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UNIT A: Energy and Matter Exchange in the Biosphere
General Outcome 1: Explain the constant flow of energy through the biosphere and ecosystem.
Ecology (Greek – a house or a home): The study of relationships between living things (organisms)
and their non-living surroundings (the environment). [1866 Ernst Haeckel]
System: an object or group of
objects that a scientist chooses to
study. Everything other than the
system is referred to as the
surroundings. Systems are
separated from their surroundings by
a boundary (distinct or gradual).
Open systems: allows both energy
and matter to cross the boundary.
Closed systems: only allows energy
to cross the boundary.
Biosphere: all of the areas on Earth that are inhabited
by and support life. It is composed of three main areas
(Atmosphere, Geosphere (Lithosphere), Hydrosphere).
Section 1.1: How energy Enters the Biosphere
Energy enters the biosphere from the Sun, through a process of photosynthesis (or from
minerals through chemosynthesis). Photosynthesis is the chemical process within plants that
converts solar energy into chemical energy. During this process carbon in the atmosphere (CO2) is
chemically altered to produce the high energy compound glucose (C6H12O6).
Carbon dioxide + water
CO2
H2O
carbohydrates + oxygen
C6H12O6
O2
Energy Input: Sunlight
Solar Radiant Energy reaching the Earth:
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30% is reflected back (Albedo Effect – reflection of energy from light colored
matter; clouds, atmospheric dust, water surface,
ice, snow, sand, etc.)
 19% is absorbed by gases (water vapour, carbon
dioxide, methane, etc.). Some of this absorbed
energy heats the atmosphere, while some is
radiated back into space.
 51% reaches the Earth’s surface and is absorbed by
land, oceans, and plants. This heats the Earth’s surface.
The resulting heat radiates upward into theatmosphere –
where it is either absorbed by atmospheric gases
(greenhouse gases) or radiated out to space.
 Of the energy absorbed by Earth, only a
small portion is used for photosynthesis.
 Of the total radiant energy reaching the
Earth, 1-2% is used for photosynthesis.
 This allows producers to generate ~ 150-200 billion tones of organic
matter each year.
Energy Output: chemical energy (glucose/starch/carbohydrates)
Since plants make their own energy, they are referred to as autotrophs (self feeders) or
producers. Most of the chemical energy made by the plant is used by the plant for life functions
(movement, growth, repair, transport, reproduction, exchange of materials with the environment,
response to stimuli). Some of the chemical energy is stored for future use (usually as starch).
Chemosynthetic Producers
(chemotrophs) convert inorganic chemicals
(minerals, hydrogen sulfide) into organic
energy. These organisms are usually found in
extreme environments (volcanic deep-sea
vents, cold-water seeps, hot springs, intensely
salty lakes, deep caves).
Chemotrophs (tube worms) living on or
around the volcanic deep-sea vents (black smokers which release hydrogen sulfide, minerals, and
heat into the water) have no access to sunlight, are heat-resistant, and contain bacteria within their
tissues that are able to split the hydrogen sulfide in order to capture the chemical
energy. Sulfuric acid is produced as a by-product.
Another example of a chemotroph is nitrifying bacteria within soil. They
convert ammonia (NH3) in the soil to other nitrogen compounds (nitrate ions and
nitrite ions – same as in fertilizer) which are then used by other plants and micro-organisms.
When other organisms eat plants, it is the stored energy from the plant that is converted to
usable energy for the organism through the process of cellular respiration. Cellular respiration is the
process of converting the chemical energy of high energy compounds (glucose) into ATP (adenosine
triphosphate). This is a combustion reaction that also releases heat.
Carbohydrates + oxygen
carbon dioxide + water + heat
Energy Input: chemical energy (glucose/starch/carbohydrates)
Energy Output: chemical energy (ATP) and heat
Organisms that must eat plants (or other organisms) to obtain energy are referred to as
heterotrophs (other feeders) or consumers. Consumers are classified based upon how they obtain
their food, although many organisms can obtain food from multiple sources:
By eating plants and other organisms, the energy from the sun is transferred throughout the
biosphere, while matter is constantly recycled through the biosphere.
Herbivores – consume primarily plants (primary consumers)
Carnivores – consume the flesh of other animals.
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Secondary consumers – consume mainly herbivores
Tertiary consumers – consume secondary consumers
Decomposers – obtain energy-rich molecules from eating/absorbing
left-over or waste matter.
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Feces
Dead organisms/body parts
Decomposers return organic and inorganic matter to the
biosphere which can then be re-used by producers.
Energy Transfer has a one-way flow:
First Law of Thermodynamics: energy cannot be
created or destroyed. It can only be converted from one form to
another, or transferred from one object to another.
