APES Notes 1.9 & 1.10 - Trophic Levels & The 10% Rule
Summary
TLDRThis video covers topics related to trophic levels and the 10% rule in ecosystems. It explains how energy and matter flow through trophic levels, emphasizing that only 10% of energy is transferred between levels, with the rest lost as heat. Key concepts include the conservation of energy and matter, the first law of thermodynamics, and examples like photosynthesis. The video also discusses how the 10% rule applies to biomass and provides calculations to determine energy at different trophic levels, illustrating why larger ecosystems can support only a small number of top predators.
Takeaways
- 🌞 Energy and matter are conserved through ecosystems, never created or destroyed, only transformed.
- 🌿 Photosynthesis demonstrates both the conservation of matter and energy by converting sunlight into chemical energy (glucose).
- 🔥 The first law of thermodynamics states that energy is never destroyed, just transformed into different forms.
- 🐰 As energy moves through trophic levels, a significant portion is lost as heat, limiting the energy available for higher levels.
- 🔋 Only 10% of energy moves up to the next trophic level, while the other 90% is used for processes like movement and metabolism.
- 🌲 Producers form the base of the trophic pyramid, with primary consumers (herbivores) eating plants and secondary consumers (carnivores) eating primary consumers.
- 📉 The 10% rule applies to both energy and biomass, meaning that only 10% of the biomass from one trophic level can support the next.
- 🌳 Large ecosystems, like forests, can only support a small number of top predators (e.g., wolves) due to the limited energy available at higher trophic levels.
- 🔢 Calculating energy across trophic levels is done by dividing by 10 or moving the decimal point one place to the left.
- 📊 Practice questions involve explaining why large ecosystems support few top predators and calculating available energy for tertiary consumers.
Q & A
What are the two main topics covered in this video?
-The video covers trophic levels and the 10% rule, which explain how energy flows through ecosystems and how the available energy decreases as we move up the trophic pyramid.
What is the first objective of the lesson?
-The first objective is to explain how energy and matter flow through trophic levels.
What is the second objective of the lesson?
-The second objective is to determine how energy decreases as it flows through an ecosystem.
What does the first law of thermodynamics state?
-The first law of thermodynamics states that energy is never created or destroyed, it is only transformed from one form to another.
What happens to the matter when a tree dies?
-When a tree dies, its matter (carbon, nitrogen, water, phosphorus) is conserved and transformed into different forms, such as being returned to the soil or atmosphere, or absorbed by decomposers.
What is the 10% rule in the context of trophic levels?
-The 10% rule states that only 10% of the energy from one trophic level is transferred to the next level, while 90% is lost as heat or used by the organism for life processes.
Why is the trophic pyramid shaped the way it is?
-The trophic pyramid is wide at the bottom and narrows at the top because energy decreases with each step up the pyramid, meaning fewer organisms can be supported at higher trophic levels.
How does energy transfer from the sun to a rabbit through photosynthesis?
-Energy from the sun is converted into chemical energy in the form of glucose by plants through photosynthesis. When a rabbit eats the plant, it absorbs this chemical energy, which it uses for growth and movement.
How is energy lost when it is transferred from one form to another?
-Each time energy is transferred from one form to another (e.g., chemical to electrical to light energy), some of it is lost as heat and becomes unusable by organisms.
Why can a large forest only support a small number of wolves?
-A large forest can only support a small number of wolves because, according to the 10% rule, only a small fraction of the energy available from plants is passed up to the wolves at the top of the trophic pyramid. Most of the energy is lost as heat or used up by organisms at lower levels.
Outlines
📚 Introduction to Trophic Levels and Energy Flow
In this paragraph, the presenter, Mr. Smees, introduces the topics of trophic levels and the 10% rule. He explains how energy flows through ecosystems and decreases as it moves up the trophic pyramid. The objectives include explaining energy and matter flow through trophic levels and calculating energy decrease. The importance of the conservation of matter and energy is emphasized, using the example of a tree decomposing and the conversion of matter in ecosystems.
🌞 Photosynthesis and Conservation of Matter and Energy
This section explores the concept of conservation of matter and energy through photosynthesis. The presenter explains how light energy from the sun is converted into chemical energy (glucose) by plants, emphasizing that matter and energy are not lost but transformed. He also introduces the first law of thermodynamics, reinforcing the idea that energy cannot be created or destroyed, only converted.
