GCSE Biology - Pyramids of Biomass #87

Summary

This video explains biomass pyramids, illustrating the decreasing mass of organisms across trophic levels in a food chain. It uses an example with grass, rabbits, snakes, and hawks, highlighting how only about 10% of biomass and energy is transferred to the next level due to consumption inefficiencies, indigestibility, and energy use for respiration. The video concludes with a formula to calculate biomass transfer efficiency as a percentage.

Takeaways

• 🌿 Biomass pyramids represent the mass of living organisms at each trophic level in a food chain.
• 🐰 Grass is the producer, rabbits are primary consumers, snakes are secondary consumers, and hawks are tertiary consumers.
• 📊 The bars in the pyramid decrease in size as you move up the trophic levels, indicating a reduction in total mass of organisms.
• 🐍 Even though a snake is heavier than a rabbit, there are fewer snakes, leading to less total biomass.
• 🔄 Approximately 10% of biomass and energy is transferred to the next trophic level with each consumption.
• 🦅 Organisms don't consume every part of what they eat, leading to biomass loss.
• 💩 Consumed parts that aren't absorbed are excreted as waste, reducing the biomass passed on.
• 🔥 Most absorbed nutrients are used for energy release through respiration, not stored indefinitely.
• 📉 Biomass is often released as waste products like CO2 and urea, not retained by the organism.
• 📊 To calculate biomass transfer efficiency, use the formula: (biomass transferred / biomass available) * 100.

Q & A

What does a pyramid of biomass represent?

A pyramid of biomass represents the total mass of living organisms at each trophic level in a food chain.

What is the significance of the bars in the biomass pyramid?

The bars in the biomass pyramid get smaller as you go up the trophic levels, indicating that the total mass of organisms decreases with each level.

Why do the bars get smaller as you move up the trophic levels?

The bars get smaller because only about 10% of the biomass and energy is transferred to the next trophic level when one organism is consumed by another.

What are the three main reasons that only about 10% of the biomass and energy gets passed on each time?

The three main reasons are: 1) Organisms don't eat every part of their prey, 2) Some parts consumed are not absorbed and are excreted, and 3) Most nutrients absorbed are used for respiration and are released as waste products.

Why might a hawk not eat the entire snake it catches?

A hawk might not eat the entire snake because it doesn't consume parts like the skeleton or teeth, which are not digestible.

What is meant by biomass being 'used for respiration'?

Biomass being 'used for respiration' means that the nutrients are used to release energy, which is then released as waste products like carbon dioxide and urea, rather than being stored within the organism.

How is the efficiency of biomass transfer calculated?

The efficiency of biomass transfer is calculated as the percentage of biomass that has passed on to the next trophic level, using the formula: (biomass transferred to the next level / biomass available at the previous level) * 100.

What is the efficiency of biomass transfer between rabbits and snakes in the given example?

The efficiency of biomass transfer between rabbits and snakes is 10.4 percent, calculated as (15 kg / 144 kg) * 100.

What is the efficiency of biomass transfer between snakes and hawks in the given example?

The efficiency of biomass transfer between snakes and hawks is 10.7 percent, calculated as (1.6 kg / 15 kg) * 100.

Why is it important to understand the efficiency of biomass transfer?

Understanding the efficiency of biomass transfer is important because it helps us understand how energy and nutrients flow through an ecosystem and how much is lost at each trophic level.

Outlines

00:00

🌿 Understanding Biomass Pyramids

This paragraph introduces the concept of biomass pyramids, which visually represent the biomass at each trophic level within a food chain. The example given includes grass as the producer, rabbits as primary consumers, snakes as secondary consumers, and hawks as tertiary consumers. Biomass refers to the total mass of living organisms at each level. The paragraph explains that the bars in the pyramid decrease in size as you move up the trophic levels, indicating a reduction in total mass. This is due to the fact that energy and biomass are lost or used at each level, with only about 10% being transferred to the next level. The reasons for this inefficiency are outlined: organisms do not consume every part of their prey, not all consumed parts are absorbed, and most nutrients are used for respiration rather than growth.

Keywords

💡Pyramids of Biomass

Pyramids of Biomass are graphical representations that illustrate the biomass at each trophic level within an ecosystem. In the context of the video, the pyramid shows the mass of grass, rabbits, snakes, and hawks, demonstrating how biomass decreases as one moves up the food chain. This concept is central to understanding energy flow and the efficiency of energy transfer in ecosystems.

💡Trophic Levels

Trophic levels refer to the position an organism occupies in a food chain based on its feeding relationships. The video script describes grass as a producer, rabbits as primary consumers, snakes as secondary consumers, and hawks as tertiary consumers. Understanding trophic levels is crucial for analyzing the flow of energy and nutrients through an ecosystem.

💡Biomass

Biomass is defined as the total mass of all the organisms in a given area or ecosystem. In the video, biomass is used to quantify the amount of living matter, such as the total mass of grass or rabbits. It is a key metric for assessing the health and productivity of an ecosystem.

💡Producers

Producers are organisms that can create their own food from inorganic substances, typically through the process of photosynthesis. In the video, grass is mentioned as an example of a producer, forming the base of the food chain and supporting all other life forms by converting sunlight into energy.

💡Primary Consumers

Primary consumers, also known as herbivores, are organisms that feed on producers. In the script, rabbits are given as an example of primary consumers, which eat the grass and are, in turn, a food source for other organisms higher up in the food chain.

