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Chapter 5
Lecture
Outline
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Learning Outcomes
After studying this chapter, you should be able to answer the following
questions:
• What are nine major terrestrial biomes, and what
environmental conditions control their distribution?
• How does vertical stratification differentiate life zones in
oceans?
• Why are coral reefs, mangroves, estuaries, and wetlands
biologically important?
• What do we mean by biodiversity? List several regions of
high biodiversity.
• What are four major benefits of biodiversity?
• What are the major human-caused threats to biodiversity?
• How can we reduce these threats to biodiversity?
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In the end, we conserve only what we love.
We will love only what we understand.
We will understand only what we are taught.
–Baba Dioum
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5.1 Terrestrial Biomes
• Biodiversity-the number and variety of
species.
• Biomes-broad types of biological communities
with characteristic types of environments that
occur in different conditions of temperature
and precipitation.
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Figure 5.3 Biomes most likely to occur in the absence of human disturbance or other
disruptions, according to average annual temperature and precipitation. Note: This
diagram does not consider soil type, topography, wind speed, or other important
environmental factors. Still, it is a useful general guideline for biome location.
Source: Whitaker, Robert, C., Communities & Ecosystems, 2e. © 1975. Adapted by permission
of Pearson Education, Inc., Upper Saddle River, NJ.
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• Vertical zonation
is a term applied
to vegetation
zones defined by
altitude.
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Annual temperature and precipitation
levels in terrestrial biomes
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Tropical rainforests
• Tropical
rainforests
occur where
rainfall is
abundant—
more than 200
cm (80 in.) per
year—and
temperatures
are warm to
hot year-round
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Tropical savannas and grasslands
are dry most of the year
• Where there is
too little rainfall
to support
forests, we find
open grasslands
or grasslands
with sparse tree
cover, which we
call savannas.
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Deserts are hot or cold, but always dry
• Deserts occur
where
precipitation
is uncommon
and slight,
usually with
less than
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Temperate grasslands have rich soils
• As in tropical
latitudes,
temperate
(midlatitude)
grasslands occur
where there is
enough rain to
support abundant
grass but not
enough for forests
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Temperate forests
can be evergreen or
deciduous
• These forests by are
grouped by tree
type, broad-leaved
deciduous (losing
leaves seasonally) or
evergreen
coniferous (conebearing).
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Temperate
rainforests
• The coniferous forests
of the Pacific coast
grow in extremely wet
conditions. The
wettest coastal forests
are known as
temperate rainforest,
a cool, rainy forest
often enshrouded in
fog.
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Boreal forests lie north
of the temperate zone
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Tundra can freeze
in any month
• Compared to other
biomes, tundra has
relatively low
diversity.
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5.2 Marine Ecosystems
• Most marine communities depend on
photosynthetic organisms.
• Phytoplankton: algae or tiny, free-floating
photosynthetic plants that often support a
marine food web.
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Open ocean communities vary
from surface to hadal zone
Tidal shores support rich,
diverse communities
Coral reefs are among the best-known marine systems, because
of their extraordinary biological productivity and their diverse
and beautiful organisms
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Tidal shores continued: Mangroves
Mangroves are a diverse group of salt-tolerant trees that grow
along warm, calm marine coasts around the world
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Tidal shores continued:
Estuaries & Salt Marshes
Estuaries are bays where rivers empty into the sea, mixing fresh
water with salt water. Salt marshes, shallow wetlands
flooded regularly or occasionally with seawater, occur on
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shallow coastlines, including estuaries
Tidal shores continued: Tide pools
Tide pools are depressions in a rocky shoreline that are flooded
at high tide but retain some water at low tide.
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5.3 Freshwater Ecosystems: Lakes
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Freshwater Ecosystems continued:
Wetlands
Wetlands (swamps, marshes, &
bogs) are shallow ecosystems in
which the land surface is
saturated or submerged at least
part of the year.
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Freshwater Ecosystems continued:
Streams & Rivers
• Streams form wherever precipitation exceeds
evaporation and surplus water drains from the
land.
• As streams collect water and merge, they form
rivers.
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5.4 Biodiversity
• Biodiversity, the variety of living things.
• Three kinds of biodiversity are essential to preserve
ecological systems and functions:
– genetic diversity is a measure of the variety of
versions of the same genes within individual species
– species diversity describes the number of different
kinds of organisms within a community or
ecosystem
– ecological diversity means the richness and
complexity of a biological community
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Increasingly, we identify species
by genetic similarity
• Species are distinct organisms that persist
because they can produce fertile offspring.
