Chapter 5:
Principles of Ecology
Biomes and Aquatic Life Zones
5.1 Weather and Climate: An Introduction
 Weather refers to daily conditions such as rainfall and
temperature.
 Climate is the average weather over a long period.
 Climate determines the plant and animal life of a
region.
Major Factors That Determine
Weather and Climate
 The Earth is unequally heated, which
creates three major climatic zones:
 Tropical
 Temperate
 Polar
Figure 05.01: Climate zones. The Earth’s
surface can be roughly divided into the three
major climate zones shown here.
Figure 05.02: Global air circulation.
The Coriolis Effect
 Air tends to flow from the equator to the
poles.
 Weather within the major climatic zones is
altered by wind flow patterns.
 Wind flow patterns are profoundly influenced by
the spin of the Earth.
Topography
 Weather is also affected by topography,
especially mountain ranges.
Figure 05.03: Rain shadow effect. This shows the effect of mountain ranges on rainfall.
Ocean Currents
 Warm water from the equator flows toward the poles.
 This warms landmasses near which it passes.
Figure 05.04: Major ocean currents.
5.2 The Biomes
 The Earth’s surface can be divided into
biologically distinct zones called biomes.
 Each has a distinct climate and unique
assemblage of plants and animals.
 Regional variations occur within each biome.
Figure 05.05: The Earth’s biomes.
The Tundra
 The Arctic tundra, the northernmost biome, is
characterized by the harshest climate.
 Because the growing season is so short, life
on the Arctic tundra is extremely vulnerable to
human actions.
Courtesy of U.S. Fish & Wildlife Services
Courtesy of U.S. Fish & Wildlife Services
© Photodisc
© Photodisc
Figure 05.07A: Tundra species. (a) The ptarmigan and (b) musk ox are both well adapted
for life in the cold Arctic tundra.
Figure 05.08: Arctic oil. Oil development on Alaska’s North Slope causes significant alteration
of the delicate tundra, as shown here.
© Hugh Rose/Accent Alaska
The Taiga
 The taiga is a band of coniferous trees
spreading across the northern continents south
of the tundra.
 Its climate is milder, and its life-forms are more
diverse than those of the tundra.
 The taiga supports many
large populations of wild
animals.
are under heavy pressure
to meet rising demands for
wood and wood products.
© Photodisc/Getty Images
 The forests of this region
Figure 05.09: Old-growth forests such as
these contain species that cannot survive
in younger forests.
The Temperate Deciduous Forest Biome
 The temperate deciduous forest biome occurs in
regions with abundant rainfall and long growing
seasons.
 This biome has been heavily settled by humans
and dramatically altered.
© Photodisc
© Photodisc
Figure 05.11AB: Animals of the temperate deciduous forest. (a) Black bear, (b) white-tailed deer.
© Snehit/ShutterStock, Inc.
The Grassland Biome
 The grassland biome occurs in regions of
intermediate precipitation––enough to support
grasses but not enough to support trees.
 On most continents, the rich soil of the biome
has been heavily exploited by humans for
agriculture.
Figure 05.12: Grassland biome.
© MedioImages/Photodisc/age fotostock
The Desert Biome
 The desert biome is characterized by dry, hot
conditions.
 Often, it abounds with plants and animals
adapted to the heat and lack of moisture.
 The world’s deserts are expanding because of
human activities such as overgrazing livestock
and the production of greenhouse gases.
© Arco Images GmbH/Alamy Images
© Photos.com
Figure 05.17AB: Animals of the desert. (a) Gila monster and (b) ringtail.
© SuperStock/age fotostock
The Tropical Rain Forest Biome
 The tropical rain forest is the richest and most
diverse biome on Earth because of its
abundant rainfall and warm climate.
© Photodisc
Figure 05.18: Tropical rain forest. This endangered biome covers vast areas and is rich in species.
© Photodisc
Rain Forests
 About half of the world’s rain forest has been
destroyed.
