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A. Direct Evidence B. Indirect Evidence.  Visible evidence that organisms have changed over time  Ex. – Fossils.

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Presentation on theme: "A. Direct Evidence B. Indirect Evidence.  Visible evidence that organisms have changed over time  Ex. – Fossils."— Presentation transcript:

1 A. Direct Evidence B. Indirect Evidence

2  Visible evidence that organisms have changed over time  Ex. – Fossils

3 ▪ Paleontologists are scientists who collect and study fossils. ▪ The fossil record provides incomplete information about the history of life. ▪ Over 99% of all species that have lived on Earth have become extinct. ▪ Where are all these fossils??

4  Fossil Formation Water carries small rock particles to lakes and seas. Fossil Formation

5 Dead organisms are buried by layers of sediment, which forms new rock.

6 The preserved remains may be later discovered and studied.

7  Lucy Lucy  Coal Formation Coal Formation  The following picture is of plant fossils found in coal from the Minto area that are 300 million years old…..older than dinosaures!

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9  Relative Dating ▪ In relative dating, the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock. ▪ Rock layers form in order by age—the oldest on the bottom, with more recent layers on top. ▪ Grand Canyon Grand Canyon

10 Relative dating allows paleontologists to estimate a fossil's age compared with that of other fossils.

11 ▪ Radioactive dating ▪ Some elements are radioactive and steadily break down into nonradioactive elements. ▪ Radioactive dating is the use of half-lives to determine the age of a sample. ▪ A half-life is the length of time required for half of the radioactive atoms in a sample to decay.

12  C-14 breaks down into N-14 at a fixed rate.  The half life of C-14 is 5,760 years.  When an organism dies, the C-14 in the organism starts to change into N-14.  Knowing the half-life, you can compare the amount of C-14 to N-14 to determine the age of the fossil

13  Let’s say the fossil we are dating shows 50% C-14 and 50% N-14…….  The fossil should be 5,760 years old.  If another 5,760 years passed, what would be the ratio of C-14 to N-14?  Right!!.........C-14 25% to N-14 75%  Potassium 40 is an isotope with a half-life of 1.2 billion years!!

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16  Evidence we can look at today that suggests we may have a common ancestry with other organisms. 1. Embryological Similarities

17  2. Comparative Morphology  Homologous Structures  (Similar structure  but different  function!)

18  3. Similarities in Biochemistry  DNA similarities (98% of our DNA is the same as a chimpanzee)  Protein in all organisms is composed of the same 20 amino acids!!

19  Direct Evidence – something we can look at that takes us back in time.  Ex. Fossils  Indirect Evidence – something we can look at that show some kind of evolutionary connection between organisms.  Ex. Embryological similarities, Homologous structures, Biochemistry similarities

20  Darwin’s explanation of evolution is called Natural Selection.  What does the term Artificial Selection mean? Discuss this with a neighbour.  Samuri Crab Samuri Crab

21  Organisms don’t change to survive, they survive (or die!) because they change!


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