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LS2B
Cycle of Matter & Energy, Study Guide
Learning Target #1
Performance Expectation #3
I can develop a model to represent the flow of energy in ecosystems
between living and nonliving parts
a) Describe how energy moves through an ecosystem between producers,
consumers, & decomposers
b) Create a model of the food web/energy pyramid to identify/explain the
parts
Build your own food web interactive: http://www.gould.edu.au/foodwebs/kids_web.htm
Build a food chain:http://www.sheppardsoftware.com/content/animals/kidscorner/foodchain/foodchain.htm
Producers, consumers, or decomposers:
http://www.sheppardsoftware.com/content/animals/kidscorner/games/producersconsumersgame.htm
Building an ocean food web: http://www.coolclassroom.org/cool_windows/home.html
Chain Reaction: http://www.ecokids.ca/PUB/eco_info/topics/frogs/chain_reaction/assets/flash/chain_reaction.swf
How does energy enter into most ecosystems?
Sunlight
How is an organism’s energy role determined?
It is determined by how it obtains energy and how it interacts with other organisms
What are the three types of energy roles an organism can play in an ecosystem?
producer, consumer, decomposer
What is a producer?
Organisms that are able to make their own food from inorganic substance, which are not made
by other organisms
 An organism that can make its own food (plants, bacteria, & algae)
Producers use the energy given from sunlight through a process known as?
Photosynthesis
What actually happens during photosynthesis?
The organism uses the sun’s energy to turn water and carbon dioxide into food molecules
Where does the source of all food in an ecosystem come from?
Producers
There are some organisms that are able to produce food energy without the use of the sun, such as an
ecosystem of bacteria found in rocks deep beneath the ground. How does it get its energy?
Certain bacteria produce their own food by using hydrogen sulfide, a gas, that is found in their
environment.
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What is a consumer?
An organism that obtains energy by feeding on other organisms
What are 3 types of consumers?
Herbivores
Carnivores
Omnivores
What are herbivores?
Organisms that eat only plants
What are carnivores?
Organisms that eat only animals
What are omnivores?
Organisms that eat both plants and animals
Some carnivores, but not all can be scavengers. What is a scavenger?
A carnivore that feeds on the bodies of dead organisms
What are some examples of scavengers that are also carnivores?
Catfish, vultures, hyenas, and sharks
What is a decomposer?
It breaks down wastes of (decayed matter) dead organisms and returns the raw materials to the ecosystem
 They are important to an ecosystem because they keep dead matter from piling up & they restore
essential nutrients to the ecosystem
What is another way to describe a decomposer?
Nature’s recycler
What are some common decomposers?
Mushrooms, bacteria, mold, fungi, worms, flies, maggots, termites
What is a food web?
A way to show the flow of energy through an ecosystem.
What is located at the base of the food web?
Producers
What order does the food web move from its base?
Producers, first level consumers, second level consumers, third level consumers
What is an energy pyramid?
It a diagram that shows the amount of energy that moves from feeding level to another in a food web
Where is the most energy found in a food web or energy pyramid?
Producer level
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How much energy transfers from one level to the next in a food web?
Only about 10%
What happens to the other 90% of energy if only 10% transfers from one level to the next?
It is used for the organism’s life processes OR it is lost to the environment as heat
Why are there relatively few organisms at the top of an energy pyramid or food web?
So much energy is lost from one level to the next level up, the energy available at the top level can
support few organisms
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Learning Target #2
Performance Expectation #3
I can develop a model to represent the cycling of matter in ecosystems between
living and nonliving parts
a) Describe how energy moves through an ecosystem by water cycle, nitrogen
cycle, and the carbon cycle
b) Create a model to represent the cycling of matter (water, nitrogen, carbon)
in ecosystems
Page 48 – 49
Water Cycle
What is the water cycle?
It is the continuous process by which water moves from Earth’s surface to the atmosphere and back
What three processes make up the water cycle?
Evaporation
Condensation
Precipitation
What is evaporation?
The process by which molecules of liquid water absorb energy and change to a gas
What is water vapor?
A gas in the atmosphere that forms from liquid water
What is an example of evaporation?
Liquid water evaporates from oceans, lakes, and other surfaces and forms water vapor
Where does the energy come from for evaporation to occur?
Heat of the sun
What are examples of evaporation from living things?
Plants release water vapor from their leaves
People release water vapor when you exhale
What is transpiration?
It is a process by which moisture is carried through plants from roots to small pores on the underside of
leaves where it changes into water vapor (the evaporation of water from plant leaves)
What is condensation?
The process by which a gas changes to a liquid.
How does the process of condensation work?
