Biology 20 Unit A:
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 nonliving (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
Abiotic 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 – 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.
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.
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.
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.
Energy Conversions - Handout
• 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
• The Albedo Effect –
describes the extent to
which light is reflected
from the earth’s
surface by clouds,
snow or other highly
reflective surfaces.
• Handout
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)
Types of Organisms that exist:
• 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.
• Chemosynthesis – the process where nonphotosynthetic 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.
To Do:
• Read Section 1.1 (Pages 8-14)
• Page 15 Questions 1-8
• Species at risk worksheet (homework)
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.
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.
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
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:
To Do:
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Page 20 – Thought Lab 1.1 (Work in groups of 2-3)
Biomagnification Activity
Section 1.2 Review
Quiz tomorrow on Chapter 1 (Second Half of Class)
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
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).
The Universal Solvent
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Water is polar! What does that mean?
Contains hydrogen bonds
Do you remember adhesion and cohesion?
Water stores heat… What can you tell me about its
SHC?
Homework
• Section 2.1 Page 40
• Questions:
• 2,4,5,6,7,8
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.
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.

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.
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.
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.
Group Project - Review
• Each group will be assigned one of the cycles
• Water
• Carbon
• Nitrogen
• Phosphorus
• Sulphur and Acid deposition
• You must summarize and re-teach this concept to the
class however you choose! Be creative
• You must submit 5 test questions to me before you
present – this might be used on the exam!