Sustaining the Variety of Life

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lectures

Lectures by Greg Podgorski, Utah State University

Sustaining the Variety of LifeSustaining the Variety of Life

Current Issues in Biology, Volume 4

Scientific American


Concept Review

Sustaining the Variety of Life

• Extinction is a natural process.

• The average lifetime of a species is roughly 1 million years.

• This means that at natural or background rates, one in 1 million species is expected to become extinct each year.

• Current rates of extinction are at least 100 times higher than this background rate


Concept Review


The elevated extinction rate is due to human activities that include

• habitat destruction

• introduction of exotic species

• overharvesting

• and in the future, global warming


Concept Review


• Some species are much more vulnerable to extinction than others, and these species are geographically concentrated.

• To sustain the variety of life, special places rich in threatened species must be identified and protected.

• The intuitive notion that extinctions occur most often in areas where the most people live is wrong.

• Extinctions occur most frequently where fronts of habitat destruction, especially deforestation, overlap concentrations of vulnerable species.


Concept Review


• Probably one-half of the world’s species live in 25 mostly forested, tropical areas where human actions have removed > 70% of the natural vegetation.

• These areas are hot spots for conservation efforts.

• The laws of biogeography explain how species are distributed across the world.


Concept Review


Laws of Biogeography

• Law 1. Most species’ ranges are very small; few are very large.

• Law 2. Species with small ranges are locally scarce.

• Law 3. The number of species found in a given area varies greatly and according to common factors.

• Law 4. Species with small ranges are often geographically concentrated.


Concept Review


• The costs of sustaining biodiversity are large, but so are the benefits.

• The Millennium Ecosystems Assessment report has documented benefits that include food, water, fuel, climate regulation, and many other often undervalued services that are provided by healthy ecosystems.

• There are many possible solutions to conserving biodiversity.

• Ultimately, all solutions must benefit local human populations as well as endangered species.


Concept Review


How can biodiversity be conserved?

• By encouraging conservation groups to purchase logging leases for sensitive tropical wilderness forests.

• By providing economic alternatives to displaced poor people who now clear the majority of tropical forests.

• By connecting now-fragmented forests through forest bridges.


Concept Review


How can biodiversity be conserved?

• By promoting ecotourism to provide a cash incentive to local people to conserve the natural environment.

• By allowing preserved forest tracts to be used as capital in the Kyoto carbon-trading system.

• By promoting understanding of the economic benefits provided by intact ecosystems.



Testing Your Comprehension

At the background rate of extinction, one expects 1 in _________ species to become extinct each year. a) 10b) 1,000c) 10,000d) 1,000,000




At the background rate of extinction, one expects 1 in _________ species to become extinct each year.

d) 1,000,000




Probably of all species live in the world’s hot spots for biodiversity conservation. a) 1/10b) 1/4c) 1/2d) 9/10




Probably of all species live in the world’s hot spots for biodiversity conservation.

c) 1/2




The bulk of tropical forests are cleared by a) multinational logging companiesb) nationally sponsored logging companiesc) local logging companiesd) displaced poor people




The bulk of tropical forests are cleared by

d) displaced poor people




The Millennium Ecosystems Assessment reporta) lists economic benefits provided by ecosystemsb) focuses exclusively on ecotourismc) provides a plan for sustainable tropical forest loggingd) argues against acceptance of the Kyoto Treaty




The Millennium Ecosystems Assessment reporta) lists economic benefits provided by ecosystems



Biology and Society

It is vitally important that we protect each and every species.

StronglyAgree

StronglyDisagreeA. E.C.B. D.



Biology and Society

Since biodiversity is a global resource, binding decisions about biodiversity conservation must be made internationally.

StronglyAgree

StronglyDisagreeA. E.C.B. D.



Thinking About Science

The biogeographic laws state that 1) Most species’ ranges are very small; few are very large; 2) Species with small ranges are locally scarce; 3) The number of species found in a given area varies greatly and according to common factors; and 4) Species with small ranges are often geographically concentrated. Which of these laws imply that a small number of bird species contributes a disproportionately large number of individuals to the world’s bird population? a) Laws 1 and 2b) Laws 2 and 3c) Laws 3 and 4d) Laws 1 and 4



Thinking About Science

The biogeographic laws state that 1) Most species’ ranges are very small; few are very large; 2) Species with small ranges are locally scarce; 3) The number of species found in a given area varies greatly and according to common factors; and 4) Species with small ranges are often geographically concentrated. Which of these laws imply that a small number of bird species contributes a disproportionately large number of individuals to the world’s bird population? a) Laws 1 and 2



Interpreting Data and Graphs

The biogeographic laws state that 1) Most species’ ranges are very small; 2) Species with small ranges are locally scarce; 3) The number of species found in a given area varies greatly and according to common factors; and 4) Species with small ranges are often geographically concentrated. Which law(s) is/are supported by the figure? a) Law 1b) Law 2 c) Law 3d) Law 4




The biogeographic laws state that 1) Most species’ ranges are very small; 2) Species with small ranges are locally scarce; 3) The number of species found in a given area varies greatly and according to common factors; and 4) Species with small ranges are often geographically concentrated. Which law(s) is/are supported by the figure?

c) Law 3d) Law 4




Which of the following regions has the largest area of remaining habitat?a) West Africab) South-Central China c) Tropical Andesd) Central Chile

Region Original Habitat (thousands of km2)

Percent Remaining

West Africa

1,265 10%

South-Central China

800 8%

Tropical Andes

1,258 25%

Central Chile

300 30%




Which of the following regions has the largest area of remaining habitat?

c) Tropical Andes

Region Original Habitat (thousands of km2)

Percent Remaining

West Africa 1,265 10%

South-Central China

800 8%

Tropical Andes

1,258 25%

Central Chile

300 30%

Sustaining the Variety of Life

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