Presentation on theme: "Direct Evidence Indirect Evidence"— Presentation transcript:
1Direct Evidence Indirect Evidence Evidence of Evolution
2Direct EvidenceVisible evidence that takes us back in time and shows organisms have changedEx. – Fossils
3Fossils 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??
4How Fossils Form Fossil Formation Water carries small rock particles to lakes and seas.Fossil FormationThe fossil record provides evidence about the history of life on Earth. Most fossils are formed in sedimentary rock.
5How Fossils FormDead organisms are buried by layers of sediment, which forms new rock.The fossil record provides evidence about the history of life on Earth. Most fossils are formed in sedimentary rock.
6How Fossils FormThe preserved remains may be later discovered and studied.The fossil record provides evidence about the history of life on Earth. Most fossil formed in sedimentary rock.
7Fossils Lucy 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!
9Dating Fossils 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
10Relative DatingRelative dating allows paleontologists to estimate a fossil's agecompared with that of other fossils.
11Dating Fossils Radioactive dating (Absolute 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.
12Half-life of Radioactive Isotopes 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
13Radioactive DatingLet’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!!
16Indirect Evidence of Evolution (Evidence of a Common Ancestry) Evidence we can look at today that suggests we may have a common ancestry with other organisms.Embryological Similarities
17Indirect Evidence of Evolution 2. Comparative MorphologyHomologous Structures(Similar structurebut differentfunction!)
18Analogous Structures Similar in function but not in structure Do not show the close evolutionary connectionAnalogous Structures
19Indirect Evidence of Evolution 3. Similarities in Biochemistry (Organic Compounds)DNA similarities (98% of our DNA is the same as a chimpanzee)Protein in all organisms is composed of the same 20 amino acids!!
20Evidence of EvolutionDirect Evidence – something we can look at that takes us back in time.Ex. FossilsIndirect Evidence – something we can look at that show some kind of evolutionary connection between organisms.Ex. Embryological similarities, Homologous structures, Biochemistry similarities
21Darwin’s explanation of evolution is called Natural Selection. What does the term Artificial Selection mean? Discuss this with a neighbour.Samuri Crab
22Organisms don’t change to survive, they survive (or die Organisms don’t change to survive, they survive (or die!) because they change!