A mass extinction event is when species vanish much faster than they are replaced. This is usually defined as about 75% of the world’s species being lost in a ‘short’ amount of geological time – less than 2.8 million years

Top Five Extinctions

• Ordovician-silurian Extinction: 440 million years ago.
• Devonian Extinction: 365 million years ago.
• Permian-triassic Extinction: 250 million years ago.
• Triassic-jurassic Extinction: 210 million years ago.
• Cretaceous-tertiary Extinction: 65 Million Years Ago.

Reasons for first mass extinction

• The first mass extinction on Earth occurred in a period when organisms such as corals and shelled brachiopods filled the world’s shallow waters but hadn’t yet ventured onto land
• Cooling climate likely changed the ocean circulation pattern. This caused a disruption in the flow of oxygen-rich water from the shallow seas to deeper oceans, leading to a mass extinction of marine creatures.
• Mounting evidence points to several episodes in the Earth’s history when oxygen levels also dropped in cooling climates
• Computer modelling simulations suggested that climate cooling was likely responsible for the Late Ordovician mass extinction. They also noticed a lack of oxygen or anoxia in deep oceans during the period.
• This deep-sea anoxia affected ocean circulation. Ocean circulation is a very important component of the climatic system.
• Climate cooling may have led to changes in nutrient cycling, primary producer communities which ultimately drove the Late Ordovician mass extinction.

We are experiencing drastic changes to our planet, including extreme weather such as flooding, drought and wildfires. Research shows humans are the cause of these changes. Since the Industrial Revolution, we have been putting pressure on nature by using its resources without supporting recovery. Right now, it seems likely we are experiencing a sixth, and it is undoubtedly the result of human actions, including human-induced climate change.

How to structure:

1. Give an intro about mass extinctions
2. Briefly mention the number of mass extinctions happened so far
3. Examine the reasons for the first mass extinction
4. Mention about the ongoing debate of whether Earth is going through another mass extinction to conclude

Reference:

1. https://indianexpress.com/article/explained/explained-earth-first-ordovician-mass-extinction-7611094