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

Geological Timescale

A hierarchically divided scale marking major intervals of Earth's history including eons, eras, periods, epochs, and ages.

Deep Time

The immense scale of geological time, often referenced by significant events in Earth's history.

Relative Dating

A technique for estimating the age of fossils based on their position within rock strata.

Isotope Dating

A method of determining the age of materials using the decay rates of radioactive isotopes.

Carbon-14

An isotope used for dating organic materials less than 50 to 60 thousand years old.

Half-Life

The time required for half of the original parent isotopes to decay into daughter isotopes.

Precambrian

The eons before the diversification of multicellular life, including the Hadean, Archean, and Proterozoic.

Cambrian Explosion

A significant event marked by rapid diversification of multicellular organisms in the oceans.

Terrestrial Origin Hypothesis

The theory that life originated on Earth from simple compounds that formed complex molecules exposed to lightning.

Extraterrestrial Origin Hypothesis

The theory that organic molecules or early life arrived on Earth via meteorites.

Miller-Urey Experiment

A 1953 experiment that simulated early Earth's conditions and produced organic compounds, supporting the idea of spontaneous life formation.

Autotrophic

Organisms that synthesize complex molecules from inorganic substances; potentially how early life forms operated.

RNA World Hypothesis

The theory suggesting RNA was the first molecule to catalyze reactions and store genetic information.

Stromatolites

Layered structures created by microbial mats trapping mineral deposits, indicative of early biological activity.

Plate Tectonics

The theory describing the movement of Earth's crustal plates, affecting continental drift and evolutionary processes.

Desiccation

The process of drying out, a challenge faced by early terrestrial organisms when colonizing land.

Photosynthesis

The process by which plants convert light energy into chemical energy, contributing to an oxygen-rich atmosphere.

Anthropocene

A proposed geological epoch defined by significant human impact on the Earth's geology and ecosystems.

Binomial Nomenclature

A standardized system for naming species using two names, indicating genus and species.