the sixth extinction. a mass extinction is: - when at least half of all species (including animals...

THE ACCELERATING LOSS OF SPECIES

The Sixth Extinction

Mass Extinctions

A mass Extinction is: - When at least half of all species (including

animals and plants) die within a relatively short time.

We know these extinction occurred -Through the fossil record -Fossils of plants and animals in early layers

are suddenly not present in later rock layers. Scientist believe that 99% of all plant and

animal species that have ever lived are now extinct.

The First Extinction

Ordovician-Silurian 440 million years ago Caused by: sudden global cooling Extinction of marine organisms This was a time when the Earth was

covered with land plants.

Second Extinction

Devonian Extinction 370 million years ago Caused by: possible climate change Extinction of tropical marine species

The Third Extinction

Permian – Triassic Extinction 245 million years ago Caused by: climate change, plate

tectonic movement or possible comet or meteor impact.

Largest mass extinction – so far Killed a range of species, including

vertebrates Only 10% of species survived.

The Fourth Extinction

Triassic – Jurassic Extinction 210 mya Unknown cause Extinction of land vertebrates

The Fifth Extinction

Cretaceous-Tertiary 65 million years ago Caused by: collision of comet or meteor

and/or volcanic eruption Extinction of dinosaurs, marine life, and

many other plant and animal species 50 – 75% of animals extinct Global temperature decreased Rise of the primates

The Sixth Extinction

The sixth extinction is happening today. All other mass extinctions were caused

by natural disasters. The sixth, however is being caused by

modern humans.

When did the sixth extinction begin?

When modern homo sapiens began to radiate to different parts of the world.

Only in places where early hominids lived (Africa, Europe and Asia) did native plant and animal species survive in the beginning.

Some paleoanthropologists believe that the Neanderthals became extinct due to warfare or competition from modern humans.

Quickly after the arrival of modern humans, native species began to disappear

North America – 12,500 years ago - butchering killed off mammoths,

mastodons, and ancient buffalosCaribbean – 8000 years ago- Lost all larger native speciesMadagascar – 2000 years ago

-lost larger lemurs elephant birds, a species of hippo, etc.

How are modern humans causing the sixth extinction?

1. Pollution

2. Warfare

3. Exploitation of Species

4. Overpopulation

5. Unnatural rates of consumption

What can we do?