Lesson #2: Energy Flow in Ecosystems Flashcards
(14 cards)
Energy in Ecosystems
Most ecosystem rely on the sun to supply energy.
This energy is harvested by living organisms through the process of photosynthesis.
Photosynthesis is performed by autotrophs such as plants, eukaryotic algae
and cyanobacteria.
Heterotrophs do not use light energy directly but are indirectly dependent on it.
Heterotrophs use carbon compounds as a source of energy, carbon compounds originate in producers through photosynthesis.
The amount of energy supplied to ecosystems in sunlight varies around the
world.
The percentage of the suns energy that is harvested by producers and made
available to consumers also varies.
Photosynthesis
Producers absorb sunlight using chlorophyll and other photosynthetic pigments.
This light energy is converted into chemical energy through the production of
carbohydrates and other carbon compounds.
Producers can use that energy for their cellular activities through cellular
respiration. This energy is lost to the environment as heat.
Most of the energy remains in the cells and tissues of the producers. This is the
energy that is available to heterotrophs.
Energy flow in
Ecosystems
Chemical energy in carbon compounds flows
through the ecosystem by means of feeding.
A food chain is a sequence of organisms
through which energy is passed.
There are usually between 2-5 organisms in a
food chain.
The first organism is always a producer.
The arrows indicate the direction of energy
flow.Living things require energy to perform the cellular activities required to grow, develop and sustain life.
This energy is supplied by a compound called ATP. Every cell makes its own
ATP.
ATP is created by breaking down carbon compounds to release the chemical
energy.
This process is not 100% efficient and some energy is lost as heat.
Heat cannot be converted to other forms of energy by living things.
Energy Losses in Ecosystems
A food chain is rarely more than four or five organisms long. This is due to the
loss of energy between trophic levels. Only 10% of the energy consumed or
created by an organism gets passed on to the next trophic level.
The other 90% is used by the organism to create ATP through cellular
respiration and therefore is eventually lost as heat.
As losses occur at each stage of the food chain there is less and less energy
available.
Ecological Pyramids
Visual representations of the populations involved in a feeding relationship.
There are three types of ecological pyramids:
Pyramid of numbers
Pyramid of biomass
Pyramid of energy
Pyramid of Numbers
Often counting organisms is
used to determine the flow
of energy through an
ecosystem.
This type of diagram shows
that the relative number of
organisms decreases as we
move up trophic levels.
Not always pyramid
shaped.
Pyramid of Biomass
It is possible to estimate the
mass (in grams) of all the
organisms living in a given
area or ecosystem.
This estimation is known as
the biomass.
A pyramid can be constructed
showing that the biomass of
the producers is generally far greater than that of the
consumers.
Pyramid of Energy
A pyramid of energy is used
to represent the amount of
energy converted to new
biomass by each trophic
level in an ecological
community.
Measured in units of
energy per unit area per
unit time: kJ m-2 y-1.
Drawing Pyramids of Energy
The pyramid of energy is a type of bar chart with horizontal bars.
This means that the pyramid must be stepped.
Each bar must be labelled.
Energy in each trophic level must be shown with units.
Producers are always the lowest bar.
Food Webs
An organism’s trophic
level is its feeding
position in a food chain.
However, feeding
relationships in
ecosystems are
complex and an
organism can occupy
more than one trophic
level.
A food web is a model
that summarizes all the
possible food chains in
a community.
Within a food web there are often one or two organisms that have no
predators.
These organisms are known top carnivores and are usually found at the top
of the food web.
Humans are not considered top carnivores within any ecosystem.
Atypical Feeding Relationships:
Symbiosis
These relationships do not involve one species “eating” another.
There are three common types of symbiotic relationships:
Mutualism
Commensalism
Parasitism
Mutualism
Mutualism is an interaction
between organisms where
both derive a benefit.
Commensalism
Commensalism is an interaction between
organisms where one organism derives a
benefit and the other is unaffected.
Parasitism
Parasitism is an interaction between
organisms where one organism derives a
benefit while harming the other.
