Biology 20
Energy and Matter Exchange in
the Biosphere
"The ultimate test of a moral society is the kind
of world that it leaves to its children."
Dietrick Bonhoeffer,
German Theologian
Equilibrium in the Biosphere

According to the Gaia hypothesis, the earth is
like a complex organism where many living
(biotic) and non-living (abiotic) systems interact.
Like a living organism the earth is said to be in
dynamic equilibrium where changes are
continually occurring, but small adjustments are
made to keep the whole system stable.
Unfortunately, evidence suggests that humans
are causing a disruption to the earth’s systems
that can be detrimental to its, and our survival.
The Biosphere

refers to all areas of the
earth in which living
organisms are found.
This includes:
– Atmosphere – air
– Lithosphere – land
– Hydrosphere – water
The Biosphere
Biotic components – are the biological or
living components of the biosphere,
include all living things.
 Ex. bacteria, fish, birds, mammals, plants
A-biotic components – are the non-living
components of the biosphere, include all
chemical and physical factors.
 Ex. Temperature, weather, soil acidity,
sunlight
In studying the health of the earth, scientists find it useful to
study the biosphere at a variety of different levels. To determine
the interactions between organisms and the environment,
scientists may choose to study:
Populations – groups of organisms of a
species living in a specific place at a
specific time. Population studies allow
scientists to study the interactions
between the population and its
environment.
 Communities – all of the populations that
live in a specific area at a specific time.
Studying communities shows scientists
how populations of different species affect
one another.


Ecosystems – include communities and
their abiotic environments. Studying
ecosystems allows scientists to investigate
the interactions between the living and
non-living components or the earth.
"When one tugs at a single thing in nature...
he finds it attached to the rest of the world."
John Muir
Biodiversity
The key to healthy ecosystems, and a healthy
planet involves biodiversity.
Biodiversity – describes the biological diversity,
number and variety of organisms, in an
ecosystem.
 More diverse food chains are more stable. All
organisms in an ecosystem are either directly
or indirectly affected by one another. If one
species is removed from a limited food web, a
domino effect occurs and the system will
collapse.
Equilibrium Unbalanced
Dynamic Equilibrium – describes any
system with constant change, where the
components can adjust to the change
without disturbing the entire system.

When the dynamic equilibrium becomes
unbalanced for any reason, the healthy or
numbers or organisms in that ecosystem
are affected. Organisms can be classified
according to their degree of risk
Less
severe
risk
Most
severe
risk
Special concern – numbers are
declining at the range / fringe of
the area
Threatened – species may
become endangered if
threatening conditions are not
reversed
Extirpated – a species no longer
exists in one particular area, but
is still found in other areas
Endangered – a species is close
to extinction in all parts of their
natural habitat
Extinct – a species no longer
exists
Indicator Species

are species of organisms that provide an early
warning that an ecosystem is being affected by
some factor. Usually, these species are very
sensitive to changes in an ecosystem, or to
specific changes of ecosystem conditions.
Indicator species also play a specific role in an
ecosystem and their decline will affect other
organisms in the food web.
–
–
–
–
Fish
Amphibians
Algae
Plants
Types of Indicator Species:
Producers – plants that convert sunlight energy
into food
 Herbivores – animals that only feed on plants
 Carnivores – animals that only feed on other
animals
 Omnivores – animals that eat both plants and
other animals
 Decomposers – organisms that feed on detritus,
dead and decaying biological material and return
nutrients to the soil and water.

The Disappearing Frogs
Frogs begin as eggs and brow into tadpoles
in ponds. Next they enter their second life
as adults in forest and grassland areas.
Frogs are exposed to hazards in both their
aquatic and their terrestrial ecosystems,
where they are a part of two very different
food chains.
 Tadpoles – are herbivores and eat algae
and detritus. They are food for larger fish.
 Adult frogs – are carnivores and eat
insects and small fish. They are also food
for birds and small mammals.
Factors causing the disappearance
of specific organisms include:
Loss of Habitat - clean, healthy habitats are
often reduced or destroyed by human activity
such as farming, industry and recreation.
 Pollution – causes poor air and water quality
which are detrimental to many organisms.
 Climate Change – such as global warming
causes the abiotic conditions such as temperature
and humidity to change. Caused by pollutants.
 Ultraviolet Radiation – increases the incidence
of mutations and causes damage at the cellular
level. Caused by damage to the ozone layer.

