Chapter 16 The Origins of Life Flashcards
Identify the stages that are hypothesized to have taken place to produce the first life on earth
No life to chemistry to monomers to protocells to cells to life
Describe the experimental evidence that supports how simple biological molecules, such as amino acids and other organic acids, would form spontaneously under conditions approximating those on early earth.
What is the significance of the MIller-Urey experiment?
They tried to get rid of oxygen in the lab to simulate the atmosphere of primitive earth. They used a vacuum pump to do this and added energy. They found amino acids which shows that you could go from simple chemicals to monomers which could eventually form life.
Scientists think that lightning sparked chemical reactions in Earth’s early atmosphere. The early atmosphere contained gases such as ammonia, methane,water vapor, and carbon dioxide. Scientists hypothesize that this created a “soup” of organic molecules from inorganic chemicals. In 1953, scientists Stanley Miller and Harold Urey used their imaginations to test this hypothesis. They created a simulation experiment to see if organic molecules could arise in this way (seeFigure below ). They used a mixture of gases to represent Earth’s early atmosphere. Then, they passed sparks through the gases to represent lightning. Within a week, several simple organic molecules had formed. You can watch a dramatization of Miller and Urey’s experiment at this
Briefly describe the history of life on Earth, noting the major eras, when they occurred, and which types of life were most abundant. Describe the key events that occurred at the boundaries of eras.
15.6 The fossil record documents the history of life 1. The geologic record is based on the sequence and age of fossils in the rock strata. 2. The most recent Phanerozoic eon a. includes the past 542 million years and b. is divided into three eras i. Paleozoic, ii. Mesozoic, and iii. Cenozoic. 3. The boundaries between eras are marked by mass extinctions
Earth formed about 4.5 to 4.6 billion years ago.
At first, Earth was molten and lacked an atmosphere and oceans.
Gradually, the atmosphere formed, followed by the oceans.
Briefly describe the key events in the evolution of prokaryotes and eukaryotes.
The first cells were most likely primitive prokaryotic-like cells, even more simplistic than these E. coli bacteria. The first cells were probably no more than organic compounds, such as a simplistic RNA, surrounded by a membrane. Was it a phospholipid bilayer membrane? Probably not — it was likely a simplistic membrane able to separate the inside from the outside. Over time, as other organic compounds such as DNA and proteins developed, cells also evolved into more complex structures. Once a cell was able to be stable, reproduce itself, and pass its genetic information to the next generation, then there was life. What was needed for the first cell? Some sort of membrane surrounding organic molecules? Probably. How organic molecules such as RNA developed into cells is not known for certain. Scientists speculate that lipid membranes grew around the organic molecules. The membranes prevented the molecules from reacting with other molecules, so they did not form new compounds. In this way, the organic molecules persisted, and the first cells may have formed One cell (or group of cells), called the last universal common ancestor (LUCA), gave rise to all subsequent life on Earth. Photosynthesis evolved by 3 billion years ago and released oxygen into the atmosphere. Cellular respiration evolved after that to make use of the oxygen. The first eukaryotic cells - cells with a nucleus an internal membrane-boundorganelles - probably evolved about 2 billion years ago. This is explained by theendosymbiotic theory . As shown in the Figure below , endosymbiosis came about when large cells engulfed small cells. The small cells were not digested by the large cells. Instead, they lived within the large cells and evolved into organelles. The large and small cells formed a symbiotic relationship in which both cells benefited. Some of the small cells were able to break down the large cell’s wastes for energy. They supplied energy not only to themselves but also to the large cell. They became the mitochondria of eukaryotic cells. Other small cells were able to use sunlight to make food. They shared the food with the large cell. They became the chloroplasts of eukaryotic cells. Mitochondria and chloroplasts evolved from prokaryotic organisms. Eukaryotic cells would go on to evolve into the diversity of eukaryot
Describe the process of continental drift, and explain its significance to the history of life on Earth.
Continental drift is the movement of the Earth’s continents relative to each other. The hypothesis that continents ‘drift’ was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912. However, it was not until the development of the theory of plate tectonics in the 1960s, that a sufficient geological explanation of that movement was found.
Explain how mountains, volcanoes, and earthquakes are a consequence of plate tectonics.
Plate tectonics is the unifying theory of geology. Plate tectonics theory explains why:
Earth’s geography has changed through time and continues to change today.
some places are prone to earthquakes while others are not.
certain regions may have deadly, mild, or no volcanic eruptions.
mountain ranges are located where they are.
Plate tectonic motions affect Earth’s rock cycle, climate, and the evolution of life.
Plates of lithosphere move because of convection currents in the mantle. One type of motion is produced by seafloor spreading.
Plate boundaries can be located by outlining earthquake epicenters.
Plates interact at three types of plate boundaries: divergent, converge
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Describe the causes, frequency, and consequences of mass extinctions over the past 600 million years.
The first great mass extinction event took place at the end of the Ordovician, when according to the fossil record, 60% of all genera of both terrestrial and marine life worldwide were exterminated.
360 million years ago in the Late Devonian period, the environment that had clearly nurtured reefs for at least 13 million years turned hostile and the world plunged into the second mass extinction event.
The fossil record of the end Permian mass extinction reveals a staggering loss of life: perhaps 80–95% of all marine species went extinct. Reefs didn’t reappear for about 10 million years, the greatest hiatus in reef building in all of Earth history.
The end Triassic mass extinction is estimated to have claimed about half of all marine invertebrates. Around 80% of all land quadrupeds also went extinct.
The end Cretaceous mass extinction 65 million years ago is famously associated with the demise of the dinosaurs. Virtually no large land animals survived. Plants were also greatly affected while tropical marine life was decimated. Global temperature was 6 to 14°C warmer than present with sea levels over 300 metres higher than current levels. At this time, the oceans flooded up to 40% of the continents.
