Chapter 4
Matter and Energy in the
Ecosystem
4.1 Roles of Living Things
4.2 Ecosystem Structure
4.3 Energy in the Ecosystem
4.4 Cycles of Matter
4.1 Roles of Living Things
Objectives:
•Identify the roles of producers,
consumers and decomposers.
•Explain the concept of trophic levels.
Producers, Consumers and
Decomposers
• Organisms of most ecosystems gather food in
three ways:
– As producers
– As consumers
– As decomposers
• Energy only enters the ecosystem at the level of
•
the producers.
All other organisms depend on the energy
captured by the producers.
Producers
• Producers – organisms that make their own food
•
•
•
from inorganic molecules and energy.
Almost all producers use the sun for energy.
With this energy they combine carbon dioxide
and water through photosynthesis to produce
sugars.
Nearly all the energy entering an ecosystems
comes from the sun.
Producers
• Plants are the most important producers in
•
•
terrestrial environments.
Photosynthetic protists and bacteria are the
most important producers of aquatic
environments.
There are a few nonphotosynthetic producers.
– Bacteria that make food by using energy stored in
inorganic molecules.
– Live in extremely harsh environments:
• Hot springs
• Thermal vents of the ocean floor
Consumers
• Consumers – organisms that cannot make
their own food.
• All animals are consumers, as are some
bacteria, fungi and protists.
• Obtain their energy by eating other
organisms.
Types of Consumers
• Four basic types:
– Herbivores
– Carnivores
– Omnivores
– Scavengers
Herbivores
• Herbivores- organisms that eat only plants
• Also called Primary Consumers because they eat only
•
producers
Examples:
– Insects
– Birds
– Grazing animals – cows, deer
• Well adapted for the eating, grinding and digesting of
plants and other producers.
– Teeth
– Stomachs
Carnivores
• Carnivores – organisms that capture and
eat herbivores or other carnivores
• Carnivores that eat primary consumers are
called Secondary Consumers
• Carnivores that eat other carnivores are
called Tertiary Consumers
Carnivores
• Examples:
– Lions
– Snakes
– Hawks
– Spiders
• Bodies are well adapted for hunting,
capturing and eating prey.
Omnivores
• Omnivores – organisms that eat both producers
•
•
and consumers
Omnivores can be primary, secondary or tertiary
consumers depending on what they eat.
Examples:
– Humans
– Chimps
– Bears
Scavenger
• Scavenger – usually do not hunt living prey, but
•
•
feed on the bodies of dead organisms.
Scavengers can be primary, secondary or
tertiary consumers
Examples:
– Vultures
– Hyenas
– Many insects
• Start the process of returning nutrients from
dead organisms to the environment.
What type of consumer are you?
• If you eat a salad?
(primary)
• If you eat a hamburger?
(secondary)
• If you eat a tuna salad sandwich?
(tertiary)
Decomposers
• Decomposers - bacteria and fungi that consume
•
•
•
the bodies of dead organisms and other organic
wastes.
Consume a variety of dead material from fallen
leaves to the bodies of dead herbivores and
carnivores
Also break down organic material in animal
waste.
Recycle nutrients from organisms back into the
environment.
Decomposers
• Without decomposers we would quickly run out
•
•
of nutrients.
They complete the cycle of matter in the
ecosystem.
Convert organic matter from organism back into
simpler forms, which are then returned to the
soil where plants can use them. Plants then use
these nutrients to grow and the cycle begins
again.
Cycle of Matter
sun
Returns nutrients
To the ground
Grass (producer)
Bacteria
(Decomposer)
Grasshopper
(primary consumer)
Turkey Vulture
(scavenger)
(Hawk Dies)
Hawk
(tertiary consumer)
Robin
(secondary consumer)
Trophic Levels
• Trophic Levels - a layer in the structure of
feeding relationships in an ecosystem.
• Word break down:
– Troph- means “to feed or nourish”
– -ic means “related to”
Trophic Levels
• Producers make up the first and largest
trophic level.
– Because they make their own food producers
are also called autotrophs.
• Autotroph means “self-nourisher”
• Autotrophs are the sole point of entry for
energy into the ecosystem.
Trophic Levels
• Consumers form the second and higher trophic
•
levels
Because consumers cannot produce their own
food they are also called heterotrophs
– Heterotroph means “other-nourisher”
• Primary consumers eat producers and make up
•
•
the second trophic level.
Secondary consumers make up the third trophic
level
Ominvores, scavengers and decomposers feed
at all trophic levels above the first.
Trophic Levels
• Most ecosystems have three, four or five
trophic levels
• Each trophic level is dependent on the one
below it.
Review
• What is a producer and what is its role?
• What is a consumer and what is its role?
• What is a decomposer and what is its
role?
• What is a trophic level?
4.2 Ecosystem Structure
Objectives
•Describe food chains and food webs.
•Examine how ecosystem structure is related
to population changes and the transfer of
pollutants.
Review
• What is an autotroph?
• What is a heterotroph?
• What type of consumer are you if you eat
a salad for lunch?
Food Chains
• Food Chain – a series of organisms that transfer
•
•
food between the trophic levels of an
ecosystem.