The Biosphere and Climate
Layers of the Atmosphere
Troposphere – up to 12 km, contains
80% of earth’s atmospheric mass (water
vapour and dust). Weather systems occur
here.
 Stratosphere – up to 50 km above the
troposphere, oxygen absorbs UV radiation
forming ozone.
 Mesosphere – up to 90 km above the
stratosphere, cold temperatures, trace
amounts of gas.



Ionosphere – above the mesosphere,
contains ionized gases that produce the
northern lights and absorb harmful X rays
and gamma rays from the sun.
Magnetosphere – above the ionosphere,
created by the earths magnetic field,
deflects large particles that are emitted
from the sun or from space.
Threats to the Biosphere
Ozone Thinning – in specific global
areas, the ozone levels in the ozone layer
have been reduced. Scientists believe this
phenomenon is caused by chemicals such
as CFC’s released into the atmosphere.
The result is an increase in the amount of
harmful ultra-violet radiation that reaches
the earth, which causes increased rates of
skin cancers and eye problems.
 Stratospheric Ozone: Background Material
 Total Ozone Mapping Spectrometer ozone
images


The Albedo
Effect –
describes the
extent to which
light is reflected
from the earth’s
surface by
clouds, snow or
other highly
reflective
surfaces.
Energy Flow in the Biosphere
ONE WAY
 Most
of the energy in the biosphere
comes from the sun, however only a
small portion of the sun’s energy
reaches the earth’s atmosphere.
30% - is reflected by clouds or the Earth’s surface
44% - heats the atmosphere and maintains Earth’s
temperatures
25% - heats water and drives the water cycle
1% - generates wind and weather patterns
.02% - is used by photosynthesis to produce food
energy
Energy Transfer and Food Webs
Living things can be categorized according
to where they are in a hierarchy of
energy.
Trophic Level – category that defines
how living things gain energy for life
processes. (feeding level)
 Producers / Autotrophs – organisms
that produce their own energy from
either sunlight (photosynthesis) or
chemical energy (chemosynthesis)

Heterotrophs – organisms that feed on
other organisms
 Primary consumers – feed on
autotrophs (herbivores)
 Secondary consumers – feed on
primary consumers (carnivores)
 Top Carnivores – organisms that are not
consumed by any other organism.

Food Chains

single sequences illustrating a one way
flow of energy in an ecosystem.
Food Webs

are interlocking food chains that illustrate
more complex feeding relationships between
organisms.
Energy Conversions

Photosynthesis – is the process where
producers capture solar energy and converted
into food.
CO2(g) + H2O(l)

+ sunlight 
C6H12O6(s) + O2(g)
Cellular Respiration – is the process where
consumers break down glucose into carbon
dioxide and water, releasing useable energy.
C6H12O6(s) + O2(g)  CO2(g) + H2O(l)
+ energy

Chemosynthesis – the process where
non-photosynthetic organisms convert
inorganic chemical compounds such as
sulphur, iron, ammonia and hydrogen
sulphide into energetic organic molecules.
Bacteria capable of doing this are called
chemoautotrophs.
In all food chains, the amount of available energy
decreases as you move up the chain. Valuable
energy is lost in each and every energy
conversion. So why is energy transfer so
inefficient?
1. Most of the energy produced by
autotrophs is used to promote the
survival and growth of the organism.
2. Consumers don’t process all of the food
they eat. Some is eliminated through
waste. Much of the energy metabolized
is also lost as heat. (also a necessary
process for homeotherms)
3. Some of the energy taken in by a
consumer is required to acquire, digest
and metabolize the food eaten.
4. Energy transfer in biological systems
always follows the first and second laws
of thermodynamics:
–
–
–
First Law – energy cannot be created or
destroyed, it can only be converted to other
forms.
Second law – during any energy conversion,
some of the energy is converted to heat, a
form that is not recovered.
http://www.mhhe.com/biosci/genbio/tlw3/eB
ridge/Chp29/animations/ch29/ecosystem_or
ganization.swf
If Bessie here eats 100 kJ of energy, how
much energy is available as heat and for
use?
Scientific Models

