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The Earth’s
Ecosystems
Chapter 17
Section 1
Land Ecosystems
Abiotic
= nonliving factors that influence the
types of plants & animals that live in the area.
The Earth’s Biomes
Biome
= a geographic area characterized by
certain types of plant & animals communities. A
biome contains a number of smaller but related
ecosystems within it.
Section 1
Forests
They
develop where there is enough rain & where
the temperature is not too hot in the summer or too
cold in the winter. 3 types of forest biomes:
Temperate Deciduous Forests
Deciduous
= trees that lose their leaves in the fall
to conserve water during the water.
In
a temperate deciduous forest, mammals,
birds, & reptiles thrive on the abundance of
leaves, seeds, nuts, & insects.
Section 1
Forests: Cont.
In
forests, plant growth occurs in layers.
•
The leafy tops of the trees reach high above the
forest floor, where they receive full sunlight.
•
Beneath the tree layer, woody shrubs & bushes
catch the light that filters through the tree.
•
Grasses, herbs, ferns, & mosses are scattered
across the forest floor. Most of the flowering
plants bloom, & produce seeds in early spring,
before the trees leaf out.
Section 1
Forests: Cont.
Coniferous Forests
Don’t change very much from summer to winter.
Found in areas with long, cold winters. These
forests consists mainly of evergreen trees
Conifers = trees that produce seeds in cones.
Identified by their compact, needlelike leaves.
These needles have a thick waxy coating that
prevents them from drying out & being damaged
during the winter.
Not many large plants grow beneath conifers,
partly because very little light reaches the ground.
Section 1
Forests: Cont.
Tropical Rain Forests
 The tropical rain forest has more biological
diversity than any other biome on the planet
 Diversity = more species than any other biome
 Canopy or treetop are the preferred living site for
animals here.
 Nutrients are in the vegetation – not the soil.
Farmers who cut down the forest have to move
after 2 years.
Section 1
Grasslands
 Regions
where grasses are the major type of
vegetation.
Temperate Grasslands
 Mainly grasses mixed with a variety of flowering
plants. There are few trees because fires prevent
the growth of most slowing growing plants. The
world’s temperate grasslands support small, seedeating mammals, such as prairie dogs & mice, &
large herbivores, such as the bison of North
America
Section 1
Grasslands: Cont.
Savanna
Savanna = a tropical grassland with scattered
clumps of trees. During the dry season, the grasses
die back, but the deep roots survive even through
months of drought. During the wet season, the
savanna may receive as much as 150 cm of rain.
The savannas of Africa are inhabited by the most
abundant & diverse groups of large herbivores in
the world. These include elephants, giraffes,
zebras, gazelles, & wildebeests.
Section 1
Deserts
 Deserts
= hot, dry regions that support a variety of
plants & animals. Most water that falls to the
ground evaporates. Organisms have evolved ways
to survive the extreme temperatures & little water.
 Cactus store water in their stems & roots
 Some flowering plants bloom, bear seeds, & die
within weeks after a heavy rain.
 Kangaroo rats never need to drink. They recycle
water from the foods they eat.
 Jack rabbits’ huge ears help them get rid of body
heat.
Section 1
Tundra
 Tundra
= in the far north (Arctic tundra) & on the
tops of high mountains (Alpine tundra), the
climate is so cold that no trees can grow
Arctic Tundra
 During the short growing season, only the surface
soil thaws
 Permafrost = the soil below the surface stays
frozen all the time.
 The layer of unfrozen soil above the permafrost is
too shallow for deep-rooted plants to survive.
Section 1
Tundra: Cont.
 Grasses, sedges, rushes, & small woody shrubs
are common. A layer of mosses & lynches grows
beneath these plants on the surface of the ground.
 Tundra animals include large mammals such as
caribous, musk oxen, & wolves, as well as
smaller animals, such as lemmings, shrews, &
hares. Migratory birds are abundant in summer.
Alpine Tundra
 Receive a lot of sunlight & precipitation, mostly
in the form of snow
Section 1
Land Ecosystems: REVIEW
1. How is the climate of temperature grasslands
different from that of savannas?
