Biogeochemical Cycles

Summary

This environmental science video explains biogeochemical cycles, focusing on the movement of nutrients like carbon, nitrogen, phosphorus, and sulfur between the biotic and abiotic worlds. It highlights the importance of conserving matter on Earth, with key cycles including the water, carbon, nitrogen, phosphorus, and sulfur cycles, each playing a critical role in sustaining life. The video also touches on the concept of limiting nutrients and the potential environmental issues like eutrophication.

Takeaways

• 🌍 Biogeochemical cycles are the processes by which nutrients like carbon, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS) move between the living (biosphere) and nonliving (atmosphere, lithosphere, hydrosphere) parts of the Earth.
• 🌞 The sun is the primary source of energy that drives these cycles, including the water cycle, carbon cycle, nitrogen cycle, phosphorus cycle, and sulfur cycle.
• 💧 The water cycle involves evaporation, condensation, precipitation, and runoff, moving water between the Earth's surface and atmosphere.
• 🌿 Plants obtain carbon through photosynthesis, while animals get it through their diet, and carbon dioxide is released back into the atmosphere through cellular respiration.
• ⚛️ Nitrogen fixation by bacteria is crucial for converting atmospheric nitrogen into a form that living organisms can use, contributing to the nitrogen cycle.
• 🌱 The phosphorus cycle is slow and involves the weathering of rocks, uptake by plants, and eventual return to the environment through decay and erosion.
• 🔁 The sulfur cycle includes the conversion of sulfur in the oceans to dimethyl sulfide by bacteria, its release into the atmosphere as sulfur dioxide, and its return to the Earth as sulfuric acid.
• 🌳 Plants absorb nutrients from the environment through their roots, while animals obtain these nutrients by consuming plants or other animals.
• 🐄 Consumers, including humans, contribute to the recycling of nutrients back into the environment through processes like excretion and decay.
• 🚫 Limiting nutrients like nitrogen and phosphorus can lead to eutrophication when they accumulate in water bodies, causing rapid algal growth and oxygen depletion.
• 🔍 Understanding biogeochemical cycles is essential for appreciating the conservation of matter on Earth and the interconnectedness of all living and nonliving systems.

Q & A

What is the main focus of the environmental science video 11?

The main focus of the video is biogeochemical cycles, which describe how nutrients move between the living and nonliving components of the Earth.

Who is George Rhoads and what is he known for?

George Rhoads is an inventor known for creating giant kinetic sculptures, such as those found in museums where billiard balls are lifted and move according to a designed mechanism.

What does the acronym CHNOPS represent in the context of nutrients needed by life?

CHNOPS is a mnemonic for the key nutrients needed by life, standing for Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

What are the three main components of the abiotic factors on Earth?

The three main components of the abiotic factors are the atmosphere, lithosphere, and hydrosphere.

Why are nitrogen and phosphorus considered limiting nutrients?

Nitrogen and phosphorus are considered limiting nutrients because life requires them in significant amounts for growth, and their availability can limit the rate of biological processes.

What is eutrophication and how can it be related to the nitrogen and phosphorus cycles?

Eutrophication is a process where an excess of nutrients, particularly nitrogen and phosphorus, leads to an overgrowth of algae in water bodies, which can deplete oxygen levels and harm aquatic life.

How does the water cycle involve the transformation of water from a liquid to a gas?

The water cycle involves evaporation and evapotranspiration, where water is transformed from a liquid state to water vapor, which then condenses in the clouds and precipitates back to the Earth.

What is the role of bacteria in the nitrogen cycle?

Bacteria play a crucial role in the nitrogen cycle by fixing atmospheric nitrogen into ammonia through a process called nitrogen fixation, making it available for plants and other organisms.

How does the phosphorus cycle differ from the nitrogen cycle in terms of its speed and components involved?

The phosphorus cycle is slower and does not involve the atmosphere. It involves the movement of phosphorus through rocks, soil, water, and living organisms, eventually settling in ocean sediments.

