catastrophes
Changes in life forms, the geologic time scale, and additions and extinctions are studied throughout Earth's history. The end of each era was caused by a major catastrophe that also resulted in a mass extinction. Some of the main catastrophes have been climate change, volcanic activity, and the impact of an asteroid or comet.
Climate change
The climate is constantly changing and has impacted the life forms within in it. Early on, life forms had to adapt to changing conditions based on the formation of the atmosphere and oceans.
volcanic activity
Volcanic activity has been present from the earliest days of Earth and was one of the most common events during the Precambrian time. Often species could not survive massive eruptions that blocked out the Sun's light and produced extreme heat.
impact of an asteroid or comet
Scientists believe an asteroid or comet impacted the Earth at the end of the Mesozoic Era. The impact caused a chain reaction of events where dust and smoke rose into the air blocking sunlight and changing the atmosphere. Without sunlight many plants died, followed by the animals that relied on plants as a food source. This impact caused the disappearance of many groups of animals, including the dinosaurs.
extinction
A species is extinct if no members of that species are still alive. Almost all of the organisms that have ever lived are now extinct. Endangered species have very few remaining species alive; meaning that if nothing is done, they will become extinct. Extinct and endangered species can be studied to determine what caused them to become extinct or endangered and identify ways to prevent it from happening to similar species.
natural factors
Natural causes of extinction have occurred throughout Earth's history. Not all extinctions are considered negative because they allow for new life forms to thrive.
Some natural factors of extinction include:
Volcanic eruptions
Global Warming
Global Cooling
Oxygen levels in sea water
Massive impact from asteroid or comet
Some natural factors of extinction include:
Volcanic eruptions
Global Warming
Global Cooling
Oxygen levels in sea water
Massive impact from asteroid or comet
man-made factors
Man-made causes of extinction have become prominent in more recent times. If humans continue living the way we are today, many more species are likely to become endangered or extinct in the near future.
Some man-made factors of extinction include:
Rainforest cutting
Removal of Natural Habitats
Over-harvesting
Pollution
Some man-made factors of extinction include:
Rainforest cutting
Removal of Natural Habitats
Over-harvesting
Pollution