2. What is a Biome?
• Biomes are large regions characterized
by a specific type of climate and certain
types of plant and animal communities.
• Each biome is made up of many
individual ecosystems.
3. Biomes and Vegetation
• Biomes are described by their vegetation
because plants that grow in an area determine
the other organisms that can live there.
• Plants in a particular biome have
characteristics, specialized structures, or
adaptations that allow the plants to survive in
that biome.
• These adaptations include size, shape, and
color. For example, plants in the tundra tend to
be short because they cannot obtain enough
water to grow larger.
4. Biomes and Climate
• Climate is the average weather conditions
in an area over a long period of time.
• Climate is the main factor is determining
which plants can grow in a certain area,
which in turn defines the biome.
• Temperature and precipitation are the two
most important factors that determine a
region’s climate.
5. Temperature and Precipitation
• Most organisms are adapted to live
within a particular range of
temperatures and will not survive at
temperatures too far above or below
their range.
• Precipitation also limits the organisms
that can be found in a biome because all
organisms need water, and the bigger
the animal, the more water it needs.
6. Temperature and Precipitation
• Biomes that do not receive enough rainfall to
support large trees support communities
dominated by small trees, shrubs, and grasses.
• In biomes where rainfall is not frequent, the
vegetation is mostly cactuses and desert
shrubs. In extreme cases, lack of rainfall
results in no plants, no matter what the
temperature is.
• The higher the temperature and precipitation
are, the taller and denser the vegetation is.
8. Latitude and Altitude
• As latitude and altitude increase, biomes
and vegetation change.
• Trees of tropical rainforests usually grow
closer to the equator, while mosses and
lichen of the tundra grow closer to the
poles.
• The temperate region includes biomes such
as temperate forests and grasslands,
which usually have moderate temperatures
and fertile soil that is ideal for
agriculture.
10. Forest Biomes
• Of all the biomes in the world, forest
biomes are the most widespread and the
most diverse.
• The large trees of forests need a lot of
water, so forests can be found where
temperatures are mild to hot and where
rainfall is plenty.
• There are three main forest biomes of the
world: tropical, temperate, and coniferous.
11. Tropical Rain Forests
• Tropical rain forests are forests or jungles
near the equator. They are characterized by
large amounts of rain and little variation in
temperature and contain the greatest known
diversity of organisms on Earth.
• They help regulate world climate an play vital
roles in the nitrogen, oxygen, and carbon cycles.
• They are humid, warm, and get strong sunlight
which allows them to maintain a fairly constant
temperature that is ideal for a wide variety of
plants and animals.
12. • Most nutrients are within the plants, not the
soil.
• Decomposers on the rain-forest floor break
down dead organisms and return the nutrients
to the soil, but plants quickly absorb the
nutrients.
• Some trees in the tropical rain forest support
fungi that feed on dead organic matter on the
rain-forest floor. In this relationship, the fungi
transfer the nutrients form the dead matter
directly to the tree.
Nutrients in Tropical Rain
Forests
13. • Nutrients from dead organic matter are
removed so efficiently that runoff from rain
forests is often as pure as distilled water.
• Most tropical soils that are cleared of plants
for agriculture lack nutrients and cannot
support crops for more than a few years.
• Many of the trees form above ground roots
called buttresses or braces that grow sideways
from the tree to provide it with extra support
in the thin soil.
Nutrients in Tropical Rain
Forests
14. Layers of the Rain Forest
• The emergent layer is the top foliage
layer in a forest where the trees
extend above surrounding trees.
• Trees in this layer grow and emerge into
direct sunlight reaching heights of 60
to 70 m and can measure up to 5 m
around.
• Animals such as eagles, bats, monkeys,
and snakes live in the emergent layer.
15. Layers of the Rain Forest
• The canopy is the layers of treetops that
shade the forest floor, and is considered
to be the primary layer of the rain forest.
• The tall trees, more than 30 m tall, form a
dense layer that absorbs up to 95 percent
of the sunlight.
• The canopy can be split into and upper and
lower canopy with the lower canopy
receiving less of the sunlight.
16. Layers of the Rainforest
• Epiphytes are plants that use another plant for
support but not for nourishment, and are
located on high trees in the canopy.
• Growing on tall trees in allows them to reach
the sunlight needed for photosynthesis, and to
absorb the water and nutrients that run down
the tree after it rains.
