Question

The greatest extinction in the history of life on Earth: a. occurred at the end of the Permian period. b. occurred at the end of the Cretaceous period. c. occurred at the end of the Ordovician period. d. occurred at the end of the Cambrian era. e. may be occurring now.

Short answer

The greatest extinction in the history of life on Earth occurred at the end of the Permian period.

Step-by-step solution

Research the Extinction Events

Identify and research major extinctions that happened at the end of each period listed in the options. Pay attention to the magnitude of the extinction events.

Identify the Greatest Extinction

Based on your research in Step 1, identify the greatest extinction in the history of life on Earth.

Match the Extinction to the Periods

Match the period in which the greatest extinction occurred to the options listed in the question.

Key concepts

Permian Extinction

The Permian Extinction, sometimes dubbed "The Great Dying," marks the most significant extinction event in Earth's history. This catastrophic event occurred approximately 252 million years ago, at the end of the Permian geological period. During this extinction, an astonishing 96% of marine species and about 70% of land species vanished. Scientists believe this mass extinction was triggered by a series of volcanic eruptions in what is now Siberia.
These eruptions led to massive amounts of volcanic gases entering the atmosphere, causing drastic climate changes.

• Rapid global warming occurred, affecting ecosystems worldwide.
• Ocean anoxia, where oceans lose oxygen, severely impacted marine life.
• Acid rain and habitat loss on land contributed to terrestrial species' extinction.

Understanding the Permian Extinction is crucial as it provides insights into how climate shifts and environmental changes can impact life on Earth.

Cretaceous Extinction

The Cretaceous Extinction, known for the demise of the dinosaurs, occurred roughly 66 million years ago. It marks the end of the Cretaceous geological period. Unlike the Permian Extinction, which was the largest, the Cretaceous Extinction is perhaps the most famous due to its effect on the dinosaurs, among other species. This extinction event is largely attributed to an asteroid impact that created the Chicxulub crater in modern-day Mexico.

• The impact generated massive dust clouds, significantly altering the climate.
• Reduced sunlight affected photosynthesis, disrupting plant life and the animals depending on them.
• Tidal waves and wildfires add to the destruction, leading to a significant loss of life across multiple species.

Despite the dramatic loss of species, this event paved the way for the rise of mammals and eventually human beings, altering the course of evolutionary history.

Major Extinction Events

Throughout Earth's history, several Major Extinction Events have significantly reshaped life. Each event led to substantial losses of species, wiping out large percentages of life forms and reorganizing ecological systems.

• Ordovician-Silurian Extinction: Occurred about 444 million years ago, severely affecting marine life due to significant climate changes.
• Late Devonian Extinction: Around 375 million years ago, with 75% of species wiped out, primarily affecting shallow seas.
• Triassic-Jurassic Extinction: Saw the demise of many large land animals approximately 200 million years ago, giving rise to the dinosaurs.

These events demonstrate how environmental factors like climate shifts, volcanic activities, and celestial impacts have intermittently challenged Earth’s biological diversity and resilience.

Geological Periods

Geological Periods are divisions in Earth's history, categorizing vast intervals of time marked by significant geological, climate, and biological events. These periods provide a timeline for the evolutionary history of life and the planet's transformations.

• Paleozoic Era: Known for the development of early life forms and spanning several periods including Cambrian, Ordovician, and Permian.
• Mesozoic Era: Often referred to as the "Age of Reptiles," encompassing the Triassic, Jurassic, and Cretaceous periods.
• Cenozoic Era: The current era, starting about 66 million years ago, following the Cretaceous Extinction, marking the rise of mammals and hominids.

Each geological period is characterized by unique life forms and significant geological events, offering a framework for understanding Earth's dynamic history and the evolution of life.