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Chapter 5: How Ecosystems Work

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Mallory Cox

on 3 February 2016

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Transcript of Chapter 5: How Ecosystems Work

Chapter 5: How Ecosystems Work
How is secondary succession different from primary succession?
Section 1: Energy Flow in Ecosystems
Bell Ringer
1. Describe what occurs in cellular respiration.

2. Describe the role producers play in an ecosystem.

3. Describe how energy is transferred from one
organism to another.

4. Explain the difference between an herbivore and an

5. Compare energy transfer in a food chain to energy
in a food web.
Section 3:
How Ecosystems Change

Life Depends on the Sun
Energy from the sun enters an ecosystem when plants use sunlight to make sugar molecules.
This happens through a process called
Photosynthesis is the process by which plants, algae, and some bacteria use
sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.
End result of photosynthesis is a
carbohydrate (sugar molecules).
Gives you energy to do daily activities.

Producers Consumers

Organisms that get their energy by eating other organisms are called
A consumer is an organism that eats other organisms or
organic matter
instead of producing its own nutrients or obtaining nutrients from inorganic sources.
Consumers are also called
heterotrophs, or other-feeders

Because plants make their own food, they are called
A producer is an organism that can make
organic molecules from inorganic molecules
Producers are also called
autotrophs, or self-feeders
Some producers get their energy directly from the sun by absorbing it through their leaves.
Consumers get their energy indirectly by eating producers or other consumers.

An Exception to the Rule
Deep-ocean communities of worms, clams, crabs, mussels, and barnacles, exist in total darkness on the ocean floor, where photosynthesis cannot occur.
The producers in this environment are
bacteria that use hydrogen sulfide
present in the water.
Other underwater organisms eat the bacteria or the organisms that eat the bacteria.

What Eats What?
Organisms can be classified by what they eat.

Types of Consumers:

eat only plants

eat only animals

eat both plants and animals

eat dead organic matter

Consumers that eat producers to get energy are what we call
primary consumers.
In other words they are
Most of the energy will be used up by the consumer (herbivore).
A consumer that eats another consumer is called a
secondary consumer.

Cellular Respiration:
Burning the Fuel
An organism obtains energy from the food it eats.
This food must be broken down within its body.
The process of breaking down food to yield energy is called
cellular respiration

Cellular respiration is the process by which cells produce
energy from carbohydrates
; atmospheric oxygen combines with glucose to form water and carbon dioxide.
Cellular respiration occurs inside the
of most organisms.

During cellular respiration, cells
absorb oxygen and use it to release energy from food.
Through cellular respiration, cells use
glucose (sugar)
and oxygen to produce carbon dioxide, water, and energy.

Part of the energy obtained through cellular respiration is used to carry out daily activities.
Excess energy is stored as
fat or sugar

Each time an organism eats another organism, an
energy transfer
This transfer of energy can be traced by studying
food chains, food webs, and trophic levels

Energy Transfer
food chain
is a sequence in which energy is transferred from one organism to the next as each organism eats another organism.

Ecosystems, however, usually contain more than one food chain.

food web
shows many feeding relationships that are possible in an ecosystem.

Trophic Levels
Each step in the transfer of energy through a food chain or food web is known as a
trophic level.
trophic level
is one of the
steps in a food chain or food pyramid
; examples include producers and primary, secondary, and tertiary consumers.

Each time energy is transferred, some of the energy is lost as

is available to organisms at higher trophic levels.
One way to visualize this is with an


Each layer of the pyramid represents one
Producers form the
of the energy pyramid, and therefore contain the

The pyramid becomes smaller toward the top, where less energy is available.

Energy Loss Affects Ecosystems
Decreasing amounts of energy at each trophic level affects the organization of an ecosystem.
Energy loss affects the
number of organisms
at each level.
Energy loss limits the
number of trophic levels
in an ecosystem.

What is the percentage of energy loss at each level?

1. Humans 1.2 calories
2. Trout ~ 6 calories
3. Smelt (small fish) 30 calories
4. Small aquatic animals 150 calories
5. Algae 1000 calories

Section 2:
The Cycling of Materials

The Carbon Cycle
carbon cycle
is the movement of carbon from the nonliving environment into living things and back
Carbon is the essential component of
proteins, fats, and carbohydrates
, which make up all organisms.

Carbon exists in
air, water, and living organisms.
Producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis.
Consumers obtain carbon from the carbohydrates in the producers they eat.

During cellular respiration, some of the carbon is released back into the atmosphere as
carbon dioxide
Some carbon is stored in limestone, forming one of the largest
“carbon sinks”
on Earth.

Carbon stored in the bodies of organisms as
fat, oils, or other molecules
, may be released into the soil or air when the organisms dies.
These molecules may form deposits of
coal, oil, or natural gas,
which are known as
fossil fuels.
Fossil fuels store carbon left over from bodies of organisms that dies millions of years ago

How Humans Affect the Carbon Cycle
Humans burn fossil fuels, releasing carbon into the atmosphere.
The carbon returns to the atmosphere as carbon dioxide.
Increased levels of carbon dioxide may contribute to global warming.
Global warming is an increase in the temperature of the Earth.

