Ecosystem Ecology: Links in the Chain - Crash Course Ecology #7

Summary

This script explores the concept of ecosystems, challenging the common understanding of what they are and how they function. It likens ecosystems to Magic Eye posters, complex and interconnected, with no clear edges. The video delves into energy and material flow, trophic structures, and the roles of primary producers and various consumers. It also discusses ecosystem efficiency, bioaccumulation of toxins, and the importance of considering lower trophic levels for healthier consumption, offering a comprehensive yet accessible look into the intricate workings of ecosystems.

Takeaways

• 🤔 Familiarity with a concept does not equate to understanding it deeply, as with the common but often vaguely defined idea of 'pop music'.
• 🌿 The concept of an ecosystem is complex and not easily defined, often likened to a Magic Eye poster that reveals a clear picture only after prolonged observation.
• 🔄 Ecosystem ecology focuses on the flow of energy and materials into, through, and out of an ecosystem, highlighting the interconnectedness of its components.
• 🈚️ Ecosystems do not have clear edges but rather blend into one another, making their boundaries often subjective and dependent on the scope of study.
• 🌳 Plants, as primary producers, are the foundation of most ecosystems, converting solar energy into chemical energy through photosynthesis.
• 🐦 The flow of energy in an ecosystem is hierarchical, with primary consumers (herbivores), secondary consumers (carnivores), and so on, up the food chain.
• 🕸️ Food webs illustrate the complex interactions and energy transfers between organisms, often deviating from a simple linear food chain.
• 🌡️ Factors like water and temperature, which affect plant growth, in turn, influence the size and scope of the food web and the productivity of an ecosystem.
• ⚖️ Ecosystem efficiency is generally low, with most energy lost during transfer between trophic levels, except for toxins which can bioaccumulate.
• ⚠️ Bioaccumulation of toxins like mercury is a significant concern, as they become more concentrated at higher trophic levels, posing risks to top predators and humans.
• 🍽️ The implications of ecosystem ecology for human consumption suggest that eating lower on the food chain can be safer in terms of avoiding toxin accumulation.

Q & A

What is the main point the speaker makes about our understanding of common concepts?

The main point is that just because we are familiar with a concept, like pop music or ecology, it doesn't mean we truly understand it deeply.

How does the speaker compare an ecosystem to a Magic Eye poster?

The speaker compares an ecosystem to a Magic Eye poster by saying that both appear as a jumble of elements that only make sense when viewed from a certain distance or perspective, and by suggesting that the picture that emerges in an ecosystem is dictated by the organisms within it.

What is the fundamental property of ecosystems that the speaker emphasizes?

The fundamental property emphasized is the flow of energy and nutrients, which are imported, absorbed by the ecosystem's organisms, and then passed on or expelled, sometimes into another ecosystem.

Why does the speaker say that defining an ecosystem can be difficult?

Defining an ecosystem can be difficult because ecosystems do not have clear edges; they have fuzzy, ill-defined gradients that blend into neighboring ecosystems.

What role do plants play in an ecosystem according to the script?

Plants, as autotrophs, play the role of primary producers in an ecosystem. They convert solar energy into chemical energy through photosynthesis, providing the foundation for all other organisms to get their energy and nutrients.

What is the concept of trophic structure in an ecosystem?

The trophic structure in an ecosystem refers to the organization of organisms into a food chain, with each organism occupying a specific place and transferring energy as they consume one another.

Why are food webs considered a more accurate representation of ecosystems than food chains?

Food webs are considered more accurate because they account for the complex interactions between organisms, including the consumption of dead matter and the fact that organisms do not strictly adhere to hierarchical levels.

What is the concept of ecosystem efficiency discussed in the script?

Ecosystem efficiency refers to the transfer of energy within an ecosystem, highlighting that most of the energy is lost during each transfer, with only a small percentage being converted into the consumer's biomass.

What is bioaccumulation and how does it relate to the food chain?

Bioaccumulation is the process by which toxins, such as mercury, become more concentrated in organisms as they move up the food chain. Each consumer retains 100% of the toxin while only assimilating a small percentage of the energy from its food.

Why does the speaker suggest eating lower on the food chain?