🐇 Energy Transfer Between Organisms and the 10% Rule
This paragraph explains how energy is transferred between organisms in ecosystems, using the example of a rabbit eating a leaf. As energy transfers between trophic levels, a significant portion is lost as heat, resulting in only 10% of energy being passed on. The 10% rule, where only a fraction of the energy is retained at each level, is discussed in detail, along with the pyramid representation of trophic levels.
🌱 Decreasing Energy and Biomass Through the Trophic Pyramid
Here, the presenter dives deeper into the decreasing availability of energy as it moves up the trophic pyramid. Using the example of a producer receiving energy and an elk eating the grass, the presenter highlights how 90% of energy is used up by organisms for development, metabolism, and heat. The 10% rule is applied to biomass as well, explaining that only a small percentage of biomass can be supported at higher trophic levels, creating a narrow pyramid shape.
📐 Applying the 10% Rule in Energy and Biomass Calculations
In this section, the presenter walks through calculating energy and biomass available at different trophic levels. Using examples, he shows how to move the decimal place or divide by 10 to determine energy available at primary, secondary, and tertiary consumer levels. He also explains how the same rule applies to biomass, with a practical exercise for calculating energy and biomass at each level of a trophic pyramid.
Mindmap
Keywords
💡Trophic Levels
💡10% Rule
💡Energy Flow
💡Conservation of Matter
💡First Law of Thermodynamics
💡Biogeochemical Cycles
💡Producers
💡Primary Consumers
💡Heat Loss
💡Biomass
Highlights
Introduction to trophic levels and the 10% rule: Energy decreases as it flows through ecosystems.
First objective: Explain how energy and matter flow through trophic levels.
Second objective: Determine how energy decreases as it flows through an ecosystem.
Conservation of matter: Matter is never created or destroyed, only changes forms.
Photosynthesis as an example of energy and matter conservation: Sunlight is converted into glucose, conserving both energy and atoms.
The First Law of Thermodynamics: Energy is never created or destroyed, just transformed.
Biogeochemical cycles demonstrate conservation of matter: Nutrients are recycled and transformed.
Conservation of energy through food webs: Energy is transferred from plants to animals but most is lost as heat.
Energy loss in ecosystems: Only 10% of energy transfers to the next trophic level, the rest is lost as heat.
Explanation of energy transfer in a trophic pyramid: Each level gets narrower because of energy loss.
Real-world example of energy loss: In a coal power plant, only 35% of energy is converted to electricity; the rest is lost as heat.
10% Rule in energy transfer: Only 10% of energy is passed from one trophic level to the next, creating a pyramid shape.
Trophic levels explained: Producers, primary consumers, secondary consumers, and tertiary consumers.
10% Rule applied to biomass: Only 10% of the biomass can be supported at the next trophic level.
Calculation practice for energy and biomass: Moving the decimal point to the left to determine energy available at higher trophic levels.