What are the sources of sulfur in the sulfur cycle?

The sulfur cycle includes sulfur from the oceans, which is converted by bacteria into dimethyl sulfide or sulfur oxides, and sulfur dioxide from volcanic activity and industrial emissions.

How is the carbon cycle connected to the process of photosynthesis and cellular respiration?

In the carbon cycle, plants acquire carbon dioxide through photosynthesis, converting it into organic compounds. Animals obtain carbon by consuming plants or other animals, and carbon is released back into the atmosphere through cellular respiration as carbon dioxide.

Outlines

00:00

🌿 Introduction to Biogeochemical Cycles

Mr. Andersen introduces the concept of biogeochemical cycles, emphasizing the conservation of matter on Earth. He mentions George Rhoads' work with kinetic sculptures as a metaphor for how energy drives cycles like the water and rock cycles. The script outlines the importance of understanding how nutrients, remembered by the mnemonic CHNOPS (Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur), move between the biotic (biosphere) and abiotic (atmosphere, lithosphere, hydrosphere) worlds through biological, chemical, and geological processes. The video promises to cover the water, carbon, nitrogen, phosphorus, and sulfur cycles, highlighting the role of bacteria in nitrogen fixation and the concept of limiting nutrients that can lead to eutrophication.

05:03

💧 The Water and Carbon Cycles

The script delves into the water cycle, detailing how plants and animals obtain water and the process of evaporation, condensation, precipitation, and runoff. It then transitions to the carbon cycle, explaining how plants fix carbon through photosynthesis and animals obtain it through their diet. The carbon cycle includes the release of carbon dioxide through cellular respiration and the formation of fossil fuels, which are then extracted and combusted, releasing carbon dioxide back into the atmosphere. The importance of carbon as a building block for life's macromolecules is underscored.

⚫ The Nitrogen and Phosphorus Cycles

The nitrogen cycle is explored, starting with the abundance of nitrogen gas in the atmosphere and the necessity of nitrogen fixation by bacteria to convert it into a form usable by living organisms. The script describes the process of decay and the role of nitrifying and denitrifying bacteria in the nitrogen cycle, which includes the potential for eutrophication when nitrogen enters water bodies. The phosphorus cycle is highlighted as a slow process involving rock uplift, weathering, erosion, and the eventual settling of phosphorus in ocean sediments, forming phosphate rocks that are part of the geological cycle.

🔄 The Sulfur Cycle and Recap

The sulfur cycle is discussed, beginning with the release of sulfur from oceans and its conversion by bacteria into dimethyl sulfide or sulfur oxides through industrial and volcanic activity. The script explains how sulfur dioxide in the atmosphere leads to the formation of sulfuric acid and sulfates, which are then assimilated by plants and enter the water supply, completing the cycle. The video concludes with a recap of the importance of biogeochemical cycles in the conservation of matter, the role of limiting nutrients, and the potential environmental impacts such as eutrophication.

Keywords

💡Biogeochemical cycles

Biogeochemical cycles refer to the processes by which nutrients and elements circulate between the biotic (living) and abiotic (non-living) parts of the Earth's environment. In the video, these cycles are central to understanding how matter is conserved and how energy from the sun or within the Earth drives processes like the water and rock cycles. The script uses biogeochemical cycles to explain the movement of nutrients such as carbon, nitrogen, phosphorus, and sulfur.

💡Biosphere

The biosphere represents the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere. In the script, the biosphere is the part of the Earth where the nutrients cycle between living organisms and is integral to the conservation of matter.

💡CHNOPS

CHNOPS is a mnemonic for the six essential nutrients needed by life forms: Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), Phosphorus (P), and Sulfur (S). The script uses this mnemonic to help remember the key elements involved in the biogeochemical cycles and their importance in sustaining life.