The speaker suggests eating lower on the food chain because organisms higher up accumulate more toxins due to bioaccumulation, making them potentially harmful to human health.

How does the script explain the importance of water and temperature in an ecosystem's productivity?

The script explains that water and temperature are crucial for plant growth, which in turn affects the availability of primary producers. In ecosystems with limited water, like the Sonoran desert, there are fewer plants, leading to less trophic action and lower overall productivity.

Outlines

00:00

🤔 The Misconception of Understanding Ecosystems

This paragraph introduces the common misconception that people understand certain concepts simply because they are frequently discussed, such as pop music and ecology. The speaker uses the analogy of Magic Eye posters to describe the complex nature of ecosystems, which are composed of living and nonliving elements that interact in specific areas. Ecosystem ecology is distinguished from other branches of ecology by focusing on the flow of energy and materials within an ecosystem, emphasizing the importance of understanding the roles of various organisms in this process. The paragraph concludes with the goal of demystifying ecosystems and highlighting their interconnectedness and lack of clear boundaries.

05:00

🌿 Energy and Materials in Ecosystem Dynamics

The second paragraph delves into the sources of energy and materials in ecosystems, highlighting the role of autotrophs, such as plants, in converting solar energy into chemical energy through photosynthesis. It explains the hierarchical structure of ecosystems, with primary producers, consumers, and decomposers, and introduces the concept of trophic levels. The paragraph also discusses the inefficiency of energy transfer between these levels, with most energy being lost as heat during metabolic processes. It further explores the concept of bioaccumulation, where toxins like mercury become more concentrated at higher trophic levels, and concludes with the implications of these processes for human consumption and environmental health.

Keywords

💡Ecosystem

An ecosystem is a community of living organisms, such as plants, animals, and microbes, interacting with each other and their nonliving physical environment, which includes air, water, and soil. It is central to the video's theme, illustrating the complex interactions within a specific area. The script uses the analogy of a Magic Eye poster to describe how ecosystems are a jumble of components that only make sense when viewed as a whole.

💡Ecology

Ecology is the branch of biology that studies the relationships between living organisms and their environment. It is the overarching theme of the video, emphasizing the importance of understanding how ecosystems function. The script mentions different types of ecology, such as population and community ecology, to highlight the various levels at which ecologists study biological interactions.

💡Trophic Structure

Trophic structure refers to the arrangement of organisms in an ecosystem according to the food they consume and their position in the food chain. It is essential to understanding energy flow within ecosystems, as depicted in the script. The video explains the hierarchy from primary producers, which convert solar energy into chemical energy, to various levels of consumers and decomposers.

💡Primary Producers

Primary producers are organisms, typically plants, that can produce their own food through the process of photosynthesis. They are the base of the food chain and are crucial to the video's discussion on energy transfer in ecosystems. The script uses plants as an example to illustrate how energy from the sun is captured and transformed into a form that can be used by other organisms.

💡Herbivores

Herbivores are animals that consume plant material and are known as primary consumers in the trophic structure. They play a key role in the script's explanation of how energy moves from primary producers to other organisms. The video mentions herbivores as the first link in the chain that transfers energy from plants to the rest of the ecosystem.

💡Carnivores

Carnivores are animals that eat other animals and are categorized as secondary or tertiary consumers, depending on their position in the food chain. The script discusses carnivores in the context of energy transfer, highlighting how they obtain energy by consuming herbivores or other carnivores.

💡Detritivores

Detritivores are organisms that break down dead plant and animal material, playing a vital role in nutrient cycling within ecosystems. The script mentions detritivores, such as earthworms and dung beetles, to explain how they contribute to the ecosystem by decomposing waste and returning nutrients to the soil.

💡Food Web

A food web is a more complex and realistic representation of the feeding relationships among organisms in an ecosystem than a linear food chain. The script uses the concept of a food web to illustrate the interconnectedness of different species and the multiple pathways that energy can take as it moves through an ecosystem.

💡Biomass

Biomass refers to the total mass of living organisms within an ecosystem and is a measure of the amount of living material present. The script discusses biomass in the context of ecosystem productivity, indicating how it can be used to assess the total weight of living organisms and their ability to grow and regenerate.

