Transcript Mass Extinctions

3/21 B-BAT: EXPLAIN THE SIXTH MASS
EXTINCTION IN THEIR OWN WORDS
• Do Now!
• What mass extinctions do
you know of?
• How did those animals go
extinct?
MASS EXTINCTION
Mass extinctions are periods in Earth's
history when unusually large numbers of
species die out simultaneously or within
a limited time frame
MASS EXTINCTION
• There have been FIVE mass
extinctions in the history of
earth
• Are we currently going through
a sixth?
CREATE A CHART IN YOUR NOTEBOOK
Name
Number
Year
Causes
ORDOVICIAN– SILURIAN
EXTINCTION
• First Mass Extinction
• Occurred ~439 million years ago
• Caused for this extinction include
• Fluctuations in sea level
• extensive glaciations
• global warming
ORDOVICIAN– SILURIAN EXTINCTION
Approximately 25% of the families
and nearly 60% of the genera of
marine organisms were lost
LATE DEVONIAN EXTINCTION
nd
2
•
Extinction
• ~364 million years ago
• Global cooling after large
exploding meteor impacts
may have been responsible
LATE DEVONIAN EXTINCTION
• 22% of marine families
• 57% of marine genera
• including nearly all jawless
fishes
PERMIAN – TRIASSIC EXTINCTION
• 3rd Extinction (THE GREAT DYING)
• ~251 million years ago
• Causes are debated
•The leading candidate is flood
volcanism
•This led to profound climate change
•The volcanism may have been initiated
by a meteor impact
PERMIAN– TRIASSIC EXTINCTION
• 95% of all species (marine as
well as terrestrial) were lost,
including
• 53% of marine families,
• 84% of marine genera, and
• 70% of land plants, insects,
and vertebrates
END TRIASSIC EXTINCTION
• 4th Extinction
• ~199–214 million years ago
• Opening of the Atlantic Ocean by
seafloor spreading related to
massive lava floods that caused
significant global warming
• Marine organisms were most
strongly affected
• 22% of marine families and
• 53% of marine genera were lost
• But terrestrial organisms also
experienced much extinction
CRETACEOUS– TERTIARY EXTINCTION
• 5th Extinction
• ~65 million years ago
• Causes are debated
• A giant asteroid impact in the Gulf of
Mexico
• Climatic changes resulting from
volcanic floods in India
CRETACEOUS– TERTIARY EXTINCTION
• 16% of families,
• 47% of genera of marine
organisms, and
• 18% of vertebrate families were
lost
THINK – PAIR - SHARE
• Close your notebooks
• Turn to your partner
• List the five mass extinctions
and name some of their
characteristics
THE SIXTH MASS EXTINCTION
• Currently happening right now
• Named Anthropocene
• It is estimated there are 5 to 30 million
living species on Earth
• Humans have accelerated, over the
past 200 to 300 years, global species
extinction rates 100 to 1,000 times
Earth’s historical geological background
rate
THE SIXTH MASS EXTINCTION
• Currently threatened with extinction
•12% of birds,
•23% of mammals,
•32% of amphibians,
•52% of cycads (a group of evergreen
palm like plants),
•and 25% of conifers
• In the last several decades, 20% of
Earth’s coral reefs have been degraded
and another 20% destroyed
• Only 44,838 of Earth’s 1,642,189
described species have been assessed
in terms of conservation status by the
International Union for Conservation of
Nature (IUCN) Red List.
• Over 1/3 (i.e., 16,928 species) of the
44,838 species on the IUCN Red List are
threatened with extinction
Based on the trends of nearly 5,000
populations of 1,686 species of
mammal, bird, reptile, amphibian,
and fish, a 30% decline in
biodiversity has been observed from
1970 to 2005
• At present, over half of Earth’s
tropical humid forests have been
destroyed and countless
undiscovered species lost.
• At the current deforestation rate, it
is estimated the remaining tropical
humid forests and the species they
contain will be destroyed by 2060
(1) the spread of invasive species and
genes
(2) overexploitation of species
(3) habitat modification, fragmentation,
and destruction
(4) pollution
(5) climate change
SPECIES THAT HAVE GONE EXTINCT
THREATENED AND ENDANGERED SPECIES
https://www.youtube.com/watch?v=z9gHuAwxwAs
We need to look at the two main
factors causing global
environmental degradation:
(1) the current size of the human
population and
(2) the current natural-resource
consumption rate of the human
population.