1. Ch10, Section 2: Biodiversity at Risk
Standards: SEV1a, 1d, 1e
Biodiversity

2. What is the difference between
threatened, endangered, & extinct?
• Threatened- species is
declining so much it is likely
to become endangered if
not protected.
• Endangered- species that is
likely to become extinct if
not protected.
• Extinct- last members of a
species die.
– Local extinction- species is
extinct in local area/region
– Global extinction- species is
extinct on entire planet

3. What are natural causes of extinction?
• There have been 5 major
natural mass extinctions
since the beginning of
geologic time.
• These are caused by
– Asteroids
– Major volcanic eruptions
– Both caused drastic
changes in climate.
• Many species could not
adapt quickly enough so
they died.

4. What is the “6th extinction”?
• “6th extinction” is not
caused by natural
events- caused by
humans.
• Rate of extinction has
increased by multiple of
50 since 1800.

5. What types of species are prone to
extinction?
• Generalist species
– Large populations & adapt
easily
– NOT likely to become extinct
– Ex: cockroach, rat, racoon
• Specialist species
– Small populations & can’t
adapt easily b/c they have
specialized needs for food or
habitat
– Includes many species that
migrate-whooping crane
– May be exploited by humans
– Ex: giant panda, salamanders

6. How do humans cause extinctions?
• Remember H-I-P-P-O
– These are the 5 ways
humans cause
extinctions.
•
•
•
•
•
H- Habitat Destruction
I- Invasive exotic species
P- Pollution
P- Poaching
O- Overharvesting

7. H- Habitat Destruction/Fragmentation
• Humans use land to
– Build homes
– Build roads, canals
– For agriculture
• Using the land, we destroy &
fragment animal habitats
• Causes 75% of all extinctions
• Ex: Florida Panther- range
consisted of entire southeast,
now restricted to
southernmost tip of Florida
thanks to habitat
fragmentation. Need lots of
territory to live & hunt

8. I- Invasive exotic species
• Endemic- native to an area and
usually limited in number
• Exotic species- not native to a
particular area.
• Invasive- cause damage in a
particular area.
• Invasive exotics are more
successful than endemics b/c:
– Do not have natural predators
– Outcompete endemic species for
space/food
• Ex: kudzu, fire ants, zebra
mussels, snakehead fish

9. Invasive exotics introduced
intentionally…?
• Invasive exotic mongoose
was brought to Hawaii to
get rid of another invasive
species- rats.
• Rats are active at night.
• Mongoose was active
during the day.
• Instead of eating rats,
mongoose ate native
birds & their eggs.
• Epic Fail.

10. P- Pollution
• Types of pollutants
– Cleaning agents
– Drugs & other chemicals
– Burning fossil fuel- makes
water acidic for fish &
amphibians
– Pesticides
• Ex: DDT- used in 1950’s
• Caused egg shells of bald eagles
to become too thin.
• Mother birds sat on eggs to
incubate and they would break.
• Main reason bald eagles were
on endangered species list.
• DDT banned in 1970s and now
bald eagle populations have
recovered.

11. P- Poaching
• Poaching- illegal hunting of an
organism
• Laws are established in many
countries to prevent illegal
hunting.
• In developing countries these
organisms may be a source of
food, medicine or income.
• Should they stop killing “pretty
animals” or feed their families
with them?
• Ex: all large cats (skin, teeth
gallbladders), elephants (ivory
tusks), rhinos (horns for
“medicine”)

12. O- Overharvesting
• In the past, catching fish
or whales was done
with small boats,
harpoons, rods/reels
• Now technology
enables us to locate &
harvest them in large
quantities.
• Ex: most commercial
fish are overharvested

13. What regions have the most critical
levels of biodiversity?
• Tropical rainforest
– Cover less than 7% of land but have
50% of world’s species
– Still many unknown species that may
benefit man (medicine)
• Cora reefs & coastal ecosystems
– Invertebrate “nurseries”- many
mollusks & crustaceans lay eggs here
& babies grow up here
– Used for food, ecotourism
– Protect mainland from waves, storms
– Not well protected by lawsoverfishing & pollution
• Islands
– Have distinct & limited number of
species
– Very vulnerable to disturbances by
people

14. What is a biodiversity hotspot?
• Biodiversity hotspots
– The most threatened areas
of high species diversity.
– Have high number of
endemic species and
threatened by human
activities
– Most have lost 70% of their
original habitat thanks to
human encroachment.
– Ex: Madagascar (see map)

15. Are any biodiversity hotspots in U.S.?
• Yes!
• Some of our hotspots:
–
–
–
–
–
FL Everglades
Midwestern Prairies
CA coastal region
Pacific northwest rainforest
Hawaii
• Organisms threatened by
– Land use for agriculture &
housing
– Dam construction
– Overuse of water
– Mining