• Most animals that live in the rain forest live in
the canopy because they depend on the
abundant flowers and fruits that grow there.
17. Layers of the Rainforest
• The understory is the foliage layer that is
beneath and shaded by the main canopy of a
forest.
• Little light reaches this layer allowing only
trees and shrubs adapted to shade to grow
there.
• Most plants in the understory do not grow more
that 3.5 m tall.
• Herbs with large flat leaves that grow on the
forest floor capture the small amount of light
that penetrates the understory.
18. Species Diversity
• The diversity of rain-forest vegetation has
led to the evolution of a diverse community
of animals.
• Most rainforest animals are specialists
that use specific resources in particular
ways to avoid competition and have
adapted amazing ways to capture prey and
avoid predators.
• Insects use camouflage to avoid predators
and may be shaped like leaves or twigs.
19. Threats to Rain Forests
• Every minute of every day, 100 acres of
tropical rainforest are cleared for logging
operations, agriculture, and oil exploration.
Exotic-pet trading robs the rain forests of
rare and valuable plant and animal species only
found there.
• Habitat destruction occurs when land inhabited
by an organism is destroyed or altered.
• If the habitat that an organism depends on is
destroyed, the organism is at risk of
disappearing.
20. Threats to Rain Forests
• An estimated 50 million native peoples live
in tropical rain forests and are also
threatened by habitat destruction.
• Because they obtain nearly everything they
need form the forest, the loss of their
habitat could force them to leave their
homes and move into cities.
• This drastic change of lifestyle may then
cause the native peoples too lose their
culture and traditions.
21. Temperate Forests
• Temperate rain forests are forests
communities that are characterized by
cool, humid weather and abundant rainfall,
where tree branches are draped with
mosses, tree trunks are covered with
lichens, and the forest floor is covered
with ferns.
• They occur in North America, Australia,
and New Zealand, and are dominated by
evergreen trees such as the Douglas fir
and Sitka spruce.
22. Temperate Forests
• Although located north of most other rain
forests, the temperate rain forest of the
Pacific Northwest still maintains a moderate
temperature year round.
• It rarely freezes because the nearby Pacific
Ocean waters keep temperatures mild by
blowing cool ocean water over the forest.
• As the ocean winds meet the costal Olympic
Mountains, a large amount of rainfall is
produced which keeps the temperature cool and
moist.
23. Temperate Deciduous Forests
• Temperate deciduous forests are forests
characterized by trees that shed their leaves
in the fall, and located between 30º and 50º
north latitude.
• The range of temperatures can be extreme,
with summer temperatures soaring to 35ºC and
winter temperatures often falling below
freezing.
• They receive 75 to 125 cm of precipitation
annually which helps to decompose dead organic
matter contributing to the rich soils of the
forest.
24. Plants of Deciduous Forests
• Plants in the deciduous forests grow in layers
with tall trees, such as birch, dominating the
canopy while shrubs cover the understory. Also,
more light reaches deciduous forest floors than
rain forests floors allowing more plants to grow.
• Temperate-forest plants are adapted to survive
seasonal changes. In the fall and winter, trees
shed their leaves and seeds go dormant under
the insulation of the soil. With the returning
warmth in the spring, the trees grow new leaves
and seeds germinate.
25. Animals of Deciduous Forests
• The animals of temperate deciduous
forests are adapted to use the forest
plants for both food and shelter.
• Birds cannot survive the harsh winter of
the deciduous forests so each fall they fly
south for warmer weather and better
availability of food.
• Other animals, such as mammals and
insects, reduce their activity so that they
do not need as much food for energy,
enabling them to survive the winter.
26. Taiga
• The taiga is the region of evergreen,
coniferous forest below the arctic and
subarctic tundra regions.
• The taiga has long winters and little
vegetation.
• The growing season can be as short as 50
days with most plant growth occurring
during the summer months because of
nearly constant daylight and larger
amounts of precipitation.
27. Plants of the Taiga
• A conifer is a tree that has seeds that develop
in cones. Their leaves’ arrow shape and waxy
coating helps them to retain water in the
winter. The conifer’s shape also helps the tree
shed snow to the ground and not get weighed
down.
• Conifer needles contains substances that make
the soil acidic when they fall to the ground
preventing plants from growing on the floor.
• Also, soil forms slowly in the taiga because the
climate and acidity slow decomposition.