💡Water cycle

The water cycle, also known as the hydrologic cycle, is the continuous movement of water on, above, and below the surface of the Earth. The script describes the stages of the water cycle, including evaporation, condensation, precipitation, and runoff, illustrating how water moves through the abiotic components of the planet.

💡Carbon cycle

The carbon cycle is the process by which carbon atoms move through the Earth's atmosphere, land, oceans, and living organisms. The script explains how plants obtain carbon through photosynthesis and how it is released back into the atmosphere through respiration and the burning of fossil fuels.

💡Nitrogen fixation

Nitrogen fixation is the process by which certain bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), making it available for plants to use. The script highlights the role of bacteria in the nitrogen cycle, emphasizing their importance in converting nitrogen into a form that can be assimilated by plants.

💡Eutrophication

Eutrophication is the over-enrichment of water bodies with nutrients, leading to excessive growth of algae and other aquatic plants, which can deplete oxygen levels and harm aquatic life. The script mentions eutrophication in the context of nitrogen and phosphorus cycles, explaining how an excess of these nutrients can lead to rapid algal growth and subsequent negative impacts on water ecosystems.

💡Phosphorus cycle

The phosphorus cycle involves the movement of phosphorus through the Earth's crust, oceans, and biosphere. The script describes how phosphorus is weathered from rocks, taken up by plants, and eventually returned to the environment through decay and excretion, emphasizing its role as a limiting nutrient in the growth of life forms.

💡Sulfur cycle

The sulfur cycle is the process by which sulfur atoms move through the Earth's ecosystems. The script explains the various stages of the sulfur cycle, including its release from the oceans and conversion into sulfur oxides through biological and volcanic activity, and its return to the environment through precipitation as sulfuric acid.

💡Matter conservation

Matter conservation is the principle that matter cannot be created or destroyed, only transformed. The script repeatedly emphasizes this concept, explaining that the nutrients necessary for life are not created anew but cycled through the biotic and abiotic spheres of the Earth.

💡Limiting nutrients

Limiting nutrients are elements that are required by organisms for growth but are present in quantities that restrict the rate of growth. The script identifies nitrogen and phosphorus as limiting nutrients, explaining how their availability can significantly influence the growth of life forms and potentially lead to eutrophication.

Highlights

Introduction to biogeochemical cycles and the concept of energy and nutrient conservation on Earth.

Mnemonic CHNOPS for remembering essential nutrients: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

Explanation of the water cycle, including evaporation, condensation, precipitation, and runoff.

The carbon cycle, emphasizing photosynthesis, respiration, and the role of fossil fuels.

Nitrogen fixation by bacteria and its importance in the nitrogen cycle.

The role of bacteria in the nitrogen cycle, including nitrification and denitrification processes.

Eutrophication as a consequence of nitrogen and phosphorus availability in aquatic ecosystems.

The phosphorus cycle, detailing its slow movement through rock, soil, and water.

Sulfur cycle's movement from oceans to atmosphere and its transformation by bacteria and volcanoes.

The impact of human activities, such as factory emissions, on the sulfur cycle.

The recycling of nutrients through the atmosphere, hydrosphere, and lithosphere.

The necessity of nutrients for life, with a focus on their role in biological processes.

The biosphere as the living part of the planet and its interaction with abiotic factors.

The significance of the lithosphere, hydrosphere, and atmosphere in the movement of nutrients.

The concept of limiting nutrients and their critical role in the rapid growth of life.

The unique role of bacteria in the nitrogen and sulfur cycles, facilitating the conversion of gases into usable forms.

The environmental implications of biogeochemical cycles, including the potential for eutrophication and climate change.

