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Chapter 5
Lecture
Outline
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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.
• Four 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
– Functional diversity means the richness of organisms (or
systems) capable filling the same role in a given habitat
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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
Invasive species are a growing threat
Pollution poses many different types of risk
Population growth
Overharvesting & commercial collection
predator and pest control
Fragmentation reduces habitat to small, isolated patches
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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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