Second Law of Thermodynamics: With each conversion
or transfer of energy, there is less energy available to do useful
work because some energy is lost as heat.
Eventually, with enough conversions, there will be no
useful energy left within the system. Therefore a constant supply
of energy is needed to sustain life.
Section 1.2: How Energy is Transferred in the Biosphere
Ecosystems (Ecological System) – made up of all the
organisms that live in an area (biotic factors – organisms, their
wastes and remains) and the physical environment of that area
(abiotic factors – sunlight, water, minerals). The biotic and
abiotic interactions form a self-regulating system through which energy and matter are transferred.
1920’s – Charles Elton and Victor Summerhays studied organisms on an island off the coast of
Norway (Bear Island). The island was desolate, and the researchers were able to easily observe the
organisms on the island and their feeding interactions. They came up with the concepts of food
chains and food webs to describe the feeding interactions they were seeing. As well, they recognized
a pattern between the trophic levels of organisms (energy available at each trophic level) and the
number (and/or size) of the organisms at each trophic level.
Food Chain: a model describing the linear pathway through which
food (energy) is transferred from producers to primary consumers
to higher trophic levels. These best describe the specific feeding
actions of individual organisms.
Food Webs: a model of food (energy) transfer in an ecosystem that
shows the multiple connections between organisms since organisms
(consumers) may prey on more than one species.
Food chains and food webs generally have only a few trophic levels (between 3 and 6)
because of the limits on the transfer of energy (second law of thermodynamics).
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When an organism eats other organisms, most of the energy obtained is used for life
functions, some is lost as heat, and a small amount is stored. As well, often the
consumer doesn’t ingest all of its prey.
Generally, the efficiency of energy transfer from one trophic level to another varies
between 5-20%.
For the purpose of convenience, ecologists assume 10% of the energy is transferred
between trophic levels. This is called the Rule of 10.
Ecological Pyramids: the pattern between the number/size/mass of trophic levels and the energy
available at each trophic level.
Pyramid of Numbers:
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General pattern - animals at higher trophic levels are fewer in number than organisms
at lower trophic levels.
Limits - when producers are very large (trees), the number of producers may be
smaller than the number of primary consumers.
Pyramid of Biomass
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Biomass is the dry mass of living (or once-living) organisms per unit area (g/m2), and
indicates the amount of energy present in the living tissue of a trophic level or
ecosystem.
General pattern –Lower trophic levels have greater biomass than higher trophic levels.
Limits –
o scientists may define biomass in different ways
o Ocean ecosystems – the biomass of the producers (phytoplankton) may be less
than the biomass of primary consumers (zooplankton) because the producers
are eaten as quickly as they reproduce.
Pyramid of Energy
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Shows the total amount of energy that is transferred through each trophic level, and
clearly demonstrates how little energy is left at the highest trophic level.
General pattern – lower trophic levels always have more energy than higher trophic
levels.
Note: the stability of feeding relationships in ecosystems decreases with a decrease in the number or
species (biodiversity) – especially the number and variety of producers. Decreases in biodiversity
may result from:
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Loss of habitat
Over hunting/fishing
Increased stress or competition between
species
Biomagnification of toxins through the
trophic levels of an ecosystem
General Outcome 2: Explain the cycling of Matter through the Biosphere
Section 2.1: The Role of Water in Cycles of Matter
Biogeochemical Cycles: the routes that matter (water and chemical nutrients) take as they are
recycled through the biotic and abiotic
components of the biosphere. Elements
that can easily travel between both water
and air can be cycled globally (oxygen,
carbon, nitrogen, and sulfur).
Nutrient Reservoirs – at each step
in a biogeochemical cycle, substances are
temporarily stored – in organisms, soil, air,
or water.
Rapid Cycling – When substances cycle between nutrient
reservoirs relatively quickly.
Slow Cycling – When substances accumulate and are
unavailable to organisms.
Hydrologic Cycle – The Water Cycle
Water is vitally important in the biosphere due to its chemical and physical properties:
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Universal solvent due to its hydrogen bonding and polarity
Relatively high melting point and boiling points (high specific heat capacity)
Water has hydrogen bonding – which causes it to expand when frozen (ice has a lower
density than water)
Has special adhesive (attraction of water to other substances - dissolving) and
cohesive (attraction of water to itself – surface tension) properties
Section 2.2: Biogeochemical Cycles
The Carbon and Oxygen Cycles
Carbon and oxygen are interconnected through the
biotic processes of photosynthesis and cellular respiration.
Plants consume more carbon dioxide than is released from
living organisms. However, carbon dioxide is released into the
atmosphere in much greater amounts by the processes of
decomposition, forest fires, and human activities.
Oxygen is rapidly cycled throughout the biosphere.
Carbon can be rapidly cycled, or can be stored in nutrient reservoirs called carbon sinks (trees,
sediment, fossil fuels) for hundreds to millions of years.