Transcripts
hey everybody it's Mr smees and today
we'll be covering topics 1.9 and 1.10
which are trophic levels and the 10%
rule so we'll be talking about how
energy flows through ecosystems and how
the available energy decreases as we
move up the trophic
pyramid we're combining two different
topics here today so we have two
different objectives and two skills to
practice the first objective is to be
able to explain how energy and matter
flow through trophic levels and the
second objective is to be able to
determine and how energy decreases as it
flows through an ecosystem the two
skills we'll practice at the end of
today's video are explaining an
environmental concept or process and
then calculating an accurate answer with
units so we will be doing some math at
the end of this video so before we talk
about how energy flows through
ecosystems we have to establish the
conservation of both matter and energy
so very important to remember that
matter is never created or destroyed it
only changes forms this is key to
understanding how both matter and energy
flow through ecosystems so let's take a
look at an example when a tree dies the
tree will get decomposed and we may not
see the tree physically anymore but all
of its matter was conserved so the
carbon the nitrogen the water and the
phosphorus within the tree were all
returned to either the soil or the
atmosphere or went into the bodies of
decomposers and so we did not actually
lose any of the matter it looks
different but it still exists and it's
just transformed into a different state
let's talk about this with regard to
energy as well so if we look at
photosynthesis we have the sun's rays
which represent light energy and they're
going to be converted into chemical
energy by the plant and that's glucose
so if we look at the diagram and we were
to actually count up all of the atoms
involved in that process we'd see that
all of the carbon oxygen and hydrogen
entering the plant as carbon dioxide and
as water flowing from the soil are all
going to be conserved either as glucose
or
as oxygen that leaves the plant's leaves
during photosynthesis so photosynthesis
helps us kind of grasp here the
conservation of matter also the
conservation of energy because we have
the sun's rays that hit the leaf that's
a form of energy but once those Rays hit
the leaf they're not destroyed they're
just transformed into glucose which
again is chemical energy so
photosynthesis is a really helpful way
to remember both the conservation of
matter and energy we have a fancy name
for this it's called the first law of
thermodynamics
and that's just a reminder that energy
is never created or destroyed it's just
transformed into a different
form biog geochemical cycles that we've
spent the last couple days on so water
cycle carbon cycle nitrogen and
phosphorus Cycles those all demonstrate
that there's conservation of matter so
again when an animal dies the nitrogen
in its body is never destroyed it's just
transformed it goes through modification
returns to the soil as ammonia and then
can be used for plant growth in the
future food food webs which we'll focus
on today and tomorrow are how we
demonstrate the conservation of energy
so we talked about the conservation of
energy with photosynthesis but let's
look at it with an animal here so let's
uh imagine that a rabbit is going to eat
the leaf that produce that Sugar through
photosynthesis so the leaf is no longer
there but the energy in the leaf has
been transferred to the rabbit the
glucose in the leaf is going to be
broken down by the rabbit's body it's
going to feel growth of the rabbit so
some of it might be converted into
muscle
or fat tissue within the rabbit some of
it might go to Fu the rabbit's movement
so the energy is conserved it's never
destroyed even though the leaf was eaten
by the rabbit now we'll talk about what
happens to energy as it transfers
between trophic levels so each time
energy transfers from one form to
another some of it is lost as heat now
it's not destroyed but it's just given
off to this Shing environment and it's
no longer useful energy that can be used
by organisms and so we'll talk about
what that means here in a second
so let's take a look at an example with
electricity generation if we have this
Coal Fired power plant here and all of
the potential energy in the bonds of
that coal are released and converted
into electricity only about 35% of the
energy that was in the coal is going to
actually make it to electricity the
other 65% is going to be lost as heat
while the coal is being burned then as
that electricity is Flowing down
transmission wires another 10% or so is
going to be lost and only about 90% of
the electricity is going to actually
make it into your home then when you
turn on a light bulb 95% of the energy
flowing into the light bulb is lost as
heat meaning only 5% is coming through
as actual light energy so what this
demonstrates is each time we transfer
energy from one form to another so from
chemical energy in Coal to electrical
energy to light energy we're losing some
of it as heat now we can think about
what this means as it applies to
ecosystems
so each time energy is transferred from
one organism to another the amount of
available energy is decreasing and
that's because the organism that was
just eaten had used up most of the
energy for things like movement
development and just cellular
respiration fueling all of the processes
its body needs in order to survive so we
can look at an example here with an
ecosystem if we have a th jewles of
light energy that the producers are
receiving remember they're going to need
to use 90% of that so they're going to
use 9990 Jews for their growth for their
metabolism all of those things and only
about 10 Jews are going to be available
to the elk when the elk eats the grass
it gets those 10 jewels of energy but
then it's going to use up nine of those
Jewels for again development cellular
respiration and it's going to be lost as
heat to the atmosphere then when the
lion eats the elk and I don't know what
kind of ecosystem we're in here where
line eats elk but it's just a helpful
diagram it's only going to get that one
