AP Biology, Chapter 25 The History of Life on Earth – Flashcards
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1. Give examples of macroevolutionary change.
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Emergence of terrestrial vertebrates Impact of mass extinctions on diversity Origin of key adaptations like flight
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2. Describe the four stages of the hypothesis for the origin of life on Earth.
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Abiotic synthesis of small organic molecules Abiotic synthesis of macromolecules Protocells Self-replicating RNAs undergoing natural selection
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3. Describe the contributions that A. I. Oparin, J. B. S. Haldane, and Stanley Miller made toward developing a model for the abiotic synthesis of organic molecules.
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Oparin and Haldane: conditions on the early Earth favored the formation of small organic molecules Miller simulated conditions on the early Earth Water for oceans H2, NH3, and CH4 for reducing atmosphere Sparks for lightning Formed amino acids
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4. Describe alternative scenarios for the origins of organic molecules on Earth.
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Not a reducing atmosphere N2 and CO2 Simulations still show formation of organics Localized reducing conditions near volcanoes or deep-sea vents From space in cosmic dust and carbonaceous chondrite meteorites
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5. Describe the key properties of protocells in the evolution of the first cells.
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Protocells are aggregates of abiotically produced molecules Properties If enzymes are included they metabolize Selective permeability Can discharge membrane potential = excitability Can absorb materials and split into smaller units Lack hereditary traits
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6. Describe the evidence that suggests that RNA was the first genetic material. Explain the significance of the discovery of ribozymes.
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Ribozymes have a variety of catalytic functions; pre-date enzymes RNA is central to information transfer in cells RNA can be copied abiotically
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7. Describe how natural selection would have worked in an early RNA world.
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RNAs with stability and replicability are favored in vivo Complementary catalytic functions allow groups of RNAs Quasispecies in hypercycle" could recombine into a single, multi-trait molecule Covalent linkage with amino acids may have enhanced catalytic function
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8. What are the characteristics of species preferentially found in the fossil record.
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Abundant Widespread near water Possessed hard shells, skeletons, etc.
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9. Distinguish between relative dating and absolute dating.
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Relative dating Older vs. younger By position in the rock pile Superposition: deeper, older; shallower, younger Radiometric dating In years Involves measuring isotopes
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10. Explain how isotopes can be used in absolute dating.
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Assumes we know the starting ratio of isotopes Assumes changes in the sample are due to radioactive decay alone Current ratio is measured; half-life used to calculate time Examples: C-14 (5700 years), U-238 (4.5 billion years)
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11. Explain how the racemization of amino acids is used to estimate fossil age.
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Mixtures of enantiomers are called racemic mixtures Organisms use L-amino acids After death the L-amino acids begin changing to the D- forms Making assumptions about the rates allows calculation of the age
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12. Describe the major events in Earth's history from its origin up to about 2 billion years ago. In particular, note when Earth first formed, when life first evolved, and what forms of life existed up until about 2 billion years ago.
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4.6 billion years ago (bya) Earth forms 3.9 bya conditions suitable for life 3.5 bya oldest fossils Stromatolites in fossil record match those growing today = mounds formed of layered biofilms and sediment 2.7 bya oxygen gas appears in large amounts
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13. Describe the timing and significance of the evolution of photosynthesis.
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3.5 bya (?) non-oxygenic photosynthesis 2.7 bya oxygenic photosynthesis Accumulating oxygen reacted with iron metal Banded iron oxide sediments appear 2.7 bya 2.2 bya significant accumulation of atmospheric oxygen Killed many anaerobes Made cellular respiration possible
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14. Describe the hypothesized origin of the nuclear membrane and the endomembrane system.
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Both from infolding of plasma membrane Nuclear membrane protects and controls DNA Endomembrane system compartmentalizes differentiated gene products
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15. Describe the evidence that supports the theory that mitochondria and plastids evolved by serial endosymbiosis. Explain what living organisms are the likely relatives of the prokaryotes that gave rise to mitochondria and plastids.