2. Describe three ways that plants & animals are
adapted to the desert climate.
3. Where are most of the nutrients in a tropical rain
forest?
4. Could arctic tundra accurately be called a frozen
desert? Why or why not?
Section 2
Marine Ecosystems
almost three-quarters of the Earth’s surface.
Contain almost 97% of the Earth’s water supply.
 The largest animals on Earth inhabit them, along
with billions of microscope creatures.
 Marine = ecosystem is one that is based on salty
water.
 Their habitats range from dark, cold, highpressure depths to warm sandy beaches; from icy
polar waters to rocky coastlines.
 Cover
Section 2
Abiotic Factors Rule
 Shaped
by abiotic factors = temperature, the
amount of sunlight penetrating the water, the
distance from land, & the depth of the water.
Sunny Waters
 Phytoplankton = the most abundant producers in
the ocean; they are microscopic photosynthetic
organisms that float near the surface of the water.
 Zooplankton = consumers that feed on the
phytoplankton; small animals that along with
phytoplankton, form the base of the oceans’
feeding relationships.
Section 2
Wonderful Watery Biomes
The Intertidal Zone
 This area is above water part of the day, when the
tide is out, & is often battered by waves. Mud
flats, rocky shores, & sandy beaches are all in the
intertidal area.
The Neritic Zone
 Water in this area is generally less than 200 m
deep & usually receives a lot of sunlight. Diverse
& colorful coral reefs exist in the water over the
continental shelf, where the water is warm, clear,
& sunny.
Section 2
Wonderful Watery Biomes: Cont.
The Oceanic Zone
 Past the continental shelf, the sea floor drops
sharply. This is the deep water of the open ocean.
To a depth of about 200 m, phytoplankton are the
producers. At greater depths, no light penetrates,
so most organisms obtain energy by consuming
organic material that falls from the surface.
Section 2
Wonderful Watery Biomes: Cont.
The Benthic Zone
 The benthic zone is the sea floor. It extends from
the upper edge of the intertidal zone to the bottom
of the deepest ocean waters. Organisms that live
on the deep-sea floor obtain food mostly by
consuming material that filters from above. Some
bacteria are chemosynthetic, which means they
use chemicals in the water near thermal vents to
make food. A thermal vent is a place on the ocean
floor where heat escapes through a crack in the
Earth’s crust.
Section 2
A Closer Look
 Marine
environments provide most of the water
for Earth’s rainfall through evaporation &
precipitation.
 Humans
harvest enormous amounts of food from
the oceans & dump enormous amounts of waste in
to them.
Section 2
A Closer Look: Cont.
Coral Reefs
 One
of the most biologically diverse biomes.
 Corals
live in a close relationship with singlecelled algae. The algae produce organic nutrients
through photosynthesis. This provides food for the
coral. The coral provide a place in the sun for the
algae to live. The foundation of the reef is formed
from coral skeletons that have built up over
thousands of years.
Section 2
A Closer Look: Cont.
The Sargasso Sea
 In the middle of the Atlantic Ocean is a large
ecosystem with no land boundaries.
 Sargassum = a type of algae usually found
attached to rocks on the shore of North America,
but it forms huge floating rafts in the Sargasso
Sea.
 Animals adapted to this environment live among
the algae. Most of the animals are the same color
as the Sargassum.
Section 2
A Closer Look: Cont.
Polar Ice
 Make
up a very unusual marine biome because of
the ice.
 The
waters are rich in nutrients from the
surrounding landmasses. These nutrients support
large populations of plankton.
 The
plankton in turn support a great diversity of
fish, seabirds, penguins, & sea mammals, such as
sea lions.
Section 2
A Closer Look: Cont.
Estuaries
 Estuary = an area where fresh water from streams
& rivers spills into the ocean.
 The amount of salt in an estuary changes
frequently. The fresh water that spills into an
estuary is rich in nutrients that are carried by
water running off the land. Because estuaries are
so nutrient-rich, they support large numbers of
organisms. They are crowded with masses of
plankton, which provide food for many larger
animals.
