unit 3 b ch 10 s2 biodiversity at risk
TRANSCRIPT
Biodiversity
Ch10, Section 2: Biodiversity at RiskStandards: SEV1a, 1d, 1e
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
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.
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.
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
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
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
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
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.
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.
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”)
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
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 laws- overfishing
& pollution
• Islands– Have distinct & limited number of
species– Very vulnerable to disturbances by
people
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)
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