The Nitrogen Cycle
nitrogen cycle
is the process in which nitrogen circulates among the air, soil, water, plants, and animals in an ecosystem.
All organisms need nitrogen to
build proteins,
which are used to build new cells.
Nitrogen makes up
percent of the gases in the atmosphere.

Nitrogen must be
altered, or fixed,
before organisms can use it.
Only a few species of bacteria can fix atmospheric nitrogen into chemical compounds that can be used by other organisms.
These bacteria are known as

Nitrogen-fixing bacteria
bacteria that convert
atmospheric nitrogen into
These bacteria live within the
roots of plants called
, which
include beans, peas, and clover.
The bacteria use sugar provided by the legumes to produce nitrogen-containing compounds such as
Excess nitrogen fixed by the bacteria is released into the soil.

Decomposers and the Nitrogen Cycle
Nitrogen stored within the bodies of living things is returned to the nitrogen cycle once those organisms die.

break down decaying plants and animals, as well as plant and animal wastes.
After decomposers return nitrogen to the soil, bacteria transform a small amount of the nitrogen into

nitrogen gas
which then returns to the atmosphere to complete the nitrogen cycle.

The Phosphorus Cycle
is an element that is part of many molecules that make up the cells of living organisms.
Plants get the phosphorus they need from
soil and water
, while animals get their phosphorus by
eating plants or other animals
that have eaten plants.
phosphorus cycle
is the cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment.

Phosphorus may enter soil and water when rocks erode.
Small amounts of phosphorus dissolve as
, which moves into the soil.
Plants absorb phosphates in the soil through their roots.
Some phosphorus washes off the land and ends up in the ocean.
Because many phosphate salts are not soluble in water, they sink to the bottom and
accumulate as sediment

, which people use to stimulate and maximize plant growth, contain both nitrogen and phosphorus.
Excessive amounts of fertilizer can enter terrestrial and aquatic ecosystems through
Excess nitrogen and phosphorus can cause
rapid growth of algae, algal bloom.
Excess algae can deplete an aquatic ecosystem of important nutrients such as
, on which fish and other aquatic organisms depend.

When fuel is burned, large amounts of nitric oxide is release into the atmosphere.
In the air,
nitric oxide
can combine with oxygen and water vapor to form
nitric acid
Dissolved in rain or snow, the nitric acid falls as
acid precipitation.

Fertilizers and the Nitrogen and Phosphorus Cycles
Acid Precipitation
If only bacteria n use nitrogen from the atmosphere, how do plants and animals take part in the nitrogen cycle?
How are fertilizers produced?

What impact do they have on the environment?

Why would some environmentalists say that nitrogen fertilizers harm the environment twice?
the Cycles
Make a ven diagram of the carbon, nitrogen, and phosphorus cycles.
In what ways are the carbon, nitrogen, and phosphorus cycles similar? In what ways are they different?
Ecosystems are constantly changing.

Ecological succession
is a gradual process of change and replacement of the types of species in a community.
Each new community that
arises often makes it
harder for the previous
community to survive.

Ecological Succession
Primary Succession

Primary succession
is a type of succession that occurs on a surface where
no ecosystem existed before
It begins in an area that previously did not support life.
Primary succession can occur on
rocks, cliffs, or sand dunes.

Secondary Succession

Secondary succession
occurs on a surface where an ecosystem has
previously existed
It is the process by which one community replaces another community that has been
partially or totally destroyed
Secondary succession can occur in ecosystems that have been
disturbed or disrupted
by humans, animals, or by natural process such as storms, floods, earthquakes, or volcanic eruptions.

Fire and
Secondary Succession
pioneer species

is a species that colonizes an

uninhabited area
and that starts an ecological cycle in which many other species become established.
Over time, a pioneer species will make the new area habitable for other species.
climax community
is the final, stable community in equilibrium with the environment.
Even though a climax community may change in small ways, this type of community may remain the same through time if it is not disturbed.

Natural fires
caused by lightning are a necessary part of secondary succession in some communities.
Minor forest fires remove
accumulations of brush and deadwood
that would otherwise contribute to major fires that burn out of control.
Some animal species also depend on occasional fires because they feed on the vegetation that sprouts after a fire has cleared the land.

Oil-Field Succession

Old-field succession
is a type of
secondary succession
that occurs when farmland is abandoned.
When a farmer stops cultivating a field, grasses and weeds quickly grow and cover the abandoned land.
Over time, taller plants, such as perennial grasses, shrubs, and trees take over the area.

Primary succession
can occur on new islands created by
volcanic eruptions
Primary succession is much slower than secondary succession. This is because it begins where there is no soil.

The first pioneer species to colonize bare rock will probably be
bacteria and lichens
, which can live without soil.
The growth of lichens
breaks down the rock
, which with the action of water, begins to form soil.

Primary Succession
Bell Ringer
1. Describe the 2 processes of the carbon cycle.

2. Describe how the burning of fossil fuels affects
the carbon cycle.

3. Explain how the excessive use of fertilizer
affects the nitrogen cycle and the phosphorus

4. Explain why the phosphorus cycle occurs
more slowly than both the carbon cycle and
the nitrogen cycle.
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