QXT2 Task 7 Mass Extinctions
Over 4.6 billion years ago the earth came into existence and life on earth 3.5 billion years ago. Since the inception of life on earth millions of species have existed, yet large percentages of these organisms have gone extinct leaving few if any remains. The geologist, Hutton and Lyell proposed that the earth is old and the earth changes over time. Change in the earth directly correlates with the organisms that exist on earth. When examining the geologic record it shows periods of mass extinctions created by catastrophic events or gradual changes. The mechanisms believed to have initiated the most significant changes are: meteorites, human activities, oxygen entering the atmosphere, and continent formations.
Meteorite impacts have become one of the most accepted theories for extinction events supported by the geologic record. Scientific studies have examined the impact of both small and large collisions between the earth and different sizes of meteorites; which are rock fragments from outside the atmosphere that burn and glimmer …show more content…
History has revealed significant periods of major mass extinction phases since the beginning of written history, and although extinction is a natural part of evolution, the current rate of loss is unprecedented. The extinction rate use to be one to five species per year. Today we are losing dozens species every day solely because of human activities. Habitat loss, the introduction of invasive species, and global warming are a few of the human activities that have claimed so many species. Scientists calculated that 99% of the current endangered species are at risk because of human endeavors. Our endeavors create the potential risk of entire food webs collapsing and biodiversity as we know it ending. Species diversity engenders stability within the ecosystem and long term survival for each