Ecology
• Ecologists study interactions among organisms
at different levels
• They also study how abiotic (non living)
factors (such as land, sun, water) affect
organisms
• All organisms depend on each other for food,
shelter, reproduction, or protection
• Populations-a group of organisms of one
species that interbreed and live in the
same place at the same time, they
compete with each other for food,
shelter, and other resources
• A population is made of individuals
• A community is a collection of interacting
populations
• A change in one population in a community
will cause changes in the other populations
• An ecosystem is made of the interactions
among the populations in a community and
the abiotic factors in a community
Habitat vs. Niche
• A habitat is the place where an organism lives
out its life
• A niche is the role and position a species has
in its environment and how it meets its needs
and interacts
Relationships between species AKA
symbiotic relationships
• Predator Prey
• Commensalism-one species benefits and the
other is not harmed and it does not benefit
• Mutualism-both species benefit
• Parasitism-one organism benefits at the
expense of another
How do organisms get their energy?
• Ultimately from the sun
• Think about it…what did you (the organism)
have for breakfast?
– Cereal? Comes from grains which get energy from
the sun.
– Bacon? Comes from a pig which eats plants that
get their energy from the sun.
• Autotrophs-organisms that use energy from
the sun or energy stored in chemical
compounds to make their own food
• Heterotrophs-organims that cannot make
their own food
• Scavengers-do not kill for food, they eat
animals that have already dies (some birds,
etc..)
• Decomposers-break down and absorb
nutrients from dead organisms (bacteria,
fungi, etc…)
How does energy flow in an ecosystem?
• Food chains-paths for energy, nutrients go
from autotrophs to heterotrophs to
decomposers
• Food chains are used by drawing arrows that
show the way the energy moves (energy is
highest at the beginning as it is lost as heat
throughout the chain)
• Each organism in a food chain represents a
step in a trophic level (levels away from the
sun)
• Many species may occupy the same trophic
level, so a food web is used to show this
Food webs
• Food webs-express all the possible feeding
relationships at each trophic level in a
community
• Ecological pyramids are also used to model
the distribution of energy within an ecosystem
• The base of the pyramid is the first trophic
level/the autotrophs
• Higher up trophic levels are layered on top of
one another.
• The energy that actually makes it up a trophic
level varies but is closer to 10%
• Why? Energy is lost in getting the food,
metabolism, heat, and waste
What can an ecosystem be?
• A puddle of water to a large forest, but all
ecosystems must have the flow of energy and
the cycling of chemical elements
• They also have structure, living and nonliving
parts, processes, and change over time
• Nested ecosystems-ecosystems that are one
inside another
• Ecosystems do not always have definable
edges, most are blurred. This blurred edge is
called an ecotone
Biogeochemical cycles
• the cycling of chemical elements required by
life between the living and nonliving parts of
the environment. Some examples of these
chemical elements are H2O, P, S, N2, O2 and C.
• These elements cycle in either a gas cycle or a
sedimentary cycle; some cycle as both a gas
and sediment.
Biogeochemical cycles
• In a gas cycle elements move through the
atmosphere. Main reservoirs are the
atmosphere and the ocean.
• In a sedimentary cycle elements move from
land to water to sediment. Main reservoirs are
the soil and sedimentary rocks.
Biogeochemical cycles
• Gas Cycles:
• Carbon
Nitrogen
Oxygen
Sedimentary Cycles:
Phosphorus
Sulfur
Biogeochemical cycles…carbon
• 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.
Biogeochemical cycles…carbon
• 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 life forms become buried by sand.
• Instead of returning to the atmosphere, the carbon
from these life forms is trapped within the Earth. Over
millions of years more and more of the carbon on Earth
has been trapped in this manner. Today, almost 99% of
all the carbon on Earth has been locked up deep within
the Earth.
Biogeochemical cycles…carbon
• As rocks weather, this carbon is slowly
released back into the atmosphere, creating a
balance. 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
Biogeochemical cycles…carbon
• This important balance has been altered
significantly in the past century, as humans have
begun using fossil fuels to produce energy. By
burning the Earth’s store of carbon, mankind is
able to create the energy needed to operate our
communities. However, we must be careful as we
do so. By releasing more carbon into the
atmosphere than is being locked up, we risk
causing damage to the delicate carbon cycle.
Biogeochemical cycles…oxygen
• Oxygen exists in our modern atmosphere in great
amounts. Approximately 21% of the atmosphere is
comprised of oxygen. This was not always the case
however.
• Billions of years ago, it is believed that there was
virtually no oxygen found in the atmosphere at all.
What caused an increase in oxygen levels?
• Most of the oxygen now found in our atmosphere was
released by plants, as a bi-product of photosynthesis.
Over millions of years, as plants around the globe
released oxygen, the levels continued to rise, until they
reached a balance around 1 billion years ago.
Biogeochemical cycles…oxygen
• For the last billion years, the amount of oxygen has
remained relatively constant. At the same time that
plants continue adding oxygen to the atmosphere, it is
also being removed by various processes.
• Oxygen is highly reactive. As the oxygen in our
atmosphere interacts with other substances, it often
bonds to them, becoming trapped. Many life forms
also remove oxygen from the atmosphere, as they
breath. This oxygen is used by these life forms to carry
out the functions of life.