28. Animals of the Taiga
• The taiga has many lakes and swamps that in
the summer attract birds that feed on insects.
• To avoid the harsh winters, birds migrate, while
some year round residents, such as shrews,
burrow underground for better insulation.
• Other animals, such as snowshoe hares, have
adapted to avoid predation by shedding their
brown summer fur and growing white fur that
camouflages them in the winter snow.
29. Grassland, Desert, and Tundra
Biomes
• In climates that have less rainfall, forest
biomes are replaced by savanna, grassland,
and chaparral biomes.
• As even less rain falls in these biomes,
they change into desert and tundra biomes.
• As precipitation decreases in an area, the
diversity of the species in the area also
decreases. But, the number of individuals
of each species present may still be very
large.
30. Savannas
• Savannas are plains full of grasses and
scattered trees and shrubs that are found
in tropical and subtropical habitats. Found
mainly in regions with a dry climate, such
as East Africa and western India.
• Although savannas receive little
precipitation throughout the year, they do
have a wet season and a dry season.
• Many animals are only active during the
wet season. Grass fires help to restore
nutrients to the soil during the dry season.
31. Plants of the Savanna
• Because most of the rain falls during the wet
season, plants must be able to survive prolonged
periods without water.
• Some plants have large horizontal root systems
to help them survive the dry season. These
roost also enable the plant to grow quickly
after a fire.
• The grasses also have coarse vertical leaves
that expose less surface area to help conserve
water, while some trees shed their leaves.
Almost all have thorns for protection from
herbivores.
32. Animals of the Savanna
• Grazing herbivores, like the elephant, have
adopted migratory ways of life, following
the rains to areas of new grass and fresh
watering holes. Predators often stalk
these animals for food.
• Many savanna animals give birth only during
the rainy season, when food is abundant
and the young are more likely to survive.
• Some species of herbivores reduce
competition for food by eating vegetation
at different heights than other species do.
33. Temperate Grasslands
• Temperate grasslands are communities (or
biomes) that are dominated by grasses, have
few trees, and are characterized by hot
summers and cold winters, with rainfall that is
intermediate between that of a forest and a
desert.
• Temperate grasslands have the most fertile soil
of any biome. Few natural temperate grasslands
remain because many have been replaced by
grazing areas and farms growing crops such as
corn, soybeans, and wheat.
34. Temperate Grasslands
• Temperate grasslands are located on the
interiors of continents where too little rain
falls for trees to grow and include the prairies
of North America.
• Mountains often play a crucial role in
maintaining grasslands as rain clouds from the
west are blocked. However, rainfall does
increase as you move eastward, allowing taller
grasses to grow.
• Heavy precipitation is rare in the grasslands,
allowing the hot temperatures in the summer to
make the grasslands susceptible to fires.
35. Plants of Temperate Grasslands
• The roots system of prairie grasses form
dense layers that survive drought and fire
allowing the plants to come back from year
to year.
• Few trees survive on the grasslands
because of the lack of rainfall, fire, and
the constant winds.
• The amount of rainfall in the area
determines the types of plants that will
grow in that area with varying root depth
and grass height.
36. Animals of Temperate
Grasslands
• Some grazing animals, such as the bison
and pronghorn antelope, have large, flat
teeth for chewing the coarse prairie
grasses.
• Other grasslands animals, such as
prairie dogs, owls, and badgers, live
protected in underground burrows that
protect them from predators on the
open grasslands.
37. Threats to Temperate
Grasslands
• Farming and overgrazing have changed the
grasslands.
• Grains crops cannot hold the soil in place
as well as native grasses can because the
roots of crops are shallow, so soil erosion
eventually occurs.
• Erosion is also caused as the grasses are
constantly eaten and trampled.
• Constant use can change the fruitful
grasslands into desertlike biomes.
38. Chaparral
• Chaparral is a type of temperate woodland
biome with vegetation that includes broad
leafed evergreen shrubs and is located in
areas with hot, dry summers and mild, wet
winters.
• Chaparrals are located in the middle
latitudes, about 30° north and south of
the equator.
• Chaparrals are located primarily in coastal
areas that have Mediterranean climates.
39. Plants of the Chaparral
• Most chaparral plants are low-lying, evergreen
shrubs and small trees that tend to grow in
dense patches and include chamise, manzanita,
scrub oak, and herbs like sage and bay.
