APES Notes 1.9 & 1.10 - Trophic Levels & The 10% Rule

Summary

This 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

00:00

📚 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.

05:00

🌞 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.

10:00

🐇 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.

Keywords

💡Trophic Levels

Trophic levels refer to the different stages in a food chain, representing the flow of energy through an ecosystem. In the video, it’s explained that energy flows from producers (like plants) to primary consumers (like herbivores), then to secondary consumers (like carnivores or omnivores), and finally to tertiary consumers (apex predators). This concept is crucial for understanding how energy is transferred between organisms.

💡10% Rule

The 10% Rule states that only about 10% of the energy at one trophic level is passed on to the next level, with the remaining 90% lost as heat or used up by organisms for activities like movement and growth. This principle is highlighted in the video to show why energy decreases as it moves up the food chain, and why ecosystems can only support smaller populations of top predators.

💡Energy Flow

Energy flow describes how energy moves through an ecosystem, from the sun to producers (plants) and then through various consumers. The video emphasizes that energy is conserved but becomes less available as it moves up trophic levels due to losses as heat. This process is illustrated through examples like rabbits eating plants or lions eating elk, and how each transfer reduces the available energy.

💡Conservation of Matter

The conservation of matter refers to the principle that matter is neither created nor destroyed, only transformed. The video explains this using examples like trees decomposing and matter being returned to the soil or atmosphere. It’s key to understanding biogeochemical cycles such as the carbon or nitrogen cycles, where matter continually moves and changes forms within ecosystems.

💡First Law of Thermodynamics

The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. In the video, this law is used to explain how energy from the sun is converted into chemical energy by plants (via photosynthesis) and then transferred through trophic levels in ecosystems, with some energy being lost as heat during each transfer.

💡Biogeochemical Cycles

Biogeochemical cycles describe the movement of elements like carbon, nitrogen, and phosphorus through ecosystems. The video touches on these cycles to illustrate the conservation of matter, showing how, for example, nitrogen in a decomposing animal’s body is transformed and reused in the environment, often for plant growth. These cycles are vital to ecosystem functioning.

💡Producers

Producers are organisms, usually plants, that create energy-rich compounds (like glucose) through processes such as photosynthesis. In the video, producers form the base of the trophic pyramid, converting sunlight into usable chemical energy, which then flows through the rest of the ecosystem. They are essential for supporting all other organisms by providing the initial energy source.

💡Primary Consumers

Primary consumers are herbivores that eat producers (plants) to gain energy. In the video, they occupy the second trophic level, consuming plants and passing energy up the food chain. Examples given include animals like rabbits, which feed on plant matter, using the energy stored in plants for their own growth and metabolic activities.

💡Heat Loss

Heat loss refers to the energy lost as heat during each transfer between trophic levels. The video explains that while energy is not destroyed, much of it is dissipated as heat when organisms use energy for movement, cellular respiration, and other processes. This explains why only a small percentage of energy is passed on to the next trophic level, and why the 10% rule applies.

💡Biomass

Biomass is the total mass of all living organisms in a particular trophic level. The video explains that the 10% Rule applies not only to energy but also to biomass, meaning that as energy decreases up the trophic pyramid, so does the amount of biomass each level can support. This explains why there are far more producers than primary consumers, and why apex predators are so few in an ecosystem.

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