Are they communicating ideas?

Have you ever heard the concept energy can't be created or destroyed?

It can only be transferred from one form to another.

It's one of the most fundamental concepts behind the laws of thermodynamics in physics, and you can see it everywhere, even here at the zoo.

Energy transfers through ecosystems too, beginning with the transfer of energy from the sun to producers like plants or algae.

So how does that energy transition work?

Stay tuned to "Spotlight Earth" to find out.

(bright music) In our journey to find answers, let's go to the studio, where Ellen picks up the story.

Hey, Jarrell.

Looks like a lot of good energy at the zoo.

We're gonna try to keep it up here.

Understanding trophic levels helps us appreciate the delicate balance of nature and how all living beings in an ecosystem are interconnected.

The trophic levels are hierarchical levels within an ecosystem, each one comprised of the organisms that share the same function in the food chain and the same nutritional relationship to the primary energy source.

Imagine an ecosystem as a big food pyramid where each level represents a different group of organisms.

The lowest level, called the producers, includes plants and some algae that create their own food through photosynthesis using sunlight and water.

They're like the foundation of the pyramid, providing energy for all other levels.

It's easy to remember because they produce the energy for a food chain.

Moving up the pyramid, we have the primary consumers at the second level.

These are the herbivores that feed directly on the producers.

They could be animals like rabbits, deer, or even insects.

At the third level, we have the secondary consumers, which are carnivores that eat other animals.

They might be predators like foxes, hawks, or snakes, which rely heavily on herbivores for their energy.

Finally, we reach the top of the pyramid, the tertiary consumers, also known as the top predators or apex predators.

These are animals like lions, wolves, or eagles, which have no natural predators themselves.

Each trophic level depends on the one below it for food and energy.

When organisms die, decomposers like fungi and bacteria break down the remains, returning the nutrients to the soil, which restarts the cycle.

In nature, the trophic levels rarely go higher than four or five levels.

So much energy is lost between each level that there are rarely enough producers at the first level or the base of the pyramid to support more than three levels or above.

Humans are part of the trophic food web too.

If you're a vegetarian, you are a primary consumer, and when you eat meat and dairy products, you're a secondary consumer.

Many secondary consumers are omnivores, which means they eat both meat and plants.

You can find lots of examples of producers and consumers at the zoo.

So let's check back in with Jarrell, who's doing some deep research.

Jarrell, you and your friend there, take it away.

Thanks, Ellen.

The zoo is a great place to see this system in action.

I have more for you.

Come get that.

And even though these zoo ecosystems are manmade, you can get pretty up close and personal with everything from the producer level right up to the apex predators.

Michelle Lewis is the curator of education here at the Virginia Zoo.

Michelle, can you tell us how energy moves through an ecosystem?

Absolutely.

So if we use the one right behind me-- Yeah.

(laughs) Energy is all gonna start with our sun, which of course the clouds have covered right now.

(Jarrell laughs) But that sun is gonna be the source of energy for our plants.

Yeah.

Our plants are gonna grab that energy, and those are our primary producers, which are then going to be consumed by our primary consumers up here like our giraffe.

Yeah.

And our giraffe, our prey animal, which will then be hunted by a predator like perhaps our lions.

And in this ecosystem, our lions may be our apex predator or our secondary consumer in the web that we just sort of weave.

So a tertiary consumer or apex predator ends up with all that energy?

Not exactly.

Okay.

There is always going to be some heat loss in between transfer from one to another, so-- Okay.

For example, the giraffe is going to have to eat quite a lot of plants.

Right.

And then you're gonna have a little bit less that's eaten and a little less.

Is it easy to track energy and energy loss through an ecosystem?

So in the simple one that I gave you, yes.

But our ecosystems are a lot more complex than that.

Okay.

So you've got, instead of just that chain that I did, you've got food webs going-- Right.

Where you're also going to add in decomposers who are bringing energy back into the ecosystem.

So it's a lot more complex than the simple chain that we made.

Okay.

Thank you so much for explaining that concept, Michelle.

I really appreciate it.

Absolutely.

Do you wanna feed some giraffes?

You already know I do.

(laughs) Let's get back to the studio, where Ellen is standing by to show us how we can quantify these trophic relationships.

That's right, Jarrell.

It's math time.

Examining trophic levels helps us understand how energy transfers in nature, but it's important for environmental scientists to be able to calculate the actual energy figures between species.

Energy in an ecosystem is usually calculated in units called kilocalories.

We know that only 10% of energy is conserved from trophic level to trophic level.

So if a primary producer provides 10,000 kilocalories of energy, how much does a tertiary consumer end up with?

In our example today, let's use a grassland ecosystem.

The producers are grasses and trees that convert light and heat from the sun into energy.

Let's assume that these producers provide 10,000 kilocalories to the ecosystem.

The primary consumer is a grasshopper.

A grasshopper who eats these producers are only getting 10% of the 10,000 kilocalories, which means they absorb 1,000 kilocalories.

The snake, which is the secondary consumer, gets 10% of the energy from the grasshopper, so the snake ends up with 100 kilocalories.

And the tertiary consumer is a fox, which is an apex predator in the grassland ecosystem.

The fox only gets 10% of the snake's energy, so the fox ends up with 10 kilocalories.

We started with the first law of thermodynamics, which is the fact that energy cannot be created or destroyed.

It can only be transferred from one form to another.

This holds true in nature.

Energy is a precious resource, and it moves through the sun to the primary producers and up through the food chain.

What happens to energy that doesn't make it to the top of the food web?

(playful music) It's lost in the ecosystem through heat and other body functions.

(manure splats) If you're still wondering, how can only 10% of the energy be transferred, and wondering where the rest goes, maybe you can visualize this as a log burning in a fire.

The tree photosynthesized the energy from the sun and turned it into wood.

When we burn the wood, it separates into heat, smoke, and ash.

Nothing is destroyed, but the energy in the wood is no longer available to us.

This is actually the second law of thermodynamics that when you change or transform matter, like burning the wood, you increase entropy, the disorder in the system, and there's less energy available.

Ecosystems are a delicate balance of producers, predator-prey relationships, and decomposers.

Even small disruptions to the ecosystems can cause even less energy to reach those apex predators.

That's why it's so important to protect our environment, to ensure all Earth's inhabitants have the energy they need.

Thanks for joining us on "Spotlight Earth."

See you next time.

(bright music)