All food chains begin with producers
Next is herbivores, followed by one or more
carnivores.
All organisms are consumed by decomposers
•
• Figure 4.4 page 56
• Few ecosystems are simple enough to be
represented by a food chain.
Food Webs
• Food Web – a network of food chains
•
•
•
representing the feeding relationships among
the organisms in an ecosystem.
Include all the food chains in a ecosystem
The interactions of a food web link organisms in
an ecosystem.
Changes in the population of one organism can
affect other populations.
– This can be seen when an important consumer is
removed from an food web.
– Figure 4.5 page 57
Antarctica Food Web
• Main producer is microscopic algae
• Krill feed on this algae
• Krill are the main source of food for Baleen whales,
•
•
•
•
seals, squid, penguins and fish
Because of whaling the Baleen whale population
decreased
As a result the krill population increased
The population of seals, squid, penguins and fish
increased due to the increase in the krill population.
Figure 4.6 page 58
Diversity and Stability
• The more diverse an ecosystem, the more connections
•
•
•
•
there are in the food web.
The more connections in the food web the more stable
the ecosystem is.
When there is a loss of a organism there is other
organisms with the same function that the ecosystem
can recover.
A deciduous forest is diverse and a small disturbance has
little effect.
A tundra lacks diversity and a small disturbance has long
lasting effects.
Biological Magnification
• Biological Magnification – the increasing
concentration of a pollutant in organisms
at higher trophic levels in a food web.
• Many pollutants can concentrate this way
and have devastating effects on an
ecosystem.
– DDT, mercury
DDT
• DDT was a pesticide used by farmers.
• It washed into streams and other water sources.
• The plants growing in the water became contaminated
•
•
•
•
•
with the DDT.
Fish would eat the plants
The fish were eaten by bald eagles
DDT was almost responsible for the extinction of our
national symbol
DDT caused problems with the reproduction and caused
the shells of their eggs to be weak.
DDT is no longer used and through conservation efforts
the bald eagle is recovering.
Review
• Why is biological magnification such a
problem?
• Why does diversity mean a more stable
ecosystem?
4.3 Energy in the Ecosystem
Objective:
Investigate the movement of energy
through an ecosystem.
Define ecological pyramid, and explain its
relationship to energy in an ecosystem.
Review
• What is biological magnification?
• What makes a more stable ecosystem?
Energy and Food
• Energy from the sun travels as waves to Earth.
• Some of this energy is immediately reflected
•
•
back into space and some is absorbed by Earth’s
surface and atmosphere.
Plants receive less than 1% of the energy that
reaches the Earth from the sun.
Of this energy less than 30% is stored in the
form of organic matter made during
photosynthesis.
– With this energy plants make about 170 billion tons of
organic matter.
Sun and Earth
Biomass
• Biomass – the total amount of organic matter
•
•
•
present in a trophic level.
Is potentially food for the next trophic level
Scientists use biomass to track the flow of
energy from one trophic level to the next.
Energy in the form of biomass is transferred as
one trophic level feeds on the next.
– Only part of this energy is transferred.
– Some energy is used for movement, heat and other
functions necessary for life.
– Figure 4.8 page 61
Energy
• It is because of the loss of energy from
one trophic level to the next that the size
and number of trophic levels is limited.
• Example: Owls
– Owls are not typically preyed upon
– The owl population is not sufficient to support
an additional trophic level.
Ecological Pyramids
• Ecological Pyramid – A diagram that
shows the relative amounts of energy in
different trophic levels in an ecosystem.
• Can show:
– Energy
– Biomass
– Number of organisms in a food web
Energy Pyramid
• Figure 4.9 page 61
• Base of the pyramid is the producers, the first trophic
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•
•
•
•
•
•
level.
Second level is the primary consumers
Third level is the secondary consumers
Fourth level is the tertiary consumers
The producers get 100% of the energy
Only 10% of this energy is available for the 2nd level
Only 1% of the energy from the 3rd level is available for
the 4th .
Only 0.1% of the energy from the 4th is available
Energy Pyramid
Tertiary consumers
0.1%
1% Secondary
Consumers
10% Primary
Consumers
Energy from
the sun
100% Producers
Biomass Pyramid
• Figure 4.10 page 62
• Shows the mass of organic matter at each
trophic level
• Base is producers
• Biomass pyramids often follow the same
pattern as energy pyramids
Biomass Pyramid
50 g owl
500g of mice
5,000g of grasshoppers
50,000g of plants
Numbers Pyramid
• Figure 4.10 page 62
• Number of organisms may be different at each
•
•
level.
The one shown has 1000 plants and one owl,
this is a common pattern
An exception would be one tree that supports
1000 insects
– The one tree has a large amount of biomass and
energy
– The 1000 insects have a smaller amount of biomass
Numbers Pyramid
1 owl
10 mice
100 grasshoppers
1,000 plants
Energy and Trophic Levels
• Energy moves between the trophic levels
in the form of food
• Food also contains matter
– Carbon, hydrogen, nitrogen and oxygen
• Important to the production of food
• Growth of producers is limited by the amount of
these elements, not by the amount of energy from
the sun.
