Mass extinction

Definition

Mass extinction refers to a widespread and rapid decrease in biodiversity on Earth, where a significant percentage of species go extinct in a relatively short geological time frame. These events have profound impacts on the evolution of life and the environment, shaping the course of biological history and altering ecosystems dramatically.

5 Must Know Facts For Your Next Test

1. There have been five major mass extinctions in Earth's history, including the Permian-Triassic extinction and the Cretaceous-Paleogene extinction.
2. Mass extinctions can be caused by various factors such as volcanic eruptions, asteroid impacts, climate change, and changes in sea levels.
3. The aftermath of mass extinctions often leads to periods of increased biodiversity as surviving species evolve and fill ecological niches.
4. The current rate of species extinction is estimated to be much higher than the natural background rate, raising concerns about a potential sixth mass extinction driven by human activities.
5. Mass extinctions not only affect animal life but also have significant consequences for plant life and entire ecosystems.

Review Questions

• How do mass extinctions influence the evolutionary trajectory of life on Earth?
  • Mass extinctions significantly reshape the evolutionary landscape by removing dominant species and opening up ecological niches. This allows for adaptive radiation, where surviving species evolve rapidly to fill newly available roles in the ecosystem. As these new species emerge and diversify, they can lead to an increase in biodiversity over time, ultimately contributing to the complex web of life we see today.
• Discuss the major causes of historical mass extinctions and how they relate to changes in Earth's environment.
  • Historical mass extinctions have been triggered by factors such as volcanic eruptions, asteroid impacts, and drastic climate changes that alter habitats and disrupt food chains. For example, the Cretaceous-Paleogene extinction is attributed to an asteroid impact that caused significant environmental changes, including a 'nuclear winter' effect that drastically cooled temperatures. These events highlight the intricate connections between biological evolution and Earth's changing environment.
• Evaluate the implications of the current extinction crisis in relation to previous mass extinctions and future biodiversity.
  • The current extinction crisis is characterized by an alarming rate of species loss primarily driven by human actions such as habitat destruction, pollution, and climate change. Compared to previous mass extinctions, which were natural events, this ongoing crisis is largely anthropogenic and may lead to a sixth mass extinction. The potential loss of biodiversity not only threatens ecosystems but also jeopardizes human survival through the loss of ecosystem services that are vital for life, such as clean water, pollination, and climate regulation.

Related terms

biodiversity: The variety of life in a particular habitat or ecosystem, encompassing the diversity of species, genes, and ecosystems.

extinction event: A specific period in Earth's history during which a large number of species die out simultaneously or in a relatively short time span.

adaptive radiation: The process by which organisms diversify rapidly into a wide variety of forms to adapt to different environments, often following a mass extinction event.