Biogeochemical cycles…nitrogen
• Nitrogen is the most abundant element in our
planet’s atmosphere. Approximately 78% of the
atmosphere is comprised of this important
element.
• Nitrogen is used by life forms to carry out many
of the functions of life. This element is especially
important to plant life. Yet nitrogen in its gaseous
form is almost entirely unusable to life forms. It
must first be converted or ‘fixed’ into a more
usable form. The process of converting nitrogen is
called fixation.
Biogeochemical cycles…nitrogen
• There are specialized bacteria whose function
it is to fix nitrogen, converting it, so that it can
be used by plants. There are still other
bacteria who do the reverse. That is, they
return nitrogen to is gaseous form.
• After nitrogen is fixed, it can be absorbed, and
used by plants, and subsequently by animals.
Biogeochemical cycles…nitrogen
• The process of nitrogen being fixed, used by
plants and animals, and later returned to the
atmosphere is referred to as the nitrogen
cycle.
The water cycle aka The Hydrologic
Cycle
• Water is found throughout the biosphere, and
is probably the most important substance
needed to sustain life forms. Humans can
survive for many weeks without the energy
obtained by eating food, however, we would
only last a few days without water.
Biogeochemical cycles…phosphorus
• Phosphorus is an essential nutrient for plants
and animals in the form of ions PO43- and
HPO42-. It is a part of DNA-molecules, of
molecules that store energy (ATP and ADP)
and of fats of cell membranes. Phosphorus is
also a building block of certain parts of the
human and animal body, such as the bones
and teeth.
Biogeochemical cycles…phosphorus
• Phosphorus can be found on earth in water,
soil and sediments. Unlike the compounds of
other matter cycles phosphorus cannot be
found in air in the gaseous state. This is
because phosphorus is usually liquid at
normal temperatures and pressures.
Biogeochemical cycles…phosphorus
• It is mainly cycling through water, soil and
sediments. In the atmosphere phosphorus can
mainly be found as very small dust particles.
Phosphorus moves slowly from deposits on
land and in sediments, to living organisms,
and than much more slowly back into the soil
and water sediment.
Biogeochemical cycles…phosphorus
• Phosphorus is most commonly found in rock
formations and ocean sediments as phosphate
salts. Phosphate salts that are released from
rocks through weathering usually dissolve in
soil water and will be absorbed by plants.
Because the quantities of phosphorus in soil
are generally small, it is often the limiting
factor for plant growth. That is why humans
often apply phosphate fertilizers on farmland.
Biogeochemical cycles…phosphorus
• Phosphates are also limiting factors for plantgrowth in marine ecosystems, because they
are not very water-soluble. Animals absorb
phosphates by eating plants or plant-eating
animals.
Phosphorus cycles through plants and animals
much faster than it does through rocks and
sediments.
Biogeochemical cycles…phosphorus
• When animals and plants die, phosphates will
return to the soils or oceans again during
decay. After that, phosphorus will end up in
sediments or rock formations again, remaining
there for millions of years. Eventually,
phosphorus is released again through
weathering and the cycle starts over.
Biogeochemical cycles…sulfur
• Sulfur is one of the components that make up
proteins and vitamins. Proteins consist of
amino acids that contain sulfur atoms. Sulfur
is important for the functioning of proteins
and enzymes in plants, and in animals that
depend upon plants for sulfur. Plants absorb
sulfur when it is dissolved in water. Animals
consume these plants, so that they take up
enough sulfur to maintain their health.
Biogeochemical cycles…sulfur
• Most of the earth's sulfur is tied up in rocks
and salts or buried deep in the ocean in
oceanic sediments. Sulfur can also be found in
the atmosphere. It enters the atmosphere
through both natural and human sources.
Natural recourses can be for instance volcanic
eruptions, bacterial processes, evaporation
from water, or decaying organisms.
Biogeochemical cycles…sulfur
• When sulfur enters the atmosphere through
human activity, this is mainly a consequence
of industrial processes where sulfur dioxide
(SO2) and hydrogen sulphide (H2S) gases are
emitted on a wide scale.
When sulfur dioxide enters the atmosphere it
will react with oxygen to produce sulfur
trioxide gas (SO3), or with other chemicals in
the atmosphere, to produce sulfur salts.
Biogeochemical cycles…sulfur
• Sulfur dioxide may also react with water to
produce sulphuric acid (H2SO4). Sulphuric acid
may also be produced from demethylsulphide,
which is emitted to the atmosphere by plankton
species.
All these particles will settle back onto earth, or
react with rain and fall back onto earth as acid
deposition. The particles will than be absorbed by
plants again and are released back into the
atmosphere, so that the sulfur cycle will start
over again.
The water cycle aka The Hydrologic
Cycle
• Water is used to carry out the many
important, and complex chemical reactions
that all life forms must perform in order to
survive. Water carries nutrients to various
parts of a life form, and carries waste away
from the different parts of a life form. Because
water is so important, the most abundant
substance in any organism is water.
The water cycle aka The Hydrologic
Cycle
• The water found within your body as you read
this article has been used, and re-used by
organisms throughout the history of Earth. It
is quite possible that there is water found in
your body, that was once inside of a
tyrannosaurus rex, or inside of Julius Caesar.
• The process of water moving through the
environment is referred to as the hydrologic
cycle.