💡Productivity

Productivity in an ecological context refers to the rate at which biomass is produced within an ecosystem. The video uses productivity as a key metric to understand how efficiently an ecosystem can generate new organic matter and how this can impact neighboring ecosystems.

💡Bioaccumulation

Bioaccumulation is the process by which harmful substances, such as toxins like mercury, become more concentrated in organisms as they move up the food chain. The script warns about the dangers of bioaccumulation, explaining how toxins can accumulate to higher concentrations in top predators, impacting human health when we consume seafood.

Highlights

The concept of pop music is familiar, but its definition is often vague, illustrating the gap between familiarity and understanding.

Ecology is a common term, yet defining an ecosystem or its importance can be challenging for many.

An ecosystem can be likened to a Magic Eye poster, a complex image that only makes sense when viewed from a distance.

Ecosystem ecology focuses on the flow of energy and materials within a system, rather than interactions between species.

Ecosystems lack clear edges, blending into adjacent ecosystems, making their definition context-dependent.

The ecosystem of a mountain stream relies on surrounding terrestrial ecosystems for sustenance.

Energy and nutrients in ecosystems are imported, circulated, and exported, often crossing into other ecosystems.

Ecosystem definitions are based on the specific interests of the researcher, from a tree knot to the North Pacific Gyre.

Ecosystem parameters such as biomass and productivity are crucial for understanding ecological health and impact on neighbors.

Energy sources in ecosystems are primarily solar, with plants as the primary producers converting sunlight into chemical energy.

Herbivores, as primary consumers, and carnivores, as secondary consumers, form the basis of the food chain in ecosystems.

Food webs account for the complex interactions and energy transfers between organisms, rather than linear food chains.

Environmental factors like water and temperature significantly influence the size and scope of an ecosystem's food web.

Ecosystem efficiency is low, with most energy lost during transfer between trophic levels.

Toxins like mercury bioaccumulate in ecosystems, becoming more concentrated with each trophic level.

Eating lower on the food chain is advised due to the reduced concentration of toxins in primary producers and consumers.

The importance of understanding ecosystem ecology is emphasized for its practical implications on environmental health and human consumption.

Transcripts

There's a lot of ideas that we just assume that we know a lot about because we hear about them all the time.

For instance, I know what pop music is, but if you were to corner me at a party and say,

"Hank, what is pop music?",

I'd be like, "It's, uh...it's like, uh...the music that plays on the pop station?"

Just because we're familiar with a concept does not mean that we actually understand it.

Ecology's kind of the same way, even though it's a common,

everyday concept and "ecosystem" is a word that we hear a lot,

I think most of us would be a little stumped if somebody actually asked us what an ecosystem is,

or how one works, or why they're important, etc.

I find it helps to think of an ecosystem

-- a collection of living and nonliving things interacting in a specific place --

as one of those Magic Eye posters, for those of you who were sentient back in 1994.

An ecosystem is just a jumble of organisms, and weather patterns, and geology,

and other stuff that don't make a lot of sense together until you stare at 'em long enough,

from far enough away and then suddenly a picture emerges.

And just like with Magic Eye posters, it helps if you're listening to Jamiroquai while you're doing it.

So the discipline of ecosystem ecology, just like other types of ecology we've been exploring lately,

looks at a particular level of biological interaction on Earth.

But unlike population ecology, which looks at interactions between individuals of one species,

or community ecology, which looks at how bunches of living things interact with each other,

ecosystem ecology looks at how energy and materials come into an ecosystem,

move around in it, and then get spat back out.

In the end, ecosystem ecology is mostly about eating --

who's eating whom and how energy, nutrients, and other materials are getting shuffled around within the system.

So today, we're setting the record straight: no more not understanding how an ecosystem works, starting now!

[Theme Music]

So ecosystems may be a lot like Magic Eye posters,

but the way that they're not like a Magic Eye poster is in the way that posters have edges.

Ecosystems, I'll just come out and say it:

NO EDGE, only fuzzy, ill-defined gradients that bleed into the ecosystems next-door.