• These plants have small, leathery leaves that
contain oils that promote burning, allowing
natural fires to destroy competing trees.
• Chaparral plants are well adapted to fire and
can resprout from small bits of surviving plant
tissue.
40. Animals of the Chaparral
• A common adaptation of chaparral
animals Is camouflage, shape or coloring
that allows an animal to blend into its
environment.
• Animals such as quail, lizards,
chipmunks, and mule deer have a
brownish gray coloring that lets them
move through the brush without being
noticed.
41. Threats to the Chaparral
• Worldwide, the greatest threat to
chaparral is human development.
• Humans tend to develop lands of the
chaparral for commercial and residential
use because these biomes get a lot of
sun, are near the oceans, and have a
mild climate year round.
42. Deserts
• Deserts are regions that have little or no
vegetation, long periods without rain, and
extreme temperatures.
• Although there are hot and cold deserts,
one characteristic they both share is the
fact that they are the driest places on
Earth.
• Deserts are often located near large
mountain ranges because mountains can
block the passage of moisture-filled
clouds, limiting precipitation.
43. Plants of the Desert
• All desert plants have adaptations for obtaining
and conserving water, which allows the plants to
live in dry, desert conditions.
• Plants called succulents, such as cactuses, have
thick, fleshy stems and leaves that conserve
water. Their leaves also have a waxy coating to
prevent water loss, while sharp spines on the
plant keep animals away.
• Many plant roots spread out just under the
surface to absorb as much rain as possible.
44. Plants of the Desert
• Some plants are adapted to survive for
long periods of time without water.
• When conditions are too dry, these plants
die and drop their seeds that stay dormant
until the next rainfall. Then, new plants
quickly germinate, grow, and bloom before
the soil becomes dry again.
• These plants can survive their water
content dropping to as low as 30 percent
of their mass.
45. Animals of the Desert
• Animals of the desert have adapted many
different ways to prevent water loss.
• Reptiles have thick, scaly skin that
prevents water loss. Amphibians survive by
estivating, or burying themselves in the
ground and sleeping through the dry
season. Insects are covered with body
armor that helps them retain water.
• In addition, most desert animals are
nocturnal, meaning they are active mainly
at night or dusk when it is cooler.
46. Tundra
• The tundra is a treeless plain that is
located in the Arctic or Antarctic and that
is characterized by very low winter
temperatures, short, cool summers, and
vegetation that consists of grasses,
lichens, and perennial herbs.
• Summers are short in the tundra, so only
the top few centimeters of soil thaw.
• Permafrost is the permanently frozen
layer of soil or subsoil and can be found in
the tundra regions.
47. Vegetation of the Tundra
• Mosses and lichens, which can grow
without soil, cover vast areas of rocks in
the tundra.
• The soil is thin, so plants have wide shallow
roots to help anchor them against the icy
winds.
• Most flowering plants are short, which
keeps them out of the wind and helps them
absorb heat from the sunlit soil. Woody
plants and perennials have evolved dwarf
forms that grow flat along the ground.
48. Animals of the Tundra
• Millions of migratory birds fly to the tundra to
breed in the summer when food is abundant.
• Caribou migrate throughout the tundra in
search of food and water. Hunters such as
wolves prey on migratory caribou, deer, and
moose.
• Rodents stay active, but burrow underground to
avoid the cold. Other year-round residents,
such as arctic foxes, lose their brown summer
coat for white fur that camouflages them with
the snow.
49. Threats to the Tundra
• The tundra is one of the most fragile biomes on
the planet. The food chains are relatively
simple so they are easily disrupted.
• Until recently these areas have been
undisturbed by humans. But oil was located in
parts of the tundra, and oil exploration,
extraction, and transport has disrupted many
tundra habitats.
• Pollution caused by spills or leaks of oil and
other toxic materials may also poison the food
and water sources of organisms of the tundra.
50. Freshwater Ecosystems
• The types of organisms in an aquatic
ecosystem are mainly determined by the
water’s salinity. As a result, aquatic
ecosystems are divided into freshwater
and marine ecosystems.
• Freshwater ecosystems include ponds,
lakes, streams, rivers, and wetlands.
• Wetlands are areas of land that are
periodically under water or whose soil
contains a great deal of moisture.
51. • Factors such as temperature, sunlight,
oxygen, and nutrients determine which
organisms live in which area of the
water.
