Transcript SB Ch. 6 Extinction Lecture

Chapter 6 Extinction
How is it related to biodiversity?
Sacred Balance Extinction Crisis
 SB (p. 216-219) Suzuki states “Our tenuous inferences
about life in the past are based on fossil remains
suggesting that species expand in number and
complexity and then are suddenly reduced through
successive spasms of extinction.” What evidence does
Suzuki give to support this statement?
Extinction
 Biodiversity: the
variety of life on Earth.
 Evolutionary survival
strategy.
 Biodiversity has
suffered some major
setbacks during the
past 500 million years.
History of Extinction SB Pg.216
Dinos
175 MY
Humans
1 MY
Extinction
Due To:
1.Climate
Change
2. Volcanic
Eruption
3. Meteor
Impact
Biodiversity Recovery
 Process takes millions of
years
 Recovery involves new
species evolving and
replacing old ones.
How many species are there in
the world?
 Approximately 1.4 million species have been
named.
 Of these more than half (751,000) are insects.
 About 248,000 species of plants have been
described
 281,000 non-insect animals (fish, reptiles, birds,
mammals, crabs, starfish, sea urchins, jellyfish,
worms, etc.).
 Relatively few Protists (57,700), fungi (69,000) and
prokaryotes (4,800) have been named.
Background Extinction Rates
 Normal Background
Extinction Rate: 10-25
species/year
 Current rate (SB p.217-218)
 50,000/year
 137/day
 6/hour
Rivet Hypothesis
 Rivet hypothesis suggests that just as a plane can lose the
odd rivet an ecosystem may withstand the loss of one or
a few species without any discernable effect.
 However, like a plane that loses one rivet too many, it
may then suddenly collapse.
Cute Cuddlies vs. Stinky Uglies
Importance of Preserving
Ecosystems
 Trophic Pyramid
 What can happen
if the top is
damaged?
 What can happen
if the bottom is
damaged?
Sacred Balance p. 217
 “We are fortunate to have evolved when biological
diversity has been at the greatest level ever achieved.
Succeeding human generations will not be as fortunate:
the current extinction crisis is without precedent—never
before has a single species been responsible for such a
massive loss of diversity”
 Relationship between population and resources
Resources Demo
Next Generations?
Man vs. Nature: Ikei Island
 Industrialization of Japan causes its coast to become polluted.
 Fish migrate to Ikei Island to cleaner waters
 Dolphins follow fish
 Fish prices increase because there is a decrease in the coastal fish population
due to pollution.
 Fishermen compete with eachother employing new technologies (hand held
lines vs. gill nets) because fish prices increase further decreasing fish
population (overfishing)
 Fishermen compete with dolphins for fish.
 Blame dolphins for low catch rates instead of pollution and overfishing caused
by humans.
 Herd and kill dolphins to thin their numbers.