Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is the only known planet not named after a Greek or Roman deity.
Overview
- Composition: Terrestrial body with a metallic core, silicate mantle, and crustal shell.
- Atmosphere: Nitrogen-oxygen mix supporting aerobic respiration and protecting against solar radiation.
- Hydrosphere: Surface covered ~71% by water, primarily liquid oceans.
- Age: Approx. 4.54 billion years.
Biological History & Fossil Record
Earth’s biosphere has undergone multiple mass extinctions and radiations. Key faunal groups include:
- Trilobites: Ancient marine arthropods demonstrating significant evolutionary endurance.
- Thrived for over 270 million years across global marine environments.
- Recognizable for distinctive fossil preservation; their extinction events remain subjects of ongoing paleontological study regarding environmental pressures and adaptive limits.
- Source analysis: Trilobites: Enduring Success and Mysterious Extinction of Ancient Arthropods