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Deforestation = returns 2 gigatones (Gt) of carbon to
atmosphere each year
Oceans trap 38 000 Gt of carbon in dissolved carbon
dioxide
Ocean floor sediment = holds 11 000 Gt of carbon as
methane hydrates.
Since the industrial revolution (late 1800’s)
atmospheric carbon dioxide levels have increased by
30%
The Sulfur Cycle
All organisms require sulfur for the formation of proteins and vitamins.
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Plants/algae – use sulfate (SO42-(aq)) 
decomposition releases the sulfur as hydrogen
sulfide (H2S) which causes the sulfur smell.
Bacteria use sulfur compounds in
photosynthesis and cellular respiration
o Sulfate reducers convert sulfate to
sulfide
o Sulfur oxidizers convert sulfide to
elemental sulfur and sulfate
o Waste that is generated from one type
of bacteria becomes the required
material for a different type of bacteria.
Some sulfur in the soil is stored as sediment (rocks and fossil fuels)  which is then released
into the atmosphere when high sulfur containing fossil fuels are burned, or through volcanic
activity.
o Released as sulfur dioxide (SO2)
o Sulfur dioxide reacts with water and
oxygen in the atmosphere to form
sulfurous acid (H2SO3) and sulfuric
acid (H2SO4)  acid deposition or
acid rain.
The Nitrogen Cycle
Nitrogen gas makes up the majority of our atmosphere (78.1%) and is biologically inert –
most living organisms cannot use nitrogen when it is in its elemental form (N2). However, living
organisms need nitrogen for the formation of proteins, enzymes, and DNA.
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Bacteria in the soil (nitrogen fixers) can convert nitrogen gas into ammonium (NH4+) which is
then taken up by plants (fertilizer). These bacteria are
found in nodules along the roots of legumes.
 Ammonium is also produced when decomposers break
down organic matter – nitrogen in the waste/dead
organism is converted from proteins/DNA into ammonia
 ammonification.
 Some soil bacteria convert nitrite (NO2-) to nitrate
(NO3-). Nitrate is also used by plants to promote growth.
 Denitrifying bacteria convert nitrite or nitrate back into
nitrogen gas. This process of denitrification occurs in
low oxygen environments.
The Phosphorus Cycle
Phosphorus is an essential nutrient, but is available in limited quantities in the environment. It
is concentrated in living organisms (DNA, ATP, used heavily in metabolic pathways –
phosphorylation, and found in bones and teeth). Phosphorus does not cycle through the
atmosphere – it is found only in soil and water.
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Animals obtain phosphorus by
consuming other organisms.
Producers can only obtain phosphorus if
it is in the form of phosphate (PO43-).
The scarcity of phosphorus keeps algae
growth in balance.
o Human activities increase
phosphate in the environment
through waste (feed lots), fertilizer
use, and detergent use.
o This excess phosphate enters the
water through runoff or improperly
treated waste water and causes massive growth of algae (algal bloom).
 The bloom of algae blocks sunlight to other aquatic plants  these plants die
and are decomposed
 Decomposition of organic material in water causes a decrease in oxygen (the
decomposers use up the oxygen)
 The large mass of algae also starts to die, increasing the organic waste in the
water  decomposition occurs
 Oxygen levels drop rapidly
 Organisms (aquatic invertebrates, vertebrates like fish) do not have enough
oxygen and they die  fish kills.
All the biogeochemical cycles are linked – through water and through the biotic
components of the biosphere. They are also linked to the transfer of energy (chemical energy, trophic
levels, etc) through the biosphere. An imbalance in one will cause subsequent effects in the others.
General Outcome 3: Explain the balance of energy and matter
exchange in the biosphere, as an open system, and explain how this maintains equilibrium
Section 2.3: The Balance of the Matter and Energy Exchange
Net Productivity – the total amount of radiant energy that is transformed to chemical energy by
producers minus the amount used by the producers during cellular respiration.
Remember – there is a constant input of energy into the biosphere from the Sun and a constant
output of radiant energy (heat) to space.
Productivity – the rate at which an ecosystem’s producers capture and store energy within organic
compounds over a certain length of time.
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Measured in energy per area per year [J/m2/a]
Can be expressed as the biomass of vegetation ADDED to
an ecosystem per area per year [g/m2/a]
o The rate at which organisms produce new biomass
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The rate of productivity in terrestrial ecosystems depends
upon:
o Number of producers present in the ecosystem
o The amount of heat
o The amount of light
o The amount of rainfall – moisture is the key limiting factor in productivity in terrestrial
ecosystems.
