The Earth’s Ecosystems
Land Ecosystems – The Earth’s Biomes
A biome is a geographic area
characterized by certain types of
plant and animal communities
which are determined by the
abiotic, or nonliving factors in the
area. A biome contains a number
of smaller but related ecosystems.
For example, a tropical rainforest is a
biome that contains river ecosystems,
treetop ecosystems, forest-floor
ecosystems, and many others.
A biome is NOT a specific place. For
example, a desert biome does not
refer to a particular desert. A desert
biome refers to any and all desert
ecosystems on the Earth.
Forests
Forest biomes develop where there is enough rain and where the temperature is not too
hot in the summer or too cold in the winter. There are 3 main types of forest biomes.
The type of forest that develops depends on the area’s temperature and rainfall.
Temperate Deciduous Forests contain several different species of trees
and support a variety of animals, such as bears and woodpeckers.
Trees that are deciduous, which comes from a Latin word meaning
“to fall off”, lose their leaves in the fall which allows them to
conserve water in the winter.
Average Temperature: Summer: 28C (82.4 F) Winter: 6C (42.8 F)
Average Yearly Rainfall: 75 – 125 cm (29.5 – 49 in.)
Forests
Coniferous Forests do not change very much from summer to winter.
They are found in areas with long cold winters and consist mainly of
evergreen trees which are trees that don’t lose their leaves and stay
green all year. Most of these trees are conifers: trees that produce
seeds in cones. A coniferous forest is home to many insects, birds,
moose, deer, fox, and lynxes.
Average Temperature: Summer: 14C (57.2 F) Winter: -10C (14 F)
Average Yearly Rainfall: 35 – 75 cm (14 – 29.5 in.)
Forests
Tropical Rain Forests have more biological diversity than any other
biome on the planet = it contains more species than any other
biome. A huge variety of animals live in the canopy, or treetops of
the forest. Most of the nutrients in a tropical rain forest biome are in
the vegetation.
Average Temperature: Daytime: 34C (93 F) Nighttime: 20C (68 F)
Average Yearly Rainfall: Up to 400 cm (157.5 in.)
Grasslands
Grasslands are regions where grasses are the major type of vegetation. Names for these regions are:
plains, steppes, savannas, prairies, pampas. Gasslands are found between forests and deserts.
They exist on every continent. Most grasslands are flat or have gently rolling hills.
Temperate Grassland vegetation is mainly grasses mixed with a variety
of flowering plants. Fires prevent the growth of most slow-growing
plants like trees. Temperate grasslands support small, seed-eating
mammals, such as prairie dogs and mice, and large herbivores,
such bison.
Average Temperatures: Summer: 30C (86 F) Winter: 0C (32 F)
Average Yearly Rainfall: 25-27 cm (10-29.5 in.)
Grasslands
The Savanna is a tropical grassland with scattered clumps of trees. During
the dry season, the grasses die back but the roots survive. During the
wet season, the savanna may receive as much as 150 cm of rain. The
savannas of Africa are home to the most abundant and diverse groups of
large herbivores in the world: elephants, giraffes, zebras, gazelles, and
wildebeats.
Average Temperatures: Dry Season: 34C (93 F) Wet Season: 16C (61 F)
Average Yearly Rainfall: 150 cm (59 in.)
Deserts
Deserts are hot, dry regions
where most of the water that
falls to the ground evaporates.
A variety of plants and animals
that have adapted to limited
water supply live in deserts.
For example, some plants have
shallow widespread roots to absorb
water quickly during a storm, and
most animals are active only at night
when temperatures are cooler. Jack
rabbits’ huge ears help them get rid
of body heat. Kangaroo rats recycle
water from the foods they eat.
Average Temperatures:
Summer: 38C (100 F)
Winter: 7C (45 F)
Average Yearly Rainfall:
Less than 25 cm (10 in.)
Tundra
In the far north, and on the tops of high mountains where the climate is so cold
that no trees can grow is where we find a biome called the tundra.
Only the surface of the soil thaws during the short growing season of
the Arctic Tundra. The soil below the surface, the permafrost stays
frozen all the time. This is the major feature of the arctic tundra.
There is little rain, but the permafrost keeps the rainwater from
draining; surface soil stays wet. Lakes and ponds are common.
Grasses, sedges, rushes, small woody shrubs, mosses, and lichens
are common. Tundra animals include: caribou, musk oxen, wolves,
lemmings, shrews, hares, and migratory birds in the summer.
Tundra
Average Temperatures: Summer 12C (53.6 F) Winter: -26C (-14 F)
Average Yearly Rainfall: 30 – 50 cm (12 – 20 in.)
Alpine Tundra is found above the tree line of very high mountains.
Alpine tundra receives a lot of sunlight and precipitation, mostly in
the form of snow.
Marine
Ecosystems
A marine ecosystem is one that is
based on salty water: oceans
& seas
They cover almost ¾ of the
earth’s surface and contain
almost 97% of Earth’s water
supply.
Marine ecosystems support a
broad diversity of life, from
some of the largest animals on
earth, like the humpback
whale, to microscopic
creatures like phytoplankton.
Biodiversity in our oceans.
Abiotic
Factors Rule
Like terrestrial biomes, marine biomes are
shaped by abiotic factors.
Temperature, the amount of sunlight
penetrating the water, the distance from
land, and the depth of the water, are
used to define certain areas of the
ocean.
Water absorbs light, so sunlight can only
penetrate about 200 m below the ocean’s
surface.
Most producers use sunlight for
photosynthesis, so most producers are
found only where light penetrates. The
most abundant producers in the ocean,
called phytoplankton, are microscopic,
photosynthetic organisms that float near
the surface of the water.
Zooplankton are consumers that feed on
phytoplankton. These small animals,
along with phytoplankton, form the base
of the ocean’s trophic relationships.
