U2L1: Origin of Life

• this states that life originated on another planet outside the solar system and then was carried to earth on a meteorite or asteroids that colonized earth


  extraterrestrial origin
• "seed" of life exists all over the universe and can be propagated through space, and that life on earth originated from those seeds


  panspermia
• this theory states that life was put on earth by divone forces. this is common to many religions


  divine creation
• this theory states that life arose on earth from inanimate matter after earth had cooled. random events then probably produced stable molecules that could self replicate. natural selection then favored changes in the rate of reproduction, which eventually led to the first cell


  origin from nonliving matter
• 1. life began back when conditions were quite different from earths current environment. the atmosphere lacked oxygen; rich in carbon dioxide, carbon monoxide, hydrogen, and nitrogen. the surface was bombarded with meteorites, volcanic eruptions, and intense radiation from the sun. so it's believed that in this condition, life may have originated from nonliving matter.
• 2. life started from chemicals that already existed in the environment. water, clay, minerals, in the ocean, gases present in the atmosphere. energy that was present on earth → caused these chemicals to react with one another → forming complex chemicals: amino acids, dna, carbohydrates, lipids, that made life possible
• who are the people that replicated early earth on an experiment

  stanley miller, harold urey
• they provided proof through their experiments that amino acids and other organic molecules can be formed.

  stanley miller, harold urey
• (1) the atmosphere introduced into flasks contained simple molecules that is present in early earth's atmosphere: hydrogen, carbon dioxide, methane, water vapor, nitrogen, ammonia, carbon monoxide
• (2) they heated the mixture → zapped it with electrical sparks to stimulate lightning
• (3) within days, a dark, smelly mixture developed → many complex molecules had formed
• (4) amino acids that are the building blocks of protein
• (5) using slightly different combination of starting molecules, miller and other scientists generate many amino acids, rna and dna, nucleotides, lipids, carbohydrates, and adenosine triphosphate (atp)
• >1 crucial feature that seperates the cell from its environment is the cell membrane, which contains lipids
• >2 these tiny spheres of lipids may have been the first stage in the origin of cell
• >3 lipids mix with water → forms bubbles called coacervate
• >4 these bubbles: coacervate, had double layered membranes similar to the lipid bilayer of the cell membrane
• >5 early oceans might have contained numerous, small lipid coacervates that formed and eventually dispersed
• >6 coacervates are unable to obtain energy from materials found in their environment. so they might have developed these capabilities and were able to transfer these to other coacervates overtime
• >7 for millions of years, coacervates that floated in the oceans joined together to form larger molecules → reacted with each other → forming more complicated structure that has ability to replicate. these then developed into cell like structure that eventually became the first true cells
• were believed to be the first cell


  prokaryotes
• organisms whose cell have no nucleus


  prokaryotes
• the first prokaryotes were anaerobic— they did not need and could not tolerate free oxygen
• organisms that do need oxygen in early earth couldnt have survived because earth lacked free oxygen
• many anaerobic prokaryotes still live in earth today in places where there is no free oxygen
• earth's age


  4.5 ga
• the oldest rock is aged


  3.8 ga
• the oldest fossil discovered were 3.5 billion year old rocks that were once sediments on the ocean floor
• these are the tiny fossils that were found in these ancient rocks/sediments

  bacteria
• enumerate the four possibilities on how life could have formed

  extraterrestrial origin, panspermia, divine creation, origin from non living matter
• two groups of bacteria according to the composition of their cell walls, cell membrane, and protein structure


  eubacteria, archaebacteria
• considered the true bacteria 


  eubacteria
• this is most living bacteria


  eubacteria
• this bacteria causes disease and decay

  eubacteria
• this is considered the ancient bacteria


  archaebacteria
• this bacteria is considered rare


  archaebacteria
• this bacteria is found mainly in hostile environments where conditions resemble those of early earth like salty lakes, hot springs, swamps, and the ocean floor


  archaebacteria
• this is the bacteria that produced oxygen of early earth's atmosphere at 3 gya


  cynobacteria
• this bacteria carried out photosynthesis, causing oxygen gas to be released onto oceans. oxygen then bubbles out of the water and into the air. with oxygen continously adding up, it led to the present composition of the atmosphere


  cynobacteria
• life was only able to move onto land because of change in atmosphere