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In the ocean, productivity depends upon:
o The available nutrients
 Obtained from estuaries (the mouth of rivers
into the oceans)
 Obtained from upwelling zones on the west
side of continents
 Obtained from the seasonal melting of ice
The available sunlight – the amount of solar radiation - limits a
regions productivity
Homeostasis – the state of equilibrium, or balance.
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Individual organisms must maintain steady conditions (within certain limits or range of
tolerance) in order to live.
Ecosystems also must be in balance for organisms to thrive. (Predators and prey,
biogeochemical cycles, climate change)
Gaia Hypothesis (James Lovelock, 1979) – considers homeostasis on a global level.
o Proposed that the biosphere acts like an organism – in that it is self regulating within
its range of tolerance (it maintains environmental
conditions within certain limits).
o Both the biotic and abiotic components of the
biosphere are involved in maintaining or changing
the conditions.
 Living thing affect non-living conditions,
and non-living conditions affect living
things.
 Ex. The presence of humans in a room
causes and increase in carbon dioxide 
the increased carbon dioxide causes
people to yawn more and feel sleepy.
Evidence of how life has affected the biosphere:
 Stromatolites – sedimentary rocks formed from ancient mats/beds of micro-organisms. (3.8 –
2.5 billion years ago)
o The atmosphere lacked free oxygen (oxygen only present in mineral compounds) -Anoxic
o Non-oxygen using bacteria and
micro-organisms grew – forming
mats / beds
o The bacteria utilized ions
dissolved in the shallow oceans –
iron ions were present in larger
amounts.
 Iron ions react with oxygen
readily, so any oxygen in the water was trapped by the iron, and then taken in by
the bacteria.
o Around 2.5 billion years ago, the iron sediments increased, suggesting more oxygen
available to react with iron – due to the activity of photosynthetic organisms like
cyanobacteria
o After 1.8 billion years ago the iron oxides disappear, suggesting no more iron ions in the
water – with the oceans iron store depleted, the oxygen produced by the bacteria was
free to build up
The difficulty of replicating the complexity of Earth’s Biosphere:
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Biosphere 2 – a large scale experiment where researchers tried to create an artificial, selfregulating and homeostatic biosphere.
o Partly to better understand the interactions of our own biosphere
o Partly to prepare for sustainable space travel and planet colonization.
o Designed for researchers to live in the biosphere completely self-contained for 2 years.
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Included:
o Plants/producers – from algae and phytoplankton to crops
 To produce oxygen and remove carbon dioxide, and to filter water
o Consumers – humans, micro-organisms (decomposers), and entire food chains
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Result:
o Researchers were only able to live in the biosphere for a few months before oxygen
levels dropped and carbon dioxide levels became dangerous.
o Showed that energy and matter exchange in our biosphere is a very complex, delicate,
and interrelated system.
o Similar projects have moved forward from the Biosphere 2’s
information.
 ALS (NASA’s Advanced Life Support) program to
research how plants may be grown in a space colony
for food and oxygen regeneration.
 International field project on Devon Island in the
Canadian Arctic that models a hypothetical colony on
Mars – includes living and research facilities as well as
a fully enclosed greenhouse.
Human Activities on the Biosphere
The “control of Nature” is a phrase
conceived in arrogance, born of the
Neanderthal age of biology and
philosophy, when it was supposed that
nature exists for the convenience of man.
- Rachel Carson, Silent Spring
Dead Zones – regions of lakes or oceans in which aquatic life has suffocated due to algal blooms.
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Approximately 150 dead zones in the oceans
May occur seasonally
Pollution also contributes to algal blooms
o Erosion of soil nutrients
o Sewage
o Surface run-off
o Chemical fertilizer use
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o Persistent chemicals – especially
persistent organic pollutants
(POP’s) like PCB and DDT can
continuously cycle through the
environment and become
biomagnified in food chains.
Solutions to removing pollutants/excess nutrients from water
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Wetlands – act as filters. Plants utilize or uptake a large proportion of the nutrients and
pollutants before the water moves into oceans or lakes.
o Bogs, marshes, swamps
o Many wetlands destroyed to allow for human homes/roads, etc
Calcutta, India
o One of the most populated cities in the world – vast amounts of sewage
o Built a vast network of canals and wetlands to treat the city’s sewage
o Algae and bacteria in the wetlands feed on the organic material
o Fish have been added to feed on the algae to prevent algal blooms
o People can support themselves by growing vegetables or fishing in the wetlands, then
selling the produce and fish
Phytoremediation
Using the natural ability of plants and micro-organisms to degrade or remove contaminants
from soil and water. This can be a somewhat slower process, as plants can only grow at a specific
rate. However, using fast-growing plants like bamboo or weeds can speed up the process, or using
micro-organisms which rapidly reproduce.
The contaminants become incorporated into the organism’s tissues – often converted to nonharmful compounds, but not always.