So actually defining an ecosystem can be kind of hard; mostly it depends on what you want to study.

Say you're looking at a stream in the mountains.

The stream gets very little sunlight because it's so small that the trees on its banks totally cover it with shade.

As a result, very few plants or algae live in it, and if there's one thing that we know about Planet Earth,

it's that plants are king -- without plants, there are no animals.

But somehow, there's a whole community of animals living in and around this mountain stream,

even though there are few plants in it.

So what are the animals doing there, and how are they making their living?

From the land, of course -- from the ecosystems around it.

Because no stream is an island, it isn't there all by itself.

All kinds of food, and nutrient,s and other materials drop into the stream from the trees,

or are washed into it when it rains.

Leaves and bugs, you name it, flow down from neighboring terrestrial ecosystems.

And that stuff gets eaten by bigger bugs, which get eaten by fish,

which in turn are eaten by raccoons and birds and bears.

So even though this stream's got its own thing going on, without the rest of the watershed,

the animals there wouldn't survive.

And without the stream, plants would be thirsty and terrestrial animals wouldn't have as many fish to eat.

So, where does the ecosystem of the stream start and where does it end?

This is a perennial problem for ecologists because the way it works:

energy and nutrients are imported in from some place,

they're absorbed by the residents of an ecosystem and then passed around within it for a little while,

and then finally passed out, sometimes into another ecosystem.

This is most obvious in aquatic systems where little streams eventually join bigger and

bigger waterways until they finally reach the ocean.

This flow is a fundamental property of ecosystems.

So at the end of the day, how you define an ecosystem just depends on what you want to know.

If you want to know how energy and materials come in, move through,

and are pooped out of a knot in a tree that has a very specific community of insects and protists living in it,

you can call that an ecosystem.

If you want to know how energy and materials are introduced to, used,

and expelled by the North Pacific Gyre, you can call that an ecosystem.

And if you want to know how energy and materials move around a cardboard box

that has a rabbit and a piece of lettuce in it, you can call that an ecosystem.

I might tell you that your ecosystem is stupid, but go ahead, do whatever you want.

The picture you see in an ecosystem's Magic Eye is actually dictated by the organisms that live there,

and how they use what comes into it.

An ecosystem can be measured through figuring out things like its biomass,

that is, the total weight of living things in the ecosystem, and its productivity --

how much stuff is produced and how quickly stuff grows back, how good the ecosystem is at retaining stuff.

And of course, all these parameters matter to neighboring ecosystems as well

because if one ecosystem is really productive, the ones next-door are going to benefit.

So, first things first, where do the energy and materials come from?

And to be clear, when I talk about materials, I'm talking about water or nutrients like phosphorus or nitrogen,

or even toxins like mercury or DDT.

Let's start out by talking about energy because nothing lives without energy

and where organisms get their energy tells the story of an ecosystem.

You remember physics, right?

The laws of conservation state that energy and matter can neither be destroyed or created;

they can only get transferred from place to place to place.

The same is true of an ecosystem.

Organisms in an ecosystem organize themselves into a trophic structure,

with each organism situating itself in a certain place in the food chain.

All of the energy in an ecosystem moves around within this structure,

because when I say energy, of course I mean food.

For most ecosystems, the primary source of energy is the sun,

and the organisms that do most of the conversion of solar energy into chemical energy -- you know this one.

Who rules the world? The plants rule the world.

Autotrophs like plants are able to gather up the sun's energy,

and through photosynthesis, make something awesome out of it: little stored packets of chemical energy.

So whether it's plants, bacteria, or protists that use photosynthesis,

autotrophs are always the lynchpin of every ecosystem --

the foundation upon which all other organisms in the system get their energy and nutrients.

For this reason, ecologists refer to plants as primary producers.

Now obviously, the way that energy gets transferred from plant to animals is by the animal eating the plant.

For this reason, herbivores are known as primary consumers,

the first heterotrophs to get their grubby paws on that sweet, sweet energy.

After this stage of the trophic structure,

the only way to wrestle the solar energy that was in the plants that the herbivore ate is to -- you guessed it --

eat the herbivore, which carnivores, known as secondary consumers, are very happy to do.