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Modern endosymbiotic relationships Similarities between bacteria and mitochondria and chloroplasts Cell / organelle size Prokaryote-type membrane components Replication by binary fission Single, circular DNA without histones Similar transcriptional and translational apparatus Mitochondria most resemble proteobacteria; plastids cyanobacteria
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16. Describe the timing of key events in the evolution of the first eukaryotes and later multicellular eukaryotes. Describe the snowball-Earth hypothesis.
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2.1 bya oldest definite eukaryote fossils 1.5 bya multicellular eukaryotes by DNA sequence 1.2 bya fossil multicellular algae 575 mya large diverse multicellular fossils Corresponds to the thawing of snow-ball Earth
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17. Critique the textbooks emphasis on a "Cambrian Explosion."
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Most extant major animal groups originates earlier in the Ediacaran Only Chrodates and Echinoderms first appear in Cambrian Only extant groups shown; at least as many major forms are now extinct Cambrian adaptations Hard parts for predations and protection Fossilize more easily; bias makes Cambrian seem bigger
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18. Describe the timing of key evolutionary adaptations as life colonized land.
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1 bya microscopic terrestrial life 500 mya macroscopic terrestrial; waterproofing tissues
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19. How are speciation and extinction rates related to evolutionary succession?
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Major adaptations allow rapid speciation, low extinction Replacement adaptations reverse that ratio
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20. Describe the process and practical importance of plate tectonics.
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Convection moves large section of Earth's crust Sea floor is recycled every 200 my Forms mountains, splits continents causes volcanoes and earthquakes
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21. Describe two dramatic chapters in the history of continental drift. Explain how those movements affected biological evolution.
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250 million years ago; formation of Pangaea Once isolated populations became mixed Habitat changes: less coastline, drier interiors 180 million years ago: break up of Pangaea Reinstated widespread geographical isolation Current biogeographical patterns are the result
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22. Explain how mass extinctions have occurred and how they affected the evolution of surviving forms.
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Permian, 250 million years ago Massive volcanic eruptions Release of large amounts of CO2 è warming Anoxic oceans from reduced mixing Cretaceous, 65.5 mya Asteroid impact Killed dinosaurs
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23. Describe the evidence related to the impact hypothesis associated with the Cretaceous extinctions. Describe the hypothesized consequences of such an impact.
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Evidence Iridium-rich layer on top of the Cretaceous rocks Chicxulub; large crater of the right age Consequences Dust released blocked sunlight for years; photosynthesis blocked Minerals released caused acid precipitation Molten debris rained on North America
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24. Is a sixth mass extinction under way?
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Caused by habitat destruction and global climate change? Current extinction rates 100-1000 times background Way below mass extinction rates
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25. Describe the major consequences of mass extinctions.
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Snuffs out lineages Causes major ecological changes by eliminating adaptations Opens up niches for adaptive radiations
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26. Define and exemplify adaptive radiation.
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= formation of many species from a common ancestor Worldwide Adaptive Radiations Dinosaurs dominated until extinction Until that time mammals were small and nocturnal Regional Adaptive Radiations Migration to new varied environments Ex.: finches to Galapagos
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27. Explain how the evolution of changes in temporal and spatial developmental dynamics can result in evolutionary novelties.
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Relatively few genes control timing and proportions Small genetic alterations can have big effects Changes in Rate and Timing Heterochrony: evolution of morphology from modifying relative growth rates in different parts Paedomorphosis: retention of juvenile characteristics in the adult due Changes in Spatial Pattern May involve changes in the expression of homeotic genes in animals
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28. Define exaptation and illustrate this concept with an example.
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Exaptation involves a new advantageous use for an old trait Example: originally feathers may have conserved heat/energy
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29. Explain why extracting a single evolutionary progression from a fossil record can be misleading.
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Lining up fossils out of context implies uninterrupted direct lineage A series of changes does not imply an ultimate goal
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30. Define and illustrate the concept of species selection. Explain why evolutionary trends are not directional.
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Successful, long-lived, widespread species speciate more often The traits of the long-lived, fecund species appear as a trend in the fossil record Traits making species fecund, like better dispersal, make it look like all the species traits are important