Ecological Pyramids - can be used to
represent the energy flow in food chains
or food webs by showing the amount of
energy, the number of organisms or the
biomass. All pyramids illustrate the first /
lowest trophic level on the bottom with
successive trophic levels towards the top.
Pyramids of Energy – illustrates the decreasing
amount of energy available at each successive
trophic level.
Pyramids of Numbers – describe the number of
organisms at each successive level of the food
chain. These pyramids can often appear
“inverted” when consumers are very small or
producers are very large.
Pyramids of Biomass – represents the dry mass
of plant and animal tissues in a food chain. The
amount of dry mass decreases at each trophic
level.
Here is a comparison of the three types of
pyramids:
The Cycling of Matter in the
Biosphere

The earth is a closed system, so although
energy from the sun can come into the
system and heat energy can leave, matter
cannot. All of the molecules that make up
everything on our planet stay here.
Matter in the biosphere regularly changes
form or cycles. Food molecules become
cellular structures that become tissues
and organisms. Eventually, those tissues
and organisms become food for other
organisms or decompose becoming part of
the soil. The cycling of matter is a
necessary part of all living things.
Water

Water is required by all living things. It is
important for a variety of reasons:
– it absorbs and releases thermal energy
– most metabolic reactions take place in water
solutions
– it is an excellent solvent due to its polar nature
– it supplies hydrogen in photosynthetic
reactions and oxygen during cellular
respiration
– it dissociates into acidic H+ and basic OH– it exists as a solid, liquid or a gas in earth’s
atmosphere
Water Cycle - Animated Diagram
The Hydrologic Cycle
Transpiration – is the loss of water to
the atmosphere through the leaves of
plants.
 Percolation – is the movement of water
through porous soil.
 Leaching – is the removal of soluble
minerals by percolation.
 Acid Deposition – is the precipitation of
acidic solutions due to SOx and NOx gases
combining with water (acid rain).

Carbon


On earth, all organic substances are
compounds of carbon, including those that
make up living things. Carbon is also
found in inorganic forms such as CO2 and
carbonates. Combustion, decomposition
and cellular respiration all produce
inorganic carbon dioxide. Photosynthesis
is required to capture inorganic carbon
and convert it to organic carbon. These
processes together are known as the
carbon cycle.
http://www.nodvin.net/snhu/SCI219/demos/Cha
pter_3/Chapter_03/Present/animations/51_1_2_
1.html
The Carbon Cycle
Global Warming and the Greenhouse
Effect
Scientists believe that the average annual
global temperatures are increasing. A
number of theories exist that account for
this phenomenon, however one of the
more prevalent theories is the greenhouse
effect.
 Greenhouse effect – is caused by
increased amounts of atmospheric gases
(CO2 and CH4) that prevent heat from
escaping causing in increase in
temperature on the earth’s surface.
 Energy Flows: The Greenhouse Effect

Nitrogen
Nitrogen is an important building block of
proteins and nucleic acids. Proteins are
required to build tissues and enzymatically
mediate biochemical reactions. Nucleic
acids (DNA, RNA and ATP) are components
of key hereditary and metabolic
compounds in all living things. Nitrogen
gas is abundant on our planet and
accounts for 79% of the atmosphere. To be
useful to organisms, however, nitrogen
must be in a more useable form like
nitrate.
 http://www.nodvin.net/snhu/SCI219/demos/Chapt
er_3/Chapter_03/Present/animations/32_2_1a.ht
ml

The Nitrogen Cycle
Nitrogen fixation is the process by which
atmospheric nitrogen is converted to a useable
form, nitrates. This is done by lightening and
nitrogen fixing bacteria.
Denitrification is the process where bacteria convert
nitrates to nitrites, then to nitrogen gas which is
released back into the atmosphere.
Ammonification is the process where decomposers
break down organic nitrogen containing compounds
into simpler chemicals like ammonia. Bacteria in
turn, change the ammonia into useable nitrates.
 These conversions of nitrogen are all part of the
nitrogen cycle.
The Nitrogen Cycle
Phosphorus
 Phosphorus
is required in cell
membranes, ATP, DNA and in bone
formation. Phosphorus cycles
though the earth’s crust and through
living organisms.
 Library of Crop Technology Lessons
The Phosphorus Cycle
Fertilizers and Ecosystems
Fertilizers – are materials used to restore
nutrients to plants. Most fertilizers
contain a ratio of Phosphorus, Nitrogen
and Potassium (PNK)
 The accumulation of phosphates and
nitrogen caused by fertilizer use and
spring runoff, allows algae to grow very
rapidly in ponds and streams. When the
algae die, bacteria use the available
oxygen to decompose them. This results
in less oxygen available for fish and other
aquatic organisms.