The History of Life
The Big Bang occurred 13.7 billion years ago, creating the universe.
4.6 billion years the solar system formed from a ball of gases called a nebula. – The oldest rocks on Earth are only 3.9 million years old!?!
Earth’s early atmosphere contained –methane –ammonia –hydrogen –water vapor –maybe nitrogen
Conditions on Earth High amount of UV radiation Volcanoes Meteorites Extreme heat
The oceans formed when water vapor condensed and fell to Earth.
SSSSimple organic compounds collected in the water and formed the building blocks of life.
The simple organic compounds collected and reacted to form larger ones. These were primitive “pre-cells”, large molecules with membrane-like structures around them. Scientists have formed structures similar to “pre- cells” – microspheres and coacervates –These structures form spontaneously –Do not have genetic information –Display some properties of life
3.5 billion years ago life appeared! The 1 st organisms were anaerobic prokaryotic heterotrophs. They obtained energy from the molecules in their environment.
When food started to become scarce, organisms began to make their own food – autotrophs Similar to archea Use chemosynthesis to get food
AAAAround 3 billion years ago, photosynthetic organisms appeared. TTTThey produced oxygen and changed the Earth’s atmosphere. TTTThe Ozone layer was formed! –P–Provided protection from UV radiation and life could exist on land
The O 2 in the atmosphere allowed aerobic respiration to occur. –This allowed more energy to be extracted from food molecules. –Allowed for greater complexity and prokaryotes diversified.
Eukaryotic organisms appeared. - Possibly from endosymbiosis. –Mutualistic relationship between primitive eukaryotic organisms and prokaryotes –How mitochondria and chloroplasts formed