Mass-Extinctions-A-History-of-Lifes-Great-Resets.pptx

Science

1. Mass Extinctions: A History of Life's Great Resets Throughout Earth's long history, life has faced several cataclysmic events that drastically reshaped its biodiversity. These "mass extinctions" offer critical insights into the fragility and resilience of ecosystems.

2. Five Great Extinction Events 1 Ordovician Extinction Around 443 million years ago, a severe ice age led to massive sea level drops, decimating marine life. 2 Devonian Extinction Roughly 359 million years ago, this prolonged crisis primarily affected marine species, possibly due to oceanic anoxia. 3 Permian Extinction The "Great Dying" about 252 million years ago wiped out 90% of Earth's species, linked to volcanic activity and climate change. 4 Triassic Extinction Around 201 million years ago, volcanic eruptions caused rapid climate shifts, leading to the extinction of many large amphibians and reptiles. 5 Cretaceous Extinction Famously, 66 million years ago, an asteroid impact caused global devastation, ending the age of dinosaurs.

3. The Unfolding Crisis: Modern Day Extinction Today, scientists warn that we are in the midst of a sixth mass extinction, driven primarily by human activities. Species are disappearing at an alarming rate, far exceeding natural background extinction rates. This loss threatens the stability of ecosystems and vital services they provide. The consequences for future generations are profound. Understanding the causes of this unprecedented decline is crucial for conservation efforts.

4. Factors Threatening Our Biodiversity Habitat Loss The primary driver of species extinction, often resulting from deforestation, agriculture, and urbanization. Habitat Fragmentation When large habitats are broken into smaller, isolated patches, limiting gene flow and increasing vulnerability.

5. The Silent Invaders: Introduced Species When species are introduced to new environments, either intentionally or accidentally, they can become invasive. They often outcompete native species for resources. They can introduce new diseases or become predators. This disrupts delicate ecosystems and can lead to the decline or extinction of local flora and fauna. Examples include the zebra mussel in North America or the cane toad in Australia, which have devastated native populations.

6. Environmental Contamination: Pollution's Deadly Toll Algal Blooms Excess nutrients from agricultural runoff or sewage can cause rapid growth of algae, depleting oxygen and creating "dead zones" in aquatic environments. Acid Rain Caused by industrial emissions, acid rain damages forests, acidifies lakes, and corrodes infrastructure, severely impacting ecosystems.

7. Overexploitation: Depleting Our Natural Resources Overexploitation refers to the harvesting of renewable resources to the point of diminishing returns. This includes overfishing, unsustainable logging, and excessive hunting. Many species, like the passenger pigeon, were driven to extinction due to relentless human predation. Current practices continue to threaten numerous populations, from marine life to exotic timber. Sustainable practices and conservation are essential to prevent further losses.

8. Reflect and Act: Quiz Time! Now that we've explored the history and causes of extinction, let's test your knowledge and consider what actions can be taken to protect biodiversity.