaceous Jurassic Triassic Vendian650–544 Section 17-1 Figure 17-5 Geologic Time Scale

10 EraPeriodTime Permian Carboniferous Devonian Silurian Ordovician Cambrian (millions of years ago) EraPeriodTime (millions of years ago) EraPeriodTime (millions of years ago) 290 – – – – – – –present 65– –65 208– –208 Quarternary Tertiary Cretaceous Jurassic Triassic Vendian650–544 Section 17-1 Figure 17-5 Geologic Time Scale

11 17–2Earths Early History A.Formation of Earth Earths early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water

12 17–2Earths Early History B.The First Organic Molecules Organic molecules would have been able to be constructed but the oxygen in atmosphere was to reactive and would destroy any organic molecules that formed

13 17–2Earths Early History C.How Did Life Begin? 1. Formation of Microspheres- protection that allowed for the growth of organic molecules 2. Evolution of RNA and DNA- still unanswered but scientists are searching

14 17–2Earths Early History D.Free Oxygen The rise of oxygen in the atmosphere drove some life forms to extinction, while other life forms evolved new, more efficient metabolic pathways that used oxygen for respiration

15 17–2Earths Early History E.Origin of Eukaryotic Cells The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms

16 Aerobic bacteria Ancient Prokaryotes Ancient Anaerobic Prokaryote Primitive Aerobic Eukaryote Primitive Photosynthetic Eukaryote Chloroplast Photosynthetic bacteria Nuclear envelope evolving Mitochondrion Plants and plantlike protists Animals, fungi, and non-plantlike protists Figure Endosymbiotic Theory Go to Section:

17 17–2Earths Early History F.Sexual Reproduction and Multicellularity A few hundred million years after the evolution of sexual reproduction, evolving life forms crossed to developing multicellular organisms from single celled (unicellular) organisms

18 17–3Evolution of Multicellular Life A.Precambrian Time- life existed only in the sea B.Paleozoic Era- rich with evidence of many types of marine life C.Mesozoic Era- increasing dominance of dinosaurs, appearance of flowering plants D.Cenozoic Era- mammals evolved adaptations that allowed them to live in various environments, on land, water and air

19 Section 17-3 Geologic Time Scale with Key Events Glaciations; mammals increased; humans Mammals diversified; grasses Aquatic reptiles diversified; flowering plants; mass extinction Dinosaurs diversified; birds Dinosaurs; small mammals; cone-bearing plants Reptiles diversified; seed plants; mass extinction Reptiles; winged insects diversified; coal swamps Fishes diversified; land vertebrates (primitive amphibians) Land plants; land animals (arthropods) Aquatic arthropods; mollusks; vertebrates (jawless fishes) Marine invertebrates diversified; most animal phyla evolved Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life Cenozoic Mesozoic Paleozoic Precambrian Time Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian 1.8–present 65– –65 208– – – – – – – – –544 Key EventsEraPeriodTime (millions of years ago)

20 17–4Patterns of Evolution A. Mass Extinctions- dinosaurs B. Adaptive Radiation- species evolved into several different forms that live in different ways C. Convergent Evolution- unrelated organisms come to resemble one another

21 17–4Patterns of Evolution D. Coevolution- process by which two species evolve in response to changes in each other over time E. Punctuated Equilibrium- patterns of long, stable periods interrupted by brief periods of more rapid change Gradualism- patterns of slow, gradual change

22 17–4Patterns of Evolution F. Developmental Genes and Body Plans- changes in developmental genes, revealing major news about evolution of life

23 Flowchart that are can undergo inunder formin Species Unrelated Related Inter- relationshiops Similar environments Intense environmental pressure Small populations Different environments Coevolution Convergent evolution Extinction Punctuated equilibrium Adaptive radiation Go to Section:

24 A Trip Around the World While on his voyage around the world aboard the H.M.S. Beagle, Charles Darwin spent about one month observing life on the Galápagos Islands. There, he encountered some unique animals, such as finches and tortoises. Section 15-1

25 1. On a sheet of paper, list five animals that you have encountered in the past two days. 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in your textbook.) 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.

26 A.Voyage of the Beagle B.Darwins Observations 1.Patterns of Diversity 2.Living Organisms and Fossils 3.The Galápagos Islands C.The Journey Home Section –1The Puzzle of Lifes Diversity

27 Giant Tortoises of the Galápagos Islands Pinta Island Intermediate shell Hood Island Saddle-backed shell

28 Figure 15–1 Darwins Voyage

29 My, How Youve Changed! Prior to the 1800s, life scientists knew that living things changed over generations. They just didnt know how these changes were brought about.