Transcripts

Hi. It’s Mr. Andersen and this is environmental science video 11. It is on biogeochemical

cycles. This is a picture of George Rhoads. You have probably never seen him before but

you may have seen his work. If you have ever seen a giant kinetic sculpture at a museum

where billiard balls are lifted up and then they move down again, he invented that and

has installed lots of those around the world. Here is a planning document. In this one he

is trying to show how energy from the sun or within the earth can drive things like

the water cycle and the rock cycle. And it is a really good model for how nutrients move

around on our planet. The carbon and the nitrogen that we have is set and it just moves around

between the living and nonliving world. #00:00:41-4#

And so the matter on our planet is conserved. We have a set amount and it moves between

the biotic, or living, and abiotic world. The living world is called the biosphere on

our planet. And the nutrients that we need are best remembered in this mnemonic, CHNOPS.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. If we look at the abiotic factors,

that is going to be the atmosphere, lithosphere and hydrosphere. And so these biogeochemical

cycles are going to be how the nutrients move between the living and nonliving. Now why

is it such a long word? Bio, geo and chemical are the biological, chemical and geological

processes by which the nutrients move around. You are probably most familiar with the water

cycle. We will start there. Then talk about the carbon cycle and following that the nitrogen

cycle. One thing you are probably not familiar with with the nitrogen cycle is the importance

of bacteria and how they can nitrogen fix or take nitrogen out of the atmosphere and

put it into the living world. We will then move to the phosphorus, one of the slowest

turning cycles. It involves rock but no atmosphere. Now both nitrogen and phosphorus are what

are called limiting nutrients. That means life really needs them and is waiting for

them. And once it gets those nutrients then it grows really really quickly. It is a good

thing but sometimes can lead to eutrophication. And then finally we will finish with the sulfur

cycle. #00:01:57-7#

And so the energy on our planet remember starts in the sun, moves through producers to consumers,

other consumers and eventually is lost as heat. But as we move to matter everything

on the planet is conserved. There is no sun anymore. And so how do the producers get the

nutrients that they need? It is from their environment. From the atmosphere, from the

hydrosphere, from the lithosphere. How do consumers get the matter they need? By eating

plants or eating consumers that ate plants. How does the matter go back into the environment

again? Through these biogeochemical cycles. #00:02:30-8#

And so what are the nutrients that life needs? What are the billiard balls of life? Well

a good mnemonic is CHNOPS. Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. If

we organize that into the five cycles we have the water cycle, carbon cycle, nitrogen cycle,

phosphorous cycle and sulfur cycle. So why do we need all of this matter? We are filled

with water. We also use the oxygen to release energy and transfer energy with the hydrogen.

We are built out of macromolecules. That is what carbon is the building block of. The

nitrogen and the sulfur are both big components in the proteins that make us up. And then

the phosphorous is found in DNA, RNA and the ATP. And so if we do not have these nutrients,

if we do not have these atoms then life cannot exist. So we need to pull them out of our

environment. #00:03:17-8#

So let’s start with the water cycle. How do plants get water? They are going to take

it in through their roots. What about a cow? They are simply going to drink the water.

But how does it move through the abiotic parts of our planet? First of all we are going to

have evaporation off of oceans, lakes and streams. And then we are going to have evapotranspiration.

So it is evaporating but also it is being transpired through the leaves of a plant.

It is now moving from a liquid to a gas. What eventually happens is that we are going to

have condensation in the clouds. We have precipitation. And then we have run off over the surface

and through ground water. And the whole thing begins again. #00:03:49-4#

If we start with carbon, how does a plant get carbon? It is going to be through photosynthesis.

Both in plants on land and then phytoplankton that are going to be found in the ocean. What

about an animal like this cow, it is simply gets the carbon through its diet. It eats

the plant. Or if something eats a cow, like you, you are taking the carbon from the meat

of the cow. So what happens to that carbon? It is eventually released through cellular

respiration. It goes back into the atmosphere again as carbon dioxide. So a lot of that

carbon is going to be in the atmosphere as carbon dioxide. Now we can also take that

carbon and it can be covered by rock and we can create coal and oil, fossil fuels. So

we are storing that carbon in the rock. We can extract it again by digging a well. And

then we can have combustion where a factory releases that carbon dioxide back into the

atmosphere and the whole cycle continues again. #00:04:37-8#

The nitrogen cycle is a little different. Most of the nitrogen is going to be found

in the atmosphere as nitrogen gas. And to get it into the living systems we have to

do nitrogen fixation. So there are bacteria that live lots of times on the roots of plants

in these nodules and they are converting the nitrogen in the atmosphere into usable ammonia.

