Summary of Major Events in the Summary of Major Events in the Evolution of LifeEvolution of Life

18 Billion Years Ago18 Billion Years Ago

BIG BANGBIG BANG The universe began with the so called Big The universe began with the so called Big

Bang, an event aboutBang, an event about 13 - 18 billion13 - 18 billion years years ago, during which all the matter in the ago, during which all the matter in the universe was scattered in enormous universe was scattered in enormous explosion.explosion.

4.6 Billion Years Ago4.6 Billion Years Ago

Big Rock: Earth FormsBig Rock: Earth Forms The first atmosphere began to form from: The first atmosphere began to form from:

CO2, CO,CO2, CO, water vapor, water vapor, N2, H2S,N2, H2S, and small and small traces of traces of CH4,CH4, and and NH3NH3..

Lack of Oxygen.Lack of Oxygen.

3.8 Billion Years Ago3.8 Billion Years Ago

THE ORIGIN OF THE ORIGIN OF LIFE.LIFE.

First Prokaryotic Cells First Prokaryotic Cells Appear.Appear.

3.2 Billion Years Ago3.2 Billion Years Ago

Autotrophs.Autotrophs. Little change in atmosphere.Little change in atmosphere.

2.8 Billion Years Ago2.8 Billion Years Ago

Strong evidence of photosynthetic Strong evidence of photosynthetic organisms.organisms.

Oxygen is given off into atmosphere, but Oxygen is given off into atmosphere, but still is less than 1%.still is less than 1%.

2.0 Billion Years Ago2.0 Billion Years Ago

Blue-Green Algae.Blue-Green Algae. Ozone screen begins to form.Ozone screen begins to form.

1.5 Billion Years Ago1.5 Billion Years Ago

First eukaryotic cells First eukaryotic cells appear.appear.

2% oxygen in 2% oxygen in atmosphere.atmosphere.

670 Million Years Ago670 Million Years Ago

Multicellular organisms.Multicellular organisms. 7% oxygen in atmosphere.7% oxygen in atmosphere.

550 Million Years Ago550 Million Years Ago

Shelled Animals.Shelled Animals. Early Land Plants.Early Land Plants. 10 % Oxygen in Atmosphere.10 % Oxygen in Atmosphere.

500 Million Years ago500 Million Years ago

Fishes.Fishes. Land plants.Land plants. Atmosphere same as today, 20% oxygen.Atmosphere same as today, 20% oxygen. Complete ozone screen.Complete ozone screen.

395 Million Years Ago395 Million Years Ago

First amphibians.First amphibians.

321 Million Years Ago321 Million Years Ago

First reptiles.First reptiles.

225 million years Ago225 million years Ago

First flowering plants.First flowering plants. First birds and mammals.First birds and mammals.

MammalsMammals

1 - 2 Million Years Ago1 - 2 Million Years Ago

Human Kind - Homo sapiens.Human Kind - Homo sapiens.