History of Living ThingsEARLY EARTH

THE FIRST ORGANIC MOLECULES

RNA WORLD HYPOTHESIS

ENDOSYMBIOSIS THEORY

SIGNIFICANCE OF SEXUAL REPRODUCTION

Early EarthEarth is 4.6 billion years old

The earth started off much hotter than today.

The earth’s atmosphere had evidence of high methane, carbon dioxide, ammonia, water vapor, and hydrogen concentrations.

The first life on earth was around 3.5 billion years ago.

What was the Earth’s Early Atmosphere?

Early atmosphere similar to volcanic gases with lots of water vapor, carbon dioxide and nitrogen.

Where did the First Organic Molecules come from?

In 1953 Miller and Urey recreated the early earth environment to see if organic molecules would be created.

Their experiment produced 21 amino acids.

What were the first living molecules?

“RNA World” Hypothesis

Some scientists hypothesize that RNAevolved before DNA

What were the first living organisms? Because of the harsh conditions on earth, and the lack of oxygen, scientists hypothesize that anaerobic prokaryotic bacteria were the first organism to survive on earth.

These organisms either living in hot springs or deep sea vents.

Where did the Oxygen in our Atmosphere come from? Around 2.2 billion years ago photosynthetic bacteria started to grow and used photosynthesis to change the atmosphere.

The produced oxygen combined with iron in the oceans which sank to ocean floor and formed large deposits (This the iron we mine today)

The oceans changed color from brown to blue-green.

As the bacteria reproduced, oxygen gas began to accumulate in the atmosphere and the ozone layer formed and the skies turned from pink to blue.

How did prokaryotes turn into eukaryotic cells?

Endosymbiotic Theory:

Prokaryotic cells entered ancestral eukaryotes and began living inside them.

Mitochondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate energy-rich ATP.

Chloroplasts evolved from endosymbiotic prokaryotes that had the ability to photosynthesize.

What is the significance of Sexual Reproduction and life on earth?

Sped up evolutionary change because sexual reproduction increases genetic variation.

History of Living Things Flowchart