9.1 and 9.2 notes

Chapter 9 – Sustaining Biodiversity Sections 9.1 and 9.2
Biological Extinction – When a species can no longer be found
anywhere on the earth
Trophic cascade – occurs when there is a sharp decline in top
predators resulting in degradation of habitats and ecosystem
Example – Sea otters and kelp forests
A mass extinction occurs when an estimated 50 to 95% of the
earth’s species become extinct. Five may have occurred in the
past. The causes are poorly understood.
Extinction is natural .
Background extinction is the rate that existed before modern
humans evolved.
This is estimated to be 1 species per year for every 1 million
It is estimated that today’s rate of extinction is 100 to 1,000
times the background rate. Average loss is 2 to 27 species per
We may lose as many as 50% of the earth’s species by the end
of the century.
How would this effect ecosystem services? Air and water
purification, pollination, pest control
Why may an extinction rate 10,000 that of background
extinction be considered low?
1) threats to ecosystem services will continue as human
population increased
2) biodiversity hotspots are at great risk EX. Rainforests
3) We are eliminating diverse environments that serve as
potential sites for the emergence of new species
Endangered – so few individuals they could become extinct
Threatened (vulnerable) – enough remaining to survive in the
short term
Who is the IUCN?
Critically endangered species
What does it mean to become functionally extinct?
Examples: Baiji dolphin, white rhino
List several characteristics of endangered species and include
examples for each.
Low reproductive
Blue whale, giant
panda, rhinoceros
Blue whale, giant
panda, Everglades
Feeds at high
trophic level
Bengal tiger, bald
eagle, grizzly bear
Large territories
African violet,
some orchids
California condor,
grizzly bear, Florida
9.2 Does it matter if species become extinct?
Explain the three reasons why we should try to prevent