1 / 93

NOTES: CH 25 - The History of Life on Earth

NOTES: CH 25 - The History of Life on Earth. History of Life. Eras. Boundaries between units in the Geologic Time Scale are marked by dramatic biotic change. 4500. Origin of Earth. Overview: Lost Worlds. ● Past organisms were very different from those now alive

fredericka-kelley
Télécharger la présentation

NOTES: CH 25 - The History of Life on Earth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NOTES: CH 25 - The History of Life on Earth

  2. History of Life Eras Boundaries between units in the Geologic Time Scale are marked by dramatic biotic change 4500 Origin of Earth

  3. Overview: Lost Worlds ● Past organisms were very different from those now alive ● The fossil record shows macroevolutionary changes over large time scales, for example: • The emergence of terrestrial vertebrates • The impact of mass extinctions • The origin of flight in birds

  4. Prebiotic Chemical Evolution: ● Earth’s ancient environment was different from today: -very little atmospheric oxygen -lightning, volcanic activity, meteorite, bombardment, UV radiation were all more intense

  5. ● Chemical evolution may have occurred in four stages: 1) abiotic synthesis of monomers 2) joining of monomers into polymers (e.g. proteins, nucleic acids) 3) formation of protocells (droplets formed from clusters of molecules) 4) origin of self-replicating molecules that eventually made inheritance possible (likely that RNA was first)

  6. Oparin / Haldane hypothesis (1920s):the reducing atmosphere and greater UV radiation on primitive Earth favored reactions that built complex organic molecules from simple monomers as building blocks

  7. Miller / Urey experiment: Simulated conditions on early Earth by constructing an apparatus containing H2O, H2, CH4, and NH3. Results: ● They produced amino acids and other organic molecules. ● Additional follow-up experiments have produced all 20 amino acids, ATP, some sugars, lipids and purine and pyrimidine bases of RNA and DNA.

  8. 20 200 Number of amino acids Mass of amino acids (mg) 10 100 0 0 2008 2008 1953 1953

  9. ●Protocells: collections of abiotically produced molecules able to maintain an internal environment different from their surroundings and exhibiting some life properties such as metabolism, semipermeable membranes, and excitability (experimental evidence suggests spontaneous formation of protocells)

  10. Abiotic genetic replication

  11. possible formation of protocells; self-repliating RNA as early “genes”

  12. Origin of Life - Different Theories: *Experiments indicate key steps that could have occurred. ●Panspermia: some organic compounds may have reached Earth by way of meteorites and comets meteorite

  13. ●Sea floor / Deep-sea vents: hot water and minerals emitted from deep sea vents may have provided energy and chemicals needed for early protobionts ● Simpler hereditary systems (self-replicating molecules) may have preceded nucleic acid genes.

  14. Phylogeny: the evolutionary history of a species ● Systematics: the study of biological diversity in an evolutionary context ●The fossil record: the ordered array of fossils, within layers, or strata, of sedimentary rock ●Paleontologists: collect and interpret fossils

  15. FOSSILS ● A FOSSILis the remains or evidence of a living thing -bone of an organism or the print of a shell in a rock -burrow or tunnel left by an ancient worm -most common fossils: bones, shells, pollen grains, seeds.

  16. Present Figure 25.4 Dimetrodon Rhomaleosaurus victor 100 mya 1 m 175 Tiktaalik 0.5 m 200 270 300 4.5 cm Hallucigenia Coccosteus cuspidatus 375 400 1 cm Dickinsonia costata 500 525 2.5 cm Stromatolites 565 600 1,500 Fossilized stromatolite 3,500 Tappania

  17. Examples of different kinds of fossils PETRIFICATION is the process by which plant or animal remains are turned into stone over time. The remains are buried, partially dissolved, and filled in with stone or other mineral deposits. A MOLD is an empty space that has the shape of the organism that was once there. A CAST can be thought of as a filled in mold. Mineral deposits can often form casts. Thin objects, such as leaves and feathers, leave IMPRINTS, or impressions, in soft sediments such as mud. When the sediments harden into rock, the imprints are preserved as fossils.

  18. PRESERVATION OF ENTIRE ORGANISMS: It is quite rare for an entire organism to be preserved because the soft parts decay easily. However, there are a few special situations that allow organisms to be preserved whole. FREEZING: This prevents substances from decaying. On rare occasions, extinct species have been found frozen in ice. AMBER: When the resin (sap) from certain evergreen trees hardens, it forms a hard substance called amber. Flies and other insects are sometimes trapped in the sticky resin that flows from trees. When the resin hardens, the insects are preserved perfectly.

  19. TAR PITS: These are large pools of tar. Animals could get trapped in the sticky tar when they went to drink the water that often covered the pits. Other animals came to feed on these animals and then also became trapped. TRACE FOSSILS: These fossils reveal much about an animal’s appearance without showing any part of the animal. They are marks or evidence of animal activities, such as tracks, burrows, wormholes, etc.

  20. The fossil record ●Sedimentary rock: rock formed from sand and mud that once settled on the bottom of seas, lakes, and marshes Methods for Dating Fossils: ●RELATIVE DATING: used to establish the geologic time scale; sequence of species ●ABSOLUTE DATING: radiometric dating; determine exact age using half-lives of radioactive isotopes

  21. Where would you expect to find older fossils and where are the younger fossils? Why?

  22. Relative Dating: ● What is an INDEX FOSSIL?  fossil used to help determine the relative age of the fossils around it  must be easily recognized and must have existed for a short period BUT over wide geographical area.