💡Secondary Consumers

Secondary consumers are predators that feed on primary consumers. Snakes are used as an example in the video, illustrating how they consume rabbits and are part of the energy transfer process in the ecosystem.

💡Tertiary Consumers

Tertiary consumers are higher-level predators that feed on secondary consumers. Hawks, as mentioned in the video, are tertiary consumers that eat snakes, representing the top of the food chain in this example.

💡Energy Transfer

Energy transfer refers to the process by which energy moves from one trophic level to the next. The video explains that only about 10% of the energy from one level is transferred to the next, which is a fundamental principle in ecological systems.

💡Efficiency of Biomass Transfer

The efficiency of biomass transfer is the percentage of biomass that is passed from one trophic level to the next. The video provides a formula to calculate this efficiency, which is important for understanding the limitations of energy flow in ecosystems.

💡Respiration

Respiration is the process by which organisms release energy from the nutrients they consume. The video mentions that most of the nutrients absorbed by animals are used for respiration rather than growth, which is why not all biomass is passed on to the next trophic level.

💡Waste Products

Waste products are the byproducts of an organism's metabolism, such as carbon dioxide and urea. The video explains that much of the biomass an organism consumes is released as waste products, which is why the biomass at each trophic level decreases.

Highlights

Pyramids of biomass represent the mass of living organisms at each trophic level in a food chain.

The example food chain includes grass (producer), rabbits (primary consumer), snakes (secondary consumer), and hawks (tertiary consumer).

Biomass refers to the total mass of living organisms at each level.

The pyramids show a decrease in total mass as you move up the trophic levels.

Although individual snakes may weigh more than rabbits, there are fewer snakes, resulting in lower total biomass.

Only about 10% of biomass and energy is transferred to the next trophic level.

Organisms do not consume every part of what they eat, leading to biomass loss.

Consumed parts that are not absorbed are excreted as waste.

Most absorbed nutrients are used for respiration rather than growth.

Biomass is released as waste products like carbon dioxide and urea.

The efficiency of biomass transfer is calculated as a percentage.

Efficiency is calculated by dividing the biomass transferred to the next level by the biomass available at the previous level.

The example calculation shows 10.4% efficiency between rabbits and snakes.

The example calculation also shows 10.7% efficiency between snakes and hawks.

Understanding biomass transfer efficiency is crucial for studying food chains and ecosystems.

The video provides a clear explanation of biomass and its transfer in food chains.

The video concludes with a call to action for viewers to like and subscribe for more content.

Transcripts

in this video we're looking at pyramids

of biomass

which show the biomass of each trophic

level in a food chain

so this pyramid here could represent a

food chain like this

with grass as the producer

rabbits as the primary consumer

snakes as the secondary consumer

and hawks as a tertiary consumer

now the term biomass just means the mass

of living organisms

so this bar at the bottom

represents the total mass of all of the

grass in the food chain

whereas this next bar represents the

total mass of all the rabbits

then the next one represents the total

mass of all the snakes

and so on

the important thing to notice is that

the bars get smaller as you go up the

trophic levels

which means that the total mass of the

organisms in each level is decreasing

so even though each individual snake

might weigh more than each rabbit

there would be a lot fewer snakes than

rabbits

so the total mass of snakes is much

lower than the total mass of rabbits

the reason for this is that every time

one organism is consumed by another and

remove upper trophic level

most of the biomass and energy is either

lost or used

only about 10 of it actually gets

transferred up to the next level

so if we think about all the biomass of

the grass

only about 10 of it will be passed on to

the rabbits

and then only 10 of that rabbit biomass

will be passed on to the snakes

and so on

now there are a whole bunch of reasons

why only 10 of the biomass and energy

gets passed on each time

but there are three main reasons that

you need to know

the first is that organisms don't

normally eat every single part of the

organism they're consuming

for example the hawks wouldn't eat the

snake skeleton or teeth

the second is that even the bits that

they do eat might not be absorbed if

they can't break them down properly

such as the scales or something so those

beds just get adjusted as feces

which is the technical way of saying

pooped out

the most important reason though is that

most of the nutrients that animals do

absorb are used to release energy

through respiration rather than for

growth

this means that the biomass gets

released as waste products like carbon

dioxide and urea

rather than being stored within the

organism forever

so when the organism ends up being eaten

by something

it doesn't pass on all the biomass that

is consumed throughout its life

because it's been using most of it for

everyday functions

the last thing we need to cover is how

to calculate the efficiency of biomass

transfer

which is basically just the percentage

of the biomass that has passed on each

time and for this we'll need some actual

values for the biomass in each trophic

level

the equation is that efficiency equals

the biomass transferred to the next

level

divided by the biomass that was

available at the previous level

and we have to times the whole thing by

100 to turn it into a percentage

so if we wanted to find the efficiency

between snakes and rabbits

were to just do 15 kilos

which is the biomass that must have been

transferred to the snakes

divided by 144 kilos

which is the biomass that was available

in the form of rabbit biomass

we just multiply that by 100

to get an efficiency of 10.4 percent

which means that 10.4 percent of the

rapid biomass got passed on to the

snakes

or for the efficiency between snakes and

hawks

would just do 1.6

divided by 15 times 100

which gives us 10.7 percent for the

efficiency

anyway that's everything for this video

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