• Aquatic ecosystems contains several
types of organisms that are grouped by
their location and by their adaptation.
• Three groups of aquatic organisms
include plankton, nekton, and benthos.
Characteristics of Aquatic
Ecosystems
52. • Plankton are the mass of mostly microscopic
organisms that float or drift freely in the
water, and can be microscopic animals called
zooplankton or microscopic plants called
phytoplankton.
• Nekton are all organisms that swim actively in
open water, independent of currents.
• Benthos are bottom-dwelling organisms of the
sea or ocean and are often attached to hard
surfaces.
• Decomposers are also aquatic organisms.
Characteristics of Aquatic
Ecosystems
53. Lakes and Ponds
• Lakes, ponds, and wetlands can form
naturally where groundwater reaches the
Earth’s surface.
• Humans intentionally create artificial lakes
by damming flowing rivers and streams to
use them for power, irrigation, water
storage, and recreation.
• Lakes and ponds can be structured into
horizontal and vertical zones. The types of
organisms present depend on the amount
of sunlight available.
54. Life in a Lake
• The littoral zone is a shallow zone in a
freshwater habitat where light reaches
the bottom and nurtures plants and aquatic
life is diverse and abundant.
• Some plants hare rooted in the mud
underwater with their upper leaves and
stems above water. Other plants have
floating leaves.
• In open water, plants, algae, and some
bacteria capture solar energy to make
their own food during photosynthesis.
55. • Some bodies of fresh water have areas so deep
that there is too little light for photosynthesis.
• Bacteria live in the deep areas of freshwater.
Fish adapted to cooler, darker water also live
there.
• Eventually, dead and decaying organisms reach
the benthic zone.
• The benthic zone is the region near the bottom
of a pond, lake or ocean which is inhabited by
decomposers, insect larvae, and clams.
Life in a Lake
56. • Animals that live in lakes and ponds have
adaptations that help them obtain what
they need to survive.
• For example, water beetles use the hairs
under their bodies to trap surface air so
that they can breathe during their dives
for food.
• And, in regions where lakes partially
freeze in the winter, amphibians burrow
into the littoral mud to avoid freezing
temperatures.
Life in a Lake
57. How Nutrients Affect Lakes
• Eutrophication is an increase in the amount
of nutrients, such as nitrates, in an aquatic
ecosystem.
• As the amount of plants and algae grow,
the number of bacteria feeding on the
decaying organisms also grows.
• These bacteria use the oxygen dissolved in
the lake’s waters. Eventually the reduced
amount of oxygen kills oxygen loving
organisms.
58. How Nutrients Affect Lakes
• A lake that has large amounts of plant
growth due to nutrients is known as a
eutrophic lake.
• Lakes naturally become eutrophic over a
long period of time.
• However, eutrophication can be
accelerated by runoff, such as rain, that
can carry sewage, fertilizers, or animal
wastes from land into bodies of water.
59. Freshwater Wetlands
• Freshwater wetlands are areas of land
that are covered with fresh water for part
of the year.
• The two main types of freshwater
wetlands are marshes and swamps.
Marshes contain nonwoody plants, while
swamps are dominated by woody plants.
• Most freshwater wetlands are located in
the southeastern United States, with the
largest in the Florida Everglades.
60. Freshwater Wetlands
• Wetlands perform several important
environmental functions.
• Wetlands act like filters or sponges that
absorb and remove pollutants from the
water. They also control flooding by
absorbing extra water when rivers
overflow.
• These areas provide a home for native and
migratory wildlife in addition to feeding
and spawning for many freshwater game
fish.
62. Marshes
• Freshwater marshes tend to occur on low,
flat lands and have little water movement.
• In shallow waters, plants root themselves
in the rich bottom sediments while their
leaves stick out about the surface of the
water year-round.
• There are several kinds of marshes, each
of which is characterized by its salinity.
Brackish marshes have slightly salty water,
while salt marshes contain saltier water.
63. Marshes
• The benthic zones of marshes are nutrient
rich and contain plants, numerous types of
decomposers, and scavengers.
• Water fowl, such as ducks, have flat beaks
adapted for sifting through the water for
fish and insects. While water birds, such
as herons, have spearlike beaks they use to
grasp small fish and probe for frogs in the
mud.
• Marshes also attract migratory birds from
temperate and tropical habitats.
