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