Major Ocean Areas
(“Watery Biomes”)
The Intertidal Zone is the area where the
ocean meets the land. This area is
above water when the tide is out. Mud
flats, rocky shores, and sandy beaches
are all in the intertidal area.
Sea grasses, periwinkle snails, herons, sea
stars, anemones, crabs, clams, and
conchs are common in intertidal areas.
The next zone outward from shore is the
Neritic Zone. The water becomes
gradually deeper towards the edge of the
continental shelf, but is generally less than
200 m deep and receives a lot of sunlight.
Producers in this area include phytoplankton
and seaweed. Sea turtles, dolphins,
corals, sponges, and colorful fish live here.
In the Oceanic Zone, past the continental
The Benthic Zone is the sea floor. It extends
shelf, the sea floor drops sharply. This is
from the upper edge of the intertidal zone to
the deep water of the open ocean. Very
the bottom of the deepest ocean waters.
little to no light penetrates, so most
Organisms here obtain food mostly by
organisms obtain their energy by
consuming material that filters from above.
consuming organic material that falls
Some bacteria are chemosynthetic, which
from the surface.
means they use chemicals in the water near
Animals adapted for darkness and high
thermal vents, a place on the ocean floor
pressures live here, like whales, squids,
where heat escapes through a crack in the
and fish that glow.
Earth’s crust, to make food.
A Closer Look…
Marine environments provide most of the
water for Earth’s rainfall through
evaporation and precipitation. Ocean
temperatures and currents have major
effects on world climates and wind
patterns (El Nino & La Nina). Humans
harvest enormous amounts of food from
the oceans and dump enormous amounts
of waste into them…..
El Nino - Ocean Current and Temperature - NOAA
Special Ocean Environments
Coral reefs: Corals live in a close relationship with single-celled algae. The algae
produce organic nutrients through photosynthesis that provides food for the coral.
The coral provide a place in the sun for the algae to live. Coral reefs are home to
many marine species.
Sargasso Sea: In the middle of the Atlantic Ocean is a large ecosystem with no land
boundaries – the Sargasso Sea. Sargassum is a type of algae, usually found
attached to rocks, but it forms huge floating rafts in the Sargasso Sea. Many animals
adapt to this environment and live among the algae.
Polar ice: The Arctic Ocean and the open waters surrounding Antarctica make up a
marine biome that includes ice. The icy waters are rich in nutrients from the
surrounding landmasses. These nutrients support large populations of plankton
which support a great diversity of fish, birds and mammals.
Estuaries: Areas where fresh water from streams and rivers spills into the ocean are
called estuaries. The fresh water is rich in nutrients. It supports large numbers of
plankton, which provide food for many larger animals.
Intertidal Areas: mudflats, sandy beaches, rocky shores. Organisms that live here
include: worms, crabs, shorebirds, clams, plankton, and sea stars among others.
Fresh Water Ecosystems
Like other ecosystems, freshwater ecosystems are characterized by
abiotic factors, primarily the speed at which the water is moving.
Water on the Move
Brooks, streams, and rivers are ecosystems based
on moving water.
Water begins flowing from melting ice or snow, or it
may come form a spring where water flows up to
the surface of the earth. Each trickle or stream
of water that joins a larger trickle or stream is
called a tributary.
Fast moving water: As more tributaries join a
stream, the stream becomes larger and wider,
forming a river.
Aquatic plants line the edge of the river. Fish live in
the open waters. Burrowers, such as clams and
mussels make their home in the muddy bottom.
Organisms that live in moving water require special
adaptations to avoid being swept away with the
current. Some cling to rocks, live under rocks
and some have suction disks to hold them to the
rocks.
Slower water: As a river grows wider, it may
meander back and forth across the landscape
depositing organic material and sediment on the
bottom building deltas. Dragonflies, water
striders, and other invertebrates live in and on
slow-moving water.
Still Waters
Ponds and lakes have different ecosystems than
streams and rivers. Lake Superior, the largest
lake in the world, has more in common with a
small beaver pond than with a river. Lakes
are divided into three zones:
Littoral Zone: This is the zone closest to the edge
of the land. Plants that grow here include:
cattails, rushes, water lilies, and pond weeds.
These plants provide a home for small animals
such as: snails, small arthropods, and insect
larvae. Clams, worms, frogs, salamanders,
water turtles, fish and water snakes also live in
this area.
Open-water Zone: This zone extends from the
edge of the littoral zone across the top of the
water and only goes as deep as light can
reach. Bass, blue gills, lake trout, and other
fish live here. Phytoplankton are the most
abundant producers in the open-water zone.
Deep-water Zone: This zone is below the openwater zone, where no light reaches. Catfish,
carp, worms, insect larvae, crustaceans, fungi,
and bacteria live here. These organisms feed
on dead organic material that falls from above.
Wetlands
A wetland is an area of land where the water level is near or above the surface
of the ground for most of the year. They support a variety of plant and animal
life and play an important role in flood control and replenishing underground
water supplies.
Marshes
A marsh is a treeless wetland
ecosystem.
Freshwater marshes are found in
shallow waters along shores of
lakes, ponds, rivers , and streams.
Grasses, reeds, bulrushes, and wild
rice are common marsh plants
Muskrats, turtles, frogs, and redwinged blackbirds are animals
commonly found in marshes.
Swamps
A swamp is a wetland ecosystem
where trees and vines grow.
Swamps are found in low-lying
areas and beside slow moving
rivers.
Most swamps are flooded only part
of the year.
Trees include: willows, cypresses,
oaks, and elms. Vines, such as
poison ivy grow up the trees
and Spanish moss hangs from
the branches.
Swamps provide a home for a
variety of fish, snakes and
birds.