 Huge tracts could be eliminated in the near
future, with devastating effects on climate,
plants, and wildlife if current trends continue.
Altitudinal Biomes
 Because climate varies with altitude, the
distribution and abundance of life also
change.
Figure 05.19: Altitudinal biomes.
Alpine tundra
Figure 05.20: Alpine tundra.
© Harald Høiland Tjøstheim/ShutterStock, Inc.
5.3 Aquatic Life Zones
 Aquatic systems are divided into distinct
regions, known as aquatic life zones.
 They may be freshwater or saltwater.
 The abundance of life is determined by
energy and nutrient levels.
 Phytoplankton form the base of aquatic food
chains.
© T.E. Adams/Visuals Unlimited
© Cabisco/Visuals Unlimited
© John D. Cunningham/Visuals Unlimited
Figure 05.21A: Phytoplankton. Unicellular
algae like these are called phytoplankton and
form the base of many aquatic food chains.
Figure 05.21B: Phytoplankton. Unicellular algae
like these are called phytoplankton and form the
base of many aquatic food chains.
Figure 05.22: Zooplankton. These
organisms feed on algae and are
consumed by small fishes.
Freshwater Lakes
 Each has very different conditions and,
consequently, very different life-forms.
 Lakes are divided into four regions:
 the littoral zone
 the limnetic zone
 the profundal zone
 the benthic zone
Figure 05.23:
Zones of a lake.
Figure 05.24: Thermal stratification and turnover in lakes.
Rivers and Streams
 Rivers and streams are complex ecosystems
that rely more on agitation for oxygenation of
their waters than lakes do.
 Many nutrients in streams that support
aquatic life come from neighboring terrestrial
ecosystems.
 The quality of water in a stream is profoundly
influenced by activities in the watershed.
Protecting Freshwater Ecosystems
 Like lakes and ponds, streams are self-
purging but extremely vulnerable to
pollution if sources exceed the capacity to
self-cleanse.
Saltwater Life Zones
 The oceans cover over 70% of the Earth’s
Courtesy of Mr. Mohammed Al
Momany, Aqaba, Jordan/NOAA
© krishnacreationz/ShutterStock, Inc.
surface
 The oceans can be divided into ecologically
distinct life zone
Figure 05.27: The coral reef is bathed in
sunlight and found in warm water. These
features and ample nutrients make it the
richest of all marine aquatic zones.
Figure 05.28A: Coral reef inhabitants.
Coral reefs house some of the most
spectacular fishes known to science.
The Coastal Life Zones
 The coastlines are highly productive waters.
 They are characterized by abundant sunlight
and a rich supply of nutrients, both of which
contribute to an abundance of life-forms.
Figure 05.27: The coral reef is bathed in
sunlight and found in warm water. These
features and ample nutrients make it the
richest of all marine aquatic zones.
Courtesy of National Estuarine Research Reserve
Collection/NOAA
Figure 05.25: Coastal wetland. Aerial view of an estuary and mangrove swamp.
Courtesy of National Estuarine Research
Reserve Collection/NOAA
The Coastal Life Zones
 Estuaries are nutrient-rich zones at the
mouths of rivers.
 They are often associated with coastal
wetlands, together forming the estuarine
zone.
 The estuarine zone is highly productive
and of great value to humans and other
species.
 Human activities severely threaten this
important biological asset.
The Coastal Life Zones
 The shorelines of the world are rocky or
sandy regions.
 They are home to a surprising number of
organisms adapted to the tides and the
turbulence created by wave action.
 Coral reefs are the aquatic equivalent of
the tropical rain forests and are being
rapidly destroyed.
The Marine Ecosystem
 The marine ecosystem consists of
four ecologically distinct life zones,
similar to those found in lakes.
Figure 05.28B: Brightly colored anemones filter food from the water.
© Photos.com
Figure 05.29: Ocean zones.