The Sixth Extincion

PAST MASS EXTINCTIONS

ORDOVICIAN 88%(440 MYA)

• Mayor climate change (sudden ice age)
• Many sea creatures went extinct
• Supercontinent Godwana in the south pole
• Formation of ice sheets (sea levels fell 70-100)
• Warm-adapted species had nowhere to migrate

DEVONIAN 87%(370 MYA)

• Impact on most marine groups
• Shallow tropical oceans ceased to exist
• Major environmental change
• Lack of oxygen in ocean
• Large volcanic eruptions

PERMIAN 97%(245 MYA)

• Both marine and land animals affected
• Only mass extinctions for insects
• Pangea stretched (hot-dry conditions)
• Highest temperature ever seen
• Lava across Siberia (7x size of france)

TRIASSIC 75% (245 MYA)

• Most large amphibians went extinct
• Dinosaurs had little terrestrial competition
• Lack of sediments to study
• Falling sea level (probable cause)
• A lot of volcanic activity

CRETACEOUS 75% (65 MYA)

• Extinction of dinosaurs
• Mammals and birds emerged dominant
• Large asteroid impact
• Intense volcanic activity
• Dead plants, starved predators and hervibores.

BACKGROUND

30,000 species go extinct per year. (3 per hour) 1000 times more than the background rate

The first phase started when humans dispersed around the world. Everywhere they arrived there was a decline in native species (100,000 years ago)

Second phase was the start of agriculture. Human population grew exponentially. No longer a part of the ecosystem either (10,000 years ago)

Mass extinctions are like a house of cards because by taking out a key card (animal) the whole house goes down (ecosystem)

CAUSES OF

HABITAT DESTRUCTION

• Filling wetlands
• Dredging rivers
• Mowing fields
• Cutting down trees
• Fires in the wild

INVASIVE SPECIES

• Generalists (live everywhere)
• 42% of endangered species
• Spread by human activity
• Prey on native species
• Outcompete native species

OVEREXPLOITATION

• Hunting and fishing
• Trapping
• Collecting
• Pets
• Medicine

THE POLAR BEAR

Polar bears are the most carnivorous of all bears species. Their diet consists mainly on seal and they have no mayor competitors on land

Polar bears need ice to breed, hunt, and denning. This is their most important need. Their life revolves around ice.

POLAR BEARS

Untitled Slide

Polar bears are endangered because of the ice losses due to global warming. They desperately need ice.

If polar bears went extinct there would be overpopulation of seals, since they are the seals major predator

They have been seen on land near ice so it is believed they are getting used to living in land. However some populations in ice are increasing.