Medical Free Books: Prescott’s Microbiology 9th Edition PDF – In February 2012, the National Aeronautics and Space Administration (NASA) reported that over 2,000 potential planets had been discovered by the 2009 Kepler mission.
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Using a telescope in space, the light emanating from stars as far as 3,000 light-years away had been monitored every half-hour. The Kepler telescope identified planets as they circulated their star and caused a brief decrease in emitted light; just as an object is detected as a blip by radar, a blip of “darkness” indicates a planet.
Unless you are a science fiction fan, you might wonder why NASA is interested in finding planets. By finding other planets, scientists can gather evidence to support or refute current models of planet formation. Prescott’s Microbiology 9th Edition PDF
These models predict a process that is chaotic and violent. Planets are thought to begin as dust particles circling around newly formed stars. As these particles collide, they grow in size, forming larger chunks. Eventually a series of such collisions results in planet-sized bodies. Astrobiologists are interested in identifying characteristics of a planet that may allow it to support life. Using Earth as a model, they hypothesize that life-supporting planets will share many features with Earth. But how will life be recognized? Again, scientists look to life on Earth to answer this question, and increasingly they are turning to microbiologists for help. Earth formed 4.5 billion years ago. Within the next billion years, the first cellular life forms-microbes-appeared. Prescott’s Microbiology 9th Edition PDF
Since that time, microorganisms have evolved and diversified to occupy virtually every habitat on Earth: from oceanic geothermal vents to the coldest Arctic ice. The diversity of cellular microorganisms is best exemplified by their metabolic capabilities. Some carry out respiration, just as animals do. Others perform photosynthesis, rivaling plants in the amount of carbon dioxide they capture, forming organic matter and releasing oxygen into the atmosphere. Indeed, Prochlorococcus, a cyanobacterium (formerly called a blue-green alga), is thought to be the most abundant photosynthetic organism on Earth and Artist’s rendition of the six planets orbiting a star called Kepler-11. The drawing is based on observations made of the system by the Kepler spacecraft on August 26,2010. Some are Earth-sized and may be habitable by life. thus a major contributor to the functioning of the biosphere. In addition to these familiar types of metabolism, other microbes are able to use inorganic molecules as sources of energy in both oxic (oxygen available) and anoxic (no oxygen) conditions.
Medical Free Books: Prescott’s Microbiology 9th Edition PDF