Lesson 24: Earth's History and the Diversification of Life

Geological Timescale

A chronological framework that divides Earth’s history into eons, eras, periods, and epochs based on major geological and biological events.

Continental Drift

The gradual movement of Earth’s continents over geological time due to plate tectonics.

Plate Tectonics

The theory that Earth’s lithosphere is divided into plates that move and interact, causing earthquakes, volcanic activity, and continental drift.

Fossil Record

The preserved remains or traces of organisms in sedimentary rock, providing evidence of life’s history and evolution.

Isotope Decay

The process by which unstable isotopes lose energy and transform into more stable forms, used in radiometric dating to determine ages of rocks and fossils.

Miller-Urey Experiment

A landmark experiment that simulated early Earth conditions and demonstrated that organic molecules could form from inorganic precursors.

RNA World Hypothesis

The idea that early life was based on RNA molecules, which could store genetic information and catalyze chemical reactions before DNA and proteins evolved.

Carbon Fixation

The process of converting inorganic carbon (CO₂) into organic compounds, essential for photosynthesis and life.

Stromatolites

Layered structures formed by microbial mats, representing some of the oldest evidence of life on Earth.

Biomarkers

Chemical compounds preserved in rocks that indicate the presence of past life or specific biological processes.

Glaciation

Periods when large ice sheets covered significant portions of Earth’s surface, influencing climate and evolution.

Endosymbiosis

The theory that eukaryotic cells originated when one cell engulfed another, leading to organelles like mitochondria and chloroplasts.

Cambrian Explosion

A rapid diversification of life forms about 540 million years ago, resulting in the appearance of most major animal groups.

Anthropocene

A proposed geological epoch marked by significant human impact on Earth’s ecosystems and geology.