30 1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.

31 2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument. 3. Which of the items in your lists do you think you might pass on to your children? Explain your answer

32 15–2 Ideas That Shaped Darwins Thinking A. An Ancient, Changing Earth 1.Huttons Theory of Geological Change 2.Lyells Principles of Geology

33 15–2Ideas That Shaped Darwins Thinking B.Lamarcks Theory of Evolution 1.Tendency Toward Perfection 2.Use and Disuse 3.Inheritance of Acquired Traits 4.Evaluating Lamarcks Theory C.Population Growth

34 Huttons Theory of Geological Change In 1975, geologist James Hutton proposed that layers of rock form very slowly. Some rocks are moved up by forces beneath the Earths surface, others are buried. Resulting rocks, mountains, and valleys are then shaped by a variety of natural forces- including rain, heat and cold temperatures

35 Lyells Principles of Geology Lyells work explained how awesome geological features could be built up or torn down over long periods of time. His work influenced Darwin in two ways: If the earth could change overtime, might life change as well? He realized that it must have taken many, many years, earth must be very old

36 Movement of Earths Crust Sedimentary rocks form in horizontal layers When part of Earths crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. New sediment is then deposited above the exposed older rock surface.

37 Lamarcks Theory of Evolution 1.Tendency Toward Perfection He proposed that all organisms are continually changing and acquiring features that help them live more successfully in their environment

38 2.Use and Disuse He proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways. Conversely, if a winged animal did not use its wings (ex. of disuse) the wings would decrease in size over generations and finally disappear

39 3.Inheritance of Acquired Traits Lamarck thought that acquired characteristics could be inherited By this reasoning, if you spent much of your life lifting weights to build muscles, your children would inherit big muscles, too.

40 4.Evaluating Lamarcks Theory He was incorrect in many ways Lamarck, like Darwin, did not know how traits are inherited or that behavior has no effect on its inheritable characteristics One of first to develop scientific theory of evolution and realize that organisms are adapted to their environment

41 Figure 15–7 Lamarcks Theory of Evolution

42 15–3Darwin Presents His Case A. Publication of On the Origin of Species –Darwin(1859)proposed a mechanism for evolution called natural selection –Continuous for millions of years and continues in all living things –Others strongly opposed

43 15–3 Darwin Presents His Case B. Natural Variation and Artificial Selection –Natural variation is the differences among individuals of a species, is found in all types of organisms –Artificial Selection occurs through a technique called selective breeding, that would determine which individuals to use for breeding based on the natural variation that was found

44 15–3 Darwin Presents His Case C.Evolution by Natural Selection 1.The Struggle for Existence- means that members of each species compete regularly to obtain food, living space, an other necessities of life

45 15–3 Darwin Presents His Case C. Evolution by Natural Selection 2.Survival of the Fittest Fitness- the ability of an individual to survive and reproduce in its specific environment Adaptation- is any inherited characteristics that increase an organisms chance of survival

46 15–3 Darwin Presents His Case C. Evolution by Natural Selection 2.Survival of the Fittest Individuals that are better suited to their environment-that is, with high levels of fitness-survive and reproduce most successfully

47 15–3 Darwin Presents His Case C. Evolution by Natural Selection 2.Survival of the Fittest Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness in its environment

48 15–3 Darwin Presents His Case C. Evolution by Natural Selection 3.Descent With Modification Each living species has descended, with changes, from other species over time

49 15–3 Darwin Presents His Case D. Evidence of Evolution 1.The Fossil Record provided evidence that living things have been evolving for millions of years. Sometimes fossil records includes similar, intermediate forms of a group of organisms that together suggest gradual modification over time

50 includes Evidence of Evolution Physical remains of organisms Common ancestral species Similar genes which is composed ofwhich indicateswhich implies The fossil record Geographic distribution of living species Homologous body structures Similarities in early development

51 D.Evidence of Evolution 2. Geographic Distribution of Living Species Animals living under similar ecological conditions, were exposed to similar pressures of natural selection Because of these similar selection pressures, different animals ended up evolving certain striking features in common

52 Figure 15–14Geographic Distribution of Living Species Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara

53 D.Evidence of Evolution 3. Homologous Body Structures structures that have different mature forms and functions but develop from the same embryonic tissues

54 Figure 15–15 Homologous Body Structures Turtle AlligatorBird Mammals Typical primitive fish

55 D.Evidence of Evolution 4.Similarities in Early Development early stages, or embryos, of many animals with backbones are so similar that they can be hard to tell apart

56 E.Summary of Darwins Theory Organisms in nature differ, some variation is inherited Survival of the fittest Natural Selection Variation

57 1. Make a list of physical traits that you think are influenced by genes. Then, write next to each trait whether you have the trait or not (e.g., a widows peak) or whether there are many variations of the trait (e.g., hair color).