And assuming that the ecosystem is big enough and productive enough,

there might even be a higher level of carnivore that eats other carnivores, like an owl that eats hawks,

and these guys are called tertiary consumers.

And then there are the -vores that decompose all the dead animal and plant matter, as well

as the animal poop: detritivores.

These include earthworms and sea stars and fiddler crabs and dung beetles and fungi

and anything else that eats the stuff that none of the rest of us would touch with a three-meter pole.

So that's a nice hierarchical look at who's getting energy from what or whom within an ecosystem,

but of course organisms within an ecosystem don't usually abide by these rules very closely,

which is why these days we usually talk about food webs rather than food chains.

A food web takes into consideration that sometimes a fungus is going to be eating nutrients from a dead squirrel,

and other times squirrels are going to be eating the fungi.

Sometimes a bear likes to munch on primary producers, blueberry bushes,

and other times it's going to be snacking on a secondary consumer, like a salmon.

And even at the tippy-tippy top, predators get eaten by stuff like bacteria in the end,

which might or might not be the same bacteria that eat the top predator's poopies. Circle of life!

It's also worth noting that the size and scope of the food web in an ecosystem has a lot to do with things

like water and temperature, because water and temperature are what plants like, right?

And without plants, there isn't going to be a whole lot of trophic action going on.

Take for example the Sonoran desert, which we've talked about before.

There aren't many plants there, compared to say, the Amazon rainforest,

so the primary producers are limited by the lack of water,

which means that primary consumers are limited by lack of primary producers.

And that leaves precious few secondary consumers: a few snakes and coyotes and hawks.

All this adds up to the Sonoran not being a terribly productive place, compared to the Amazon at least,

so you might only get to the level of tertiary consumer occasionally.

Now all this conversation about productivity leads me to another point, about ecosystem efficiency.

When I talk about energy getting passed along from one place to another within an ecosystem,

I mean that in a general sense organisms are sustaining each other, but not in a particularly efficient way.

In fact, when energy transfers from one place to another, from a plant to a bunny or from a bunny or a snake,

the vast majority of that energy is lost along the way.

So let's take a cricket. That cricket has about one calorie of energy in it.

And in order to get that one calorie of energy, it had to eat about 10 calories of lettuce.

Where did the other nine calories go? It is not turned into cricket flesh.

Most of it is used just to live, like to power its muscles or run the sodium-potassium pumps in its neurons.

It's just used up.

So only the one calorie of the original 10 calories of food is left over as actual cricket stuff.

And then right after his last meal, the cricket jumps into a spider web and is eaten by a spider,

who converts only 10% of the cricket's energy into actual spider stuff.

And don't get me started on the bird that eats the spider; this is not an efficient world that we live in.

But do you want to know what's scary efficient? The accumulation of toxins in an ecosystem.

Elements like mercury, which are puffed out of the smokestacks of coal-fired power plants,

end up getting absorbed in the ocean by green algae and marine plants.

While the tiny animal that eats the algae only stores 10% of the energy it got, it keeps 100% of the mercury.

So as we move up the chain, each trophic level consumes ten times more mercury than the last.

And that's what we call bioaccumulation.

Concentrations get much higher at each trophic level

until a human gets ahold of that giant tuna that's at the top of the marine food chain,

and none of that mercury has been lost.

It's all right there in that delicious tuna flesh.

Because organisms only hold on to 10% of the energy they ingest,

each trophic level has to eat about ten times its biomass to sustain itself.

And because 100% of that mercury moves up the food chain,

that means that it becomes ten times more concentrated with each trophic level it enters.

That's why we need to take the seafood advisory seriously.

As somebody who could eat anything you wanted, it's probably safest to eat lower on the food chain:

primary producers or primary consumers.

The older, bigger, higher-in-the-food-chain, the more toxic it's going to be.

And that's not just my opinion, that's ecosystem ecology.

Thank you for watching this episode of Crash Course: Ecology

and thank you, everyone who helped us put this episode together.

If you want to review any of the topics we went over today, there's a table of contents

over there that you can click on,

and if you have any questions or comments for us, we're on Facebook or Twitter or,

of course, down in the comments below. We'll see you next time.