Background extinction rate

Definition

The background extinction rate is the average rate at which species go extinct over long periods of geological time, typically estimated to be around 1 to 5 species per million species per year. This concept provides a baseline for understanding biodiversity loss and is crucial for analyzing mass extinction events, such as those occurring at the end of significant geological periods.

5 Must Know Facts For Your Next Test

1. The background extinction rate serves as a standard for comparing the severity of mass extinction events, which are characterized by significantly higher rates of species loss.
2. During the end-Ordovician extinction, estimates suggest that the extinction rate was much higher than the background level, leading to a major loss of marine biodiversity.
3. The end-Cretaceous extinction event saw an estimated 75% of Earth's species wiped out, far exceeding the background extinction rate, primarily due to catastrophic events like asteroid impacts.
4. Understanding the background extinction rate helps scientists predict future biodiversity losses and assess the impacts of human activities on ecosystems.
5. Factors such as climate change, habitat destruction, and pollution have contributed to rising extinction rates in modern times, pushing many species beyond their natural background extinction rates.

Review Questions

• How does the background extinction rate help scientists assess the impact of mass extinctions?
  • The background extinction rate provides a baseline for understanding normal levels of species loss over geological time. By comparing current extinction rates to this baseline, scientists can determine whether a mass extinction event is occurring. For example, during both the end-Ordovician and end-Cretaceous extinctions, the rates of extinction far exceeded the background rate, indicating significant ecological disruptions.
• Discuss how the end-Ordovician and end-Cretaceous extinctions illustrate variations from the background extinction rate.
  • Both the end-Ordovician and end-Cretaceous extinctions highlight dramatic deviations from the background extinction rate. The end-Ordovician extinction involved a loss of around 85% of marine species due to climatic changes and glaciation, whereas the end-Cretaceous event led to approximately 75% of species disappearing, largely due to an asteroid impact. These events show how external factors can trigger rapid biodiversity loss that starkly contrasts with normal background levels.
• Evaluate the implications of current extinction rates compared to historical background extinction rates and their significance for biodiversity conservation.
  • Current extinction rates are alarmingly high compared to historical background rates, largely driven by human activities like habitat destruction and climate change. This unprecedented acceleration in species loss threatens ecosystems and reduces biodiversity, impacting ecological stability. Evaluating these trends is essential for effective conservation strategies aimed at preserving remaining biodiversity and mitigating future extinctions, emphasizing the urgent need for action in light of this crisis.

Related terms

Mass extinction: A rapid and widespread decrease in the biodiversity on Earth, characterized by the extinction of a large number of species in a relatively short period.

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

Species resilience: The ability of a species to withstand environmental changes and recover from disturbances, which can impact its survival rates and influence extinction patterns.