58 2. Are most of the traits you listed clear-cut or are they mostly traits that have many variations? Which traits in your list are difficult to categorize?

59 3. Compare your list with that of another student. Did he or she think of any traits that you missed? Why do you think some traits are clear-cut, while others are not?

60 16–1Genes and Variation A. Darwins Ideas Revisited Without an understanding of heredity, Darwin was unable to explain two important factors. First, he did not know the source of the variation that was so central to his theory. Second, he could not explain how inheritable traits were passed from one generation to the next.

61 16–1Genes and Variation B. Gene Pools is the combined genetic information of all the members of a particular population

62 16–1Genes and Variation C.Sources of Genetic Variation Mutations- is any change in a sequence of DNA Gene Shuffling- occurs during the production of gametes (23 chromosomes in sperm and 23 in egg=46 Zygote) Crossing over- exchange of genetic material between chromosomes

63 16–2Evolution as Genetic Change C.Genetic Drift In small, populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population

64 16–2Evolution as Genetic Change D.Evolution Versus Genetic Equilibrium 1.Random Mating Ensures that each individual has an equal chance of passing on its alleles

65 16–2Evolution as Genetic Change D.Evolution Versus Genetic Equilibrium 2.Large Population Important in maintaining genetic equilibrium Genetic drift has less effect on large populations

66 16–2Evolution as Genetic Change D.Evolution Versus Genetic Equilibrium 3.No Movement Into or Out of the Population Keep gene pool together and separate of other populations

67 16–2Evolution as Genetic Change D.Evolution Versus Genetic Equilibrium 4.No Mutations

68 16–2Evolution as Genetic Change D.Evolution Versus Genetic Equilibrium 5.No Natural Selection

69 Sample of Original Population

70 Founding Population A Sample of Original Population Founding Population B

71 Founding Population A Sample of Original PopulationDescendants

72 Country Cousin/City Cousin What happens when a population or group of living things is divided into two separate groups in two separate environments? To understand what goes on, think about someone who lives in another part of the United States or in another country.

73 1. Make a list of everyday things that this person encounters that you dont. For example, does he or she eat different kinds of food? Does he or she live in a climate different from yours? 2. All humans are the same species. What might happen if groups of humans were separated for millions of years in very different environments, such as those you have just described?

74 16–3 The Process of Speciation A. Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other 1. Behavioral Isolation- two populations are capable of interbreeding, but differences in courtship rituals

75 2. Geographic Isolation- two populations are separated by geographic barriers such as rivers, mountains, or bodies of water 3. Temporal Isolation- two or more species reproduce at different times (orchid in the rainforest)

76 16–3 The Process of Speciation B. Testing Natural Selection in Nature 1. Variation- Grants concluded that there is a great deal of variation of inheritable traits among the Galopagos finches 2. Natural Selection- when food for finches was scarce, individuals with the largest beaks were more likely to survive 3. Rapid Evolution- changes in beaks occurred over decades instead of thousands of years

77 16–3 The Process of Speciation C. Speciation of Darwins Finches 1.Founders Arrive 2.Separation of Populations 3.Changes in the Gene Pool 4.Reproductive Isolation 5.Ecological Competition 6.Continued Evolution

78 16–3 The Process of Speciation C. Speciation of Darwins Finches 1.Founders Arrive Once they arrived on one of the island, they managed to survive and reproduce

79 16–3 The Process of Speciation C. Speciation of Darwins Finches 2.Separation of Populations Species crossed islands

80 16–3 The Process of Speciation C. Speciation of Darwins Finches 3.Changes in the Gene Pool Over time natural selection would have caused that population to evolve larger beaks, forming a separate population

81 16–3 The Process of Speciation C. Speciation of Darwins Finches 4.Reproductive Isolation Gene pools of the two bird populations remain isolated from each other

82 16–3 The Process of Speciation C. Speciation of Darwins Finches 5.Ecological Competition Overtime, species evolve in a way that increases the differences between them

83 16–3 The Process of Speciation C. Speciation of Darwins Finches 6.Continued Evolution Over many generations, it produced the 13 finch species found there today

84 results from which include produced by which result in Reproductive Isolation Isolating mechanisms Behavioral isolationTemporal isolation Geographic isolation Behavioral differencesDifferent mating times Physical separation Independently evolving populations Formation of new species

85 The End


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