Evolution Review Sheet Answer Key 4.5.2017 1. Relative dating is using comparison to date rocks or fossils. Law of superposition and index fossils are both examples of relative dating. Relative dating provides an estimate of age versus absolute dating that gives an exact age based on radioactive decay of Carbon-14 or Uranium-235. Absolute dating is the most exact method for determining age of geologic samples. 2. Trilobites and ammonites are both index fossils because they both lived on multiple continents and existed for a short amount of time. 3. A half-life is the amount of time it takes for one-half of a radioactive isotope to decay or break down. Carbon-14, Uranium-235, Plutonium-238 4. The question asks how much of a 96 g sample will be left after 8.1 days when the half- life is 2.7 days. 3 half-lives of gold go by in 8.1 days.
# of Half- Time Amount lives 0 0-2.6 96g 1 2.7 48g 2 5.4 24g 3 8.1 12g
5. The theory of continental drift is Alfred Wegener’s theory that the Earth is made of plates that move, or “drift” over time. The theory suggests the continents were all once together as Pangea. The puzzle-like fit of continents, fossils of plants and animals found at the boundaries of continents that are now apart, and the magnetic reversals on the sea-floor at points of sea-floor spreading are all evidence for continental drift. 6. An ice core is a cylinder of ice drilled from the Antarctic or Greenland ice sheets. Ice cores have dissolved gases trapped inside. Scientists are able to study the gases in the ice cores to understand past climate (weather) conditions. 7. Genetic variation naturally occurs as genes combine or mutate, there is variation among organisms. When variation or mutation gives an organism an advantage for survival, then that organism is more “fit” for its environment. When an environment changes and the more fit organisms survive, that is survival of the fittest. 8. Homologous structures are when organisms have anatomical features that have the same structure even though they may have a different function. The wings of a bat, legs of a cat, and human arms are all examples. Homologous structures indicate common ancestry. 9. Genetic variation is when there is naturally occurring variation in a population due to the way genes combine (dominant and recessive) or mutations. Examples of variation are: eye color, hair color, freckles, face shape, stripes, dimples 10. The law of superposition says that youngest rocks or fossils are found in the top rock layers, oldest at the bottom. 11. A, B, and C are all rock layers. D is a fault. E is an intrusion. Evolution Review Sheet Answer Key 4.5.2017 B, A, C, E, D 12. An analogous structure is when organisms have features that serve the same purpose but their structure or the way they are built is different. Bird and butterfly wings; fins and flippers on fish or whales 13.
Time Period Biotic Abiotic Pre-Cambrian First signs of bacteria/life Pangea/supercontinent was all one Beginning of Earth Paleozoic Age of Invertebrates Earth largely aquatic habitat (lots o’ fish!) Trilobites & ammonites Mesozoic Dinosaurs Roar! Extinction believed to be due to asteroid impact that blocked sunlight. Pangea splits Cenozoic Era Mammals appeared! Age of Ice Age Mammals! Current time!
14. There are THREE types of plate boundaries: divergent is where sea-floor spreading occurs, convergent forms mountains and mountain ranges, transform faults cause earthquakes. 15.
Example Type of Dating Description Carbon-14 Absolute Used for dating living things Ice cores Relative Tells of past climate and atmosphere Index fossils Relative Used for relative dating. Trilobites and ammonites Uranium Absolute Really long half-life; used to date older materials Rock layers Relative Youngest on the top; oldest on bottom