Earth's Early History

Earth's Early History

Page 72

Essential Question: What do scientists hypothesize about early Earth & the origin of life?
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Slide 1: Slide
Biology10th Grade

This lesson contains 13 slides, with interactive quizzes and text slides.

Items in this lesson

Earth's Early History

Page 72

Essential Question: What do scientists hypothesize about early Earth & the origin of life?

Slide 1 - Slide

Intro to Earth
  • After the big bang (13.7 billion years ago), pieces of cosmic debris were flying throughout the universe. 
  • As cosmic debris collided, large planetary bodies were formed.  
  • Gravitational forces caused these planetary bodies to begin orbiting larger objects, such as stars, causing the planets to round out.  

Slide 2 - Slide

How did Earth form?

  • Earth formed from the collision of cosmic debris.
  • Early Earth was incredibly volcanic, suffered many collisions, and had little to no oxygen & no liquid water. 
  • Around 4.2 billion years ago, the surface of Earth cooled and atmospheric water vapor cooled.  It fell as rain and formed our oceans.

Slide 3 - Slide

Early Earth's Atmosphere
  • Early Earth's atmosphere contained almost no oxygen.  It was mainly carbon dioxide, water vapor, and nitrogen.
  • At that time, the sky was pinkish-orange and a taking a breath would be toxic enough to kill you.

Slide 4 - Slide

So, how did life form?
  • Many basic building blocks (such as amino acids) can be found on modern meteorites and comets.  
  • Scientists hypothesize that many organic building blocks, such as amino acids, were found on early Earth as well.

Slide 5 - Slide

Miller-Urey Experiment
  • In 1953, two scientists name Miller & Urey wanted to test if early Earth's atmosphere and the organic molecules we know were present could spark life.
  • The Miller-Urey experiment supported the idea that organic compounds necessary for life could have arisen from non-living compounds found on Earth when energy was applied.

Slide 6 - Slide

Review question: What do amino acids combine to make (hint: which macromolecule are amino acids the monomer of)?
Nucleic acids

Slide 7 - Quiz

Review Question (again!): Which macromolecule makes up cell membranes?
Nucleic Acids

Slide 8 - Quiz

From amino acids to cells...
  • Just like amino acids, simple lipids called "fatty acids" could be formed from non-living compounds on early Earth.
  • These fatty acids could have assembled to form the first membrane-enclosed "protocells."
  • Just like the Miller-Urey experiment, protocells have also been generated in labs by simulating early Earth's conditions.

Slide 9 - Slide

The RNA Hypothesis
  • Because RNA is less complex than DNA and is used directly in the production of proteins, it is hypothesized that early protocells carried their genetic information on RNA.
  • DNA evolved later on.

Slide 10 - Slide

Slide 11 - Slide

                  Atmospheric Changes
  • The first prokaryotic cells in the fossil record are from 3.5 billion years ago.
  • Roughly 2.2 billion years ago, photosynthetic structures appeared within these early bacteria.  They began converting Earth's carbon dioxide to oxygen.  At this time, the ozone layer formed & the sky changed to blue.

Slide 12 - Slide

The Rise of the Eukaryotes

  • The first eukaryotic cells in the fossil record are from 2.1 billion years ago.
  • Early eukaryotic cells most likely formed from the joining together of smaller prokaryotic cells, called endosymbiosis.
  • Lots of evidence, including the fact that the mitochondria has its own DNA and are roughly the same size as a prokaryotic bacteria, support the endosymbiotic theory.

Slide 13 - Slide