64. Swamps
• Swamps occur on flat, poorly drained land,
often near streams and are dominated by
woody shrubs or water loving trees.
• Freshwater swamps are the ideal habitat
for amphibians because of the continuous
moisture. Birds are also attracted to
hollow trees near or over the water.
• Reptiles are the predators of the swamp,
eating almost any organism that crosses
their path.
65. Human Impact on Wetlands
• Wetlands were previously considered to be
wastelands that provide breeding grounds
for insects.
• As a result, many have been drained, filled,
and cleared for farms or residential and
commercial development.
• The importance of wetlands is now
recognized, as the law and the federal
government protect many wetlands while
most states now prohibit the destruction
of certain wetlands.
66. Rivers
• At its headwaters, a river is usually cold
and full of oxygen and runs swiftly
through a shallow riverbed.
• As a river flows down a mountain, it may
broaden, become warmer, wider, slower,
and decrease in oxygen.
• A river changes with the land and the
climate through which it flows.
67. Life in a River
• In and near the headwater, mosses anchor
themselves to rocks by using rootlike
structures called rhizoids. Trout and minnows
are adapted to the cold, oxygen rich water.
• Farther downstream, plankton can float in the
warmer, calmer waters. Plants here can set
roots in the river’s rich sediment, and the
plant’s leaves vary in shape according to the
strength of the river’s current. Fish such as
catfish and carp also live in these calmer
waters.
68. Rivers in Danger
• Industries use river water in
manufacturing processes and as
receptacles for wastes. In addition, people
have used rivers to dispose of their
sewage and garbage.
• These practices have polluted rivers with
toxins, which have killed river organisms
and made river fish inedible.
• Today, runoff from the land puts
pesticides and other poisons into rivers
and coats riverbeds with toxic sediments.
69. Marine Ecosystems
• Marine ecosystems are located mainly in
coastal areas and in the open ocean.
• Organisms that live in coastal areas
adapt to changes in water level and
salinity.
• Organisms that live in the open ocean
adapt to changes in temperature and
the amount of sunlight and nutrients
available.
70. Coastal Wetlands
• Coastal land areas that are covered by salt
water for all or part of the time are known
as coastal wetlands.
• Coastal wetlands provide habitat and
nesting areas for many fish and wildlife.
• They also absorb excess rain, which
protects them from flooding, they filter
out pollutants and sediments, and they
proved recreational areas for boating,
fishing, and hunting.
71. Estuaries
• An estuary is an area where fresh water from
rivers mixes with salt water from the ocean.
• As the two bodies meet, currents form and
cause mineral rich mud with many nutrients to
fall to the bottom making in available to
producers.
• Estuaries are very productive because they
constantly receive nutrients from the river and
ocean while the surrounding land protects the
estuaries from the harsh force of ocean waves.
72. Plants and Animals of Estuaries
• Estuaries support many marine organisms
because they receive plenty of light for
photosynthesis and plenty of nutrients for
plants and animals.
• The light and nutrients support large
populations of rooted plants as well as plankton.
Plankton in turn provide food for fish, which
can then be eaten by larger animals such as
dolphins.
• Oysters and clams live anchored to rocks and
feed by filtering plankton from the water.
73. Plants and Animals of Estuaries
• Organisms that live in estuaries are able to
tolerate variations in salinity because the salt
content of the water varies as fresh water and
sat water mix when tides go in and out.
• Estuaries also proved protected harbors,
access to the ocean, and connection to rivers.
As a result, many of the largest ports have
been built on estuaries.
• Six of the ten largest urban areas, including
New York have been built on estuaries.
74. Threats to Estuaries
• Estuaries that exist in populated areas
were often used as places to dump waste.
Estuaries filled with waste could then be
used as building sites.
• The pollutants that damage estuaries
include sewage, pesticides, fertilizers, and
toxic chemicals.
• Most of these pollutants break down over
time, but estuaries cannot cope with the
amounts produced by dense human
populations.
75. Salt Marshes
• Salt marshes are maritime habitats
characterized by grasses, sedges, and other
plants that have adapted to continual, periodic
flooding and are found primarily throughout the
temperate and subarctic regions.
• The salt marsh supports a community of clams,
fish, aquatic birds, crabs, and shrimp.
• Salt marshes, like other wetlands, also absorb
pollutants to help protect inland areas.
