Comment: 01:13 - 02:04 (00:51)
Source: Annenberg/CPB Resources - Earth Revealed - 11. Evolution Through Time
Keywords: "James Sadd", algae, fossil, Australia, Africa, "North American Continent", plant, animal, life, origin, bacteria
Our transcription: This is algae, one of the simplest organisms on Earth, and it's been around an extremely long time.
From fossil evidence we know that algae has been on Earth at least 1.8 billion years.
Even older and more primitive organisms have been found in rocks from all over the world.
The probable fossil remains of blue green algae in bacteria have been found in rocks nearly three billion years old in Australia, in Africa, and even here in North America.
The study of fossils has enabled scientists to identify thousands of species in plants and animals that once inhabited the Earth.
But the picture of ancient life is far from complete, especially our understanding of life's origins.
An enormous challenge for scientists is to fill in the gaps in our knowledge of life's history, and one of the best ways to start is to go to the rocks themselves and literally dig for clues.
Geology School Keywords