• The phylogenetic species concept, which
identifies genetic similarity, allows for asexual
organisms and sexually reproducing ones that
don’t normally encounter each other.
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Biodiversity hot spots are
rich and threatened
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5.5 Benefits of Biodiversity
• All of our food comes from other organisms
– Many wild plant species could make important
contributions to human food supplies.
• Rare species provide important medicines
– More than half of all prescriptions contain some
natural products.
• Biodiversity can support ecosystem stability
• Biodiversity has aesthetic and cultural benefits
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5.6 What Threatens Biodiversity?
• Extinction, the elimination of a species, is a normal
process of the natural world.
• Threats to biodiversity:
–
–
–
–
–
–
–
Habitat destruction is the main threat
Fragmentation reduces habitat to small, isolated patches
Invasive species are a growing threat
Pollution poses many different types of risk
Human population growth
Overharvesting & commercial collection
Predator and pest control
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5.7 Endangered Species
Management and Biodiversity
Protection
• Hunting and fishing laws protect reproductive
populations
• The endangered species act protects habitat
and species
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Endangered species act terminology
• Endangered species are those considered in
imminent danger of extinction
• Threatened species are likely to become
endangered, at least locally within the
forseeable future.
• Vulnerable species are naturally rare or have
been locally depleted by human activities to a
level that puts them at risk.
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Species Terminology
• Keystone species are those with major effects on
ecological functions and whose elimination would
affect many other members of the biological
community.
• Indicator species are those tied to specific biotic
communities or successional stages or environmental
conditions.
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Species Terminology continued…
• Umbrella species
require large blocks of
relatively undisturbed
habitat to maintain
viable populations.
• Flagship species are
especially interesting or
attractive organisms to
which people react
emotionally.
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Controversy persists in species protection:
• In 1995 the Supreme
Court ruled that critical
habitat—habitat
essential for a species’
survival—must be
protected, whether on
public or private land.
• An important test of the
ESA occurred in 1978 in
Tennessee, when
construction of the
Tellico Dam threatened
a tiny fish called the
snail darter.
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Many countries have laws
for species protection
• Canada’s Committee on the Status of Endangered
Wildlife in Canada (COSEWIC) of 1977 establishes
rules for listing and protecting endangered species.
• The European Union’s Birds Directive (1979) and
Habitat Directive (1991).
• Australia’s Endangered Species Protection Act (1992).
• The Convention on Biological Diversity (1992) is an
International agreement.
• The Convention on International Trade in
Endangered Species (CITES) of 1975.
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Habitat protection may be
better than species protection
• By focusing on populations already reduced to
only a few individuals, we spend most of our
conservation funds on species that may be
genetically doomed no matter what we do.
• It is time to focus on a rational, continentwide preservation of ecosystems that
supports maximum biological diversity rather
than a species-by-species battle for the rarest
or most popular organisms.
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Practice Quiz
1. Why did ecologists want to reintroduce wolves to Yellowstone
Park? What goals did they have, and have their goals
been achieved?
2. Describe nine major types of terrestrial biomes.
3. Explain how climate graphs (as in fig. 5.6) should be read.
4. Describe conditions under which coral reefs, mangroves,
estuaries, and tide pools occur.
5. Throughout the central portion of North America is a large
biome once dominated by grasses. Describe how physical
conditions and other factors control this biome.
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Practice Quiz continued…
6. Explain the difference between swamps, marshes, and bogs.
7. How do elevation (on mountains) and depth (in water) affect
environmental conditions and life-forms?
8. Figure 5.15 shows chlorophyll (plant growth) in oceans and
on land. Explain why green, photosynthesizing organisms
occur in long bands at the equator and along the edges of
continents. Explain the very dark green areas and yellow/
orange areas on the continents.
9. Define biodiversity and give three types of biodiversity
essential in preserving ecological systems and functions.
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Practice Quiz continued…
10. What is a biodiversity “hot spot”? List several of them (see
fig. 5.22).
11. How do humans benefit from biodiversity?
12. What does the acronym HIPPO refer to?
13. Have extinctions occurred in the past? Is there anything
unusual about current extinctions?
14. Why are exotic or invasive species a threat to biodiversity?
Give several examples of exotic invasive species (see fig. 5.27).
15. What is the Endangered Species Act? Describe some of the
main arguments of its proponents and opponents.
16. What is a flagship or umbrella species? Why are they often
important, even though they are costly to maintain?
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