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So you know about freshwater and saltwater now and you know that there's not that much Freshwater for us (and other life) to get to. So how do different animals deal with different amounts of water where they live? In this episode of Crash Course Kids, Sabrina talks about the adorable Nerpa and how they deal with rough conditions to live in freshwater!

This first series is based on 5th-grade science. We're super excited and hope you enjoy Crash Course Kids!

///Standards Used in This Video///
5-ESS2-2. Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth. [Assessment Boundary: Assessment is limited to oceans, lakes, rivers, glaciers, groundwater, and polar ice caps, and does not include the atmosphere.]

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Executive Producers: John & Hank Green
Producer & Editor: Nicholas Jenkins
Cinematographer & Director: Michael Aranda
Host: Sabrina Cruz
Script Supervisor: Mickie Halpern
Writer: Kay Boatner
Consultant: Shelby Alinsky
Script Editor: Blake de Pastino

Thought Cafe Team:
Stephanie Bailis
Cody Brown
Suzanna Brusikiewicz
Jonathan Corbiere
Nick Counter
Kelsey Heinrichs
Jack Kenedy
Corey MacDonald
Tyler Sammy
Nikkie Stinchcombe
James Tuer
Adam Winnik

[CrashCourse Kids intro]

 Introduction (0:10)

What would we do without water? No, really, what would we do without it? Probably not very much because we need freshwater to live, but some living things have found ways to get a lot out of very little.

We've talked about freshwater and the fact that there's not very much of it on Earth. To give you an idea about how little there really is, think of it this way: if all of the Earth's water were placed into a gallon jug, the freshwater would equal a single teaspoon. That's it.

But this picture does an especially good job of showing just how much of each kind of water there is on Earth. See the three blue dots? The biggest one represents all of the water on our planet, salt and fresh. So that includes all of the water in the oceans, glaciers, lakes, rivers, plus all of the groundwater and the water in the atmosphere, and even the water in you and me.

The medium-sized dot next to it represents all of our planet's liquid freshwater, including the freshwater that's underground and locked in glaciers.

And what about that teeny-tiny dot? Yeah, that little guy. Well that's all of the surface freshwater that humans, plants, and animals actually can get to. If you think that's a really small amount of freshwater for all of the living things on the planet, well, you're right. It is.

But plants and animals live and thrive all over the Earth, in places with lots of freshwater and in places with very little freshwater. So, how do they survive?

 Big Question (1:29)

Let's take a look at two different kinds of environments: one with plenty of freshwater and one with very little, to see how living things make it work in both places. We'll start somewhere with a lot of freshwater. 

 Investigation (1:43)

I can't think of a better example than Russia's Lake Baikal, the deepest lake in the world and holds about one-fifth of the world's freshwater. The nearly 2,000 plant and animal species that live in Lake Baikal have adapted to their super-huge, and wet, but very cold, home. Baikal's most famous resident? That'll be the nerpa.

The nerpa is one of the world's only species of freshwater seal. No one really knows how these guys ended up in a freshwater lake, but they've adapted pretty well to their land-locked habitat. Want an example? Check out their flippers. Their flippers are bigger and stronger than other seal's flippers. Why?

Well, during the winter almost the whole lake is covered with thick ice. Saltwater seals live under the ice in winter too, but it's usually easy for them to find places in the ocean where they can get to the surface to breathe. Lake Baikal, however, can completely freeze over in the winter and the nerpa, unfortunately, sometimes finds itself trapped under the ice.

That's when they use those super strong flippers to make big breathing holes. They stay near their holes for long periods of time, constantly scratching at them to keep them from freezing over. Nerpas also have more blood – about two liters more – than other seals, which lets them store oxygen for longer, and therefore stay underwater longer than some of their other seal buddies.

Okay, so the nerpa is awesome and a wonderful example of an animal that's adapted to the presence of lots of freshwater. Let's go someplace warmer to see what life can be like when there's not a lot of freshwater around.

Welcome to the Sahara in Africa. Deserts have very little water, with sources of surface water that can change throughout the year depending on things like rainfall. The Sahara has some bodies of water that many plants and animals depend on for freshwater, but there's not very many of them. One of these lakes, located on the edges of the Sahara, is called Lake Chad. It's tiny compared to Lake Baikal in Russia. 

Let's compare Lake Chad and Lake Baikal side-by-side using bar graphs. One shows the surface area of each lake, and the other shows how deep they are.

Wow! There's definitely a lot more freshwater for the animals near Lake Baikal than at Lake Chad, according to these graphs.

Good thing a lot of the animals in the Sahara rarely need to drink water. Why not? Because they've adapted to their really, really warm home. In the case of the addax antelope, they actually change the color of their hair. So, how does that help them deal with a lack of water? Well, in the summer the addax has a white coat that reflects sunlight. That helps it keep cool. In the winter, their coat turns to light brown to help them absorb more heat. This trick keeps their body temperature stable year-round, and this means that in the summer they don't need as much water as you or I might to cool ourselves off.

Makes me kind of wish I could change my hair color. What do you guys think about purple? No?



Okay, so what have we learned from our trips to Russia and Africa? Some animals live near lots of freshwater, and some don't. And both kinds can thrive, thanks to their adaptations to the places where they live. So to answer our big question, yes, living things can survive with limited freshwater, but only if they can adapt. 

I'm off to try on a purple wig, to see how it looks. It's probably not gonna look that great.

(Outro music)