Review
• What are the three types of ecological
pyramids and what does each tell us?
• How does energy move through the
ecosystem?
4.4 Cycles of Matter
Objectives
Describe the chemical composition of
the human body.
Explain the water cycle, the carbon
cycle, and the nitrogen cycle.
Your Body
About 96% of your body is made up of just for
elements oxygen, carbon, hydrogen and
nitrogen. See Table 4.1 p. 64
How much of your body is composed of:
Oxygen
Carbon
Hydrogen
Nitrogen
Calcium
Phosphorus
Common Elements
About 78% of the Earth’s atmosphere is
nitrogen and 21% oxygen
Carbon is present in the atmosphere as well as
in biomass and rocks
Even though these elements are common on
Earth they are not always in a usable form.
Ex. nitrogen.
Nitrogen is common in the Earth’s atmosphere, but it is not
in a form that plants can use, very little nitrogen exists in a
form plants can use. A scarcity of usable nitrogen will limit
plant
Where do you think the largest
amount of water is found?
Oceans?
Groundwater?
Glaciers?
Streams?
Answer
Oceans
In which one is there more
water found?
Streams?
Atmosphere?
Answer
Atmosphere
Water
 Plants consist of up to 90% water
 Humans consist of up to 60% water
 Of all the water on the Earth only 0.3% is usable by
humans
 The world’s water supply totals approx. 326 million
cubic miles of water
 Oceans = 97.24%
 Icecaps, Glaciers = 2.14%
 Ground Water = 0.61%
 Fresh-water lakes = 0.009%
 Inland seas = 0.008%
 Soil moisture = 0.005%
 Atmosphere = 0.001%
 Rivers = 0.0001%
Water Cycle
What is the water cycle?
The continuous recycling of water throughout the
globe.
Important Terms
Evaporation- the movement of water into the
atmosphere as it changes from a liquid to a gas
Transpiration- the evaporation of water from the
leaves of plants.
Precipitation- The process in which water falls
from clouds (rain, snow, etc.)
Condenstation- The process by which water vapor
is turned into liquid form
Water Cycle
A drop of rain falls from the sky and
becomes surface runoff
The surface runoff accumulates as a
body of water
The water then evaporates
Condenses in the clouds
And falls as precipitation
Water Cycle
Carbon Cycle
Scientists believe that when the Earth was very
young that the atmosphere was much like that
of Mars and Venus, about 95% carbon dioxide
Living things played an essential role in the
formation of Earth’s atmosphere.
Photosynthetic organisms removed some carbon
dioxide from the atmosphere and added oxygen.
This led to what our atmosphere is like today
only 0.04% carbon dioxide
Living things are still the most important part of
the carbon cycle
Photosynthesis and Respiration
The processes of photosynthesis and
respiration could not occur without carbon
Photosynthesis: H2O + CO2 + energy 
C6H12O6 + O2
Respiration: C6H12O6 + O2  CO2 + H2O +
energy
As you can see the produces of one
reaction are used by the other reaction
Carbon Cycle
Plants use CO2 and sunlight to make sugars and
starches during photosynthesis
When these nutrients are consumed by the
plant or any other organisms, CO2 and energy
are released
Biological reactions in organisms are the main
part of the carbon cycle, Figure 4.12
The amount of carbon tied up in organic matter
at any given time is larger than the amount of
carbon in the atmosphere
Carbon Cycle
Two other important sources of carbon are the
ocean and rocks
Oceans hold a great deal of carbon dioxide
because carbon dioxide dissolves easily in water.
Carbon is also stored in rocks: coal, oil and
limestone are formed from the bodies of dead
organisms. Because the bodies of these
organisms were never completely decomposed,
some of the carbon in them was never released.
The carbon from fossil fuels is released as CO2
when we burn them for energy
Carbon Cycle
Nitrogen Cycle
The nitrogen cycle is very important to living
things.
Organisms need nitrogen in order to make
amino acids, which are the building blocks of
proteins…proteins are the building blocks of
nucleic acids
Nitrogen is common in the atmosphere (78%),
however as a gas it is unusable to most
organisms. It must be in a more reactive state
to be usable
Nitrogen Cycle
There are nitrogen-fixing bacteria that can use
atmospheric nitrogen
These bacteria produce ammonia (NH3), this is a
form of nitrogen plants can use
Nitrogen-fixing bacteria live in the soil and in the
roots of legumes
Legumes- are plants such as peanuts, beans
and clover that have colonies of nitrogen-fixing
bacteria in nodules on their roots
Nitrogen Cycle
Most of the ammonia is used by other
bacteria. These bacteria produce nitrites
and nitrates (contain nitrogen and
oxygen)
Nitrates are the most common source of
nitrogen for plants
Fertilizer can also be provided to plants,
they contain nitrates.
Nitrogen Cycle
Animals get their nitrogen from the
proteins of the food they consume
Decomposers return nitrogen to the soil in
the form of ammonia and the cycle starts
again
Figure 4.13 page 67
Nitrogen Cycle
Review
• What is the most abundant element in
your body?
• What is a legume? What is an example?