7.11/7.13 - Extinction/Origin of Life on Earth

Extinction

Extinction is the termination of a species.

• Historical Context: Extinctions have occurred throughout Earth’s history, with at least five major mass extinctions identified.

• Human Impact: Human activity has significantly accelerated extinction rates due to factors like habitat destruction, pollution, and climate change.

• Ecological Stress: Extinction rates can increase during periods of ecological stress.

• Ecological Niches: When a species goes extinct, it leaves behind a niche that can be occupied by other species, leading to shifts in ecosystems.

Mass Extinctions

• Examples: The most famous mass extinction is the event that led to the demise of the dinosaurs.

• Current Concerns: Some scientists suggest we are currently experiencing a sixth mass extinction event driven by human activities.

Origin of Life on Earth

Timeline:

• Earth Formation: 4.6 billion years ago.

• Life-Supporting Environment: 3.9 billion years ago.

• Earliest Fossil Evidence: 3.5 billion years ago.

Chemosynthetic Origin of Life

Miller-Urey Experiment:

1. Background: In the 1950s, biochemists Stanley Miller and Harold Urey conducted a landmark experiment.

2. Purpose: To demonstrate that organic compounds could form spontaneously under conditions thought to resemble those of early Earth.

3. Method:

   • Setup: A mixture of water, ammonia, methane, and hydrogen was sealed in a sterile flask.

   • Simulation: The mixture was heated to produce water vapor, and electric sparks were passed through the gases to simulate lightning.

4. Results:

   • After a week, the experiment produced amino acids, the building blocks of proteins.

   • Significance: This experiment provided evidence that organic molecules necessary for life could form under prebiotic conditions.