76. Mangrove Swamps
• Mangrove swamps are tropical or
subtropical marine swamps that are
characterized by the abundance of low to
tall mangrove trees.
• The swamps help protect the coastline
from erosion and reduce the damage from
storms. They also provide a home for about
2,000 animal species.
• Mangrove swamps have been filled with
waste and destroyed in many parts of the
world.
77. Rocky and Sandy Shores
• Rocky shores have many more plants and
animals than sandy shores do because the rocks
provide anchorage for seaweed that animals can
live on.
• Sandy shores dry out when the tide goes out,
and many organisms that live between sand
grains eat the plankton left stranded on the
sand.
• A Barrier island is a long ridge of sand or
narrow island that lies parallel to the shore and
helps
protect the mainland.
78. Coral Reefs
• Coral reefs are limestone ridges found in
tropical climates and composed of coral
fragments that are deposited around organic
remains.
• Thousands of species of plants and animals live
in the cracks and crevices of coral reefs, which
makes coral reefs among the most diverse
ecosystems on Earth.
• Corals are predators that use stinging tentacles
to capture small animals, such as zooplankton,
that float or swim close to the reef.
79. Disappearing Coral Reefs
• Coral reefs are productive ecosystems, but
they are also very fragile.
• If the water surrounding a reef is too hot
or too cold, or if fresh water drains into
the water surrounding the coral, the coral
may die.
• If the water is too muddy, polluted, or too
high in nutrients, the algae that live within
the corals will either die or grow out
control. If the algae grows out of control,
it may kill the corals.
80. Disappearing Coral Reefs
• Oil spills, sewage, pesticides, and silt runoff
have also been linked to coral-reef destruction.
• Overfishing can devastate fish populations,
upsetting the balance of the reef’s ecosystem.
• A coral reef grows very slowly, and it may not
be able to repair itself after chunks of coral
are destroyed by careless divers, ships
dropping anchor, fisheries, shipwrecks, and
people breaking off pieces for decorative items
or building materials.
81. Oceans
• Because water absorbs light, sunlight that is
usable by plants for photosynthesis penetrates
only about 100 m into the ocean.
• As a result, much of the ocean’s life is
concentrated in the shallow coastal waters
where sunlight penetrates to the bottom and
rivers wash nutrients from the land.
• Seaweed and algae grow anchored to rocks, and
phytoplankton drift on the surface.
Invertebrates and fish then feed on these
plants.
82. Plants and Animals of Oceans
• In the open ocean, phytoplankton grow only
in areas where there is enough light and
nutrients, resulting in one of the least
productive of all ecosystems.
• The sea’s smallest herbivores are
zooplankton, including jellyfish and tiny
shrimp,which live near the surface with
the phytoplankton they eat.
• Fish feed on the plankton as do marine
mammals such as whales.
83. Plants and Animals of Oceans
• The depths of the ocean are very dark, so
most food at the ocean floor consists of
dead organisms that fall from the surface.
• Decomposers, filter feeders, and the
organisms that eat them live in the deep
areas of the ocean.
• Overall, the types of organisms that may
be found in the layers of the ocean at
various depths is dependent on available
sunlight.
84. Threats to the Oceans
• The oceans are steadily becoming more
polluted. Runoff from fertilized fields and
industrial waste and sewage being discharged
into rivers are major sources of ocean pollution.
• Overfishing and certain fishing methods are
also destroying some fish populations. Marine
mammals can get caught and drown in the nets.
• Although it is illegal, some ships discard fishing
lines into the ocean where they can strangle
and kill fish and seals.
85. • The Arctic Ocean is rich in nutrients from the
surrounding landmasses and supports large
populations of plankton, which feed a diversity
of fish in the open water and under the ice.
• These fish are food for ocean birds, whales
The arctic ecosystems at the North and South
Poles depend on marine ecosystems because
nearly all the food comes from the ocean.
• and seals. Fish and seals then provide food for
polar bears and people on land.
Arctic and Antarctic Ecosystems
86. • The Antarctic is the only continent never
colonized by humans. It is governed by an
international commission and is used mainly
for research.
• Even during the summer, only a few plants
grow at the edges of the continent.
• So, as in the Arctic, plankton form the
basis of the Antarctic food web,
nourishing large numbers of fish, whales,
and birds such as penguins.
Arctic and Antarctic Ecosystems
