-
(5 BYA) Solar System
The solar system began to form from a mass of gas and dust. These gases and particles were the result of supernovas (exploding stars) that produced many of the elements found on Earth today. The particles were drawn together by gravity to create the sun from a solar nebula. Collisions of space debris formed more planets that circled the sun. Thermal energy was produced from these collisions. -
Period: to
History of the Earth
-
(4.6 BYA) Formation of Earth
Earth was formed and grew by colliding with space debris. Many small pieces stuck together one after another until a large body, Earth, was formed. Gravity pulled in more debris afterwards and some of the collisions released so much energy that part of the planet's surface could have been melted. Its surface was covered with lava and volcanoes. Heat was also being produced from radioactive materials in Earth's core. Earth's age was determined by studying sedementary rock in the Earth's crust. -
(4 BYA) Accumulation of Organic Molecules
Unmelted rocks found were roughly 4 billion years old, which means that this is when the earth was cooling. Organic molecules began to accumulate. -
(4 BYA) Formation of First Cells
The first cells developed as anaerobic, heterotrophic prokaryotes. These were called archaea which were unicellular organisms that could survive harsh conditions and fed off of the organic molecules that were being formed at this time. They used chemosynthesis for food. This was the first known life on Earth. -
(3.5 BYA) Stromatolites
Fossils of stromotalites were found from this time. Stromalites are colonies of lynbgya, a cyanobacteria, cells. -
(3 BYA) Photosynthetic Organisms
The first appearance of photsynthetic organisms occurred 3 billion years ago. This is known because of scientific research of chemical traces of photosynthetic activity in fossils. Oxygen was produced because of these new photosynthetic organisms, which damaged unicellular organisms at first. Aerobic respiration began afterwards to prevent the oxygen from damaging unicellular organisms. -
(2.2 BYA) Earth appeared as it does today
By this time, Earth had cooled and was no longer covered in lava and active volcanoes. Earth had north and south poles. The moon had been earlier created from a collision and was now in orbit with Earth. The asteroid belt was full of particles left over from the formation of Earth and the other planets. -
(2 BYA) O2
At this time, the form of oxygen present in the atmosphere (O2) had risen to the levels that they are at today. -
(2-1.5 BYA) Endosymbiosis
Types of small, aerobic prokaryotic cells began to live inside a larger, anaerobic prokaryotes. The small anaerobic prokaryotes inside the larger ones became the organelles and provided energy for the larger cells. The larger cells in turn provided protection for the smaller cells. This forms the theory of how eukaryotic cells were born. -
(1 BYA) Ozone Formation
At this time, the ozone (O3) formed. It helped to protect organisms against harmful UV rays so that they could live on land in addition to water. Without ozone, life would still be limited to habitation in an aqueous environment. -
(1665) First Microscopes
Leeuwenhoek created the first mciroscope that was later modified by Robert Hooke. Hooke used an early light microscope, the first three-lens configuration, to look at cork up close. He found that cork was made of tiny chambers that he called cells. These microscopes were improved upon and are widely used today. -
(1768) Spallanzani's Experiment
Spallanzani's experiment consisted of boiling broth in multiple flasks, and sealing the experiment group of flasks. The broth in the open flask got cloudy, while the broth in the closed flask remained clear. It showed that there are micro-organisms carried in the air. -
(1862) Pasteur's Experiment
Pasteur demonstrated fermentation of micro-organisms. His experiment involved boiling broth in two different flasks, both of them open. One of the flasks had a curved neck. The broth in the straigh neck flask was cloudy. His experiment demonstrated that there are germs in the air. Germs got caught in the curved neck of the one flask, so the broth remained clear. -
(1903) Radiometric Dating
Radiometric dating allowed scientists to more accurately date Earth and find its age. It involves finding the proportion of certain elements in something like a rock and using the known decay rates of elements such as carbon. -
(1924) Oparin's Hypothesis
Oparin produced a theory of life on Earth developing through a gradual chemical evolution of carbon-based molecules.Oxygen in the atmosphere prevented the synthesis of certain organic compounds. He also proposed that at one point spontaneous generation was possible and did happen, but no longer can. -
(1952) Miller-Urey Experiment
They used an experiment to test the chemical origins of life. Their experiment simulated the conditions of early Earth. It showed that organic compounds could have been created from chemicals in the air. -
(1964) Fox
Fox studied moon rocks from the first missions to the moon. He also speculated that polymers called "proteinoids" were a mixture of amino acids subjected to intense heat were what the first living cells came from. -
(1966) Lynn Margulis
Lynn Margulis is a biology professor who wrote a paper on her theory of the origin of eukaryotic cells. This theory is called endosymbiosis and mentions that larger prokaryotic cells took in smaller prokaryotic cells to create a eukaryotic cell. -
(1982) Thomas Cech
Thomas Cech first showed that RNA has other functions. He studied how DNA and the genetic code are transcribed into RNA in unicellular organisms. This led him to find that RNA has more functions than simply carrying genetic material. -
(1668) Redi's Experiment
Redi conducted an experiment to prove that living things come from other living things. He set up 6 jars that he divided into 2 groups of 3. In half the jars he covered the tops with gause so that nothing could get in but air. He left the other half of the jars open. All of the jars contained meat. The jars that were left open had maggots after a period of time, while the other ones didn't. This showed that living things cannot spontaneous generate from non-living things (the meat).