Jewel of energy so that means that each
time the energy transfers from one
organism to another only 10% of the
energy is making it to that next
organism so because the amount of
available energy decreases with each
step you go up the trophic level we use
a pyramid shape to represent this and
trophic just means growth or nourishment
so that's a helpful way to remember what
a trophic level is and so because
there's the most energy available at the
base it's going to be the widest and
then each level up is going to get a
little bit more narrow because there's
less available energy at that level
remember we didn't actually destroy
energy it was used up by the organism so
it was lost as heat as they move around
or it was used up in cellular
respiration but only about 10% of it is
going to transfer on to the next level
and so we have a handy rule to remember
this and we call it the 10% rule 10%
rule just reminds us that only about 10%
of the energy from one trophic level
makes it to the next the other 90% is
lost as heat while the organis uses that
energy for all the processes it needs to
fuel so if we take a look at this
diagram we can kind of see that
represented here from The Producers only
about 10% of the energy is going to move
on to the rabbits who are the first
level to consume the grass 90% will be
lost as heat then onto the snakes
another 10% 90% losses Heat and the same
thing for the top predator here now
we'll talk about the names for each
trophic level as well as how the 10%
rule also applies to biomass so at the
bottom we have the producers these are
the plants and they form the base since
they are going to produce the usable
energy in every ecosystem remember
though they're not really making the
energy they're just converting light
energy into chemical energy in the form
of glucose the next level is the primary
consumer level and these are the animals
that are eating the plants to get their
energy and we call them herbivores then
we have the secondary consumer level
these are animals that are going to eat
primary consumers and so we call these
either carnivores or omnivores because
sometimes these secondary consumers also
eat from the producer level so this
example here of a blue jay a blue jay
eats some animals but it also eats some
plants same thing with the raccoon and
so we call those omnivores and they can
belong to two different tropic levels
then finally we have the tertiary
consumers and these are our top or our
apex predators so these are organisms
that are going to feed on secondary
consumers now we'll talk about the 10%
rule as it applies to biomass so because
energy is needed for growth and only 10%
of the energy from one tropic level
makes it on to the next that also means
that only about 10% of the biomass can
be supported now what is biomass biomass
just refers to the total mass of all
living things at a certain trophic level
and so if we to look at this diagram
here at the base we could support about
a th000 kilograms of producers but since
only about 10% of the energy moves on to
the primary consumer level that means we
can can only have about 10% of the
biomass as well since all biomass needs
energy in order to be developed to be
grown so we're only going to be able to
support about a 100 kilograms of primary
consumers from that thousand kilograms
of
producers then that's going to decrease
by 10% Again by 90% excuse me uh so
we'll have 10 kilograms at the secondary
consumer level and finally when we get
to the top of the pyramid there can only
be one kilogram of tertiary consumer
biomass for every ,000 kog of producer
biomass so this is really important I
want to reiterate this at the base only
10% of the energy moves on to the
primary consumer level so only 10% of
the biomass can be supported so that's
why when we look at a given ecosystem
there are far far far more plants than
any of the animals in the ecosystem and
that's because you can only support 10%
of the primary producers that you had at
the consumer level same thing with the
secondary consumers and same thing with
the tertiary
consumers so now we'll practice actually
calculating the amount of energy
available at different levels so it's a
really simple calculation to calculate
the energy available at the next tropic
level up you're just going to move the
decimal spot one place to the left or
just divide by 10 so if we use this
example where we have 95,000 jewles at
the producer level we would just move
that decimal place one spot to the left
or divide by 10 and that should give us
9,00 500 jewles roughly that would be
available to the primary producers so
what I want you to do is see if you can
calculate the secondary producer level
and the tertiary producer
level so again pretty simple we're just
moving the decimal place one spot to the
left we're dividing by 10 so at the
secondary consumer level we'd expect 950
Jews and then only about 95 Jewels
available at the tertiary consumer level
since the 10% rule also applies to
biomass we can do the same type of
calculation to determine how much
biomass would be found at each level so
starting out with 80 kilg of the
secondary consumer I want you to see if
you can work both up and down the
pyramid to figure out how much biomass
would be supported at each of those
levels so again we're just moving that
decimal place one spot to the left to
figure out the tertiary consumers which
should only be 8 kilograms but we're
actually going to do the opposite and
move the decimal PL to the right as we
go down the pyramid so that would give
us 800 kg at the primary consumer level
and 8,000 kilg at the primary prod ucer
level so our practice fqs for topics 1.9
and 1.10 today will be covering two
different skills one is explaining
environmental concept or process the
other is calculating an accurate answer
with units so first I want you to
explain why a relatively large Forest
can only support a small number of
wolves and then I want you to calculate
the amount of energy available to a
tertiary consumer in an ecosystem where
there are a 100,000 jewels of energy
produced by plants
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