As water vapor rises higher in the atmosphere, it cools down. The cooled vapor then turns back into
tiny drops of liquid water.
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What is precipitation?
Drops of water fall back to Earth in the form of rain, snow, sleet, or hail
How does the process of precipitation work?
As more water vapor condenses, the drops of water in the cloud grow larger. Eventually, the heavy
drops formed will fall back to the ground
Where does most precipitation end up on Earth?
Oceans or lakes
What happens to the precipitation that falls on the land?
It may soak into the soil and become groundwater
OR
It may run off the land, eventually flowing back into a river or ocean
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Nitrogen Cycle
What is nitrogen and how does it relate to the nitrogen cycle?
Nitrogen is an element that is found in both the living portion of our planet and the inorganic parts of
the Earth system.
 The nitrogen cycle is one of the biogeochemical cycles and is very important for ecosystems.
 Nitrogen cycles slowly, stored in reservoirs such as the atmosphere, living organisms, soils, and
oceans along its way.
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Nitrogen atoms move slowly between living things, dead things, the air, soil and water.
These movements are called the nitrogen cycle.
How are the interactions of humans affecting the nitrogen cycle?
Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is
stored in reservoirs (land, water, air) and organisms.
 The use of nitrogen-rich fertilizers can cause nutrients leaking into nearby waterways as nitrates
from the fertilizer wash into streams and ponds.
 The increased nitrate levels cause plants to grow rapidly until they use up the nitrate supply and
die.
 The number of herbivores will increase when the plant supply increases and then the herbivores
are left without a food source when the plants die. In this way, changes in nutrient supply will
affect the entire food chain.
 Additionally, humans are altering the nitrogen cycle by burning fossil fuels and forests, which
releases various solid forms of nitrogen.
 Farming also affects the nitrogen cycle.
o The waste associated with livestock farming releases a large amount of nitrogen into soil
and water.
 In the same way, sewage waste adds nitrogen to soils and water.
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What is the importance of nitrogen on Earth?
All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the
atmosphere is not in a form that they can use.
The molecules of nitrogen in the atmosphere can become usable for living things when
 they are broken apart during lightning strikes or fires,
 by certain types of bacteria, or
 by bacteria associated with bean plants.
Where do plants and animals get the nitrogen they need to grow?
 Most plants get the nitrogen they need to grow from the soils or water in which they live.
 Animals get the nitrogen they need by eating plants or other animals that contain nitrogen.
When organisms die, their bodies decompose bringing the nitrogen into soil on land or into ocean
water.
Bacteria alter the nitrogen into a form that plants are able to use.
Other types of bacteria are able to change nitrogen dissolved in waterways into a form that allows it to
return to the atmosphere.
What is the nitrogen cycle?
The nitrogen cycle describes how nitrogen moves between plants, animals, bacteria, the atmosphere
(the air), and soil in the ground.
Different Nitrogen States
For Nitrogen to be used by different life forms on Earth, it must change into different states.
 Nitrogen in the atmosphere, or air, is N2
 Other important states of nitrogen include Nitrates (N03), Nitrites (NO2), and Ammonium (NH4).
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What is the importance of the nitrogen cycle?
Nitrogen is essential for many processes and is crucial for any life on Earth.
 In plants, much of the nitrogen is used in the chlorophyll, which are essential for photosynthesis
and future growth.
o Nitrogen is a limiting factor for plant growth.
 Although Earth’s atmosphere is an abundant source of nitrogen, most is relatively unusable by
plants.
 Nitrogen is also essential to all life since it is present in all amino acids.
 Chemical processing, or natural fixation (through processes such as bacterial conversion are
necessary to convert gaseous nitrogen into forms usable by living organisms, which makes
nitrogen a crucial component of food production.
 The abundance or scarcity of this "fixed" form of nitrogen, (also known as reactive nitrogen),
dictates how much food can be grown on a piece of land.
 Nitrogen is an important element to all life on Earth.
o Animals get the nitrogen they need by consuming plants or other animals that
contain organic molecules composed partially of nitrogen.
What is organic nitrogen?
The nitrogen present in living things, and in the matter produced by the decomposition of living things,
is known as "organic nitrogen."
 The processes of the nitrogen cycle create these various molecules from each other by a
straightforward recycling process.
The picture below shows the flow of the nitrogen cycle.
 The most important part of the cycle is bacteria.
 Bacteria help the nitrogen change between states so it can be used.
 When nitrogen is absorbed by the soil, different bacteria help it to change states so it can be
absorbed by plants.
 Animals then get their nitrogen from the plants.
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Processes in the Nitrogen Cycle
Fixation
 Fixation is the first step in the process of making nitrogen usable by plants. Here bacteria
change nitrogen into ammonium.
o A special type of bacteria called nitrogen fixing bacteria take in atmospheric nitrogen
and produce ammonia.