We could also put ammonia on our fields as fertilizer. And then it is going to be assimilated.

In other words plants are going to take it in through their roots and we are going to

get it from plants simply by eating them. Now how does it get returned back to the atmosphere?

It is kind of complex. What happens is we have death. We then have decay. And so bacteria

or fungi are going to convert that nitrogen into ammonium. And then we have other bacteria,

nitrifying bacteria that are going to convert that ammonium into nitrites and then nitrates.

Now the nitrates can be leached. They can move into the water supply of our planet.

Remember nitrogen is a limiting nutrient. Plants, life, is just waiting for nitrogen

to be there. And once we get nitrogen, for example in this stream, you will get an algae

bloom. We will get a bunch of algae growing really, really quickly. Now that seems like

a good thing but all of those algae are going to quickly die. And eutrophication is this

process by which they die and then other bacteria have to break them down through respiration

and it consumes all of the oxygen. So it is not healthy for that water supply. But let’s

keep watching the nitrogen. How does it get back into the atmosphere? We will have denitrifying

bacteria that are going to return it back into the atmosphere. And so the whole thing

can begin again. #00:06:05-4#

Now the phosphorus cycle is going to turn more slowly. It starts by having rock that

have phosphorus being uplifted. We then have weathering and erosion and that is going to

move the phosphorus into the soil, into the water supply. We could also add fertilizers.

That is going to have phosphorus. And the whole thing, since it is limiting can promote

eutrophication. What happens to the phosphorus? We then have assimilation where it is taken

into plants. We can eat the plants and we get it. What eventually happens is we die.

So through excretion and decay we return that phosphorus into the water supply. It eventually

works its way to the ocean. And then it eventually settles out in these sediments. And so it

never goes to the atmosphere. It becomes part of these phosphate rocks which are then uplifted

again. And so it takes a long time for this cycle to turn because we do not include the

atmosphere. #00:06:49-0#

And then finally we have the sulfur cycle. Sulfur cycle is going to move from the oceans,

the sulfur. We have bacteria that are going to convert that into dimethyl sulfide which

eventually becomes sulfur oxide or sulfur dioxide. We can also increase sulfur dioxide

through volcanism. So volcanoes are releasing hydrogen sulfide which becomes sulfur dioxide.

And then factories are going to release sulfur dioxide as well. It is in the atmosphere now.

How does it get back to the planet? It is going to rain down as sulfuric acid and sulfates.

We can then assimilate that, take it into the living materials, same way, into plants

and then into consumers. And finally it works its way back through the water supply and

now it is going to be sulfur in the oceans. So the cycle can continue again. But we can

also have that rock cycle forming some of that into fossils fuels which can be extracted

again and the cycle continues. #00:07:41-2#

And so for each of these cycles you should be able to figure out how do plants get it?

How do animals get it? And then how does it recycle back through the atmosphere, hydrosphere

and lithosphere. #00:07:51-4#

So did you learn the following? Could you pause the video right now and fill in the

blanks? Remember matter is conserved on our planet. We have a set amount. It moves through

the biotic and abiotic spheres. A good way to remember the nutrients we need is CHNOPS.

The biogeochemical cycles are how we move it through abiotic and biotic. It is the water

cycle, carbon cycle, nitrogen cycle, which requires nitrogen fixation. Remember nitrogen

and phosphorus are limiting nutrients which can lead to eutrophication. The last cycle

is the sulfur cycle. And I hope that was helpful.