  23. Radiometric Dating: ● Calculating the ABSOLUTE age of fossils based on the amount of remaining radioactive isotopes it contains. Isotope = atom of an element that has a number of neutrons different from that of other atoms of the same element

  24. Radiometric Dating: ● Certain naturally occurring elements / isotopes are radioactive, and they decay (break down) at predictable rates ● An isotope (the “parent”) loses particles from its nucleus to form a isotope of the new element (the “daughter”) ● The rate of decay is expressed in a “half-life”

  25. Daughter Parent

  26. Figure 25.5 Accumulating “daughter” isotope Fraction of parent isotope remaining 1 2 Remaining “parent” isotope 1 4 1 8 1 16 1 2 3 4 Time (half-lives)

  27. Half life= the amount of time it takes for ½ of a radioactive element to decay. To determine the age of a fossil: 1) compare the amount of the “parent” isotope to the amount of the “daughter” element 2) knowing the half-life, do the math to calculate the age!

  28. Parent Isotope Daughter Half-Life Uranium-238 Lead-206 4.5 billion years Uranium-235 Lead-207 704 million years Thorium-232 Lead-208 14.0 billion years Rubidium-87 Strontium-87 48.8 billion years Potassium-40 Argon-40 1.25 billion years Samarium-147 Neodymium-143 106 billion years

  29. Radioactive Dating: Example: Carbon 14 ● Used to date material that was once alive ● C-14 is in all plants and animals (C-12 is too, but it does NOT decay!) ● When an organism dies, the amount of C-14 decreases because it is being converted back to N-14 by radioactive decay

  30. Example: Carbon 14 ● By measuring the amount of C-14 compared to N-14, the time of death can be calculated ● C-14 has a half life of 5,730 years ● Since the half life is considered short, it can only date organisms that have died within the past 70,000 years

  31. What is the half-life of Potassium-40? • How many half-lives will it take for Potassium-40 to decay to 50 g? • How long will it take for Potassium-40 to decay to 50 g?

  32. What is the half-life of Potassium-40? 1.2 billion years How many half-lives will it take for Potassium-40 to decay to 50 g? 2 half-lives How long will it take for Potassium-40 to decay to 50g? 2.6 billion yrs.

  33. How is the decay rate of a radioactive substance expressed? Equation: A = Ao x (1/2)n A = amount remaining Ao = initial amount n = # of half-lives (**to find n, calculate t/T, where t = time, and T = half-life, in the same time units as t), so you can rewrite the above equation as: A = Ao x (1/2)t/T

  34. ½ Life Example #1: ● Nitrogen-13 decays to carbon-13 with t1/2 = 10 minutes. Assume a starting mass of 2.00 g of N-13. A) How long is three half-lives? B) How many grams of the isotope will still be present at the end of three half-lives?

  35. ½ Life Example #1: ● Nitrogen-13 decays to carbon-13 with t1/2 = 10 minutes. Assume a starting mass of 2.00 g of N-13. A) How long is three half-lives? (3 half-lives) x (10 min. / h.l.) = 30 minutes

  36. ½ Life Example #1: ● Nitrogen-13 decays to carbon-13 with t1/2 = 10 minutes. Assume a starting mass of 2.00 g of N-13. B) How many grams of the isotope will still be present at the end of three half-lives? 2.00 g x ½ x ½ x ½ = 0.25 g

  37. ½ Life Example #1: ● Nitrogen-13 decays to carbon-13 with t1/2 = 10 minutes. Assume a starting mass of 2.00 g of N-13. B) How many grams of the isotope will still be present at the end of three half-lives? A = Ao x (1/2)n A = (2.00 g) x (1/2)3 A = 0.25 g

  38. ½ Life Example #2: ● Mn-56 has a half-life of 2.6 hr. What is the mass of Mn-56 in a 1.0 mg sample of the isotope at the end of 10.4 hr?

  39. ½ Life Example #2: ● Mn-56 has a half-life of 2.6 hr. What is the mass of Mn-56 in a 1.0 mg sample of the isotope at the end of 10.4 hr? A = ? n = t / T = 10.4 hr / 2.6 hr A0 = 1.0 mg n = 4 half-lives A = (1.0 mg) x (1/2)4 = 0.0625 mg

  40. ½ Life Example #3: ● Strontium-90 has a half-life of 29 years. What is the mass of strontium-90 in a 5.0 g sample of the isotope at the end of 87 years?

  41. ½ Life Example #3: ● Strontium-90 has a half-life of 29 years. What is the mass of strontium-90 in a 5.0 g sample of the isotope at the end of 87 years? A = ? n = t / T = 87 yrs / 29 yrs A0 = 5.0 g n = 3 half-lives A = (5.0 g) x (1/2)3 A = 0.625 g

  42. *The history of living organisms and the history of Earth are inextricably linked: ● Formation and subsequent breakup of Pangaea affected biotic diversity

  43. BIOGEOGRAPHY: the study of the past and present distribution of species ●Formation of Pangaea- 250 m.y.a. (Permian extinction) ●Break-up of Pangaea – 180 m.y.a. (led to extreme cases of geographic isolation!)  EX: Australian marsupials!

  44. Apparent continental drift results from PLATE TECTONICS

  45. Plate Tectonics: Crust ● At three points in time, the land masses of Earth have formed a supercontinent: 1.1 billion, 600 million, and 250 million years ago ● According to the theory of plate tectonics, Earth’s crust is composed of plates floating on Earth’s mantle Mantle Outer core Inner core

More Related