Section 2
A Closer Look: Cont.
Intertidal Areas
 Some amazing adaptations can be found among
the organisms that inhabit the intertidal areas.
Mud flats are home to many burrowing worms &
crabs & the shorebirds that feed on them. Sandy
beaches are also home to burrowing worms,
clams, crabs, & plankton that live among the sand
grains.
 On rock shores, organisms either have tough
holdfasts or are able to cement themselves to a
rock to avoid being swept away by crashing
waves.
Section 2
Marine Ecosystems: REVIEW
1. Explain how a coral reef is both living & dead.
2. Why do estuaries support such an abundance of
life?
3. Explain how the amount of light an area receives
determines the kinds of organisms that live in the
open ocean.
Section 3
Freshwater Ecosystems
 Characterized
by abiotic factors primarily the
speed the water is moving.
Water on the Move
 Brooks, streams, & rivers are ecosystems based on
moving water.
 Tributary = a river or stream flowing into a larger
river or lake.
 Organisms that live in moving water require
special adaptations to avoid being swept away
with the current.
Section 3
Still Waters
 Ponds
& lakes have different ecosystems than
streams & rivers. There are 3 zones lakes are
divided into.
Where Water Meets Land
 Littoral Zone = the zone closest to the land.
 This zone has many inhabitants.
 Plants: cattails, rushes, water lilies, &
submerged pond weeds
 Animals: snails, small arthropods, insect, clams,
worms, frogs, salamanders, water turtles, water
snakes & various kinds of fishes.
Section 3
Still Waters: Cont.
Life at the Top
Open-water
Zone = extends from the littoral zone
across the top of the water and only goes as deep
as light can reach.
Plants:
phytoplankton most abundant
photosynthetic organism.
Animals:
bass, blue gills, lake trout, & other fish
Section 3
Still Waters: Cont.
Life at the Bottom
Deep-water
Zone = zone below the open-water
zone, where no light reaches.
Animals:
catfish, carp, worms, insect larvae,
crustaceans, fungi, & bacteria live here.
•
These organisms feed off dead organic material
that falls down from above.
Section 3
Wetlands

Wetland = an area of land where the water level
is near or above the surface of the ground for
most of the year.
 Support a variety of plant & animal life
 These play an important role in flood control.
• During heavy rains or spring snow melt,
wetlands soak up large amounts of water.
• The water in wetlands also seeps in to the
ground, replenishing underground water
supplies.
Section 3
Wetlands: Cont.
Marshes
 Marsh = a treeless wetland ecosystem where
plants such as cattails & rushes grow.
 Found in shallow waters along the shores of lakes,
ponds, rivers, & streams.
 The plants in a marsh vary depending on the depth
of the water & on the location of the marsh.
 Plants: Grasses, reeds, bulrushes, & wild rice
 Animals: Muskrats, turtles, frogs, & redwing
blackbirds
Section 3
Wetlands: Cont.
Swamps
 Swamp = a wetland ecosystem where trees &
vines grow.
 Occur in low-lying areas & beside slow-moving
rivers. Most swamps are flooded only part of the
year depending on rainfall.
 Plants: willows, bald cypresses, water tupelos,
oaks, & elms, poison ivy, Spanish moss, water
lilies
 Animals: variety of fish, snakes, & birds.
Section 3
From Lake to Forest
How
can a lake or pond disappear?
Water entering a standing body of water usually
carries nutrients & sediment along with it.
These materials then settle to the bottom. Dead
leaves for overhanging trees & decaying plant &
animal life also settle to the bottom. Gradually, the
pond or lake fills in. Plants grow in the newly
filled areas, closer & closer toward the center.
With time, the standing body of water becomes a
marsh. Eventually, marsh turns into a forest.
Section 3
Freshwater Ecosystems: REVIEW
1. Describe some adaptations of organisms that live
in moving water.
2. Compare the littoral zone with the open-water
zone of a pond.
3. Describe how a swamp is different from a marsh.