A species is extinct if no members of that species are living. Most organisms that have ever lived on Earth are now extinct.
Natural factors can cause extinctions and have thus been documented and studied over the course of Earth's history.
- Organisms that could not survive changes due to volcanic eruptions and global warming, global cooling during ice ages, changes in oxygen levels in seawater, or a massive impact from an asteroid or comet became extinct.
- Natural extinctions due to competition for resources or inability to adapt to the environment have occurred throughout geologic history.
- When species become extinct, the opportunity exists for another species to fill that ecological niche.
- Not all extinctions that have occurred naturally throughout Earth's history have had a negative impact. Some of these extinctions have often cleared the way for new kinds of life to emerge.
- Scientists have evidence to support claims that humans have contributed to the extinction of many species throughout human history, including the woolly mammoth.
- Scientists have evidence to support the claims that many plants and animals are likely to become extinct in the near future as a result of the negative impact of human activities (clear-cutting, water and air pollution, etc.) on the environment.
- Scientists have evidence to support the claims that human effects on the environment could threaten some biological resources that organisms, including humans, may need for survival.
Natural Extinction Factors
Human-Made Extinction Factors