Nitrification
 This is the process by which ammonium gets changed into nitrates by bacteria. Nitrates are
what the plants can then absorb.
o Other bacteria use this ammonia to produce nitrates and nitrites, which are nitrogen
and oxygen containing compounds
Assimilation
 This is how plants get nitrogen. They absorb nitrates from the soil into their roots. Then the
nitrogen gets used in amino acids, nucleic acids, and chlorophyll.
o The nitrates and the nitrites are used by plants to make amino acids which are then
used to make plant proteins
o Plants are consumed by other organisms which use the plant amino acids to make their
own
Ammonification
 This is part of the decaying process. When a plant or animal dies, decomposers like fungi and
bacteria turn the nitrogen back in ammonium so it can reenter the nitrogen cycle.
o Decomposers convert the nitrogen found in other organisms into ammonia and return it
to the soil.
Denitrification
 Extra nitrogen in the soil gets put back out into the air. There are special bacteria that perform
this task as well.
o A few of these type of bacteria return nitrogen to the atmosphere by a process called
denitrification, however that amount is small.
Why is nitrogen important to life?
Plants and animals could not live without nitrogen. It is an important part of many cells and processes
such as amino acids, proteins, and even our DNA. It is also needed to make chlorophyll in plants, which
plants use in photosynthesis to make their food and energy.
Fun Facts
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Around 78% of the atmosphere is nitrogen. However, this is mostly not usable by animals and
plants.
Nitrogen is used in fertilizer to help plants grow faster.
Nitrous oxide is a greenhouse gas. Too much of it can also cause acid rain.
Nitrogen has no color, odor, or taste.
It is used in many explosives.
About 3% of your body weight is nitrogen.
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Carbon Cycle
What is the carbon cycle?
The Carbon Cycle describes the flow of carbon between living organisms and the non-living
environment.
 Carbon cycles through the environment in the form of a gas, carbon dioxide (CO2).
 The atmosphere of Earth contains .04 percent CO2.
Living organisms provide two important steps in the carbon cycle:
 Plants absorb CO2 from the atmosphere to use during photosynthesis.
 Other organisms release CO2 into the air during respiration.
Where can carbon be found in the environment?
 A large portion of the Carbon on the Earth is stored in rocks.
 The Earth's oceans hold a large amount of CO2 because it easily dissolves in water.
 Coal, oil, and limestone store carbon that once formed ancient organisms. Burning fossil fuels,
like coal and oil, will release CO2 into the atmosphere.
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What is the importance of the carbon cycle?
 All living things are made of carbon.
 Carbon is part of the ocean, air, and even rocks.
 Because the Earth is a dynamic place, carbon does not stay still. It is on the move!
 In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide.
 Plants use carbon dioxide and sunlight to make their own food and grow.
o The carbon becomes part of the plant.
 Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over
millions of years.
 When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon
dioxide.
 Carbon dioxide is a greenhouse gas and traps heat in the atmosphere.
o Without it and other greenhouse gases, Earth would be a frozen world.
o But humans have burned so much fuel that there is about 30% more carbon dioxide in
the air today than there was about 150 years ago, and Earth is becoming a warmer
place.
o In fact, ice cores show us that there is now more carbon dioxide in the atmosphere than
there has been in the last 420,000 years.
How do living things obtain carbon?
Carbon is extracted from the atmosphere by plants through the process known as photosynthesis.
 This carbon is combined with other elements in complex ways to form organic molecules
important to life.
 This carbon is later transferred to animals who consume, or eat plants.
When plants and animals die, much of their carbon is returned to the atmosphere as the organisms
decompose.
 Every so often, a plant or animal does not decompose right away.
 Their bodies are trapped in locations where decomposition can simply not take place.
 This is most common at the bottom of oceans and seas where the lifeforms become buried by
sand.
 Instead of returning to the atmosphere, the carbon from these lifeforms is trapped within the
Earth.
 Over millions of years, more and more of the carbon on Earth has been trapped in this manner.
o Today, almost 99% of all the carbon on Earth has been locked up deep within the Earth.
o As rocks weather, this carbon is slowly released back into the atmosphere, creating a
balance.
o For the past several hundred million years, the amount of carbon being locked up in the
Earth and the amount being released by weathering rocks was almost perfectly
balanced.
o This important balance has been altered significantly in the past century as humans
have begun using fossil fuels to produce energy.
o By burning the Earth’s store of carbon, mankind is able to create the energy needed to
operate our communities.
 By releasing more carbon into the atmosphere than is being locked up, we risk
causing damage to the delicate carbon cycle.
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