SBI4U RHSA
Energy Flows in Ecosystems
About 1% of the sunlight that reaches Earth is captured
by plants for photosynthesis. By converting light energy
to the chemical energy of glucose, plants are able to
produce 150-200 billion tonnes of organic material a
year. This net primary productivity or biomass is
measured in grams of vegetation per square metre per
year (g/m2/a).
From the producer level up through the consumer
levels the “Rule of 10” applies. This rule states that only
about 10% of the energy consumed is used to build cells
or new biomass in the consumer. The other 90% of the
energy consumed is “lost” to cellular respiration, heat,
feces, urine or other cell functions. Thus less biomass is
produced at every higher consumer level.
The Rule of 10 does not apply to the biomass of
decomposers in an ecosystem. However, in most
aquatic and terrestial ecosystems pyramids
representing numbers of organisms, biomass and
energy can be drawn.
SBI4U RHSA
There are some interesting exceptions to the standard
pyramid shape. Some aquatic ecosystems have an
inverted biomass pyramid because the extremely high
reproductive rate of the phytoplankton can support a
much larger mass of zooplankton.
A deciduous forest,
where there is a
large amount of
biomass in fewer
large trees also
gives an unusual
shape for a pyramid
of number of
organisms.
Homework:
Complete attached worksheet.
SBI4U RHSA
Energy Flows in Ecosystems
About ____ of the sunlight that reaches Earth is captured by plants for photosynthesis.
By converting light energy to the _____________________, plants are able to produce
_________________________________________________________________. This
net primary productivity or _______________ is measured in grams of vegetation per
square metre per year (_____________).
From the producer level up through the consumer levels the “Rule of 10” applies. This
rule states that _________________________________________________________or
new biomass in the consumer. The other 90% of the energy consumed is “lost” to
_________________________________________________________________ or other
cell functions. Thus less biomass is produced at every higher consumer level.
The Rule of 10 does ____________________________________________________ in
an ecosystem. However, in most aquatic and terrestial ecosystems pyramids
representing _____________________________, ___________________ and
____________________ can be drawn.
SBI4U RHSA
There are some interesting exceptions to the standard pyramid shape. Some ________
__________________________________________________________ because the
extremely high reproductive rate of the phytoplankton can support a much larger mass
of zooplankton.
A deciduous forest, where there
is a ______________________
_________________________
also gives an unusual shape for
a pyramid of number of
organisms.
Homework:
Complete attached worksheet.
SBI4U RHSA
Energy Flows Worksheet
Read p 444 – 450 before answering the following questions on a separate sheet of paper.
1. a) How much energy is received daily by Earth? Units!
b)
List other uses of the radiative energy from the Sun.
2.a)
In Fig 13.17, why are the arrows from the Sun different sizes?
b)
Explain how light energy is converted to chemical energy. Be sure to specify where the energy is stored.
3.
Every year about 150 billion tonnes of organic material is produced by autotrophs. Write this number in
scientific notation.
4.
List 5 factors that affect the rate of primary productivity and state if the factor is biotic or abiotic.
5.
Explain the difference between biomass and primary productivity. Use an example
6.
Use Fig 13.18 to answer the following questions.
a)
How does graph A represent terrestial biomes compared to aquatic biomes?
b)
Calculate the total percent of Earth’s surface that is water using graph A.
c)
How does graph A misrepresent this figure?
d)
Which aquatic biome has the largest net primary productivity and what is it? Units!
e)
How can oceans have 24% of Earth’s net primary productivity when they have the smallest net primary
productivity?
7.
Do the numbers shown for the caterpillar support the 10% rule? Explain.
8.
Use Fig 13.20 to answer the following questions.
a)
What does each coloured arrow represent?
b)
“Repiratory heat loss” does NOT mean heat lost while breathing. What does the “respiratory” refer to?
c)
What visual clue has the graphic artist used to represent the fact that only about 10% of the energy is
transferred up the food chain?
d)
Is energy recycled?
9.
Use Fig 13.22A and Fig 13.22B to answer the following questions.
a)
How much is the dry weight of biomass in the Florida bog?
b)
How many trophic levels are in Fig A compared to Fig B?
c)
In Fig B, it appears as if there is not enough phytoplankton. Explain how this inverted pyramid is possible.